Oil source and charge in the Wuerxun Depression, Hailar Basin, northeast China: A chemometric study

Accepted Manuscript Oil source and charge in the Wuerxun Depression, Hailar Basin, northeast China: A chemometric study Yao-Ping Wang, Fan Zhang, Yan-Rong Zou, Jia-Nan Sun, Xiao-Hui Lin, Tian Liang PII:

S0264-8172(17)30433-6

DOI:

10.1016/j.marpetgeo.2017.10.032

Reference:

JMPG 3125

To appear in:

Marine and Petroleum Geology

Received Date: 26 April 2017 Revised Date:

30 October 2017

Accepted Date: 31 October 2017

Please cite this article as: Wang, Y.-P., Zhang, F., Zou, Y.-R., Sun, J.-N., Lin, X.-H., Liang, T., Oil source and charge in the Wuerxun Depression, Hailar Basin, northeast China: A chemometric study, Marine and Petroleum Geology (2017), doi: 10.1016/j.marpetgeo.2017.10.032. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Oil source and charge in the Wuerxun Depression, Hailar Basin, northeast China: A

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chemometric study

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Yao-Ping Wanga,b, Fan Zhangc, Yan-Rong Zoua*, Jia-Nan Suna,b, Xiao-Hui Lina,b, Tian Lianga,b

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a

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Academy of Sciences, Guangzhou 510640, P.R. China

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b

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c

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P.R. China

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Abstract

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State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese

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University of Chinese Academy of sciences, Beijing 10039, P.R. China

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Exploration & Development Research Institute of Daqing Oilfield, PetroChina, Daqing, 163712,

One-hundred-fifty-four samples collected from the Wuerxun Depression, Hailar Basin,

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northeast China were analyzed using GC-MS. The K1n Formation (including K1n2 and K1n1

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members) consists mainly of argillaceous rock with relatively abundant organic matter and is

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considered to be the best source rock in the study area, whereas the K1t Formation and K1d1

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member (Damoguaihe Formation) provide a limited contribution to the Wuerxun oils.

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Chemometric methods, i.e., principal component analysis (PCA) and multidimensional scaling

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(MDS), were used for oil-oil and oil-source rock correlations in this study. Based on PCA and

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geological evidence, the oils from northern Wuerxun originated primarily from source rocks of the

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K1n1 member that were charged ca. 100 Ma, whereas those in the southern Wuerxun form separate

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genetic groups I and II. When combined with trend surface analysis, the MDS technique also

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Corresponding author. Tel.: +86 20 85290187; fax: +86 20 85290706. E-mail address: [email protected] (Y.-R. Zou).

ACCEPTED MANUSCRIPT revealed variations in the depositional conditions and the maturity of the source rocks and oils.

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Group I oils, which have relatively higher maturity, are characterized by relatively high

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saturate/aromatic hydrocarbon ratios, high Pr/Ph ratios (>1), high Ts/(Ts + Tm) ratios, a slight

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predominance of C29 regular steranes, and more positive δ13C values of saturated and aromatic

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hydrocarbon fractions, whereas, the lower maturity group II oils have relatively low

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saturate/aromatic hydrocarbon ratios, low Pr/Ph ratios (<1), low Ts/(Ts + Tm) ratios, high C29

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regular steranes and more negative δ13C values of saturated and aromatic hydrocarbon fractions.

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Analysis indicates that group I oils represent mixtures generated from the K1n1 and K1n2 members

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during the late hydrocarbon generation stage (ca. 25 Ma), whereas group II oils were primarily

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generated from the K1n1 member during the early oil generation stage (ca. 93 Ma). The

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distributions of group I and group II oils are mostly controlled by tectonic development in the

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southern Wuerxun Depression.

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Keywords: Hailar Basin; Wuerxun Depression; Biomarkers; Chemometrics; Oil-source rock

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correlation; Charge time

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Introduction

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The Hailar Basin in the western region of northeast China (Fig. 1a) is one of the most

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important petroliferous basins in the Daqing exploration areas (Li et al., 2009) and is located in the

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Inner Mongolia Autonomous Region. By the end of 2006, the Hailar Basin had 64 commercial oil

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wells, and cumulative discovered recoverable reserves of 105 million tons (Cao et al., 2011).

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Moreover, the Wuerxun Depression, a second-order tectonic unit in the Hailar Basin (Fig. 1b), has

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exploratory potential for oil and gas (Zhang et al., 2007), with an area of 2166 km2 (Gong and

ACCEPTED MANUSCRIPT Pang, 2007). Based on sedimentary architecture and fault development, the Wuerxun Depression

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is further divided into two relatively independent portions, i.e., northern and southern Wuerxun

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(Fig. 1c; Liu et al., 2009a; Sun, 2012). Thus, the source rocks and crude oils collected from the

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depression are discussed independently. Figure 1d shows the well distribution within the

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depression.

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The Wuerxun Depression contains six main sedimentary sequences resting on Paleozoic

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metamorphic basement (Du et al., 2004; Ma et al., 2007), which are listed from bottom to top as

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follows: Xinganling Group (J2x), Tongbomiao Formation (K1t), Nantun Formation (K1n),

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Damoguaihe Formation (K1d), Yimin Formation (K1y), and Qingyuangang Formation (K2q) (Fig.

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2). To date, the petroliferous horizons in the northern Wuerxun Depression are mostly found in the

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second member of the Nantun Formation (K1n2) (Fig. 3a), whereas the oil-bearing layers in the

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southern Wuerxun Depression display a wide distribution (Fig. 3b).

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Previous studies confirmed that four sets of source rocks exist in the Wuerxun Depression,

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namely, the K1d1 member (the first member of the K1d Formation), K1n2 member (the second

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member of K1n Formation), K1n1 member (the first member of the K1n Formation) and K1t

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Formation (Liu et al., 2009a; Yang et al., 2010; Zhang et al., 2004; Fig. 2). The lithology of source

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rocks is characterized by dark mudstones (Jia, 2010; Yang et al., 2010). The K1d Formation source

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rock contains thermally immature, dominantly Type III organic matter, the K1n Formation source

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rock contains mature, dominantly Type II organic matter, and the K1t Formation source rock

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contains mature to post-mature, dominantly Type II organic matter (Yang et al., 2010). Source

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rocks in the central portion of the depression have high organic carbon abundance, while other

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areas can be less than 1 wt.% (Jiang et al., 2008). The genetic relationships between the crude oils

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ACCEPTED MANUSCRIPT and the source rocks remain controversial (Dong, 2011; Hou et al., 2004; Jia, 2010; Jie et al., 2007;

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Yang et al., 2010), probably due to limited number of samples and similar geochemical

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characteristics of the source rocks. Accordingly, a large collection of both oil and source rock

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samples is required that covers the entire study area.

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In this study, chemometric methods were applied to identify the major source rock and to

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establish genetic relationship between the source rocks and the oils. Multiple variables (biomarker

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ratios) and many samples were examined using chemometric methods in which multiple

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parameters can be considered, processed, and graphically displayed (Peters et al., 2005) to yield a

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detailed oil-oil and oil-source rock correlation. Principal component analysis (PCA) has been

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frequently applied to oil-oil and oil-source rock correlations (Mashhadi and Rabbani, 2015; Peters

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et al., 2007, 2013). Moreover, a recent study showed that multidimensional scaling (MDS) is also

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a reliable multivariate oil-oil and oil-source rock correlation tool (Wang et al., 2016), if the studied

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area is complex and/or has similar geochemical characteristics among several source rocks. The

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PCA plot can display a visualization of different groups of samples in the dataset. However, if

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combined with the nonlinear MDS bi-plot (Greenacre and Primicerio, 2013), MDS can supply

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information on maturity and depositional environments of the studied oil and source rock samples

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(Wang et al., 2016). Both PCA and MDS concentrate the relevant information from multiple

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variables (i.e. biomarker ratios) into a few new independent variables (i.e. components). The

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purposes of PCA and MDS are to reduce the dimensionality of the selected biomarker variables

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that can best represent the variation in the data. PCA is a classical linear dimensionality reduction

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technique, whereas MDS belongs to a nonlinear dimensionality reduction technique (Sumithra and

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Surendran, 2015). Thus, it seems that MDS is more suitable for the nonlinear biomarker ratio data

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(Zhan et al., 2016) than PCA, since the linear methods (e.g. PCA) often work inadequately when

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the data are nonlinear.

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Samples and methods

One hundred and fifty-four samples were used in chemometrics analysis, including 28 core

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samples (mudstones) and 18 oil samples from the northern Wuerxun Depression and 71 core

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samples (mudstones) and 37 oil samples from the southern Wuerxun Depression (Table. 1). The

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oil samples are composed of crude oils and oil sands. All wells were drilled using a water-based

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mud system. The candidate source rocks (K1d1 member, K1n and K1t Formations) were chosen

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from 37 wells, and the studied oil samples occurring in the K1d, K1n and K1t formations were

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selected from 39 wells located throughout the Wuerxun Depression (Table 1; Fig. 1d). The core

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samples were cleaned using redistilled water. The samples were subsequently dried at 60 °C and

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ground to powder.

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The powdered samples (195 mudstones; Appendix A) were pyrolyzed using a Rock-Eval to

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obtain such parameters as hydrocarbon generation potential (S1 + S2), with 99 samples extracted

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for 72 h in a Soxhlet apparatus with dichloromethane (DCM) mixed with methanol (93:7). The

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group fractions (saturates, aromatics, resins and asphaltenes) of both oils and source rock extracts

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were separated using column chromatography.

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Gas chromatography-mass spectrometry was performed on the saturated fractions of oils and

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source rock extracts using a Thermo Fisher Trace GC Ultra gas chromatography coupled to a DSQ

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II mass spectrometer equipped with a capillary column (60 m × 0.25 mm × 0.25 µm). The carrier

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gas was helium. The GC oven was initially held at 60 °C for 1 min, programmed to 220 °C at a

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spectrometer was operated using an ion source temperature of 230 °C with an ionization energy of

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70 eV. The analysis was conducted using mode-combining selective ion monitoring (SIM) with

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full-scan detection in a scan range from 50 to 550 Da.

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Stable carbon isotope analysis was performed on the saturated and aromatic fractions of

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crude oils using a Finnigan Deltaplus XL IRMS instrument coupled with a CE flash 1112 EA via a

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ConfloIII interface. The results were reported relative to the Peedee Belemnite (PDB) standard.

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Each sample was analyzed at least twice, and the deviation was no more than 0.3‰.

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In this paper, chemometric methods (e.g., PCA and MDS) were applied to trace the origin of

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crude oil from the Wuerxun Depression using nine source-related biomarker ratios (marked by “#”

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in Table 1), consistent with previous studies (Peters et al., 2007, 2013; Wang et al., 2016). The

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selected biomarker parameters are less affected by biodegradation, thermal maturity and migration.

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PCA was performed using range-scale preprocessing using nine maximum factors, as computed by

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Pirouette® software (Infometrix, Inc.). Using in-house software, MDS was performed with the

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same parameters as PCA with range scale preprocessing and the Bray-Curtis distance (Wang et al.,

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2016). The relevant results are shown in Table 2.

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3.

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3.1 Organic matter enrichment and kerogen type

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3.1.1 Northern Wuerxun Depression

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Results and discussion

Rock-Eval pyrolysis data for the Wuerxun samples are supplied as supplementary material

ACCEPTED MANUSCRIPT (Appendix A). The first member of the Damoguaihe Formation (K1d1) has a total organic carbon

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content (TOC) as high as 3.22 wt%, with an average of 2.53 wt%. The TOC contents of the second

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member of the Nantun Formation (K1n2) range from 1.78 to 7.88 wt%, with an average of 2.94

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wt%, whereas those of the first member of the Nantun Formation (K1n1) range from 0.55 to 6.08

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wt%, with an average of 2.30 wt%. The genetic potentials (S1+S2) of rocks from the K1d1, K1n2

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and K1n1 members fall in the ranges of 3.79-7.37 mg HC/g rock, 2.22-29.70 mg HC/g rock, and

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1.20-17.70 mg HC/g rock, with average values of 4.91 mg HC/g rock, 9.50 mg HC/g rock, and

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7.78 mg HC/g rock, respectively. These results indicate that in the study area, the K1d1 member is

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a fair source rock, the K1n2 and K1n1 members are good source rocks (Fig. 4a; Peters and Cassa,

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1994). A cross-plot of hydrogen index (HI) versus Tmax for the rock samples from the northern

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Wuerxun Depression demonstrates that the source rocks of the K1d1, K1n2 and K1n1 members

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contain mostly Type II kerogen (Fig. 4b).

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The cross plots of S1-TOC and PI-Tmax are useful in distinguishing between nonindigenous

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and indigenous hydrocarbons presented in the source rock samples (Hunt, 1996; Peters and Cassa,

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1994). In general, a migration index (S1/TOC ratio) lower than 1.5 reveals that migrated

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hydrocarbons have not contaminated samples. Also, uncontaminated samples must meet the

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following criteria (Peters and Cassa, 1994): (1) if Tmax is in the range 390-435 oC, then PI must be

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less than 0.1; (2) if Tmax is in the range 436-445 oC, then PI must be less than 0.3; (3) if Tmax is in

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the range 445-460 oC, then PI must be less than 0.4. The diagrams of S1-TOC and PI-Tmax (Fig. 5)

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show the studied samples from the Wuerxun Depression were not contaminated by migrated oil.

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3.1.2 Southern Wuerxun Depression

Fig. 4c shows the variation of genetic potential with TOC content for source rock samples

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from the southern Wuerxun Depression. Source rock of the K1d1 member has TOC content of

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1.46-3.10 wt%, with an average of 2.19 wt%, whereas the values of genetic potential (S1 + S2) are

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relatively low, ranging from 0.79 to 7.39 mg HC/g rock, with an average of 3.66 mg HC/g rock,

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indicating fair source rock potential for the K1d1 member. TOC content varies in the K1n2 member,

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from 0.47 to 3.82 wt%, and the values for the genetic potential ranging from 0.43 to 12.20 mg

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HC/g rock, with an average of 5.13 mg HC/g rock, indicating good petroleum potential. The K1n1

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member also represents good hydrocarbon potential with respect to TOC and S1 + S2, ranging

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from 0.50 to 4.19 wt% (mean = 1.46 wt%) and from 0.49 to 77.57 mg HC/g rock (mean = 7.90 mg

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HC/g rock), respectively. The K1t Formation also has good source rock potential with TOC

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content of 0.51-2.91 wt% and petroleum generation potential of 0.94-33.38 mg HC/g rock, with a

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mean value of 10.19 mg HC/g rock. Fig. 4d demonstrates that the studied rock samples of the K1d1,

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K1n1, K1n2 members and K1t Formation are primarily Type II kerogen with some samples that plot

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in the Type I kerogen region for the K1n2 and K1n1 members.

