- Email: [email protected]
Oolitic shoal complexes characterization of the Lower Triassic Feixianguan Formation in the Yuanba Gas Field, Northeast Sichuan Basin, China
Marine and Petroleum Geology 83 (2017) 35e49
Contents lists available at ScienceDirect
Marine and Petroleum Geology journal homepage: www.elsevier.com/locate/marpetgeo
Research paper
Oolitic shoal complexes characterization of the Lower Triassic Feixianguan Formation in the Yuanba Gas Field, Northeast Sichuan Basin, China Lei Chen a, b, Yongchao Lu b, *, Xiaoyue Fu c, Fengcun Xing d, Chao Wang b, e, Chan Luo a a
School of Geoscience and Technology, Southwest Petroleum University, Chengdu, 610500, China Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education, China University of Geosciences(Wuhan), Wuhan, 430074, China Southern Exploration and Development Division Company of SINOPEC, Chengdu, 610041, China d Chengdu University of Technology, Chengdu, 610059, China e Jianghan Oil Field Branch Company of SINOPEC, Qianjiang, 433124, China b c
a r t i c l e i n f o
a b s t r a c t
Article history: Received 14 July 2016 Received in revised form 15 February 2017 Accepted 9 March 2017 Available online 10 March 2017
The Yuanba Gas Field is the second largest natural gas reservoir in the Sichuan Basin, southwest China. The vast majority of the natural gas reserve is from the Permian Changhsingian reef complexes and Lower Triassic Feixianguan oolitic shoal complexes. To better understand this reservoir system, this study characterizes geological and geophysical properties, spatial and temporal distribution of the oolitic shoal complexes and factors that control the oolitic shoals character for the Lower Triassic Feixianguan Formation in the Yuanba Gas Field. Facies analysis, well-seismic tie, well logs, seismic character, impedance inversion, and root mean square (RMS) seismic attributes distinguish two oolitic shoal complex facies e FA-A and FA-B that occur in the study area. FA-A, located in the middle of oolitic shoal complex, is composed of well-sorted ooids with rounded shape. This facies is interpreted to have been deposited in shallow water with relatively high energy. In contrast, FA-B is located in flanks of the oolitic shoal complex, and consists of poorly sorted grains with various shape (rounded, subrounded and subangular). The oolitic shoal complexes were mainly deposited along the platform margin. From the early Fei 2 Member period to the late Fei 2 Member period, the oolitic shoals complexes on the platform margin gradually migrated from the southwest to the northeast with an extent ranging from less than 100 km2 e150 km2 in the Yuanba Gas Field. The migration of oolitic shoals coincided with the development of a series of progradational clinoforms, suggesting that progradational clinoforms caused by sea-level fall maybe are the main reason that lead to the migration of oolitic shoals. Finally, this study provide an integrated method for the researchers to characterize oolitic shoal complexes by using well cores, logs, seismic reflections, impedance inversion, and seismic attribute in other basins of the world. © 2017 Elsevier Ltd. All rights reserved.
Keywords: Oolitic shoal Feixianguan Formation Lower Triassic Northeast Sichuan Basin
1. Introduction Oolitic shoal deposits form prolific reservoirs in North America and other areas, such as Mississippian oolitic reservoir in Oklahoma (Asquith, 1984), Ooids in the Jurassic Smackover Formation of the eastern Gulf of Mexico Basin (Tedesco and Major, 2012), prolific oolitic reservoir in Arab Formation (Upper Jurassic) and Khuff Formation (Upper Permian-Lower Triassic) of Saudi Arabia (Ibe, 1985; Fontana et al., 2010; Zeller et al., 2011; Hasse and Aigner, 2013;
* Corresponding author. E-mail address: [email protected] (Y. Lu). http://dx.doi.org/10.1016/j.marpetgeo.2017.03.009 0264-8172/© 2017 Elsevier Ltd. All rights reserved.
Asadi-Eskandar et al., 2013), Great Oolite Group in the Humbly Grove Oilfield in England (Sellwood, 1985), Oolite Blanche Formation in Paris Basin (France) (Makhloufi et al., 2013). To understand these systems, numerous studies have examined the sedimentology (Rankey and Reeder, 2011; Li et al., 2015; Pomar et al., 2015; Eren et al., 2016; Qiao et al., 2016), geomorphology (Qi et al., 2007; Sparks and Rankey, 2013), stratigraphy (Sparks and Rankey, 2013) and petrology (Amour et al., 2013; Lipinski et al., 2013; Kosakowski and Krajewski, 2014) to understand the factors that control sedimentary environment, geometry, distribution, heterogeneity, and evolution of oolitic deposits in modern and ancient shallow-marine environments (Reeder and Rankey, 2008; Goldstein et al., 2013; Esrafili-Dizaji and Rahimpour-Bonab, 2014; Rankey, 2014).
36
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49
Fig. 1. (A) Paleo depositional environment of the Fei 2 Member of the Triassic Feixianguan Formation in the northeastern Sichuan Basin, China. The east-west cross section across the Yuanba Gas Field in Fig. 12 is also shown. (B) Structural setting and location of the Yuanba Gas Field in the northeast Sichuan Basin (After Duan et al., 2008). Also shown are key wells, 3-D seismic survey and location of cross section shown in Fig. 10.
One geologically interesting time period with abundant ooids was the Early Triassic after the end Permian extinction. During this period, a coincidence of global paleoclimatic, eustatic change, along with the regional tectonic and paleographic conditions, resulted in the widespread deposition of oolitic shoals in South China (Chen, 1995; Hallam and Wignall, 1999; Ma et al., 2005a; Ni et al., 2007; Mei and Tucker, 2007; Mei et al., 2007; Zhang et al., 2009, 2011; Guo, 2010; Zou et al., 2011; He et al., 2012; Wu et al., 2012; Lehrmann et al., 2003, 2012; Tan et al., 2012; Chen et al., 2015). The oolitic shoal of the Lower Triassic Feixianguan Formation in the Northeast Sichuan Basin, due to its great petroleum potential and
considerable scientific importance, has drawn increasing interest for petroleum geologists (He et al., 2012; Tan et al., 2011). Although gas flow was obtained from oolitic shoal reservoirs of the Lower Triassic Feixianguan Formation from Ba 3 well in 1963, there is no breakthrough until Dukouhe Gas Field, Tieshanpo Gas Field and Luojiazai Gas Field discovered during 1996e2000 in the Northeast Sichuan Basin (Wang et al., 2002). Since then, due to a lot of drilling wells and seismic data available, more and more studies were conducted on sedimentary characteristics, reservoir features and formation of the oolitic shoals of the Feixianguan Formation in the Northeast Sichuan Basin (Cai et al., 2004; Wei et al., 2005; He et al.,
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49
37
Fig. 2. Generalized stratigraphic column of the Upper Permian Changxing Formation to the Lower Triassic Feixianguan Formation in Yuanba area, showing the limestone dominated the Feixianguan Formation and the oolitic shoals mainly developed in Fei 2 Member of the Feixianguan Formation.
2007; Yang et al., 2006, 2007), which directly lead to the discovery of the giant Puguang Gas Field in 2003 with a proven original inplace gas volume of 350 109 m3 (Ma et al., 2005b, 2007a, 2007b), Longgang Gas Field in 2006 with a proven original inplace gas volume more than 300 109 m3 and Yuanba Gas Field in 2007 with a proven original in-place gas volume of 159 109 m3. Studies on oolitic reservoirs of the Lower Triassic Feixianguan Formation in the Northeast Sichuan Basin have proved that sedimentary facies and topography control the distribution of the oolitic shoals (Yang et al., 2001, 2002; Wang et al., 2002; Guo, 2011; Zhang et al., 2011; Zou et al., 2011; He et al., 2012; Kang et al., 2012; Tan et al., 2012; Zhang et al., 2012), and dolomization lead to formation of high-quality oolitic reservoirs (Wang et al., 2002; Zhang et al., 2009; Guo, 2010; Tan et al., 2011; He et al., 2012; Zhang et al., 2013; Chen et al., 2014). Understanding the characteristics and distribution of the oolitic shoal is essential for predicting favorable reservoirs. Numerous literature related to oolitic shoal characterization of the Feixianguan Formation in the Northeast Sichuan Basin were published (Guo, 2010; He et al., 2012; Qiao et al., 2016). However, a few researches focused on the detail studies related to the facies, architecture, distribution of the oolitic shoal in the Yuanba area (Zhao et al., 2010; Chen et al., 2010; Guo, 2011; Miu et al., 2014).
This study integrates well-seismic tie, well logs, seismic reflections, impedance inversion, and seismic attribute to characterize the detailed sedimentary properties, spatial and temporal distribution of the oolitic shoal complexes of the Feixianguan Formation in the Yuanba Gas Field. At the same time, this study aims to figure out the factors that control the development of the oolitic shoals in the Feixianguan Formation in the Yuanba area. This study, in one hand, may help researchers to better understand the oolitic shoal complexes of the Feixianguan Formation, in the other hand, can provide an integrated method for the researchers to characterize oolitic shoal complexes by using well cores, logs, seismic reflections, impedance inversion, and seismic attribute in the other area. 2. Geological setting 2.1. Palaeogeographical setting The Yuanba Gas Field, located on the west flank of KaijingLiangping Trough in the northeast Sichuan Basin, is the second largest gas field in China with an area of 3200 km2 (Fig. 1A). It borders on the Jiulongshan anticlinal structural belt to the north and the Tongnanba anticlinal structural belt to the northeast
38
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49
Fig. 3. Synthetic seismogram of yb27 well, T1f1 ¼ the base of the Feixianguan Formation, T1f2 ¼ the base of the Fei 2 Member of the Feixianguan Formation, T1f3 ¼ the base of the Fei3 Member of the Feixianguan Formation, T1f4 ¼ the base of the Fei4 Member of the Feixianguan Formation, T1j1 ¼ the top boundary of the Feixianguan Formation, AC ¼ acoustic, K ¼ density, A-1DSYN ¼ synthetic seismogram.
Fig. 4. Core photograph and thin-section photomicrographs of FA-A in Fei 2 Member of the Feixianguan Formation from yb2 well and yb204 well. (A) Rudstone, in which pisolite grains are well sorted and rounded in shape, yb2 well, 6433.5 m (Porosity ¼ 3.17%, Permeability ¼ 0.4649 103mm2). (B) Rudstone composed of pisolites with concentric laminae, yb2 well, 6434.0 m (Porosity ¼ 3.17%, Permeability ¼ 0.4649 103mm2). (C) Oolitic grainstone showing ooids with concentric structures and moderate sorting, yb2 well, 6433.1 m (Porosity ¼ 2.62%, Permeability ¼ 0.1412 103mm2). (D) Oolitic grainstone with well-sorted ooids, yb204, 6557.2 m (Porosity ¼ 4.97%, Permeability ¼ 30.7782 103mm2).
(Fig. 1B). The northeast Sichuan Basin, as a part of the Upper Yangtze Platform, underwent Caledonian movement (Late Sinian to Silurian), Hercynian movement (Devonian to the Middle Permian), Indosinian movement (Late Permian to Triassic), Yanshan movement (Jurassic) and Himalayan movement (Cretaceous to Neogene) from the Sinian to Neogene. During the Late Permian to the Early Triassic periods, the northeast Sichuan Basin was situated in the eastern part of Tethys and dominated by the marine environment with a suit of carbonate deposited in this area (Chen, 2008; Duan
et al., 2008; Cheng et al., 2010). Under control of the Emei rifting activity (Luo, 1981; Du et al., 1997; Wang et al., 2006), the northwest-southeast trending Kaijiang-Liangping Through and Chengkou-Exi Through were formed in the northeast Sichuan Basin, resulting in carbonate platform and slope occurred on the east and west side of the Kaijiang-Liangping Through during the Late Permian and Early Triassic periods. Although the palaeogeography in the northeast Sichuan Basin did not change notably from the Changxing Formation (Late Permian) to the Feixianguan Formation
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49
39
Fig. 5. Core photograph and thin-section photomicrographs of FA-B in Fei 2 Member of the Feixianguan Formation from yb204, yb27 and yb2 wells. (A) Rudstone with pisolites poorly sorted and diameter more than 2 mm, yb204 well, 6405.1 m. (B) Oolitic grainstone with oolites poorly sorted, yb204 well, 6421.1 m (Porosity ¼ 1.64%, Permeability ¼ 0.0366 103mm2). (C) Rudstone with pisolites, ooids and algae grains developed together, yb27 well, 6128.84 m (Porosity ¼ 3.21%, Permeability ¼ 0.0364 103mm2). (D) Oolitic grainstone with poorly sorted and rounded ooids developed, yb27 well, 6130.65 m (Porosity ¼ 3.43%, Permeability ¼ 0.0221 103mm2). (E) Bioclastic packstone composed of poorly sorted, subangular-subrounded bioclasts, yb2 well, 6460.6 m (Porosity ¼ 1.49%, Permeability ¼ 0.0305 103mm2). (F) Bioclastic packstone made up of moderately sorted, subrounded bioclasts (including Gastropoda), yb2 well, 6460.6 m (Porosity ¼ 1.82%, Permeability ¼ 0.0084 103mm2). P¼Pisolite, B¼Bioclast, G ¼ Gastropoda.
(Early Triassic), the deposit on the platform margin changed from reef complexes in the Late Permian to oolitic shoal complexes in the Early Triassic because of the end-Permian mass extinction (Groves, 2004; Ma et al., 2005c; Ni et al., 2007; Ehrenberg et al., 2008; Zheng et al., 2009; Li et al., 2013) (Fig. 1A).
2.2. Stratigraphy
Fig. 6. The cross-plot between porosity and permeability for FA-A and FA-B of Fei 2 Member in Yuanba Gas Field in the northeast Sichuan Basin.