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3.1.3 The distribution and development of source rock

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According to the aforementioned analysis in sections 3.11 and 3.12, it can be concluded that:

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(1) the K1d1, K1n2 and K1n1 members in the northern Wuerxun Depression are fair, good and good

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source rocks, respectively; (2) the K1n2 and K1n1 members and K1t Formation in the southern

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Wuerxun Depression are good source rocks, while the K1d1 member is fair source rock. With the

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geological evidence concerning the source rock distribution and development, a rough estimation

ACCEPTED MANUSCRIPT can be made as to the contribution of the different source rocks to the oils in the study area. As

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reported in previous research, dark mudstone is most important source rock in the Wuerxun

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Depression (Yang et al., 2010). Detailed source rock distribution and development in the Wuerxun

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Depression can be found in Jia (2010). According to this study, the most developed layers of dark

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mudstone are the K1n (including the K1n2 and K1n1 members) and K1d formations, while the K1t

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Formation, which is more concentrated in the southern Wuerxun Depression, has insignificant

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development. This is also corroborated by Liu et al. (2009a) who state that the K1n Formation

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(including the K1n2 and K1n1 members) consists of 100-300 m of dark mudstone, the K1d

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Formation consists of 150-600m of dark mudstone, and the K1t Formation of dark mudstone is not

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developed. In summary, the K1n Formation is the most important contributing source rock in the

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study area, with the K1d1 member and K1t Formation contributing less to the Wuerxun oil.

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3.2 Depositional environment

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3.2.1 Northern Wuerxun Depression

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Low pristine to phytane (Pr/Ph) values (<1) indicate an anoxic depositional environment,

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whereas high values reveal oxic conditions (Didyk et al., 1978). The Pr/Ph ratios are in the ranges

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of 1.46-1.65, 0.77-1.73, and 0.62–1.68 for source rocks of the K1d1, K1n2, and K1n1 members,

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respectively (Table 1). These values suggest that the K1d1 member was deposited under relatively

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oxic conditions, but some portions of the K1n2 and K1n1 members may have been deposited under

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anoxic conditions.

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Previous research suggests that abundant C27 sterols (or steranes) indicate marine organic

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matter or lacustrine algae, whereas C29 sterols (or steranes) are related to land plant organic matter

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(Huang and Meinschein, 1979). High abundance of C29 steranes is used extensively to imply a

ACCEPTED MANUSCRIPT strong contribution of terrigenous organic matter input (Abeed et al., 2012; Ding et al., 2015, 2016;

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Dong et al., 2015; Gao et al., 2015; Huang et al., 2011; Hunt, 1996; Peters et al., 1986, 2005,

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2007), but microalgae or cyanobacteria can also be a source of C29 sterane precursors. Thus, this

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indicator should be used with caution. The relative contents of C27, C28 and C29 regular steranes for

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all of the studied samples from the northern Wuerxun Depression probably indicate major

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terrigenous and lesser contribution of aquatic algal-bacterial organic matter (Table 1), as supported

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by the sterane ternary diagram (Fig. 6a). This conclusion is also consistent with previous studies

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(Jia, 2009; Yang et al., 2010) that the crude oil within the study area was mainly derived from

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terrigenous organic matter input.

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High C35/C34 ratios for source rock and crude oil are related to strong reduction conditions

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(Peters and Moldowan, 1991). Source rocks of the K1d1 member have low C35/C34 values, whereas

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the source rocks of the K1n2 and K1n1 members have variable C35/C34 values (Table 1). These data

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are indicative of relatively oxic depositional conditions for the K1d1 member and anoxic to oxic

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depositional conditions for the K1n2 and K1n1 members, consistent with Pr/Ph ratios. It is

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commonly accepted that high a gammacerane/C31R ratio indicates a stratified water column and

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reducing conditions during source rock deposition (Fu et al., 1986; Sinninghe Damsté et al., 1995).

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The gammacerane/C31R ratios for the rock extracts from the northern Wuerxun Depression are in

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the range of 0.01-0.18, suggesting the absence of water column stratification.

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3.2.2 Southern Wuerxun Depression

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Source rocks of the K1d1 and K1n2 members have relatively higher Pr/Ph ratios (average>1),

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ranging from 0.83 to 1.83, with an average of 1.30 and from 0.4 to 2.25, with an average of 1.29,

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generally lower Pr/Ph ratios (average <1), ranging from 0.28 to 1.46, with an average of 0.72 and

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from 0.53 to 1.56, with an average of 0.93, respectively (Table 1). These data suggest that the

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studied rock samples from the southern Wuerxun Depression were deposited under a range of

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redox conditions, but the source rocks of the K1n1 member and K1t Formation were probably

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deposited under more reducing conditions than the K1d1 and K1n2 members.

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The relative contents of C27, C28 and C29 regular steranes for the studied source rocks are in

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the range of 15.02-43.31% (average = 33.02%), 11.25-37.25% (average = 16.66%), and 38.48–

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73.19% (average = 50.32%), respectively (Table 1). These values probably suggest a strong

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contribution of terrigenous organic matter input and less contribution from aquatic organisms, as

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indicated by the sterane ternary diagram (Fig. 6b).

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All of the studied source rocks from the southern Wuerxun Depression have low C35/C34

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hopane ratios ranging from 0.26 to 0.92 (Table 1), which suggests deposition under oxic

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conditions. In addition, the gammacerane/C31R ratios of source rocks from the southern Wuerxun

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Depression have low values, also indicating a general absence of water column stratification.

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3.3 Thermal maturity of source rock

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In this work, several biomarker parameters were used to evaluate the thermal maturity of

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source rock from the Wuerxun Depression. With increasing maturity, three biomarker ratios of C32

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22S/(22S + 22R) hopanes, C29 20S/(20R + 20S) and C29 ββ/(αα + ββ) steranes increased from 0 to

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approximately 0.6, 0 to 0.5 and 0 to 0.7, respectively (Seifert and Moldowan, 1980, 1986).

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Essentially the C32 22S/(22S + 22R) ratios reach equilibrium when the early oil generation

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window is approached, whereas the sterane ratios, C29 20S/(20R + 20S) and C29 ββ/(αα + ββ), can

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extend into the mature oil generation window (Seifert and Moldowan, 1986).

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3.3.1 Northern Wuerxun Depression

The C32 22S/(22S + 22R) hopane ratios of the K1d1, K1n2, and K1n1 members range from 0.54

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to 0.58, 0.57 to 0.60, and 0.51 to 0.59, respectively, indicating at least marginal thermal maturity.

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Thermal maturities at the top of the K1d1 member have values of C29 20S/(20R + 20S) and C29

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ββ/(αα + ββ) steranes ranging from 0.25-0.28 and 0.28-0.33, indicating that the source rock is

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immature. Source rocks in the middle of the K1n2 member have relatively high values of C29

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20S/(20R + 20S) and C29 ββ/(αα + ββ) ranging from 0.27-0.48 (mean = 0.37) and 0.26-0.49 (mean

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= 0.41), which indicates low mature to mature, and the K1n1 member also has a relatively high

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values of C29 20S/(20R+20S) and C29 ββ/(αα+ββ) ranging from 0.21-0.54 (mean = 0.45) and

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0.22-0.50 (mean = 0.44), which is indicative of mature source rock.

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3.3.2 Southern Wuerxun Depression

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The ratios of C32 22S/(22S + 22R) hopanes of source rocks from the Southern Wuerxun

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Depression range from 0.47 to 0.60 (average = 0.57) (Table 1), indicating that most of the source

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rocks have reached equilibrium and are thermally mature (Seifert and Moldowan, 1980). Source

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rocks at the top of the K1d1 member have C29 20S/(20R+20S) and C29 ββ/(αα+ββ) sterane ratios

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ranging from 0.35 to 0.47 (average = 0.41) and 0.42 to 0.52 (average = 0.47). Source rocks at the

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middle of the K1n2 member have C29 20S/(20R+20S) and C29 ββ/(αα+ββ) ranging from 0.21 to

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0.59 (mean = 0.46) and 0.20 to 0.53 (mean = 0.47), and the K1n1 member has C29 20S/(20R+20S)

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and C29 ββ/(αα+ββ) steranes ranging from 0.14 to 0.56 (mean = 0.39) and 0.13 to 0.60 (mean =

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0.41). Source rock at the bottom of the K1t Formation has relatively high values of C29

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to 0.53 (average = 0.48). These data suggest mature characteristics for all of the studied rock

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samples. There is a little difference among different members in terms of the level of thermal

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maturation, but overall, source rock of the K1t Formation has slightly more mature than other

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members.

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3.4 Crude oils

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3.4.1 Northern Wuerxun Depression

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The density, viscosity, wax content and freezing point of crude oils from the northern

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Wuerxun Depression are given in Table 3. The density of crude oil collected from the northern

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Wuerxun Depression is in the range of 0.8061-0.8650 g/cm3 and is largely between 0.84-0.86

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g/cm3, the viscosity is generally 4.2-21.9 mPa, the wax content is 3.3-44.4%, and the freezing

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point is 10-36 °C. Crude oils from the K1d and K1n formations have high wax content (average =

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17.8% and 19.0%) and freezing point (average = 28.7 °C and 26.9 °C), while crude oils from the

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K1t Formation have relatively low wax content (average = 10.8%) and freezing point (average =

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16.3 °C).

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The gross compositions of the representative northern Wuerxun Depression oils are given in

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Table 4 and are characterized by high saturated hydrocarbon fraction and low content of

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asphaltenes with saturate/aromatic hydrocarbon ratios >3.7, which might indicate a lack of

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degradation as well as mature character for the northern Wuerxun Depression oil. Contents of

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saturates, aromatics, resins and asphaltenes range from 68.30 to 74.88%, 14.26 to 18.40%, 8.16 to

273

11.91%, and 0.70 to 3.06%, respectively. Owing to space limitations, only representative

ACCEPTED MANUSCRIPT 274

chromatographic data and normalized n-C15 to n-C35 n-alkane distributions that are presented here

275

(Figs. 7 and 10). The analyzed oil from the northern Wuerxun Depression shows a unimodal n-alkane

277

distribution pattern, with no obvious odd-over-even predominance (Fig. 7a). The n-alkanes in the

278

northern Wuerxun oils show a wide distribution (nC14–nC35) maximizing in the nC17–nC21 range.

279

The presence of a high abundance of low molecular weight n-alkanes suggests a lack of

280

biodegradation of the studied oil samples. The Pr/Ph ratios are in the range of 0.68-1.79, and all

281

collected oil samples have low values of Pr/n-C17 and Ph/n-C18 (Table 1).

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The m/z 217 mass chromatograms are shown in Fig. 7b. The relative contents of C27, C28, and

283

C29 regular steranes range from 31.57 to 47.46% (average = 38.97%), 13.73 to 23.94% (average =

284

17.10%), and 28.60 to 53.07% (average = 43.92%), respectively (Table 1). These values probably

285

suggest a slight predominance of land plant organic matter input, as supported by the ternary

286

diagram (Fig. 8a).

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Fig. 7c shows the m/z 191 mass chromatogram of the saturated hydrocarbon fraction for a

288

representative oil sample. The northern Wuerxun oils have low C35/C34 hopanes ratios ranging

289

from 0.06 to 0.88, indicating oxic depositional conditions, which are consistent with the Pr/Ph

290

ratios. In addition, the northern Wuerxun oils have notably low values of gammacerane/C31R

291

ratios ranging from 0 to 0.13, consistent with normal water salinity and the lack of stratification

292

for the source rocks depositional settings.

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293

The ratios of C32 22S/(22S + 22R) hopanes of the studied oil sample from the northern

294

Wuerxun Depression range from 0.50 to 0.60, indicating that most have reached

295

equilibrium and are thermally mature. The ratios of C29 20S/(20R + 20S) and C29 ββ/(αα + ββ)

ACCEPTED MANUSCRIPT 296

steranes are in the range of 0.33-0.54 and 0.45-0.57, indicating that the analyzed oils are mature

297

(Seifert and Moldowan, 1986). The carbon isotopic compositions of the saturated and aromatic fractions of eight crude oils

299

from the northern Wuerxun Depression are shown in Table 4. The carbon isotopes of the saturated

300

and aromatic fractions of crude oils from the northern Wuerxun Depression have light δ13C values

301

ranging from -32.42‰ to -30.04 ‰ and from -31.44‰ to -27.70‰, respectively. These values

302

indicate that these oils were lacustrine origin, but two samples fall into the marine region (Fig. 9;

303

Sofer, 1984). This is probably because stable carbon isotope data for the lacustrine oil samples do

304

not always correspond exactly to organic matter type and can display isotopic characteristics of

305

marine organic matter (Peters et al., 1986, 1996). This is consistent with the lacustrine

306

depositional settings in the Wuerxun Depression (Jia, 2010).

307

3.4.2 Southern Wuerxun Depression

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Table 3 shows the physical properties of crude oils collected from the southern Wuerxun

309

Depression. The bulk properties of the studied oil samples varied greatly in different rock units.

310

Crude oils from the K1d Formation have low density (average = 0.8485 g/cm3), moderate viscosity

311

(average = 10.3 mPa), high wax content (average = 21.7%), and high freezing point (average

312

=29.7 °C). Crude oils from the K1n Formation are characterized by high density (average = 0.8543

313

g/cm3), low viscosity (average = 8.9 mPa), low wax content (average = 5.5%), and low freezing

314

point (average = 12.0 °C). Crude oils from the K1t Formation have moderate density (average =

315

0.8497 g/cm3), high viscosity (average = 21.2 mPa), moderate wax content (average = 14.5%), and

316

moderate freezing point (average = 28.0 °C). These different physical properties of crude oils in

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the southern Wuerxun Depression are probably the result of differences in maturity. The saturates content in the crude oils are between 52.45% and 82.46%, the contents of

319

aromatics are between 13.08% and 18.40%, the contents of resins are between 4.12% and 22.60%,

320

and the content of asphaltenes are between 0.06% and 6.55% (Table 4). Overall, the southern

321

Wuerxun oils are characterized by abundant saturated hydrocarbons and low asphaltenes.

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The n-alkane content of the selected oil samples from the southern Wuerxun Depression

323

shows a unimodal distribution pattern, analogous to that of the northern Wuerxun oil (Fig. 10 a-b).

324

In general, the n-alkanes are in the range of nC15–nC35, maximizing in the range nC17 to nC19. As

325

shown in Table 1, the studied oil samples from the southern Wuerxun Depression have Pr/Ph

326

ratios ranging from 0.34 to 2.13, suggesting a range from anoxic to oxic source rock depositional

327

conditions.