The Lower Triassic Feixianguan Formation conformably overlies the Changxing Formation (Upper Permian), which is composed of micrite and bioclastic limestone in the Lower Member (Ch1) of Changxing Formation and bioclastic limestone and dolomite in the Upper Member (Ch2) (Chen et al., 2012) (Fig. 2). The fossil assemblage in the Changxing Formation is characterized by abundant fusulinids (Palaeofusulinasinese), brachiopods (Oldhamina sp.), and ammonoids (Pseudotirolitesasiaticus and Pseudogastrioceras sp.), which are typical characteristics of the Changhsingian assemblages in South China (Chen and Liao, 2009). The Feixianguan Formation has been described as a series of oolite dolomitic limestone,
40
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49
Fig. 7. Log responses of FA-A and FA-B of Fei 2 Member of yb27 well in Yuanba Gas Field in the northeast Sichuan Basin. GR ¼ natural gamma-ray, KTH ¼ gamma ray without uranium, DEN ¼ density, CNL ¼ compensated neutron log, RD ¼ deep investigate double lateral resistivity log, RS ¼ shallow investigate double lateral resistivity log, AC ¼ acoustic. See Fig. 1 for well location.
deposited in the shallow-marine platform interior and on the platform margins during high-frequency relative fluctuations of sea level within an overall regression of the Induan Tethys Sea (Yan, 1999; Wang et al., 2002; Xu et al., 2011). According to the lithology, the Feixianguan Formation was divided into four members in the northeast Sichuan Basin: Fei1 (1st) Member, Fei2 (2nd) Member, Fei3 (3rd) Member and Fei4 (4th) Member, from bottom to top (Fig. 2). Fei1 Member was deposited following mass-extinction at the end of the Permian and consists of limestone interbedded with ooid packstone and grainstone in the carbonate platform, and argillaceous limestone and shale in the slope and shelf setting. Fei 2 Member is characterized by abundant ooids packstone and grainstone deposited with dolomite developed on the upper most part of this member. Fei3 Member includes broader platform facies that expanded to occupy nearly the whole Yuanba area, with limited distribution of oolitic shoals. Fei4 Member represents the evaporitic environment and gypsum rock dominates this interval (Fig. 2). Generally, from Fei1 Member to Fei4 Member, the succession gradually shallows upwards, the carbonate platform expanded laterally, and the system evolved from an open-marine platform to an evaporitic platform. The Feixianguan Formation is also conformably overlain by the Middle Triassic Jialingjiang Formation, which includes limestone interbedded with gypsum (Hu et al., 2010). 3. Data and methods A 1102 km2 3-D seismic survey covering the main producing
oolitic shoal reservoirs intervals in the Yuanba Gas Field was interpreted for details in stratigraphic and seismic attributes analyses. Digital well logs from 16 wells including GR (natural gamma ray) logs, KTH (gamma ray without uranium) logs, DEN (density) logs, AC (acoustic) logs, CNL (neutron) logs, RD (deep investigate double lateral resistivity log) and RS (shallow investigate double lateral resistivity log) logs were collected for this study. More than 256 m of core from five wells is available for the core analysis. More than 1000 thin sections from five wells within the seismic survey were also collected for this study. 79 core samples were collected for porosity and permeability measurement. Detailed core studies of five wells and thin section analyses of more than 150 samples provide the basis for describing the facies of the oolitic shoal complexes. The lithologic description follows the classification outlined by Dunham (1962), as modified by Embry and Klovan (1971). Based on the diameter of ooids, we divided ooid grains into two kinds: pisolite (diameter >2 mm) and ooid (diameter <2 mm). To tie the logs to the seismic data, we use acoustic and density logs with wavelet to generate a synthetic seismogram to tie well tops of different members of the Feixianguan Formation to seismic reflections (Fig. 3). Based on the well calibration, oolitic shoals were characterized by their seismic properties from seismic reflections, seismic attributes and impedance inversion. The analysis of a series seismic attributes indicated that the root mean square (RMS) amplitude attribute is the most useful to characterize the oolitic shoals.
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49
41
Fig. 8. Seismic response of oolitic shoals in the Feixianguan Formation in Yuanba Gas Field, T1f3 ¼ the bottom of Fei 3 Member, T1f1 ¼ the bottom of Fei 1 Member, the Fei 2 Member is located between T1f3 and T1f1 (black color-positive high amplitude, red color-negative). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 9. RMS slice in Fei 2 Member of the Feixianguan Formation in 3D seismic area of Yuanba Gas Field, showing the distributions of the oolitic shoals with the characteristics of low RMS (<25) amplitude based on well-seismic tie data.
42 L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49
Fig. 10. Paleo-depositional cross section and stratigraphic cross section of the Feixianguan Formation showing distribution of oolitic shoals in Yuanba Gas Field. See Fig. 1B for location of the cross section.
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49
4. Results 4.1. Facies association of oolitic shoals Based on the core description and thin section observation, two facies were identified. These facies have distinct geologic, petrophysical, and geophysical characteristics. 4.1.1. Facies association A (FA-A) FA-A is composed of rudstone and oolitic grainstone (Fig. 4). Rudstone is characterized by well sorted, rounded to well-rounded pisolites ranging in abundance from 60% to 80% (Fig. 4A and B). The pisolites, 2e3 mm in diameter, show obvious concentric layers. The oolitic grainstone consists of more than 80% ooids with diameters ranging from 0.1 to 0.3 mm and few algae fragment (Fig. 4C and D). The ooids and pisolites in the grainstone display well-developed concentric layers, small size, good sorting. The thickness of FA-A can reached up to about 30 m in maximum in the study area. In general, well-sorted, rounded to well-rounded ooids dominated the FA-A. Good sorting and psephicity of ooids, few bioclasts, large thickness of ooids and sparry calcite cementation indicate high-energy conditions in the shallow water. 4.1.2. Facies association B (FA-B) FA-B consists of rudstone, oolitic grainstone and bioclastic packstone (Fig. 5). The rudstone contains some pisolites more than 2 mm in diameter and is characterized by presence of poorly sorted ooids/pisolites with various sizes and shapes (Fig. 5A and C). Some algae grains can be found in the rudstone, which are ramdon distributed with diameter less than 0.5 mm (Fig. 5C). The oolitic grainstone contains two type of ooids; one type is rounded with the size of less than 2 mm and completely concentric laminae, whereas the other type is subrounded-to-rounded, characterized by a smaller size (diameter<0.25 mm), with faint concentric laminae (Fig. 5B and D). There are also some algae aggregate and algae
43
grains with subrounded shape in the oolitic grainstone, which have much smaller size (diameter<0.25 mm) with faint boundary and no obvious concentric laminae (Fig. 5B and D). Bioclastic packstone is characterized by subangular-subrounded bioclastic grains (eg. algae aggregate and algae grains) with random arrangement (Fig. 5E and F). In general, the ooids, pisolites and some bioclastic grains, with the content ranging between 50 and 80%, dominated the facies. Most of the space between the grains is filled by clay matrix and little is filled by sparry calcite cement. The common size of the grains in FA-B is 0.5e2 mm in diameter and the pisolites represent size greater than 2 mm. FA-B is thinner than FA-A with a range from few meters to 10 m in the study area. The poorly sorted, subrounded-subangular, random distributed grains (including ooids, pisolites and bioclasts) and abundant clay matrix filled in the space between grains suggest that FA-B occurred in the flank of the oolitic shoal complexes with a relatively low hydrodynamic condition. 4.2. Petrophysical and geophysical characteristics of oolitic shoals 4.2.1. Petrophysical properties of oolitic shoals Each Facies Association has a distinct range of porosities and permeabilities in the study area. FA-A have a wider range of porosity and permeability than FA-B (Fig. 6). The average porosity of FA-A is 4.76%, whereas FA-B have an average porosity of 3.70%. The permeability of FA-A measured between 0.02 103mm2 and 103.18 103mm2 and the average permeability is 14.62 103mm2, whereas the permeability of FA-B ranges from 0.01 103mm2 to 110.36 103mm2 with an average permeability of 3.09 103mm2, a little lower than that of FA-A. 4.2.2. Log response of oolitic shoals FA-A: gamma ray (GR) and gamma ray without uranium (KTH) logs display characteristic log patterns in FA-A. The GR log exhibits upward decreasing with low radioactivity ranging between 11 and
Fig. 11. Impedance inversion of a SW-NE oriented seismic section across the study area, showing the development characteristics of oolitic shoals of the Feixianguan Formation in Yuanba area. The Fei 2 Member is located between T1f3 and T1f1. TWT ¼ two-way travel time. Seismic section location is shown in Fig. 9.