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The m/z 217 mass chromatograms for two selected oil samples from the southern Wuerxun

329

Depression are shown in Fig. 10c-d. The relative abundance of C27, C28 and C29 regular steranes

330

for all of the studied oil samples are in the range of 23.21-42.74% (mean = 31.04%), 13.58-24.28%

331

(mean = 18.46%) and 42.15-55.72% (mean = 50.50%), respectively, probably indicating a major

332

terrigenous source (Fig. 8b).

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The m/z 191 mass chromatograms for two selected oil samples from the southern Wuerxun

334

Depression are shown in Fig. 10e-f. These oil samples have C35/C34 ratios in the range of 0.21–

335

0.87, which is indicative of oxic depositional conditions for the source (Peters and Moldowan,

336

1991). The ratios of gammacerane/C31R for the studied oil samples range from 0.01 to 0.13, within

337

the range of values for no evidence for stratification.

338

The C32 22S/(22S+22R) hopanes for the southern Wuerxun oils are close to equilibrium,

ACCEPTED MANUSCRIPT 339

ranging from 0.54 to 0.60. Values of the C29 20S/(20R+20S) ratios range from 0.26 to 0.54

340

(average = 0.44) and values of the C29 ββ/(αα+ββ) ratios range from 0.34 to 0.53 (average = 0.47),

341

indicating that the studied oil samples are mature. Stable carbon isotope compositions of saturated and aromatic hydrocarbons for the studied

343

oil samples from the southern Wuerxun Depression are given in Table 4. The oils have δ13C values

344

of saturated hydrocarbon ranging from -34.35‰ to -27.18‰ and δ13C values of aromatic

345

hydrocarbons ranging from -28.84‰ to -24.50‰ (Fig. 9), indicating a nonmarine source (Sofer,

346

1984) which is consistent with the lacustrine depositional settings in the Wuerxun Depression (Jia,

347

2010).

348

3.5 Oil-oil and oil-source rock correlation

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Chemometric methods require a large amount of geochemical data. Accordingly, the

350

chemometric method can improve the accuracy of genetic relationships and is well suited to

351

reduce the noise, extract useful information from large data sets, and determine detailed oil-source

352

rock correlation (Peters et al., 2005), and its reliability has been verified by many studies (EI

353

Diasty et al., 2016; Dong et al., 2015a, 2015b; Mashhadi and Rabbani, 2015; Peters et al., 2007,

354

2013).

355

3.5.1 Northern Wunerxun Depression

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The PCA scores and loadings plots were applied to selected parameters obtained from all oil

357

and rock biomarker data (nine ratios in Table 1) from the northern Wuerxun Depression, resulted

358

with the first two principal components accounting for 76.5% and 10.5% of the total variance in

359

the original data set, respectively. Based on the scores plot of PC1 versus PC2, the oils can be

ACCEPTED MANUSCRIPT 360

classified into only one category along the PC1, as shown in Fig. 11a. Fig. 11a shows the 2D-PCA plot of multivariate oil-source rock correlation for the northern

362

Wuerxun Depression, in which the first two components account for 87.0% of the total variance in

363

the original data set. In the 2D-PCA plot (Fig. 11a), data points of the K1d1 members are located

364

far from the oil samples, indicating little contribution to the oil accumulation. The source rocks of

365

the K1n2 member mostly have heavier PC2 loadings than the oils and partially overlap with oil

366

samples, whereas the source rocks of the K1n1 member are closely related to the oil samples. The

367

distribution of these data in 2D-PCA suggests that based on nine biomarker ratios, the oil has a

368

good affinity to the K1n1 member but is distinct from the K1n2 and K1d1 members. As discussed

369

earlier, source rocks in the K1t Formation were undeveloped in the study area, suggesting that the

370

oils occurring in the northern Wuerxun Depression were mainly derived from source rocks in the

371

K1n1 member. The K1d1 member (immature) has only fair-quality source potential, the K1n1 and

372

K1n2 members (mature) have good generation potential, and the K1t Formation (mature) has fair

373

source rock characteristics. Therefore, the oils found in the northern Wuerxun Depression are

374

believed to be primarily generated from the source rock of the K1n1 member with a minor

375

contribution from the K1n2 member. Moreover, in order to interpret the main features of each

376

principal component, there is need to examine the contribution of each variable, namely loading,

377

related to PC1 and PC2. In general, those variables with larger absolute loading values are used to

378

represent the main features of the relevant PC. Loadings plot based on the first two components

379

are plotted versus biomarker variables (or ratios) in Fig. 11b. The loadings on PC1 are dominated

380

by a positive correlation with Pr/Ph, Ts/(Ts + Tm) and C35/C34 ratios; the loadings on PC2 mainly

381

show a positive correlation with C31R/H and Pr/Ph ratios and are negatively correlated with Ts/(Ts

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ACCEPTED MANUSCRIPT + Tm) ratio. It is noteworthy that the Ts/(Ts + Tm) ratio is both a source- and maturity-related

383

parameter (Moldowan et al., 1986; Seifert and Moldowan, 1978). Since the ratio begins to

384

increase at higher maturities (> 0.9%Ro: Van Grass, 1990), and most samples from the Wuerxun

385

Depression show %Ro < 0.9 with three samples that are about 1.0%Ro (Table. 1), the Ts/(Ts + Tm)

386

ratio is assumed to be largely controlled by the source in the study area. The Pr/Ph and C35/C34

387

ratios are generally used to reflect the depositional redox conditions (Didyk et al., 1978; Peters and

388

Moldowan, 1991), while the C31R/H ratio can be used to distinguish source facies (Peters et al.,

389

2005) and represents a lacustrine depositional environment for PC2 when combined with the Pr/Ph

390

ratio (Makeen et al., 2015). Thus, PC1 could be interpreted as an indicator of a depositional redox

391

conditions, whereas PC2 can be used to define lacustrine depositional environments.

392

3.5.2 Southern Wuerxun Depression

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The analyzed oil samples collected from the southern Wuerxun Depression can be divided

394

into two groups based on PCA and MDS analysis (Fig. 12a and c). Generally, group I oils have a

395

relatively higher saturated hydrocarbon fraction and a lower content of asphaltenes with

396

saturate/aromatic hydrocarbon ratios >4, whereas group II oils contain a relatively lower saturated

397

hydrocarbon fraction and a higher content of asphaltenes with saturates/aromatics hydrocarbon

398

ratios >2.8 (Table 4), indicating that the oils of both groups have not been degraded and are

399

mature. In addition, these data suggest that group I oils are relatively more mature than group II

400

oils, which is also supported by the C29 20S/(20R + 20S) steranes and C29 ββ/(αα + ββ) steranes

401

ratios. Group I oils have relatively higher Pr/Ph ratios (>1) ranging from 1.02 to 2.13, whereas

402

group II oils have lower Pr/Ph ratios in the range of 0.34-0.97. The Pr/Ph ratios indicate that group

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ACCEPTED MANUSCRIPT I oils were deposited under more oxic depositional conditions than group II oil samples. A slight

404

predominance of C29 regular steranes (relatively high C27/C29 sterane ratios) for group I oils was

405

observed (Table 1), which is an indicator of a slightly more contribution of aquatic organisms than

406

group II oils, whereas group II oils show a predominance of C29 steranes, which probably suggests

407

a dominance of terrigenous organic matter input, as supported by the sterane ternary diagram (Fig.

408

8b). The southern Wuerxun oils can also be largely classified into two groups, as supported by the

409

relationship between the δ13C values of the saturated and aromatic hydrocarbons (Fig. 9).

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The first two components account for 89.8%. Only 10.2% of the variance was not explained.

411

In the 2D-PCA plot (Fig. 12a), source rocks of the K1d1 member and K1n2 member are mainly

412

distributed in the bottom right of the figure and have a close relationship with group I oils,

413

whereas the source rocks of the K1n1 member display a wide distribution in the figure and are

414

closely related to both groups of oils. The source rocks of the K1t Formation are evenly distributed

415

in the middle and right of the figure (Fig. 12a). In addition, Fig. 12b shows the relative

416

contribution of the nine biomarker ratios to PC1 and PC2. The C27/C29 ratio, which reflects the

417

more algal related organic matter input (Huang and Meinschein, 1979), and Ts/(Ts + Tm) ratio

418

have high positive loadings on PC1. PC1 could be interpreted as an indicator of algal related

419

organic matter input. PC2 represents more eukaryotes input (mainly higher plant and algae) than

420

prokaryotes (bacteria) and anoxic source rock depositional settings, because steranes/hopanes

421

(St/H), C35/C34 and norhopane/hopane (C29/H) ratios, which often infer organic matter input and

422

source rock redox depositional settings (Peters and Moldowan, 1993; Peters et al., 2005), have

423

high positive loadings on PC2. Based on the 2D-PCA plot (Fig. 12a), it is difficult to clearly

424

identify the origin of the crude oil due to several sets of source rocks that nearly overlap with the

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ACCEPTED MANUSCRIPT studied oil samples, suggesting that the source rocks have similar geochemical characteristics.

426

Therefore, an alternative chemometric method, MDS, was used to study the relationship between

427

the oils and the source rocks. Recent research has demonstrated that MDS is an effective

428

multivariate oil-source rock correlation tool and that its accuracy is improved by applying the

429

Bray-Curtis distance rather than the Euclidean distance to distinguish datasets (Wang et al., 2016)

430

using the biomarker ratios of oil-mixing experiments (Zhan et al., 2016). The stress of MDS is

431

calculated as 0.0453 after 1000 iterations in which the goodness-of-fit is good to excellent (Table

432

5). Stress, also known as loss function (Borg and Groenen, 2005), is a measure of how much the

433

best-fitting configuration is deviated from the original data set, and the (1.0 - stress)*100%

434

measures how well the best-fitting configuration represents the original data set (Kruskal, 1964).

435

Therefore, the first two components of MDS account for 95.46% of the original variance. In the

436

MDS plot (Fig. 12c), source rocks of the K1d1 member mainly have heavier MDS2 loadings than

437

the oil samples and partially overlap with group II oils, the source rocks of the K1n2 member

438

mainly have heavier MDS1 loadings than group II oils and are closely related to group I oils. Also,

439

the source rocks of the K1n1 member have a wide distribution in the figure with one portion

440

overlapping with group I oils and the other portion overlapping with group II oils, and the source

441

rocks of the K1t Formation are generally evenly distributed in the middle and right of the figure

442

(Fig. 12c). These observations lead to the conclusion that group I oils were mainly generated from

443

source rocks of the K1n2 and K1n1 members with lesser contributions from the K1t Formation and

444

K1d1 member, whereas group II oils were mainly derived from the K1n1 member with minor

445

contributions from the K1n2 member and K1t Formation. This conclusion is supported by the

446

source rock quality and development of the southern Wuerxun Depression. As discussed

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ACCEPTED MANUSCRIPT previously, the K1d1 member has fair source rock potential, the K1n1 and K1n2 have good

448

hydrocarbon generation potential, and the K1t Formation has a lesser contribution to southern

449

Wuerxun oils (Fig. 4c). Trend surface analysis, a mathematical method to fit the spatial

450

distribution and regional variation of geological data (Chorley and Haggett, 1965), resulting from

451

the MDS results was applied to the biomarkers ratios, as shown in Fig. 13, which reveals the

452

variations of depositional conditions and maturation on a two-dimensional plane by introducing a

453

best-fit line on the overall dataset using the regression method. Fig. 13a displays the depositional

454

condition direction using the Pr/Ph ratio as an indicator, and Fig. 13b exhibits the variation in

455

maturity when the C29 20S/(20R+20S) ratio is used as indicator, thus supporting the analytic result

456

of the MDS plot (Fig. 12c). In addition, Fig. 13 shows that there are good correlations between the

457

Pr/Ph ratio and the MDS1, and between the C29 20S/(20R+20S) ratio and the MDS2. Hence,

458

MDS1 could be roughly interpreted as an indicator of a relatively oxic depositional environments

459

and MDS-2 represents maturity trend.

460

3.6 Oil filling history

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The tectonic evolution of the Wuerxun Depression and the hydrocarbon generation and

462

expulsion history from the four main source rocks (K1d1, K1n2, K1n1 members and K1t Formation)

463

were documented (Cui and Ren, 2011; Cui et al., 2007; Gong, 2012; Hou et al., 2004).

464

Furthermore, the results of oil-oil correlations in this study suggest that only one group of oils

465

exists in the northern Wuerxun Depression, whereas two groups of oils with different maturity

466

levels exist in the southern Wuerxun Depression.

467

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For the oil reservoirs in the northern Wuerxun Depression, the only episode of oil charging

ACCEPTED MANUSCRIPT occurred during the deposition of the Yimin Formation ca. 100 Ma (Fig. 14a). In this period, a

469

large amount of petroleum from the source rocks of the K1n1 member charged the Cretaceous

470

reservoirs. Other source rocks display either low maturity, such as the K1n2 member (Fig. 14a), or

471

minor hydrocarbon expulsion (K1t Formation) because limited distribution and thickness

472

representing a minor contribution to oil pool formation. After the oil charge, local uplift halted

473

hydrocarbon generation. Subsequent subsidence was limited compared with that of the southern

474

Wuerxun Depression, and appears unlikely to cause secondary hydrocarbon generation. Therefore,

475

one oil family (Fig. 11) exists in the northern Wuerxun Depression with a maturity level

476

corresponding to the source rock of the K1n1 member. Homogenization temperatures of fluid

477

inclusions in wells HC-4 and S102 are 92-100 ºC in the northern Wuerxun Depression (Ma et al.,

478

2004), which is consistent with the K1n1 strata at 100 Ma (Cui et al., 2007).

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Two groups of oils with different maturities in the southern Wuerxun Depression were

480

recognized using chemometric methods (Fig. 12). Group I oils exhibit slightly greater maturation,

481

suggesting that the oils were generated later than group II, which filled reservoirs at ca. 93 Ma, i.e.,

482

the deepest burial depth (Fig. 14b), and are substantially equivalent to the charging time of the

483

northern Wuerxun Depression.

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It is generally accepted that there are two episodes of oil charging in the southern Wuerxun

485

Depression. Early studies suggest that the two episodes occurred, ca. 120-80 Ma and 88.5 Ma to

486

the present (Ma et al., 2004), based on authigenic illite dating and the homogenization

487

temperatures of reservoir fluid inclusions, and 94.87-92.52 Ma and the Paleogene to the present

488

(Cui and Ren, 2011) based on authigenic illite dating. However, the latest study (Gong, 2012)

489

reported pool formation ages of 100-92 Ma and 25 Ma to present and provides the burial and

ACCEPTED MANUSCRIPT thermal history of the southern Wuerxun Depression. Thus, the results of Gong (2012) were used

491

in the following discussion. It was considered that the second stage is important for the formation

492

and accumulation of oil-gas reservoirs in the Wuerxun Depression (Cui and Ren, 2011; Gong,

493

2012). However, our results demonstrate that more oils of group II were charged at ca. 93 Ma than

494

those of the late hydrocarbon generation stage from 25 Ma (Figs. 8b and 12a).

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The first hydrocarbon generation and hydrocarbon filling event occurred from source rocks

496

of the K1n1 member (Fig. 14b). However, other units (e.g., K1n2 member and K1t Formation) have

497

not reached generation nor display good generation potential. As the strata of the Qingyuangang

498

Formation underwent progressive subsidence, mature source rock (K1d1 K1n2, K1n1 members and

499

K1t Formation) in the central portion of the southern Wuerxun Depression entered the second

500

hydrocarbon generation stage (Fig. 14b). In short, the hydrocarbon accumulation period of group I

501

oils with relatively high maturity can be assigned to the second charge event and are mainly

502

derived from the K1n2 and K1n1 members, whereas the hydrocarbon accumulation period of group

503

II oils with lower maturity is believed to originate from the first charge, which is in good

504

agreement with the source rocks of the K1n1 member with lesser contributions of the K1n2 member

505

and K1t Formation. In addition, post-emplacement thermal alteration does not influence the

506

thermal maturity of the oil and source rock samples, which is consistent with the thermal history.

507

The charging history is also supported by the stable carbon isotopic compositions of saturated and

508

aromatic hydrocarbons (Fig. 9).

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509

Fig. 15a shows the locations of group I and II oil samples. Group I oils are primarily

510

distributed near mature source rock, whereas group II oils are mainly distributed far from mature

511

source rock. This observation might indicate that the two episodes of oil charging occurred under

ACCEPTED MANUSCRIPT different geological conditions and migration patterns. The geological section line A-B from the

513

southern Wuerxun Depression suggests that the mature source rocks at the maximum burial depth

514

are primarily distributed in the middle of the southern Wuerxun Depression, near the HC-1, W-18

515

and W-16 wells (Fig. 15b). As discussed previously, group I oils originated from the second

516

charge at ca. 25 Ma. In this period, the source rocks of the K1t (fair hydrocarbon potential), K1n

517

Formations and a small portion of the K1d1 member entered the generation and expulsion peak

518

(Fig. 14b). From the end of the Yimin Formation time (88.5 Ma) to Qingyuangang Formation time

519

(88.5 Ma to 65 Ma; Fig. 2), intensive tectonic compressional movement occurred with a nearly

520

EW trend, resulting in early fault reactivation and formation of a series of reverse faults and

521

inversion structures (Liu et al., 2009b; Wu et al., 2006). Accordingly, the reservoirs of group I oils

522

from the late hydrocarbon generation stage show a proximal distribution (Fig. 15a), probably

523

because the group I oils migrated vertically along the faults (Fig. 15b). The reservoirs of group II

524

oils formed from the first charge at ca. 93 Ma. During this period, the main source rock of the

525

K1n1 member was at the peak expulsion stage, and the southern Wuerxun Depression shows a

526

gentle structure and no fault development (Li, 2009). Therefore, the reservoirs of group II oils are

527

located far away from the source rocks (Fig. 15a), probably because the group II oil migrated

528

laterally along sand bodies (Fig. 15b). This observation suggests that the periphery of the southern

529

Wuerxun Depression has good prospects for petroleum exploration.

530

4.

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Conclusions

531

In this study area, the K1n2 and K1n1 members are good source rocks, and the K1d1 member

532

and K1t Formation have less contribution to the Wuerxun oil. The biomarker maturity parameters

533

show thermally mature characteristics for the source rocks of the K1n2 member, K1n1 member and

ACCEPTED MANUSCRIPT 534

K1t Formation. However, rock samples of the K1d1 member from the northern Wuerxun

535

Depression show immature characteristics, whereas the source rocks of the K1d1 member from the

536

southern Wuerxun Depression are more mature. In light of the PCA results, one oil family is present within the northern Wuerxun Depression,

538

and the oils of the southern Wuerxun Depression fall into two families (groups I and II). The

539

northern Wuerxun oils were primarily derived from the source rocks of the K1n1 member, with a

540

minor contribution of the K1n2 member, and were charged at ca. 100 Ma. The MDS plot also

541

shows the patterns of the depositional conditions and maturation of the oil and source rock

542

samples when combined with trend surface analysis. The group I oils were primarily derived from

543

a mixture of source rocks of the K1n2 and K1n1 members, with lesser contributions from the K1d1

544

member and K1t Formation, and were filled at ca. 25 Ma, whereas the group II oils were charged

545

ca. 93 Ma and were mainly derived from the source rock of the K1n1 member, with minor

546

contributions from the K1n2 member and K1t Formation. The crude oils discovered in the current

547

study more strongly appear to originate from the first oil charge at 100-90 Ma. The group I oils are

548

located near the source rocks, probably as a result of the strong tectonic movement from the end of

549

the Yimin Formation (88.5 Ma) to the Qingyuangang Formation (88.5 Ma to 65 Ma), and

550

migrated vertically along faults, whereas the group II oils are located far from the source rock,

551

probably because of weak fault development and lateral migration along sand bodies.

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In this paper, we have successfully traced the origin of crude oil from the southern Wuerxun

553

Depression using MDS, where the studied set of source rocks have similar geochemical

554

characteristics. In addition to the nonlinear MDS bi-plot, trend surface analysis can also be used to

555

indicate the directions of the maturity and the depositional conditions of the studied oil and source

ACCEPTED MANUSCRIPT 556

rock samples in the MDS plot.

557

Acknowledgements

We are deeply indebted to Drs. Ken Peters, Barry J. Katz and one anonymous reviewer who

559

provided constructive reviews and extensive improvements to the grammar in our original

560

manuscript. We also wish to acknowledge Dr. Zhan Zhao-Wen, Dr. Liao Weisen, Dr. Shi Jian-Ting

561

and Mr. Chen Ruijia for the kind help and support in this study. This study was funded by the

562

Natural Science Funding Council of China (Grant No. 41273059, 41173054), the GIGCAS 135

563

project (Grant No. Y234021001), and the SKLOG project (SKLOGA201601).

564

References

565

Abeed, Q., Leythaeuser, D., Littke, R., 2012. Geochemistry, origin and correlation of crude oils in

566

Lower Cretaceous sedimentary sequences of the southern Mesopotamian Basin, southern Iraq.

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sand bodies of Wuerxun-Beier Sag in Hailaer Basin. Journal of Central South University (Science

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and Technology) 47, 2357-2365 (in Chinese with English abstract).

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0537-0544 (in Chinese with English abstract). Liu, Z., 2008. Migration direction of oil and gas in Wuerxun Depression. Fault-Block Oil & Gas Field 15, 31-33 (in Chinese with English abstract). Liu, X., Deng, H., Di, Y., Gao, X., Wang, J., Long, G., 2009a. High quality source rocks of Nantun

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Wuerxun-Beier Sag in Hailar Basin and its geological significance. Earth Science Frontiers 16,

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the distribution and isomerization of homohopanes in petroleum. Organic Geochemistry, 17, 47–

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petroleum and ancient sediments: Englewood Cliffs, New Jersey, Prentice Hall. 363pp. Peters, K.E., Walters, C.C., Moldowan, J.M., 2005. The Biomarker Guide: Biomarkers and Isotopes in Petroleum and Earth History. Cambridge: Cambridge University Press, 1155 pp. Seifert, W. K. and Moldowan, J. M., 1986. Use of biological markers in petroleum exploration. In:

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in Wuerxun Depression. Fault-Block Oil & Gas Field 18, 696-700 (in Chinese with English

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abstract).

713 714 715

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area (Masters Dissertation). Northeast Petroleum University, Heilongjiang. Van Graas, G.W., 1990. Biomarker maturity parameters for high maturities: Calibration of the working range up the oil/condensate threshold. Organic Geochemistry 16, 1025-1032.

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Sun, W., 2012. The acient geomorphological features and hydrocarbon enrichment patterns in Wunan

the Fangzheng Fault Depression, NE China. Organic Geochemistry 102, 1-13.

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716

Wu, H., Li, Z., Feng, Z., Zhu, D., 2006. Analysis on structural features and reservoir-forming process

717

of Wuerxun and Beier sags in Hailar Basin. Acta Petrolei Sinica 27, 1-6 (in Chinese with English

718

abstract).

Yang, W., Hou, D., Li, S., Tao, S., Lu, K., Hong, H., 2010. Geochemical characteristics of oil and

720

correlation of oil to source rock in ramp region of Wunan Depression of Hailaer Basin. Clean Coal

721

Technology 16, 87-90 (in Chinese with English abstract).

724 725

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723

Zhan, Z.-W., Zou, Y.-R., Shi, J.-T., Sun, J.-N., Peng, P., 2016. Unmixing of mixed oil using chemometrics. Organic Geochemistry 92, 1-15.

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722

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Zhang, W., Chen, S., Zhou, J., 2004. Oil-gas accumulation model analysis in Hailaer Basin. Journal of Daqing Petroleum Institute 28, 8-10 (in Chinese with English abstract).

726

Zhang, Y., Sun, H., Lu, Q., 2007. Comprehensive evaluation to K1d1 cap rock in Wuwexun Depression.

727

Petroleum Geology & Oilfield Development in Daqing 26, 11-19 (in Chinese with English

728

abstrasct).

729

ACCEPTED MANUSCRIPT 730 731 732

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733 734 735

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737 738 739 740

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Figure captions

743

Fig. 1

744

Map shows the location of the study area: Hailar Basin (a), Wuerxun Depression (b), tectonic units

745

in the Wuerxun Depression (c), and well locations (d) in the study area (Jie et al., 2007; Li et al.,

746

2016b), those wells marked with star (*) are used in this study.

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747 748

Fig. 2

749

General stratigraphic column of the Wuerxun Depression in the Hailar Basin (Cui and Ren, 2011;

750

Li et al., 2016a; Liu et al., 2006; Ma et al., 2007).

ACCEPTED MANUSCRIPT 751 Fig. 3

753

Distribution of petroliferous horizons in the northern (a) and southern Wuerxun depressions (b)

754

(modified after Ma et al., 2007; Sun et al., 2011).

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752

755 Fig. 4

757

Diagram shows the variation of hydrocarbon generation potential (S1 + S2), total organic carbon

758

(TOC) content and organic matter type for samples from northern Wuerxun (a-b) and southern

759

Wuerxun (c-d). The criteria used to distinguish poor to excellent source rock are from Peters and

760

Cassa (1994).

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761

Fig. 5 Plot of production index versus Tmax (a) and S1 versus TOC (b) to distinguish between

763

nonindigenous and indigenous hydrocarbons present in the source rock samples.

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762

764 Fig. 6

766

Ternary diagram shows the relative abundance of C27, C28 and C29 regular steranes in source rock

767

extracts from the northern Wuerxun (a) and southern Wuerxun depressions (b).

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765

769

Fig. 7

770

Gas chromatogram (a), m/z 217 mass chromatograms (b) and m/z 191 mass chromatograms (c) for

771

representative crude oil of S102 well from northern Wuerxun.

772

ACCEPTED MANUSCRIPT 773

Fig. 8

774

Ternary diagram shows the relative content of regular steranes in oil samples from the northern (a)

775

and southern Wuerxun depressions (b).

RI PT

776 Fig. 9

778

Diagram of δ13C values for saturated versus aromatic hydrocarbons in crude oils from the

779

Wuerxun Depression with symbols showing the result of oil-oil correlation (Sofer, 1984).

SC

777

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780 Fig. 10

782

Gas chromatograms (a-b), m/z 217 mass chromatograms (c-d) and m/z 191 mass chromatograms

783

(e-f), for representative oil samples of W34 and W59 wells from the southern Wuerxun

784

Depression.

785

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Fig. 11

787

Principal component analysis shows the crude oil categories, correlation to source rock (a) and

788

biomarker variables (loading) employed (b). R1= Pristane/Phytane; R4= Ts/(Ts + Tm)

789

trinorhopanes; R5= C29 30-norhopane/hopane; R6= C35 homohopane/C34 homohopane; R7=

790

gammacerane/C31 homohopane 22R; R8= C31 homohopane 22R/hopane; R9= steranes/hopanes;

791

R10= %C27 regular steranes/%C29 regular steranes; R11= %C28 regular steranes /%C29 regular

792

steranes.

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793 794

Fig. 12

ACCEPTED MANUSCRIPT Results of multivariate analysis of the nine source-related parameters in oil and source rock

796

samples from the southern Wuerxun Depression: scores on the first two principal component

797

analysis (a), biomarker variables (loadings) employed (b) and scores on the first two

798

multidimensional scaling (c). R1= Pristane/Phytane; R4= Ts/(Ts + Tm) trinorhopanes; R5= C29

799

30-norhopane/hopane;

800

homohopane 22R; R8= C31 homohopane 22R/hopane; R9= steranes/hopanes; R10= %C27 regular

801

steranes/%C29 regular steranes; R11= %C28 regular steranes /%C29 regular steranes.

C35

homohopane/C34

homohopane;

R7=

gammacerane/C31

SC

R6=

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795

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802 Fig. 13

804

Trend surface analysis applied to the Pr/Ph ratio (a) and C29 20S/(20R + 20S) ratio (b) for the

805

source rock and oil samples from the southern Wuerxun Depression shows the best-fit linear

806

surface and positive and negative deviations (residual).

TE D

803

807 Fig. 14

809

Burial and thermal history of HC-4 well from (a) northern Wuerxun (after Cui et al., 2007; Cui

810

and Ren, 2011) and HC-1 well (b) southern Wuerxun Depression (after Cui and Ren, 2011; Gong,

811

2012). The well locations are shown in Fig. 1d.

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808

813

Fig. 15

814

Map of southern Wuerxun showing oil samples identified by groups (a) and geological section line

815

AB (b) (after Liu, 2008).

816

ACCEPTED MANUSCRIPT

Table captions

818

Table 1. Selected biomarker parameters for oil and source rock samples from the Wuerxun

819

Depression.

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817

820

Table 2. Chemometric results based on principal component analysis (PCA) and multidimensional

822

scaling (MDS).

SC

821

824

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Table 3. Statistics on the physical properties of crude oils in different source rock units.

825

Table 4. Gross compositions and stable carbon isotope values of saturated and aromatic fractions

827

of the crude oils.

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828 829

Table 5. MDS goodness-of-fit and stress (Kruskal, 1964; Storti, 2016).

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831

Appendix A

832

Rock-Eval pyrolysis data for the Wuerxun samples.

ACCEPTED MANUSCRIPT

Lithology

Depth (m)

Well

Lab no.