44
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49
Fig. 12. Seismic profile across wells yb2-yb1-yb5-yb4, showing the oolitic shoals' progradational development characteristics in the Yuanba Gas Field. TWT ¼ two-way travel time. See Fig. 1A for the location of the seismic profile.
13 API, and the KTH log shows low values ranging from 4.5 to 6.5 API (Fig. 7). Deep investigate double lateral resistivity log (RD) and shallow investigate double lateral resistivity log (RS) almost coincide in the interval of FA-A, and corresponded to low resistivities ranging from 1700 to 4000 U m density (DEN) log reveals that FA-A has a stable density about 2.6 g/cm3 on average (Fig. 7). Acoustic (AC) log and compensated neutron log (CNL) both show increasing upward curve patterns for this association. FA-B: Compared with FA-A, there are almost identical features in GR and KTH logs associated with varied lithofacies of FA-B, including higher radioactivity, ranging from 15 to 18 API in GR log and 5 to 7 API in KTH log (Fig. 7). RD and RS logs show no obvious change patterns (Fig. 7). The DEN log shows that FA-B has stable density just ranging between 2.6 and 2.7 g/cm3. 4.2.3. Seismic response of oolitic shoals The petroleum exploration and exploitation have proved that the “bright spot” on the seismic profiles represents the oolitic shoal complexes in Feixianguan Formation in the northeast Sichuan Basin (Wang et al., 2002; Ma et al., 2005c; Wu et al., 2011). However, because the oolitic shoals interval is thin and the resolution of seismic data is relatively low in Yuanba Gas Field (Guo, 2010, 2011), it is hard to distinguish FA-A from FA-B based on seismic reflections, all of them just show moderate amplitude, low-frequency, mounded to discontinuous reflection in the seismic profiles (Fig. 8).
4.2.4. Spatial distributions of oolitic shoals A lot of studies have confirmed that RMS amplitude attribute is a powerful technique in evaluating the spatial distribution of oolitic shoals (Zeng and Kerans, 2003; Zhang et al., 2009; Lü et al., 2012) (Fig. 9). As such, RMS amplitude attribute can be used to predict the spatial distribution of the oolitic shoals of the Feixianguan Formation in Yuanba Gas Field. In this study, based on well calibration, the interval of oolitic shoals were identified from the seismic section. Then the RMS amplitude attribute of the oolitic shoals interval was extracted. The cut-off value of the oolitic shoals from the RMS amplitude attribute was determined through analysis the RMS amplitude values in the location of the oolitic shoals interval in the drilling wells. Based on the study of 13 wells, the oolitic shoals in the RMS amplitude slice shows values less than 25. Integration of the RMS amplitude attributes, well logs, and sedimentary facies analysis indicates clearly that carbonate platform, platform margin, slope and shelf are distributed from southwest to northeast in the Yuanba area during Fei 2 Member period (Fig. 9). The oolitic shoals are scattered throughout the carbonate platform interior in the southwest and widely distributed along the platform margin in the northeast with a northwestto-southeast-oriented elongated shape parallel to the platform margin (Fig. 9).
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49 Fig. 13. RMS amplitude stratal slice showing the evolution of oolitic shoals in Fei2 Member in the Yuanba area. Stratal slice positions are showed on the left of Fig. 7 (A) Stratal slice showing the distribution of oolitic shoals in the early Fei 2 Member period, (B) Stratal slice showing the distribution of oolitic shoals in the middle Fei 2 Member period, (C)Stratal slice showing the distribution of oolitic shoals in the late Fei 2 Member period.
45
46
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49
Fig. 14. Sedimentary model for oolitic shoals in the Feixianguan Formation in Yuanba Gas Field, northeast Sichuan Basin.
5. Discussion 5.1. Development characteristics of oolitic shoals Unlike the Puguang Gas Field with thick oolitic shoals, oolitic shoals in the Yuanba Gas Field mainly occurred in the Fei2 Member of the Feixianguan Formation as thin layers with pronounced lateral migration (Fig. 10). FA-B deposited on the flanks of the oolitic shoal complexes on the platform margin, whereas FA-A occurred in the middle of the oolitic shoal complexes, forming a moundy shoal with a relatively high hydrodynamic environment (Fig. 10). Many scholars argue that open carbonate platform with gentle slope (carbonate ramp) in the Yuanba area and large-scale regression during the deposition of Fei 2 Member are the key factors that resulted in the thin deposit and lateral migration of the platform margin oolitic shoals of Fei 2 Member in the Yuanba Gas Field (Chen, 1995; Hallam and Wignall, 1999; Deng et al., 2004; Ma et al., 2006; Mei and Tucker, 2007; Mei et al., 2007; Ni et al., 2007; Zhang et al., 2009; Guo, 2010; Wu et al., 2012). Based on the oolitic shoals facies identification and well log correlations, a paleo depositional cross section through the Yuanba Gas Field was reconstructed (Fig. 10), it can be seen that carbonate platform, slope and shelf developed during the time of the Fei 1 Member's development. During the Fei 2 Member, the carbonate platform quickly expanded toward the basin and the oolitic shoals formed. The shoals exhibit obvious lateral progradational migration toward basin in Fei 2 Member period. With the migration of platform margin, oolitic shoals migrated to the northeast part of the study area and are
scattered along the platform margin during the Fei 3 Member. Evaporites dominate the whole Fei 4 Member, no oolitic shoals developed during this period (Fig. 10). In general, based on the correlation between wells, oolitic shoals were mainly deposited in Fei 2 Member. Lateral progradation of the oolitic shoals also can be observed from the impedance inversion seismic section and well-to-seismic tie data (Fig. 11, Fig. 12). Several progradational clinoforms developed and the oolitic shoals were deposited on the top of progradational clinoforms. The lateral migration of oolitic shoals appears to be associated with development of the progradational clinoforms. Many scholars have confirmed that sea-level fall happened during the Fei 2 Member in the northeast Sichuan Basin (Ma et al., 2006; Ni et al., 2007; Zhang et al., 2009; Guo, 2010; Wu et al., 2012), so the see-level fall led to the development of the progradational clinoforms, which maybe the main reason that lead to the migration of oolitic shoals during Feixianguan Formation period in the study area.
5.2. Spatial and temporal distribution of oolitic shoals in Feixianguan Formation Based on a stratal slice extracted from 3D seismic data, the spatial and temporal distribution of oolitic shoal complexes in different time during the Fei 2 Member in Yuanba Gas Field were revealed. In the early stage of the Fei 2 Member, the extent of oolitic shoals is limited to local areas, scattered throughout the carbonate platform interior in the south and extensively distributed along the platform margin in the north part of the study area (Fig. 13A). In the
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49
middle stage of the Fei 2 Member, the significant change is that the oolitic shoals migrated northeastward up to about 150 km2 into the platform margin (Fig. 13B). Meanwhile, the carbonate platform, slope and shelf all showed NE-trending migration during this time. When it comes to late period of the Fei 2 Member, the oolitic shoals continued to migrate toward the northeast covering an areas less than 100 km2, while the carbonate platform occupied the rest of the study area (Fig. 13C). Based on the distributions of oolitic shoals through different Fei 2 Member periods, it can be seen that the oolitic shoals displayed obvious migrations. 5.3. Depositional model of oolitic shoals in Feixianguan Formation The comprehensive interpretation and analysis of petrography, seismic reflections, impedance inversion and seismic attribute suggest a depositional model for the oolitic shoals of Feixianguan Formation in the Yuanba Gas Field (Fig. 14). During the Feixianguan Formation period, the oolitic shoals were mainly deposited as a belt along the platform margin and scattered throughout the carbonate platform interior. FA-A were located on the middle of the oolitic shoal complexes, while FA-B were deposited on the flanks of the oolitic shoal complexes, forming a moundy shoals. As a response to sea-level fall, a series of progradational clinoforms developed, and the oolitic shoals, which developed on the top of the progradational clinoforms, followed this migration towards the basin. Northeastward migration of oolitic shoals in Feixianguan Formation coincided with the development of progradational clinoforms in the Yuanba Gas Field, suggesting that progradational clinoforms caused by sea-level fall maybe are the main reason that lead to the migration of oolitic shoals. 6. Conclusions 1 Two facies associations, Facies Associations A (FA-A) and Facies Associations B (FA-B), were identified for the oolitic shoal complexes in the Feixianguan Formation in the Yuanba Gas Field in the northeast Sichuan Basin. FA-A mainly occurred in highenergy conditions in the shallow water and was located in the middle part of the oolitic shoal complexes, while FA-B occurred on the flanks of the oolitic shoal complexes. 2 FA-A has a wider range of porosity and permeability than FA-B. The average values of porosity and permeability in FA-A are a little higher than that in FA-B. FA-A exhibits relatively lower radioactivity and resistivity in well logs with an upward decreasing pattern. In contrast, FA-B shows relatively higher radioactivity and resistivity in well logs with an upward increasing pattern. 3 The oolitic shoals of Feixianguan Formation show lateral migration toward the shelf from the southwest to the northeast and were mainly deposited along the platform margin in Yuanba Gas Field. The spatial and temporal distribution of oolitic shoals shows that the oolitic shoals migrated through time toward the basin. In the early stage of the Fei 2 Member, the extent of oolitic shoals is limited to local areas. In the middle stage of the Fei 2 Member, the oolitic shoals extend to 150 km2 on the platform margin and migrated northeastward. When it comes to late period of the Fei 2 Member, the oolitic shoals continued to migrate toward the northeast covering an areas less than 100 km2 on the platform margin. 4 Northeastward migration of oolitic shoals in Feixianguan Formation coincided with the development of progradational clinoforms in the Yuanba Gas Field, suggesting that progradational clinoforms caused by sea-level fall maybe are the main reason that lead to the migration of oolitic shoals. .
47
Acknowledgments This study was supported by the Young scholars development fund of Southwest Petroleum University (SWPU) (No. 201599010078) and the National Natural Science Foundation of China (NSFC) programs (No. 41302089 and No. 41202086). We thank Eugene C. Rankey of the University of Kansas and Stacy L Reeder of the Schlumberger for their constructive suggestions and language help. Thanks to Hui Rong for his earlier work about the thin section analysis and core study. The authors wish to thank Zebulon Pischnotte, University of Utah at Salt Lake City, for providing language help. References s, S., Amour, F., Mutti, M., Christ, N., Immenhauser, A., Benson, G.S., Agar, S.M., Toma Kabir, L., 2013. Outcrop analog for an oolitic carbonate ramp reservoir: a scaledependent geologic modeling approach based on stratigraphic hierarchy. AAPG Bull. 97, 845e871. Asadi-Eskandar, A., Rahimpour-Bonab, H., Hejri, S., Afsari, K., Mardani, A., 2013. Consistent geological-simulation modeling in carbonate reservoirs, a case study from the Khuff formation, Persian Gulf. J. Petroleum Sci. Eng. 109, 260e279. Asquith, G.B., 1984. Depositional and Diagenetic History of the Upper Chester (Mississippian) Oolitic Reservoirs, North-Central Beaver County, Oklahoma. In: Hyne, N.J. (Ed.), Limestones of the Mid e Continent. Tulsa Geological Society, Tulsa, pp. 87e92. Cai, C.F., Xie, Z.Y., Worden, R.H., Hu, G.Y., Wang, L.S., He, H., 2004. Methane-dominated thermochemical sulphate reduction in the triassic Feixianguan Formation east Sichuan basin, China: towards prediction of fatal H2S