R1#

R2

R3

R4#

R5#

R6#

R7#

Mudstone

K1d1

1397.00

S19

WB-1

1.59

0.72

0.31

0.08

0.55

0.39

0.02

0.40

0.21

Mudstone

K1d1

1538.18

S33

WB-2

1.46

1.01

0.45

0.12

0.54

0.31

0.03

0.33

0.21

Mudstone

K1d1

1273.34

T3

WB-3

1.65

0.54

0.31

0.09

0.62

Mudstone

K1n2

1731.98

HC-4

WB-4

1.62

0.45

0.27

0.37

0.56

Mudstone

K1n2

1840.80

S103

WB-5

1.47

0.48

0.26

0.49

0.48

Mudstone

K1n2

1949.14

S103

WB-6

1.09

0.35

0.30

0.47

Mudstone

K1n2

1308.12-1316.56

S12

WB-7

0.86

0.21

0.17

Mudstone

K1n2

1316.56-1334.57

S12

WB-8

0.77

0.15

Mudstone

K1n2

1429.31-1446.49

S132

WB-9

0.96

Mudstone

K1n2

1446.49-1464.67

S132

WB-10

Mudstone

K1n2

1464.67-1480.78

S132

Mudstone

K1n2

1658.99

S33

Mudstone

K1n2

1776.08

Mudstone

K1n2

Mudstone

Northern Wuerxun Source rocks

R8#

R9#

R10#

R11#

R12

R13

R14

R15

R16

R17

R18

0.76

0.28

37.32

13.86

48.82

0.54

0.28

0.28

0.52

0.69

0.24

35.70

12.59

51.70

0.57

0.25

0.33

0.57

RI PT

Formation

SC

Table1

0.03

0.33

0.15

0.86

0.31

39.49

14.46

46.04

0.58

0.25

0.33

0.57

0.46

0.04

0.24

0.19

0.90

0.33

40.47

14.63

44.90

0.59

0.41

0.46

0.75

0.40

0.09

0.28

0.23

0.80

0.26

38.76

12.74

48.50

0.58

0.38

0.48

0.78

0.38

0.48

0.08

0.17

0.16

1.03

0.48

40.91

19.26

39.83

0.57

0.47

0.45

0.73

0.53

0.45

0.39

0.07

0.16

0.46

0.77

0.36

36.16

16.80

47.04

0.60

0.42

0.42

0.68

0.12

0.55

0.47

0.41

0.07

0.17

0.53

0.81

0.36

37.34

16.63

46.04

0.60

0.43

0.43

0.70

0.25

0.21

0.56

0.44

0.43

0.07

0.15

0.43

0.79

0.34

37.11

16.04

46.84

0.60

0.48

0.47

0.76

1.26

0.68

0.39

0.14

0.64

0.52

0.03

0.28

0.37

1.23

0.47

45.53

17.49

36.98

0.60

0.27

0.28

0.52

WB-11

1.23

0.78

0.46

0.16

0.85

0.43

0.05

0.30

0.63

1.17

0.47

44.27

17.81

37.92

0.58

0.27

0.26

0.50

WB-12

1.39

0.53

0.23

0.15

0.68

0.56

0.04

0.32

0.20

0.92

0.30

41.34

13.63

45.02

0.59

0.30

0.41

0.67

S33-2

WB-13

1.72

0.52

0.24

0.33

0.55

0.39

0.04

0.25

0.24

0.92

0.34

40.63

15.21

44.15

0.59

0.38

0.46

0.75

1896.40

S43

WB-14

1.68

0.30

0.15

0.43

0.42

0.66

0.09

0.25

0.22

1.09

0.42

43.55

16.63

39.82

0.58

0.42

0.49

0.80

K1n2

1664.62

S46

WB-15

1.39

0.67

0.35

0.16

0.56

0.73

0.04

0.34

0.36

0.93

0.37

40.45

16.16

43.39

0.57

0.29

0.30

0.54

Mudstone

K1n2

1407.95

S47

WB-16

1.73

1.00

0.31

0.33

0.78

0.33

0.06

0.24

0.33

0.90

0.34

40.14

15.19

44.67

0.60

0.30

0.43

0.70

Mudstone

K1n2

1421.82

S47

WB-17

1.09

0.88

0.29

0.28

0.75

0.33

0.05

0.25

0.39

0.95

0.33

41.76

14.48

43.77

0.60

0.30

0.43

0.70

Mudstone

K1n1

1846.19

HC-4

WB-18

1.63

0.38

0.20

0.35

0.45

0.37

0.07

0.25

0.15

0.90

0.36

39.85

16.06

44.08

0.59

0.49

0.48

0.78

Mudstone

K1n1

1799.82

S19

WB-19

1.68

0.25

0.09

0.61

0.36

0.46

0.07

0.23

0.18

0.67

0.27

34.50

14.05

51.45

0.58

0.50

0.49

0.80

Mudstone

K1n1

1953.63

S27-2

WB-20

1.14

0.15

0.11

0.50

0.41

0.50

0.18

0.17

0.38

0.73

0.53

32.23

23.34

44.43

0.51

0.26

0.24

0.48

Mudstone

K1n1

2185.04

S33

WB-21

1.02

0.11

0.07

0.74

0.31

0.48

0.16

0.25

0.29

0.71

0.32

35.03

15.69

49.28

0.56

0.53

0.50

0.82

Mudstone

K1n1

2141.38

S42

WB-22

1.27

0.17

0.09

0.62

0.30

0.46

0.11

0.25

0.22

0.87

0.38

38.59

16.81

44.60

0.56

0.53

0.47

0.76

AC C

EP

TE D

M AN U

0.36

K1n1

2173.92

S43

WB-23

1.18

0.19

0.11

0.74

0.26

0.42

0.14

0.24

0.35

0.97

0.37

41.53

15.72

42.75

0.57

0.54

0.50

0.82

Mudstone

K1n1

2178.77

S43

WB-24

1.32

0.15

0.07

0.68

0.28

0.57

0.17

0.24

0.34

0.96

0.37

41.07

16.01

42.92

0.56

0.53

0.49

0.80

Mudstone

K1n1

1744.49

S47

WB-25

0.70

0.23

0.11

0.63

0.42

0.40

0.09

0.15

0.17

0.94

0.37

40.73

16.03

43.24

0.57

0.47

0.49

0.80

Mudstone

K1n1

1754.93

S47

WB-26

0.97

0.20

0.10

0.63

0.42

0.36

0.09

0.16

0.18

0.86

0.35

38.74

15.97

45.29

0.57

0.49

0.50

0.82

Mudstone

K1n1

1620.00

S56

WB-27

1.62

1.27

0.61

0.06

0.66

0.35

0.01

0.41

0.24

0.79

0.43

35.66

19.26

45.08

0.53

0.21

0.22

0.47

Mudstone

K1n1

1500.59

T3

WB-28

0.62

0.45

0.25

0.17

0.70

0.67

0.05

0.33

0.13

0.88

0.37

39.18

16.44

44.38

0.58

0.37

0.45

0.73

Crude oil

K1d2

940.50-1004.00

T2

WB-29

0.94

0.26

0.20

0.57

0.50

Crude oil

K1n2

1787.20-1809.00

S16

WB-30

1.09

0.23

0.18

0.54

0.54

Crude oil

K1n2

1736.00-1742.00

S27

WB-31

0.70

0.29

0.37

0.63

Crude oil

K1n2

1461.00-1472.40

S29-45

WB-32

0.75

0.18

0.21

Crude oil

K1n2

1542.00-1548.00

S31

WB-33

0.97

0.32

Oil sand

K1n2

1963.24

S42

WB-34

1.17

Oil sand

K1n2

1660.22

S46

WB-35

1.03

Crude oil

K1n2

1446.60-1463.00

S102

WB-36

0.75

Crude oil

K1n2

1336.00-1339.00

T1

WB-37

0.78

Crude oil

K1n2

1007.00-1013.00

T201

WB-38

1.15

Crude oil

K1n1

2271.00-2280.00

S15

WB-39

0.89

Crude oil

K1n1

2367.00-2373.00

S15-1

WB-40

Oil sand

K1n1

2142.78

S42

WB-41

Oil sand

K1n1

2176.57

S43

WB-42

Oil sand

K1n1

1748.69

S47

Crude oil

K1t

1852.20-1859.00

S29-45

Oil sand

K1t

2205.54

S33-2

Oil sand

K1t

2214.31

S33-2

Oils

Southern Wuerxun

RI PT

Mudstone

SC

ACCEPTED MANUSCRIPT

0.13

0.19

0.31

0.99

0.41

41.31

17.08

41.60

0.59

0.43

0.47

0.76

0.88

0.06

0.18

0.37

0.85

0.36

38.57

16.11

45.32

0.59

0.49

0.48

0.78

0.37

0.47

0.02

0.16

0.11

1.39

0.69

47.46

23.94

28.60

0.60

0.49

0.57

0.98

0.52

0.50

0.41

0.07

0.16

0.32

0.87

0.30

40.05

13.73

46.22

0.57

0.44

0.50

0.82

0.22

0.41

0.55

0.56

0.10

0.19

0.34

0.74

0.33

35.70

15.99

48.31

0.58

0.33

0.45

0.73

0.26

0.19

0.62

0.38

0.40

0.06

0.20

0.14

0.66

0.28

33.94

14.51

51.55

0.58

0.53

0.49

0.80

0.25

0.21

0.47

0.44

0.53

0.05

0.21

0.24

0.60

0.29

31.59

15.35

53.07

0.57

0.47

0.47

0.76

0.17

0.20

0.52

0.48

0.41

0.07

0.15

0.39

0.88

0.33

39.71

15.09

45.21

0.59

0.48

0.50

0.82

0.21

0.22

0.54

0.51

0.35

0.08

0.15

0.25

0.92

0.43

39.17

18.16

42.67

0.60

0.45

0.53

0.88

0.27

0.17

0.51

0.50

0.13

0.08

0.19

0.36

1.00

0.42

41.45

17.20

41.36

0.59

0.44

0.47

0.76

0.13

0.13

0.67

0.42

0.10

0.00

0.21

0.70

1.11

0.55

41.84

20.56

37.59

0.50

0.54

0.49

0.80

0.68

0.12

0.14

0.72

0.36

0.07

0.06

0.18

0.78

0.96

0.42

40.30

17.66

42.03

0.53

0.50

0.56

0.95

1.27

0.18

0.11

0.63

0.29

0.51

0.09

0.26

0.17

0.75

0.32

36.33

15.54

48.13

0.57

0.52

0.48

0.78

1.79

0.27

0.11

0.66

0.29

0.44

0.13

0.23

0.30

0.89

0.38

39.22

16.63

44.15

0.59

0.54

0.50

0.82

WB-43

1.18

0.22

0.11

0.69

0.30

0.29

0.08

0.18

0.36

1.29

0.47

46.74

16.91

36.34

0.58

0.51

0.45

0.73

WB-44

0.95

0.18

0.16

0.68

0.48

0.06

0.00

0.20

0.40

0.96

0.50

38.95

20.43

40.62

0.58

0.52

0.50

0.82

WB-45

1.17

0.21

0.17

0.63

0.34

0.48

0.07

0.21

0.44

0.70

0.33

34.58

16.19

49.23

0.57

0.51

0.49

0.80

WB-46

1.08

0.24

0.18

0.69

0.36

0.49

0.08

0.22

0.44

0.71

0.35

34.63

16.78

48.59

0.56

0.49

0.49

0.80

AC C

EP

TE D

M AN U

0.17

ACCEPTED MANUSCRIPT

K1d1

2192.86

W14

WN-1

0.96

0.36

0.10

0.10

0.53

0.29

0.02

0.28

0.18

Mudstone

K1d1

2195.06

W14

WN-2

0.83

0.37

0.11

0.11

0.56

0.35

0.06

0.29

0.18

Mudstone

K1d1

2198.36

W14

WN-3

0.91

0.44

0.12

0.19

0.59

0.37

0.10

0.30

0.19

Mudstone

K1d1

2702.94

W19

WN-4

1.05

0.12

0.08

0.44

0.55

0.43

0.06

0.30

Mudstone

K1d1

2451.60

W22

WN-5

1.58

0.30

0.12

0.46

0.44

0.36

0.07

0.24

Mudstone

K1d1

2120.18

W29

WN-6

1.64

0.52

0.19

0.44

0.49

Mudstone

K1d1

2031.05

W42

WN-7

1.83

0.65

0.28

0.40

0.47

Mudstone

K1d1

2035.15

W42

WN-8

1.19

0.19

0.12

0.58

0.40

Mudstone

K1d1

2040.25

W42

WN-9

1.68

0.61

0.29

0.35

Sandstone

K1n2

2176.03

W134-92

WN-10

1.07

0.32

0.23

Mudstone

K1n2

2181.45

W134-92

WN-11

1.43

0.45

Mudstone

K1n2

2268.43

W134-92

WN-12

0.97

Mudstone

K1n2

2345.50

W134-92

WN-13

0.89

Mudstone

K1n2

2348.60

W134-92

WN-14

1.12

Mudstone

K1n2

2060.00

W18

WN-15

0.42

Mudstone

K1n2

1841.70

W21

WN-16

1.72

Mudstone

K1n2

2479.28

W22

WN-17

1.16

Mudstone

K1n2

2207.94

W29

WN-18

Mudstone

K1n2

2358.20

W33

WN-19

Mudstone

K1n2

2373.31

W33

WN-20

Mudstone

K1n2

2389.61

W33

Mudstone

K1n2

2566.53

W34

Mudstone

K1n2

2568.53

W34

Mudstone

K1n2

2570.53

W34

Mudstone

K1n2

2634.80

W34

0.30

0.29

19.05

18.34

62.61

0.59

0.42

0.47

0.76

0.34

0.31

20.84

18.76

60.41

0.59

0.44

0.52

0.86

0.37

0.32

21.68

19.09

59.22

0.60

0.44

0.51

0.84

0.25

0.88

0.39

38.80

17.06

44.13

0.59

0.38

0.42

0.68

0.07

0.72

0.29

35.82

14.44

49.74

0.59

0.46

0.50

0.82

RI PT

Mudstone

SC

Source rocks

0.06

0.21

0.09

0.72

0.27

36.07

13.77

50.15

0.60

0.39

0.48

0.78

0.65

0.06

0.25

0.13

0.94

0.35

41.09

15.24

43.67

0.58

0.35

0.45

0.73

0.66

0.08

0.22

0.17

0.69

0.34

34.02

16.83

49.15

0.57

0.47

0.44

0.72

0.46

0.67

0.08

0.26

0.17

0.90

0.36

39.82

15.96

44.22

0.58

0.37

0.44

0.72

0.60

0.47

0.26

0.08

0.20

0.13

0.69

0.25

35.56

12.91

51.53

0.59

0.36

0.46

0.75

0.25

0.60

0.44

0.26

0.01

0.19

0.13

0.68

0.30

34.35

15.07

50.58

0.58

0.34

0.45

0.73

0.42

0.33

0.67

0.43

0.37

0.08

0.21

0.13

0.74

0.27

36.86

13.55

49.58

0.58

0.47

0.49

0.80

0.33

0.30

0.75

0.29

0.33

0.12

0.21

0.11

0.83

0.30

38.96

14.24

46.79

0.57

0.53

0.51

0.84

0.27

0.20

0.73

0.30

0.34

0.09

0.22

0.16

0.87

0.38

38.74

16.93

44.32

0.57

0.52

0.50

0.82

0.52

0.38

0.06

0.88

0.38

0.02

0.48

0.24

0.21

0.16

15.02

11.79

73.19

0.52

0.28

0.29

0.53

0.51

0.15

0.04

0.72

0.28

0.03

0.43

0.10

0.69

0.31

34.61

15.42

49.97

0.57

0.21

0.29

0.53

0.08

0.07

0.57

0.37

0.41

0.09

0.29

0.12

0.57

0.26

31.20

14.01

54.79

0.57

0.48

0.50

0.82

1.93

0.26

0.10

0.52

0.40

0.33

0.09

0.23

0.08

0.66

0.26

34.22

13.68

52.10

0.58

0.46

0.50

0.82

1.13

0.60

0.39

0.74

0.28

0.37

0.08

0.22

0.14

0.74

0.33

35.68

15.97

48.35

0.59

0.50

0.49

0.80

0.96

0.30

0.23

0.60

0.34

0.34

0.08

0.24

0.18

0.64

0.36

31.98

17.92

50.11

0.59

0.47

0.49

0.80

WN-21

0.89

0.48

0.27

0.49

0.43

0.36

0.10

0.23

0.13

0.60

0.41

29.81

20.57

49.62

0.57

0.46

0.50

0.82

WN-22

1.52

0.13

0.08

0.66

0.34

0.36

0.11

0.22

0.13

0.67

0.29

34.28

14.65

51.07

0.58

0.52

0.51

0.84

WN-23

1.47

0.13

0.09

0.68

0.35

0.30

0.10

0.22

0.09

0.73

0.29

36.00

14.44

49.56

0.59

0.52

0.51

0.84

WN-24

1.36

0.20

0.16

0.75

0.32

0.32

0.12

0.20

0.08

0.88

0.31

40.28

14.16

45.56

0.59

0.51

0.53

0.88

WN-25

1.58

0.28

0.14

0.79

0.26

0.34

0.16

0.20

0.16

0.72

0.28

35.96

13.93

50.11

0.57

0.56

0.51

0.84

AC C

EP

TE D

M AN U

0.37

K1n2

2636.80

W34

WN-26

1.65

0.19

0.12

0.77

0.26

0.29

0.15

0.20

0.13

0.72

0.29

35.64

14.58

49.79

0.57

0.57

0.50

0.82

Mudstone

K1n2

2639.30

W34

WN-27

2.25

0.42

0.15

0.77

0.24

0.37

0.13

0.19

0.17

0.69

0.29

34.89

14.63

50.48

0.57

0.59

0.49

0.80

Mudstone

K1n2

2641.30

W34

WN-28

2.09

0.40

0.14

0.80

0.23

0.42

0.14

0.20

0.14

0.88

0.35

39.41

15.81

44.77

0.54

0.58

0.51

0.84

Mudstone

K1n2

2642.80

W34

WN-29

1.90

0.38

0.16

0.79

0.24

0.33

0.14

0.20

0.21

0.77

0.29

37.35

14.16

48.49

0.57

0.57

0.49

0.80

Mudstone

K1n2

1949.90

W38

WN-30

1.86

0.90

0.35

0.47

0.42

0.66

0.09

0.22

0.23

0.83

0.29

39.24

13.50

47.27

0.57

0.32

0.42

0.68

Mudstone

K1n2

1953.10

W38

WN-31

1.86

0.44

0.14

0.42

0.54

0.88

0.09

0.20

0.30

0.83

0.28

39.18

13.39

47.43

0.60

0.32

0.44

0.72

Mudstone

K1n2

1956.00

W38

WN-32

1.76

1.07

0.39

0.50

0.41

Mudstone

K1n2

2495.10

W39

WN-33

1.20

0.37

0.18

0.65

0.33

Mudstone

K1n2

1286.26

W59

WN-34

1.30

0.39

0.31

0.32

0.48

Mudstone

K1n2

2225.10

W84-106

WN-35

1.05

0.24

0.17

0.61

Mudstone

K1n2

2227.80

W84-106

WN-36

0.71

0.26

0.23

Mudstone

K1n1

1711.58

B1

WN-37

0.64

0.54

Mudstone

K1n1

1712.58

B1

WN-38

0.53

Mudstone

K1n1

2268.10

W108-112

WN-39

0.47

Mudstone

K1n1

2271.70

W108-112

WN-40

0.33

Mudstone

K1n1

2308.60

W122-95

WN-41

1.26

Mudstone

K1n1

2330.92

W122-95

WN-42

0.84

Mudstone

K1n1

2333.42

W122-95

WN-43

0.60

Mudstone

K1n1

2339.42

W122-95

WN-44

Mudstone

K1n1

2358.30

W122-95

WN-45

Mudstone

K1n1

2524.00

W132-80

WN-46

Mudstone

K1n1

2547.00

W132-80

Mudstone

K1n1

2270.69

W24

Mudstone

K1n1

2275.09

W24

Mudstone

K1n1

2439.80

W24

Mudstone

K1n1

2372.11

W29

RI PT

Mudstone

SC

ACCEPTED MANUSCRIPT

0.08

0.22

0.08

0.82

0.23

39.91

11.25

48.84

0.57

0.33

0.45

0.73

0.44

0.16

0.17

0.16

0.67

0.34

33.31

17.00

49.68

0.58

0.55

0.51

0.84

0.50

0.06

0.25

0.16

0.54

0.28

29.87

15.24

54.88

0.46

0.24

0.20

0.45

0.37

0.45

0.14

0.22

0.18

0.66

0.29

33.93

14.82

51.25

0.57

0.54

0.51

0.84

0.65

0.35

0.46

0.10

0.21

0.12

0.75

0.32

36.28

15.41

48.31

0.57

0.55

0.53

0.88

0.38

0.29

0.58

0.37

0.06

0.29

0.19

0.56

0.35

29.34

18.21

52.46

0.47

0.14

0.17

0.43

0.27

0.44

0.30

0.55

0.31

0.05

0.30

0.19

0.52

0.31

28.45

16.89

54.66

0.47

0.19

0.13

0.40

0.28

0.31

0.41

0.55

0.33

0.07

0.21

0.20

0.47

0.32

26.40

17.83

55.77

0.58

0.44

0.49

0.80

0.28

0.41

0.42

0.31

0.55

0.13

0.18

0.33

0.49

0.30

27.40

16.89

55.72

0.57

0.49

0.49

0.80

0.12

0.07

0.48

0.39

0.34

0.12

0.23

0.21

0.85

0.44

37.21

19.06

43.73

0.51

0.26

0.21

0.46

0.18

0.23

0.66

0.35

0.39

0.11

0.24

0.22

0.65

0.30

33.43

15.23

51.34

0.55

0.45

0.44

0.72

0.28

0.34

0.70

0.36

0.38

0.12

0.20

0.13

0.65

0.39

31.93

19.15

48.92

0.57

0.46

0.42

0.68

0.50

0.25

0.37

0.56

0.35

0.43

0.11

0.25

0.15

0.63

0.35

31.91

17.66

50.43

0.56

0.40

0.44

0.72

0.81

0.24

0.21

0.68

0.31

0.39

0.17

0.22

0.17

0.60

0.36

30.68

18.31

51.01

0.56

0.48

0.46

0.75

0.59

0.28

0.26

0.76

0.28

0.36

0.04

0.24

0.42

0.75

0.38

35.05

17.96

46.99

0.55

0.56

0.49

0.80

WN-47

1.19

0.47

0.18

0.67

0.36

0.43

0.16

0.25

0.33

0.62

0.34

31.57

17.21

51.22

0.56

0.54

0.48

0.78

WN-48

1.06

0.29

0.17

0.60

0.45

0.31

0.09

0.20

0.13

0.74

0.28

36.71

13.67

49.62

0.58

0.45

0.47

0.76

WN-49

0.91

0.24

0.18

0.55

0.44

0.36

0.08

0.22

0.25

0.86

0.31

39.70

14.12

46.19

0.58

0.48

0.49

0.80

WN-50

0.99

0.21

0.16

0.69

0.40

0.34

0.10

0.19

0.11

0.67

0.30

34.18

15.17

50.65

0.56

0.52

0.52

0.86

WN-51

1.36

0.12

0.08

0.75

0.26

0.39

0.16

0.24

0.11

0.76

0.35

36.05

16.49

47.46

0.56

0.56

0.52

0.86

AC C

EP

TE D

M AN U

0.70

K1n1

2209.05

W31

WN-52

1.46

0.17

0.08

0.68

0.35

0.38

0.09

0.21

0.13

0.62

0.33

31.70

16.82

51.49

0.58

0.41

0.52

0.86

Mudstone

K1n1

2297.15

W31

WN-53

1.02

0.21

0.17

0.76

0.28

0.40

0.11

0.19

0.08

0.85

0.35

38.52

15.92

45.56

0.57

0.47

0.51

0.84

Mudstone

K1n1

2560.06

W31

WN-54

0.40

0.17

0.25

0.54

0.40

0.54

0.12

0.18

0.09

0.81

0.55

34.39

23.33

42.28

0.57

0.22

0.43

0.70

Mudstone

K1n1

2478.50

W33

WN-55

0.33

0.36

0.42

0.48

0.36

0.61

0.05

0.22

0.26

0.64

0.42

31.02

20.54

48.44

0.56

0.42

0.42

0.68

Mudstone

K1n1

2165.60

W38

WN-56

0.82

0.21

0.17

0.40

0.43

0.66

0.13

0.23

0.34

0.97

0.44

40.11

18.39

41.50

0.60

0.49

0.50

0.82

Mudstone

K1n1

2345.30

W38

WN-57

0.79

0.31

0.29

0.67

0.44

0.49

0.22

0.26

0.74

0.63

0.97

24.20

37.25

38.56

0.57

0.26

0.60

1.07

Mudstone

K1n1

1846.91

W38-5

WN-58

0.37

0.35

0.44

0.32

0.44

Mudstone

K1n1

1847.86

W38-5

WN-59

0.51

0.30

0.46

0.32

0.43

Mudstone

K1n1

1825.81

W45

WN-60

0.43

0.34

0.54

0.39

0.47

Mudstone

K1n1

1826.41

W45

WN-61

0.28

0.52

0.81

0.38

Mudstone

K1t

2154.35

B16

WN-62

0.59

0.19

0.23

Mudstone

K1t

2155.85

B16

WN-63

0.79

0.18

Mudstone

K1t

2693.40

W22

WN-64

1.56

Mudstone

K1t

2457.05

W29

WN-65

1.18

Mudstone

K1t

1989.30

W40

WN-66

1.21

Mudstone

K1t

2207.66

W40

WN-67

0.75

Mudstone

K1t

2310.20

W40

WN-68

0.53

Mudstone

K1t

2312.20

W40

WN-69

0.57

Mudstone

K1t

2279.64

W46-112

WN-70

Mudstone

K1t

1726.36

W65

WN-71