concentrations. Mar. Petroleum Geol. 21, 1265e1279. Chen, J.X., Tan, Q.Y., Guo, T.L., Deng, P., Wang, R.H., Wang, Z.H., 2010. Sedimentary characteristics and evolution of the carbonate platform-margins in the Changxing Formation-Feixianguan Formation in Yuanba, northeastern sichuan. Sediment. Geol. Tethyan Geol. 30, 29e36 (In Chinese with English abstract). Chen, L., Lu, Y.C., Guo, T.L., Deng, L.S., 2012. Growth characteristics of changhsingian (late permian) carbonate platform margin reef complexes in Yuanba gas field, northeastern Sichuan Basin, China. Geol. J. 47, 524e536. Chen, P.Y., Tan, X.C., Liu, H., Ma, T., Luo, B., Jiang, X.F., Yu, Y., Jin, X.J., 2014. Formation Mechanism of Reservoir Oolitic Dolomite in Lower Triassic Feixianguan Formation, Northeastern Sichuan Basin, Southwest China, vol. 21. Journal of Central South University, pp. 3263e3274. Chen, P.Y., Tan, X.C., Yang, H.T., Jiang, Y.W., Jin, X.J., Yu, Y., 2015. Characteristics and genesis of the Feixianguan Formation oolitic shoal reservoir, Puguang gas field, Sichuan Basin, China. Front. Earth Sci. 9, 26e39. Chen, Z.Q., 1995. The globally drowning events at the end of Permian. Sediment. Facies Paleogeogr. 15, 34e39. Chen, Z.Q., 2008. Changxing Formation biohermal gas pools and natural gas exploration, Sichuan Basin, China. Petroleum Explor. Dev. 35, 148e156, 163 (in Chinese with English abstract). Chen, Z.Q., Liao, Z.T., 2009. Brachiopod faunas across the wuchiapingian changhsingian (late permian) boundary at the stratotype section and subsur€ontologie Abh. face of changxing area, south China. Neues Jahrb. für Geol. Pala 254, 315e335. Cheng, J.X., Tan, Q.Y., Guo, T.L., Deng, P., Wang, R.H., Wang, Z.H., 2010. Sedimentary characteristics and evolution of the carbonate platform-margins in the Changxing FormationeFeixianguan Formation in Yuanba, northeastern sichuan. Sediment. Geol. Tethyan Geol. 30, 29e38 (in Chinese with English abstract). Deng, Y., Zhang, Y.C., Li, Z., Wang, Q.G., Cao, M., Yu, F.R., Zhang, C.L., Wang, Y.H., 2004. Study of sedimentary facies of the lower triassic Feixianguan Formation in eastern Sichuan Basin. Prog. Explor. Geophys. 27, 371e375. Duan, J.B., Huang, R.C., Cheng, S.R., Zeng, T., Zhu, X., 2008. Depositional system and the evolution of carbonate rock platform of Changxing-Feixianguan period in Yuanba area of Northeast Sichuan, China. J. Chengdu Univ. Technol. Sci. Technol. Ed. 35, 663e668 (in Chinese with English abstract). Dunham, R.J., 1962. Classification Chineseon of Carbonate Rocks According to Depositional Texture. In: Ham, W.E. (Ed.), Classification of Carbonate Rocks. American Association of Petroleum Geologists Memoir 1, Tulsa, pp. 108e121. Du, Y.S., Yin, H.F., Wang, Z.P., 1997. The late Caledonian-early Hercynian basin's framework and tectonic evolution of Qinling orogenic belt (in Chinese with English abstract). Earth Sci. 22, 401e405. Ehrenberg, S.N., Svånå, T.A., Swart, P.K., 2008. Uranium depletion across the Permian-Triassic boundary in Middle East carbonates: signature of oceanic anoxia. AAPG Bull. 92, 691e707. Embry, A.F., Kelovan, J.E., 1971. A late devonian reef tract on northeastern banks island, northwest territories. Can. Pet. Geol. Bull. 19, 730e781. Eren, M., Güler, C., Kadir, S., Wanas, H., 2016. Sedimentological, mineralogical and € kova Bay, geochemical characteristics of the ooids in Cleopatra (Sedir Island, Go SW Turkey) and Alexandria (NW Egypt) Beach sediments: a comparison and reality of myth of the love. Chem. Erde 76, 157e169. Esrafili-Dizaji, B., Rahimpour-Bonab, H., 2014. Generation and evolution of oolitic
48
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49
shoal reservoirs in the Permo-Triassic carbonates, the South Pars Field, Iran. Facies 60, 921e940. Fontana, S., Nader, F.H., Morad, S., Ceriani, A., Al-Aasm, I.S., 2010. Diagenesis of the Khuff Formation (PermianeTriassic),northern United Arab Emirates. Arabian J. Geosciences 3, 351e368. Goldstein, R.H., Franseen, E.K., Lipinski, C.J., 2013. Topographic and sea-level controls on oolite-microbialite-coralgal reef sequences: the terminal carbonate complex of southeast Spain. AAPG Bull. 97, 1997e2034. Groves, J.R., 2004. Lower Triassic Oolites in Tethys: a Sedimentologic Response to the End-Permian Mass Extinction. 2004 Denver Annual Meeting. Guo, T.L., 2010. Diagenesis of the feixianguan oolitic shoal reservoirs in the northeastern Sichuan Basin-examples from xuanhan-daxian and Yuanba areas. Oil Gas Geol. 31, 620e631 (in Chinese with English abstract). Guo, T.L., 2011. Sequence strata of the platform edge in the Changxing and Feixianguan formations in the Yuanba area, northeastern Sichuan Basin and their control on reservoirs. Acta Pet. Sin. 32, 387e396 (in Chinese with English abstract). Hallam, A., Wignall, P.G., 1999. Mass extinction and sea-level changes. Earth-Science Rev. 48, 217e250. Hasse, M.M., Aigner, T., 2013. High-resolution anatomy of a grainstone package in Khuff sequence KS4, Oman mountains, sultanate of Oman. Geo Arab. 18, 17e44. He, Y., Guo, X.S., Zhang, K.Y., Zhao, X., Bian, S.T., 2007. Diagenesis of excellent reservoirs in Feixianguan formation in northeastern Sichuan basin. Nat. Gas. Ind. 27, 12e16. He, Y.L., Fu, X.Y., Liu, B., Hou, M.H., Zhang, X.F., Gao, J.X., Yang, Y.K., Shi, K.B., 2012. Control of oolitic beaches sedimentation and diagenesis on the reservoirs in Feixianguan Formation, northeastern Sichuan Basin. Petroleum Explor. Dev. 39, 466e475. Hu, M.Y., Wei, G.Q., Li, S.T., Yang, W., Zhu, L., Yang, Y.H., 2010. Characteristics of sequence-based lithofacies and paleogeography, and reservoir prediction of the Jialingjiang Formation in Sichuan Basin. Acta Sedimentol. Sin. 28, 1145e1152 (in Chinese with English abstract). Ibe, A.C., 1985. In situ formation of petroleum in oolites -Ⅱ: a case study of the Arab Formation oolite