Crude oil

K1d2

1302.80-1305.20

W20

Crude oil

K1d2

1470.00-1476.00

W16

Crude oil

K1d2

1507.40-1509.80

W22

Oil sand

K1d1

2032.59

W42

Group I

0.02

0.17

1.07

0.49

0.34

26.78

18.52

54.70

0.51

0.25

0.24

0.48

0.92

0.02

0.16

1.17

0.50

0.35

27.05

19.05

53.91

0.51

0.24

0.24

0.48

0.61

0.04

0.19

0.81

0.53

0.29

29.24

16.07

54.69

0.55

0.28

0.28

0.52

0.28

0.60

0.01

0.12

0.84

0.40

0.35

22.67

20.14

57.19

0.54

0.26

0.28

0.52

0.45

0.52

0.42

0.05

0.21

0.09

0.68

0.38

32.85

18.54

48.62

0.57

0.33

0.45

0.73

0.19

0.51

0.51

0.39

0.08

0.23

0.10

0.55

0.29

29.77

15.75

54.48

0.58

0.36

0.43

0.70

0.38

0.13

0.75

0.24

0.43

0.14

0.21

0.32

1.13

0.47

43.31

18.21

38.48

0.56

0.56

0.50

0.82

0.22

0.13

0.65

0.33

0.50

0.11

0.26

0.17

0.76

0.38

35.70

17.63

46.67

0.57

0.49

0.48

0.78

0.49

0.31

0.34

0.58

0.28

0.05

0.24

0.21

0.46

0.25

27.06

14.69

58.25

0.57

0.25

0.39

0.64

0.18

0.16

0.61

0.44

0.59

0.12

0.19

0.18

0.65

0.34

32.76

16.93

50.31

0.58

0.50

0.51

0.84

0.15

0.20

0.62

0.30

0.49

0.17

0.17

0.29

0.53

0.37

28.10

19.31

52.59

0.58

0.57

0.50

0.82

0.20

0.24

0.65

0.26

0.57

0.16

0.15

0.23

0.47

0.41

25.09

21.77

53.14

0.60

0.56

0.52

0.86

1.19

0.15

0.09

0.76

0.33

0.34

0.09

0.20

0.24

0.91

0.39

39.42

17.02

43.55

0.58

0.45

0.53

0.88

0.80

0.33

0.33

0.54

0.45

0.52

0.06

0.15

0.09

0.41

0.24

24.98

14.51

60.51

0.59

0.42

0.48

0.78

EP

TE D

M AN U

0.64

AC C

Oils

RI PT

Mudstone

SC

ACCEPTED MANUSCRIPT

WN-72

1.07

0.21

0.17

0.65

0.38

0.36

0.10

0.20

0.27

0.73

0.35

35.09

16.86

48.05

0.57

0.50

0.50

0.82

WN-73

1.03

0.19

0.16

0.67

0.37

0.39

0.07

0.20

0.26

0.75

0.33

35.84

16.08

48.08

0.57

0.53

0.48

0.78

WN-74

1.16

0.25

0.20

0.55

0.46

0.41

0.11

0.20

0.22

0.64

0.32

32.77

16.36

50.87

0.57

0.45

0.50

0.82

WN-75

1.13

0.20

0.12

0.55

0.42

0.45

0.13

0.23

0.16

0.76

0.32

36.61

15.50

47.89

0.60

0.49

0.44

0.72

K1n2

2061.0-2067.0

W20

WN-76

1.04

0.28

0.19

0.68

0.38

0.33

0.10

0.20

0.26

1.01

0.36

42.74

15.11

42.15

0.59

0.54

0.51

0.84

Oil sand

K1n2

2669.99

W34

WN-77

1.57

0.25

0.12

0.75

0.34

0.36

0.11

0.20

0.27

0.75

0.36

35.45

17.06

47.49

0.56

0.54

0.51

0.84

Crude oil

K1n1

2822.00-2823.00

W18

WN-78

1.10

0.22

0.14

0.64

0.45

0.63

0.13

0.22

0.27

0.93

0.40

39.79

17.29

42.92

0.60

0.50

0.48

0.78

Oil sand

K1n1

1672.66

W30

WN-79

1.62

0.22

0.11

0.61

0.36

0.45

0.13

0.21

0.15

0.70

0.30

34.90

14.96

50.15

0.56

0.48

0.47

0.76

Oil sand

K1n1

1673.07

W30

WN-80

2.13

0.16

0.07

0.58

0.38

0.51

0.09

0.22

0.15

0.72

0.32

35.35

15.58

49.07

0.58

0.46

0.50

0.82

Oil sand

K1n1

1674.74

W30

WN-81

1.32

0.19

0.12

0.60

0.36

0.40

0.11

0.21

0.15

0.69

0.29

34.68

14.85

50.47

0.57

0.48

0.47

0.76

Crude oil

K1n1

1671.0-1675.0

W30

WN-82

1.23

0.31

0.18

0.57

0.42

Oil sand

K1t

2064.26

W51-1

WN-83

1.02

0.34

0.17

0.57

0.37

Crude oil

K1d2

1807.00-1832.00

W17

WN-84

0.66

0.32

0.31

0.46

0.53

0.36

Crude oil

K1n2

1588.40-1821.60

W4

WN-85

0.79

0.10

0.12

0.33

0.52

Crude oil

K1n2

1706.40-1711.40

W4

WN-86

0.40

0.17

0.37

0.33

Oil sand

K1n2

2365.05

W33

WN-87

0.62

0.38

0.47

Oil sand

K1n2

2376.31

W33

WN-88

0.72

0.28

0.30

Oil sand

K1n2

1752.80

W38-3

WN-89

0.47

0.31

Oil sand

K1n2

1755.80

W38-3

WN-90

0.40

Oil sand

K1n2

1283.16

W59

WN-91

0.84

Crude oil

K1n2

1471.00-1474.00

W51

WN-92

0.93

Crude oil

K1n2

1471.00-1474.00

W51

WN-93

Oil-sand

K1n2

2223.19

W84-106

WN-94

Oil sand

K1n2

2342.77

W134-92

WN-95

Crude oil

K1n1

1792.00-1826.00

B1

Oil sand

K1n1

2476.79

W24

Oil sand

K1n1

2480.88

W24

Crude oil

K1n1

2493.0-2572.0

W29

Oil sand

K1n1

2287.23

W31

RI PT

Crude oil

SC

ACCEPTED MANUSCRIPT

0.09

0.19

0.17

0.90

0.34

39.79

17.29

42.92

0.59

0.50

0.48

0.78

0.40

0.10

0.15

0.15

0.70

0.47

32.19

21.56

46.25

0.57

0.39

0.48

0.78

0.06

0.22

0.19

0.67

0.26

34.77

13.58

51.65

0.58

0.36

0.42

0.68

0.27

0.02

0.13

0.25

0.66

0.36

32.67

17.98

49.35

0.57

0.30

0.41

0.67

0.53

0.21

0.08

0.15

0.25

0.66

0.36

32.71

17.77

49.52

0.57

0.32

0.42

0.68

0.58

0.37

0.54

0.05

0.21

0.26

0.50

0.36

26.94

19.37

53.69

0.56

0.49

0.44

0.72

0.59

0.37

0.59

0.10

0.23

0.32

0.53

0.42

27.31

21.45

51.25

0.57

0.49

0.48

0.78

0.54

0.31

0.54

0.59

0.02

0.17

0.30

0.52

0.39

27.16

20.52

52.32

0.56

0.36

0.45

0.73

0.32

0.56

0.27

0.62

0.60

0.03

0.16

0.35

0.53

0.42

27.10

21.59

51.30

0.56

0.35

0.45

0.73

0.45

0.50

0.37

0.45

0.47

0.12

0.15

0.12

0.46

0.34

25.71

18.92

55.37

0.56

0.28

0.34

0.58

0.29

0.36

0.42

0.49

0.36

0.07

0.16

0.23

0.54

0.34

28.74

18.21

53.05

0.55

0.29

0.37

0.62

0.87

0.28

0.36

0.41

0.49

0.41

0.05

0.17

0.22

0.50

0.34

27.09

18.55

54.36

0.55

0.29

0.37

0.62

0.97

0.28

0.17

0.50

0.38

0.47

0.07

0.20

0.17

0.80

0.42

35.86

19.11

45.03

0.57

0.49

0.53

0.88

0.85

0.51

0.47

0.64

0.41

0.33

0.01

0.18

0.12

0.65

0.32

32.87

16.38

50.74

0.58

0.50

0.53

0.88

WN-96

0.34

0.29

0.58

0.31

0.45

0.40

0.01

0.16

0.24

0.52

0.36

27.47

19.26

53.27

0.57

0.26

0.37

0.62

WN-97

0.80

0.24

0.25

0.68

0.41

0.42

0.02

0.20

0.12

0.57

0.30

30.55

16.11

53.34

0.57

0.54

0.51

0.84

WN-98

0.52

0.24

0.26

0.66

0.41

0.43

0.02

0.20

0.13

0.63

0.33

32.14

16.75

51.11

0.57

0.53

0.52

0.86

WN-99

0.61

0.21

0.22

0.63

0.37

0.41

0.09

0.21

0.48

0.68

0.46

31.83

21.35

46.83

0.56

0.51

0.49

0.80

WN-100

0.64

0.13

0.17

0.67

0.35

0.44

0.08

0.18

0.39

0.44

0.45

23.21

23.82

52.97

0.54

0.45

0.49

0.80

AC C

EP

TE D

Group II

M AN U

0.39

K1n1

2293.72

W31

WN-101

0.71

0.19

0.23

0.67

0.35

0.67

0.09

0.18

0.37

0.46

0.43

24.25

22.81

52.94

0.54

0.41

0.51

0.84

Oil sand

K1n1

2302.05

W31

WN-102

0.62

0.13

0.17

0.68

0.34

0.87

0.07

0.19

0.30

0.46

0.41

24.57

22.05

53.38

0.56

0.46

0.49

0.80

Oil sand

K1n1

2010.65

W38-3

WN-103

0.48

0.43

0.69

0.36

0.29

0.70

0.03

0.12

0.44

0.46

0.33

25.78

18.50

55.72

0.58

0.44

0.48

0.78

Oil sand

K1n1

2188.16

W108-112

WN-104

0.41

0.25

0.38

0.47

0.42

0.40

0.08

0.17

0.39

0.55

0.38

28.42

19.74

51.84

0.58

0.46

0.49

0.80

Oil sand

K1n1

2266.40

W108-112

WN-105

0.42

0.36

0.49

0.47

0.28

0.49

0.02

0.13

0.35

0.46

0.37

25.05

20.24

54.71

0.59

0.49

0.50

0.82

Oil sand

K1n1

2336.12

W122-95

WN-106

0.40

0.27

0.62

0.31

0.41

0.61

0.01

0.14

0.62

0.50

0.48

25.35

24.28

50.36

0.59

0.46

0.46

0.75

Crude oil

K1t

1848.80-1853.00

W13

WN-107

0.80

0.52

0.34

0.53

0.39

Crude oil

K1t

1835.00-1939.80

BX-2

WN-108

0.60

0.24

0.29

0.52

0.43

RI PT

il sand

SC

ACCEPTED MANUSCRIPT

0.44

0.01

0.15

0.07

0.46

0.36

25.12

19.99

54.89

0.57

0.43

0.51

0.84

0.41

0.07

0.18

0.22

0.58

0.30

30.76

16.18

53.06

0.57

0.38

0.46

0.75

M AN U

Note: “#” biomarker parameters for chemometrics calculation; R1= Pr/Ph; R2= Pr/n-C17; R3= Ph/n-C18; R4= Ts/(Tm + Ts); R5= C29/C30; R6= C35/C34; R7= Ga/C31R; R8= C31 22R/C30 hopane; R9= St/H; R10= C27/C29; R11= C28/C29; R12= C27/(C27 +C28 + C29)*100 regular steranes; R13= C28/(C27 +C28 + C29)*100 regular steranes; R14= C29/(C27 +C28 + C29)*100 regular steranes; R15= H32 22S/(22S+22R); R16= C29 ββ/(αα + ββ); R17= C29 20S/(20R+20S); R18=%Ro (vitrinite reflectance), the %Ro values are based on the equation: %Ro= 0.49*(C29 20S/20R) + 0.33 (Gürgey, 2003). Pr= Pristane; Ph= Phytane; Ts= 18α(H),21β(H)-22,29,30-trinorhopane; Tm= 17α(H),21β(H)-22,29,30-trinorhopane; C29= 17α(H),21β(H)-30-norhopane; C30= 17α(H),21β(H)-hopane;

C35=

17α(H),21β(H)-30,31,32,33,34-pentakishomohopane;

C34=

17α(H),21β(H)-30,31,32,33-tetrakishomohopane;

AC C

EP

TE D

22R-17α(H),21β(H)-30-homohopane; C29= C29 5α(H),14α(H),17α(H)-steranes; H32= 17α(H),21β(H)-30,31-bishomohopane.

GA=

Gammacerane;

C31R=

ACCEPTED MANUSCRIPT Table 2 PCA results Lithology

Formation

Depth (m)