reservoirs. J. Petroleum Geol. 8, 331e341. Kang, S.W., Liu, H., Luo, B., Qiao, L., Jiang, X.F., 2012. Sedimentary characteristics and distribution regularity of oolitic beach reservoirs in Feixianguan formation in Tieshan-Huang Nitang area of Northeast Sichuan Basin. Petroleum Geol. Eng. 26, 20e24 (in Chinese with English abstract). Kosakowski, P., Krajewski, M., 2014. Hydrocarbon potential of the Zechstein Main Dolomite in the western part of the Wielkopolska platform, SW Poland: new sedimentological and geochemical data. Mar. Petroleum Geol. 49, 99e120. Lehrmann, D.J., Payne, J.L., Felix, S.V., Dillett, P.M., Wang, H., Yu, Y., Wei, J., 2003. Permian-Triassic boundary sections from shallow-marine carbonate platforms of the Nanpanjiang Basin, South China. Palaios 18, 138e152. Lehrmann, D.J., Minzoni, M., Li, X.W., Yu, M.Y., Payne, J.L., Kelley, B.M., Schaal, E.K., Enos, p., 2012. Lower Triassic oolites of the Nanpanjiang Basin, south China: facies architecture, giant ooids, and diagenesis-Implications for hydrocarbon reservoirs. AAPG Bull. 96, 1389e1414. Li, F., Yan, J.X., Chen, Z.Q., Ogg, J.G., Tian, L., Korngreen, D., Liu, K., Ma, Z.L., Woods, A.D., 2015. Global oolite deposits across the PermianeTriassic boundary: a synthesis and implications for palaeoceanography immediately after the end-Permian biocrisis. Earth-Science Rev. 149, 163e180. Li, F.N., Yan, J.X., Thomas, J., Wu, X., 2013. Paleoceanographic conditions following the end-Permian mass extinction recorded by giant ooids (Moyang, south China). Glob. Planet. Change 105, 102e120. Lipinski, C.J., Franseen, E.K., Goldstein, R.H., 2013. Reservoir analog model for oolitemicrobialite sequences, Miocene terminal carbonate complex, Spain. AAPG Bull. 97, 2035e2057. Luo, Z.L., 1981. Taphrogensis since Late Paleozoic and its influence on forming minerals as hydrocarbon et al. in Southwest China (in Chinese with English abstract). Acta Geol. Sichuan 2, 1e17. Lü, X.J., Shou, J.F., Xu, M.R., Yang, Y., Zhou, J.G., Li, C., Liu, J.L., Pan, L.Y., 2012. Integrated seismic-geological prediction of oolitic beach microfacies in the Feixianguan Formation, Longgang area. Nat. Gas. Ind. 32, 21e23 (in Chinese with English abstract). Ma, Y.S., Mu, C.L., Guo, T.L., Tan, Q.Y., Yu, Q., 2005a. Sequence stratigraphy and reservoir distribution of Feixianguan Formation in northeastern sichuan. J. Mineralogy Petrology 25, 73e79. Ma, Y.S., Guo, X.S., Guo, T.L., Huang, R., Li, G.X., 2005b. Discovery of the large-scale Puguang gas field in the Sichuan Basin and its enlightenment for hydrocarbon prospecting. Geol. Rev. 51, 477e450 (in Chinese with English abstract). Ma, Y.S., Guo, X.S., Fan, R., 2005c. Reservoir prediction of Feixianguan Formation in Puguang gas field, northeast Sichuan province. Petroleum Explor. Dev. 32, 60e64. Ma, Y.S., Mou, C.L., Tan, Q.Y., Yu, Q., 2006. A discussion on Kaijiang-Liangping ocean trough. Oil Gas Geol. 27, 326e331 (in Chinese with English abstract). Ma, Y.S., Guo, X.S., Guo, T.L., Huang, R., Cai, X.Y., Li, G.X., 2007a. The Puguang gas field: new giant discovery in the mature Sichuan Basin, southwest China. AAPG Bull. 91, 627e643. Ma, Y.S., Mou, C.L., Tan, Q.Y., Yu, Q., Wang, R.H., 2007b. Reef-bank features and their constraint to reservoirs of natural gas, from permian Changxing Formation to triassic Feixianguan Formation in daxian-xuanhan area of sichuan province, south China. Earth Sci. Front. 14, 182e192. Makhloufi, Y., Collin, P.Y., Bergerat, F., Casteleyn, L., Claes, S., David, C., Menendez, B., Monna, F., Robion, P., Sizun, J.P., Swennen, R., Rigollet, C., 2013. Impact of
sedimentology and diagenesis on the petrophysical properties of a tight oolitic carbonate reservoir. The case of the Oolite Blanche Formation (Bathonian, Paris Basin, France). Mar. Petroleum Geol. 48, 323e340. Mei, M.X., Ma, Y.S., Deng, J., Chen, H.J., 2007. Sequence-stratigraphic frameworks and their palaeogeographic patterns for the Permian Lopingian of the Dianqiangui Basin and its adjacent areas of southwestern China. Sci. China (Series D) 50, 869e885. Mei, M.X., Tucker, M.E., 2007. Sequence-stratigraphic frameworks and sea-level changes for the late paleozoic of the dianqiangui basin and its adjacent areas of southwestern China. In: Wong, ThE. (Ed.), Proceedings of the XVth International Congress on Carboniferous and Permian Stratigraphy. Royal Netherlands Academy of Artsand Sciences, Amsterdam, pp. 417e430. Miu, Z.W., Bie, J., Ji, C.H., 2014. Reservoir prediction on the section of Feixianguan Formation in Yuanba area, northeast Sichuan. Oil Geophys. Prospect. 49, 329e337 (In Chinese with English abstract). Ni, X.F., Chen, H.D., Tian, J.C., Wei, D.X., 2007. Sedimentary framework of Changxing -Feixianguan Formations and its control on reservoiring in northeastern Sichuan basin. Oil Gas Geol. 28, 458e465 (in Chinese with English abstract). denas, B., Morsilli, M., Al-Awwad, S.F., 2015. Depositional Pomar, L., Aurell, M., Ba model for a prograding oolitic wedge, Upper Jurassic, Iberian basin. Mar. Petroleum Geol. 67, 556e582. Qi, L.S., Carr, T.R., Goldstein, R.T., 2007. Geostatistical three-dimensional modeling of oolite shoals, St. Louis Limestone, southwest Kansas. AAPG Bull. 91, 69e96. Qiao, Z.F., Janson, X., Shen, A.J., Zheng, J.F., Zeng, H.L., Wang, X.F., 2016. Lithofacies, architecture, and reservoir heterogeneity of tidal-dominated platform marginal oolitic shoal: an analogue of oolitic reservoirs of Lower Triassic Feixianguan Formation, Sichuan Basin, SW China. Mar. Petroleum Geol. 76, 290e309. Rankey, E.C., Reeder, S.L., 2011. Holocene oolitic marine sand complexes of the Bahamas. J. Sediment. Res. 81, 97e117. Rankey, E.C., 2014. Contrasts between wave-and tide-dominated oolitic systems: holocene of CrookedeAcklins Platform, southern Bahamas. Facies 60, 405e428. Reeder, S.L., Rankey, E.C., 