Well

MDS results

Lab no. PC1

PC2

MDS-1

MDS-2

Northern Wuerxun Source rocks K1d1

1397.00

S19

WB-1

1.028

0.966

/

/

Mudstone

K1d1

1538.18

S33

WB-2

0.874

0.737

/

/

Mudstone

K1d1

1273.34

T3

WB-3

1.061

0.879

/

/

Mudstone

K1n2

1731.98

HC-4

WB-4

1.241

0.405

/

/

Mudstone

K1n2

1840.80

S103

WB-5

1.279

0.212

/

/

Mudstone

K1n2

1949.14

S103

WB-6

1.183

-0.202

/

/

Mudstone

K1n2

1308.12-1316.56

S12

WB-7

1.058

-0.335

/

/

Mudstone

K1n2

1316.56-1334.57

S12

WB-8

1.111

-0.366

/

/

Mudstone

K1n2

1429.31-1446.49

S132

WB-9

Mudstone

K1n2

1446.49-1464.67

S132

WB-10

Mudstone

K1n2

1464.67-1480.78

S132

WB-11

Mudstone

K1n2

1658.99

S33

Mudstone

K1n2

1776.08

S33-2

Mudstone

K1n2

1896.40

S43

Mudstone

K1n2

1664.62

S46

Mudstone

K1n2

1407.95

S47

Mudstone

K1n2

1421.82

S47

Mudstone

K1n1

1846.19

HC-4

Mudstone

K1n1

1799.82

Mudstone

K1n1

1953.63

Mudstone

K1n1

2185.04

Mudstone

K1n1

2141.38

Mudstone

K1n1

2173.92

Mudstone

K1n1

2178.77

Mudstone

K1n1

Mudstone

K1n1

Mudstone

K1n1

1.103

-0.334

/

/

1.309

0.537

/

/

1.505

0.590

/

/

M AN U

SC

RI PT

Mudstone

WB-12

1.177

0.758

/

/

WB-13

1.252

0.464

/

/

WB-14

1.560

0.231

/

/

WB-15

1.321

0.680

/

/

WB-16

1.394

0.545

/

/

WB-17

1.152

0.360

/

/

WB-18

1.203

0.324

/

/

WB-19

1.257

0.058

/

/

WB-20

1.420

-0.367

/

/

S33

WB-21

1.379

-0.435

/

/

S42

WB-22

1.341

-0.192

/

/

S43

WB-23

1.487

-0.444

/

/

S43

WB-24

1.614

-0.345

/

/

1744.49

S47

WB-25

1.058

-0.486

/

/

1754.93

S47

WB-26

1.103

-0.371

/

/

1620.00

S56

WB-27

1.156

1.045

/

/

AC C

EP

TE D

S19

S27-2

K1n1

1500.59

T3

WB-28

1.013

0.497

/

/

K1d2

940.50-1004.00

T2

WB-29

1.239

-0.346

/

/

K1n2

1787.20-1809.00

S16

WB-30

1.400

-0.070

/

/

K1n2

1736.00-1742.00

S27

WB-31

1.275

-0.485

/

/

Crude oil

K1n2

1461.00-1472.40

S29-45

WB-32

1.001

-0.288

/

/

Crude oil

K1n2

1542.00-1548.00

S31

WB-33

1.143

-0.052

/

/

Oil sand

K1n2

1963.24

S42

WB-34

1.014

-0.165

/

/

Oil sand

K1n2

1660.22

S46

WB-35

0.955

-0.021

/

/

Crude oil

K1n2

1446.60-1463.00

S102

WB-36

1.028

-0.343

/

/

Crude oil

K1n2

1336.00-1339.00

T1

WB-37

1.078

-0.348

/

/

Crude oil

K1n2

1007.00-1013.00

T201

WB-38

1.186

-0.174

/

/

Mudstone Oils Crude oil Crude oil Crude oil

ACCEPTED MANUSCRIPT K1n1

2271.00-2280.00

S15

WB-39

1.274

-0.432

/

/

Crude oil

K1n1

2367.00-2373.00

S15-1

WB-40

1.177

-0.704

/

/

Oil sand

K1n1

2142.78

S42

WB-41

1.240

-0.127

/

/

Oil sand

K1n1

2176.57

S43

WB-42

1.588

-0.131

/

/

Oil sand

K1n1

1748.69

S47

WB-43

1.429

-0.466

/

/

Crude oil

K1t

1852.20-1859.00

S29-45

WB-44

1.107

-0.323

/

/

Oil sand

K1t

2205.54

S33-2

WB-45

1.219

-0.261

/

/

Oil sand

K1t

2214.31

S33-2

WB-46

1.289

-0.331

/

/

Mudstone

K1d1

2192.86

W14

WN-1

0.496

0.247

0.004

0.418

Mudstone

K1d1

2195.06

W14

WN-2

0.609

0.292

-0.012

0.334

Mudstone

K1d1

2198.36

W14

WN-3

0.791

0.251

0.014

0.277

Mudstone

K1d1

2702.94

W19

WN-4

1.224

0.208

0.032

0.157

Mudstone

K1d1

2451.60

W22

WN-5

1.125

-0.139

0.154

0.129

Mudstone

K1d1

2120.18

W29

WN-6

1.104

-0.098

0.138

0.154

Mudstone

K1d1

2031.05

W42

WN-7

1.365

0.112

0.111

0.186

Mudstone

K1d1

2035.15

W42

WN-8

1.271

0.132

0.044

0.067

Mudstone

K1d1

2040.25

W42

WN-9

1.330

0.166

0.097

0.169

Sandstone

K1n2

2176.03

W134-92

WN-10

1.090

-0.157

0.129

0.114

Mudstone

K1n2

2181.45

W134-92

WN-11

1.032

-0.152

0.189

0.188

Mudstone

K1n2

2268.43

W134-92

WN-12

1.193

-0.100

0.088

0.074

Mudstone

K1n2

2345.50

W134-92

WN-13

1.290

-0.293

0.157

-0.039

Mudstone

K1n2

2348.60

W134-92

WN-14

1.324

-0.240

0.141

-0.014

Mudstone

K1n2

2060.00

W18

WN-15

0.577

0.747

-0.199

0.574

Mudstone

K1n2

1841.70

W21

WN-16

0.929

0.237

0.226

0.390

Mudstone

K1n2

2479.28

W22

WN-17

1.123

-0.084

0.094

0.105

Mudstone

K1n2

2207.94

W29

WN-18

1.198

-0.294

0.192

0.097

Mudstone

K1n2

2358.20

W33

WN-19

1.247

-0.231

0.142

0.003

Mudstone

K1n2

2373.31

W33

WN-20

1.092

-0.099

0.060

0.041

Mudstone

K1n2

2389.61

W33

WN-21

1.046

-0.009

0.026

0.077

Mudstone

K1n2

2566.53

W34

WN-22

1.271

-0.283

0.154

0.030

AC C

EP

TE D

M AN U

Source rocks

SC

Southern Wuerxun

RI PT

Crude oil

K1n2

2568.53

W34

WN-23

1.266

-0.330

0.180

0.042

K1n2

2570.53

W34

WN-24

1.394

-0.382

0.193

0.002

K1n2

2634.80

W34

WN-25

1.440

-0.464

0.208

-0.022

K1n2

2636.80

W34

WN-26

1.400

-0.507

0.229

-0.005

K1n2

2639.30

W34

WN-27

1.481

-0.527

0.222

-0.044

Mudstone

K1n2

2641.30

W34

WN-28

1.618

-0.500

0.208

-0.071

Mudstone

K1n2

2642.80

W34

WN-29

1.485

-0.500

0.225

-0.027

Mudstone

K1n2

1949.90

W38

WN-30

1.385

0.051

0.118

0.127

Mudstone

K1n2

1953.10

W38

WN-31

1.468

0.336

0.134

0.193

Mudstone

K1n2

1956.00

W38

WN-32

1.352

0.019

0.190

0.131

Mudstone

K1n2

2495.10

W39

WN-33

1.302

-0.222

0.098

-0.056

Mudstone

K1n2

1286.26

W59

WN-34

0.949

0.156

0.027

0.187

Mudstone Mudstone Mudstone Mudstone Mudstone

ACCEPTED MANUSCRIPT K1n2

2225.10

W84-106

WN-35

1.246

-0.108

0.083

0.002

Mudstone

K1n2

2227.80

W84-106

WN-36

1.189

-0.051

0.051

-0.010

Mudstone

K1n1

1711.58

B1

WN-37

0.847

0.292

-0.043

0.212

Mudstone

K1n1

1712.58

B1

WN-38

0.763

0.252

-0.065

0.249

Mudstone

K1n1

2268.10

W108-112

WN-39

0.803

0.197

-0.073

0.170

Mudstone

K1n1

2271.70

W108-112

WN-40

0.891

0.189

-0.110

-0.114

Mudstone

K1n1

2308.60

W122-95

WN-41

1.249

-0.120

0.127

0.056

Mudstone

K1n1

2330.92

W122-95

WN-42

1.184

-0.084

0.054

0.003

Mudstone

K1n1

2333.42

W122-95

WN-43

1.177

-0.099

0.042

-0.047

Mudstone

K1n1

2339.42

W122-95

WN-44

1.064

0.025

0.001

-0.014

Mudstone

K1n1

2358.30

W122-95

WN-45

1.250

-0.192

0.070

-0.072

Mudstone

K1n1

2524.00

W132-80

WN-46

1.161

0.031

0.032

-0.131

Mudstone

K1n1

2547.00

W132-80

WN-47

1.365

-0.107

0.072

-0.055

Mudstone

K1n1

2270.69

W24

WN-48

1.149

-0.140

0.112

0.084

Mudstone

K1n1

2275.09

W24

WN-49

1.175

-0.001

0.055

0.085

Mudstone

K1n1

2439.80

W24

WN-50

1.181

-0.179

0.105

0.044

Mudstone

K1n1

2372.11

W29

WN-51

1.446

-0.367

0.173

-0.054

Mudstone

K1n1

2209.05

W31

WN-52

1.236

-0.224

0.129

0.034

Mudstone

K1n1

2297.15

W31

WN-53

1.336

-0.272

0.138

-0.065

Mudstone

K1n1

2560.06

W31

WN-54

1.195

0.132

0.000

-0.120

Mudstone

K1n1

2478.50

W33

WN-55

0.969

0.343

-0.120

-0.015

Mudstone

K1n1

2165.60

W38

WN-56

1.340

0.287

-0.049

-0.012

Mudstone

K1n1

2345.30

W38

WN-57

1.654

0.310

0.015

-0.193

Mudstone

K1n1

1846.91

W38-5

WN-58

0.811

0.811

-0.294

0.027

Mudstone

K1n1

1847.86

W38-5

WN-59

0.956

1.034

-0.316

0.055

Mudstone

K1n1

1825.81

W45

WN-60

0.895

0.639

-0.211

0.027

Mudstone

K1n1

1826.41

W45

WN-61

0.660

0.575

-0.360

-0.128

Mudstone

K1t

2154.35

B16

WN-62

0.952

0.183

-0.035

0.138

Mudstone

K1t

2155.85

B16

WN-63

0.995

0.069

0.020

0.125

Mudstone

K1t

2693.40

W22

WN-64

1.670

-0.294

0.157

-0.121

Mudstone

K1t

2457.05

W29

WN-65

1.351

-0.075

0.088

-0.023

Mudstone

K1t

1989.30

W40

WN-66

0.832

0.094

0.048

0.261

SC

M AN U

TE D

EP

AC C

RI PT

Mudstone

K1t

2207.66

W40

WN-67

1.231

0.124

-0.005

0.013

K1t

2310.20

W40

WN-68

1.144

-0.015

-0.029

-0.114

K1t

2312.20

W40

WN-69

1.139

-0.004

-0.039

-0.155

K1t

2279.64

W46-112

WN-70

1.388

-0.217

0.121

-0.035

K1t

1726.36

W65

WN-71

0.891

0.105

-0.113

0.129

Crude oil

K1d2

1302.80-1305.20

W20

WN-72

1.230

-0.103

0.077

0.012

Crude oil

K1d2

1470.00-1476.00

W16

WN-73

1.203

-0.062

0.057

0.022

Crude oil

K1d2

1507.40-1509.80

W22

WN-74

1.175

-0.026

0.054

0.058

Oil sand

K1d1

2032.59

W42

WN-75

1.273

-0.064

0.083

0.037

Crude oil

K1n2

2061.0-2067.0

W20

WN-76

1.409

-0.261

0.134

-0.021

Mudstone Mudstone Mudstone Mudstone Mudstone Oils Group I

ACCEPTED MANUSCRIPT K1n2

2669.99

W34

WN-77

1.527

0.116

0.026

-0.026

Crude oil

K1n1

2822.00-2823.00

W18

WN-78

1.371

-0.158

0.101

-0.020

Oil sand

K1n1

1672.66

W30

WN-79

1.337

-0.222

0.138

0.019

Oil sand

K1n1

1673.07

W30

WN-80

1.390

-0.190

0.153

0.070

Oil sand

K1n1

1674.74

W30

WN-81

1.218

-0.182

0.114

0.026

Crude oil

K1n1

1671.0-1675.0

W30

WN-82

1.267

-0.108

0.093

0.058

Oil sand

K1t

2064.26

W51-1

WN-83

1.144

-0.086

0.044

-0.029

Crude oil

K1d2

1807.00-1832.00

W17

WN-84

0.950

0.137

0.001

0.148

Crude oil

K1n2

1588.40-1821.60

W4

WN-85

0.741

0.137

-0.127

0.238

Crude oil

K1n2

1706.40-1711.40

W4

WN-86

0.760

0.105

-0.143

0.199

Oil sand

K1n2

2365.05

W33

WN-87

0.984

0.209

-0.077

0.009

Oil sand

K1n2

2376.31

W33

WN-88

1.157

0.213

-0.039

-0.028

Oil sand

K1n2

1752.80

W38-3

WN-89

0.775

0.515

-0.217

0.092

Oil sand

K1n2

1755.80

W38-3

WN-90

0.790

0.613

-0.247

0.100

Oil sand

K1n2

1283.16

W59

WN-91

0.894

0.074

-0.087

0.059

Crude oil

K1n2

1471.00-1474.00

W51

WN-92

0.894

0.085

-0.036

0.120

Crude oil

K1n2

1471.00-1474.00

W51

WN-93

0.850

0.164

-0.070

0.121

Oil-sand

K1n2

2223.19

W84-106

WN-94

1.132

0.047

0.017

0.044

Oil sand

K1n2

2342.77

W134-92

WN-95

0.965

-0.030

0.046

0.191

Crude oil

K1n1

1792.00-1826.00

B1

WN-96

0.610

0.306

-0.231

0.160

Oil sand

K1n1

2476.79

W24

WN-97

1.008

0.035

-0.038

0.096

Oil sand

K1n1

2480.88

W24

WN-98

0.985

0.103

-0.074

0.070

Crude oil

K1n1

2493.0-2572.0

W29

WN-99

1.168

0.148

-0.012

-0.051

Oil sand

K1n1

2287.23

W31

WN-100

1.049

0.121

-0.064

-0.061

Oil sand

K1n1

2293.72

W31

WN-101

1.171

0.259

-0.068

-0.075

Oil sand

K1n1

2302.05

W31

WN-102

1.202

0.412

-0.103

-0.079

Oil sand

K1n1

2010.65

Oil sand

K1n1

2188.16

Oil sand

K1n1

Oil sand

K1n1

Crude oil

K1t K1t

TE D

SC

WN-103

0.734

0.429

-0.258

-0.090

WN-104

0.890

0.211

-0.111

0.020

EP

W38-3

W108-112

2266.40

W108-112

WN-105

0.712

0.225

-0.217

-0.105

2336.12

W122-95

WN-106

0.742

0.608

-0.305

-0.018

1848.80-1853.00

W13

WN-107

0.803

0.077

-0.168

0.129

BX-2

WN-108

0.935

0.101

-0.038

0.062

AC C

Crude oil

M AN U

Group II

RI PT

Oil sand

1835.00-1939.80

Note: “/”not calculated

ACCEPTED MANUSCRIPT Table 3 3

Formation

Density (g/cm )

Viscosity (mPas)

Vax (%)

Freezing point

0.8355–0.8593

6.5–16.4

9.8–22.9

24.0–33.0

Northern Wuerxun

11.8(3)

17.8(3)

28.7(3)

4.2–21.9

3.3–44.4

20.0–33.0

0.8480(11)

12.3(9)

19.0(11)

26.9(10)

4.8–14.3

11.0–24.0

10.8(6)

16.3(6)

0.8444–0.8528 K1t

/ 0.8498(6)

Southern Wuerxun

K1n

K1t

(

8.5–12.0

19.5–23.8

25.0–35.0

0.8485(3)

10.3(3)

21.7(3)

29.7(3)

0.8155–0.9376

3.7–14.8

4.8–6.2

11.0–13.0

0.8543(6)

8.9(5)

5.5(2)

12.0(2)

0.8363–0.8630

7.5–34.9

10.7–18.2

25.0–31.0

0.8497(2)

21.2(2)

14.5(2)

28.0(2)



)

AC C

EP

TE D

Note:

0.8333–0.8562

M AN U

K1d

RI PT

K1n

0.8490(3) 0.8061–0.8650

SC

K1d

ACCEPTED MANUSCRIPT Table 4

Northern Wuerxun

δ 13 C

δ 13 C

Sat

Aro

Sat (‰)

Aro (‰)

(%)

(%)

K1d2

-31.08

-31.44

69.12

17.59

2271.00-2280.00

K1n1

-30.56

-28.11

/

S15-1

2367.00-2373.00

K1n1

-30.04

-27.70

S27

1736.00-1742.00

K1n2

-32.42

S29-45

1461.00-1472.40

K1n2

T1

1336.00-1339.00

K1n2

T201

1007.00-1013.00

K1n2

-30.61

-28.54

S29-45

1852.20-1859.00

K1t

-30.42

-29.71

W20

1302.8-1305.2

K1d2

-28.97

W16

1470.0-1476.0

K1d2

-28.94

W18

2822.0-2823.0

K1n1

-27.18

W20

2061.0-2067.0

K1n2

-28.90

W29

2493.0-2572.0

K1n1

W17

1832.0-1807

W4

1706.40-1711.40

Res

Asp

(%)

(%)

3.93

11.91

1.38

/

/

/

/

74.88

14.26

5.25

8.16

2.70

-31.34

68.30

18.40

3.71

10.23

3.06

-30.63

-29.62

71.80

16.46

4.36

10.65

1.09

-31.08

-29.30

72.45

15.21

4.76

11.63

0.70

73.60

14.57

5.05

11.07

0.76

/

/

/

/

/

-27.24

71.68

15.92

4.50

10.30

2.11

-27.75

69.43

17.36

4.00

7.86

0.80

-24.50

82.46

13.35

6.18

4.12

0.06

-27.37

79.64

13.38

5.95

5.96

1.02

-29.94

-28.75

/

/

/

/

/

K1d2

-30.59

-28.67

52.45

18.40

2.85

22.60

6.55

K1n2

-34.35

-28.84

71.50

13.08

5.47

12.53

2.90

Well

Depth (m)

Formation

T2

940.50-1004.00

S15

EP

M AN U

TE D

Note: Sat = saturates; Aro = aromatics; Res = Resins; Asp = Asphaltenes; “/” not detected.

AC C

Southern Wuerxun

Group II

SC

Group I

Sat/Aro

RI PT

Location

ACCEPTED MANUSCRIPT Table 5 Quality of configuration

Stress >0.20

Fair

0.10

Good

0.05

Excellent

0.025

Perfect

0.0

AC C

EP

TE D

M AN U

SC

RI PT

Poor

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT

Highlights

We discussed independently the northern and southern portions of the Wuerxun Depression.

RI PT

Chemometric methods (e.g., PCA and MDS) were applied to oil-oil and oil-source rock correlations.

Trend surface analysis was used to indicate the depositional environment and maturation

SC

directions.

M AN U

Crude oils were primarily derived from the first member of the Nantun Formation (K1n1) source rock.

The oil family and charge episode are different between the northern and southern portions of

AC C

EP

TE D

the depression.