2008. Relations between sediments and tidal flows in ooid shoals, Bahamas. J. Sediment. Res. 78, 175e186. Sellwood, B.W., 1985. Stratigraphy and sedimentology of the great oolite group in the humbly Grove Oilfield, hampshire. Mar. Petroleum Geol. 2, 44e55. Sparks, A.S., Rankey, E.R., 2013. Relations between geomorphic form and sedimentologic -stratigraphic variability: holocene ooid sand shoal, Lily Bank, Bahamas. AAPG Bull. 97, 61e85. Tan, X.C., Liu, H., Li, L., Luo, B., Liu, X.G., Mou, X.H., Nie, Y., Xi, W.Y., 2011. Primary intergranular pores in oolitic shoal reservoir of Lower Triassic Feixianguan Formation, Sichuan Basin, Southwest China: fundamental for reservoir formation and retention diagenesis. J. Earth Sci. 22, 101e114. Tan, X.C., Zhao, L.Z., Luo, B., Jiang, X.F., Cao, J., Liu, H., Li, L., Wu, X.B., Nie, Y., 2012. Comparison of basic features and origins of oolitic shoal reservoirs between carbonate platform interior and platform margin locations in the Lower Triassic Feixianguan Formation of the Sichuan Basin, southwest China. Petroleum Sci. 9, 417e428. Tedesco, W.A., Major, R.P., 2012. Influence of primary ooid mineralogy on porosity evolution in limestone and dolomite reservoirs: an example from the Eastern Gulf of Mexico Basin. Gulf Coast Assoc. Geol. Soc. Trans. 62, 461e469. Wang, X.Z., Zhang, F., Ma, Q., Yang, M.P., Wang, Y.G., Wen, Y.C., Yang, Y., Zhang, J., 2002. The characteristics of reef and bank and the fluctuation of sea-level in feixianguan period of late permian e early triassic, east Sichuan basin. Acta Sedimentol. Sin. 20, 249e254 (in Chinese with English abstract). Wang, Y.G., Liu, H.Y., Wen, Y.C., Yang, Y., Zhang, J., 2002. Distribution law, exploration method and prospectiveness prediction of the oolitic beach reservoirs in Feixianguan Formation in northeast Sichuan Basin. Nat. Gas. Ind. 22 (supplementary issue), 14e18 (in Chinese with English abstract). Wang, Y.G., Wen, Y.C., Hong, H.T., Xia, M.L., Zhan, J., Song, S.Y., Liu, H.Y., 2006. Petroleum geological characteristics of deep water deposits in upper PermianLower Triassic trough in Sichuan Basin and adjacent areas (in Chinese with English abstract). Oil Gas. Geol. 27, 702e714. Wei, G.Q., Yang, W., Zhang, L., Jin, H., Wu, S.X., Shen, J.H., 2005. Dolomization genetic model of Feixianguan Group oolitic beach reservoir in northeast Sichuan Basin. Nat. Gas. Geosci. 16, 162e166 (in Chinese with English abstract). Wu, B., Wang, X.Z., Zhang, F., Yang, Y.M., Li, P., 2012. Reservoir characteristics and control factor of Feixianguan Formation in northern sichuan. Geoscience 26, 168e174 (in Chinese with English abstract). Wu, L., Zhang, Y.G., Jiang, D.J., Zhao, Y.P., 2011. Reservoir prediction based on isochronous stratigraphic framework: an example of Feixianguan formation in Tongnanba Structural Belt. Oil Geophys. Prospect. 46, 944e951 (in Chinese with English abstract). Xu, L.S., Chen, J.F., Zhao, J., 2011. Trace element and sea-level change of Changxing Feixianguan Formations in Puguang gas reservoir. Nat. Gas Explor. Dev. 34, 17e22 (in Chinese with English abstract). Yan, J.X., 1999. Permian e Triassic Paleoclimate of Eastern Tethys and its Paleogeographic Implication. Earth Science-Journal of China University of Geosciences 24, pp. 13e20 (in Chinese with English abstract). Yang, Y., Wang, Y.G., Wen, Y.C., Liu, H.Y., 2001. Sedimentary facies of Feixianguan Formation and distribution of the oolitic shoals reservoir in the East Sichuan Basin. Nat. Gas Explor. Dev. 24, 18e21 (in Chinese). Yang, Y., Zeng, Y.X., Liu, W., 2002. The influence of sedimentary facies on oolitic shoals reservoir distribution of the Feixianguan Formation in the Northeast Sichuan Basin. Nat. Gas Explor. Dev. 25, 1e9 (in Chinese). Yang, W., Wei, G.Q., Jin, H., Zhang, L., Shen, J.H., Wu, S.X., 2007. Master controlling
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49 factors and genetic mode of oolitic shoal reservoir development in Feixianguan Formation, northeastern Sichuan Basin. Nat. Gas. Geosci. 18, 192e196 (in Chinese with English abstract). Yang, X.P., Zhao, W.Z., Cao, H., Yang, Y., Zhang, B.M., Tao, S.Z., 2006. Formation and distribution of Triassic Feixianguan oolitic bank favorable reservoir in the NE Sichuan Basin. Petroleum Explor. Dev. 33, 17e21 (in Chinese with English abstract). €ppelreiter, M., Aigner, T., 2011. Near well-scale Zeller, M., Koehrer, B., Adams, E.W., Po heterogeneities in a Khuff outcrop equivalent (saiq plateau, Al jabal Al akhdar, sultanate of Oman). J. Petroleum Geol. 34, 241e260. Zeng, H.L., Kerans, C., 2003. Seismic frequency control on carbonate seismic stratigraphy. A case study of the Kingdom Abo sequence, west Texas. AAPG Bull. 87, 273e293. Zhang, J.Y., Zhou, J.G., Pan, L.Y., Wang, X.F., Wang, F., Hao, Y., Gu, M.F., Zhang, R.H., Chen, W., Lv, Y.Z., 2013. The main origins of high quality reservoir in Feixianguan Formation in northeast Sichuan basin: atmospheric water eluviation and seepage-reflux dolomitization. Nat. Gas. Geosci. 24, 9e18 (in Chinese with English abstract). Zhang, T.F., Shou, J.F., Zheng, X.P., She, M., Pan, L.Y., 2012. Spatial distribution and characterization of pore and throat of oolitic dolostone of the Lower Triassic Feixianguan Formation in northeastern Sichuan Province. J. Palaeogeogr. 14,
49
187e196 (in Chinese with English abstract). Zhang, X.F., He, Y.L., Ma, Y.S., Liu, B., Zhao, P.R., Gao, J.X., Yang, Y.K., 2011. Controls of sedimentation on reservoir Formation in lower triassic Feixianguan Formation, northeastern Sichuan Basin. Earth Sci. Front. 18, 224e235 (in Chinese with English abstract). Zhang, X.H., He, Z.H., Zhao, S.W., 2009. Seismic recognition technology on oolitic beach in the northeast of Sichuan Feixianguan. Pet. Geophys. 7, 13e17 (in Chinese with English abstract). Zhao, W.G., Cai, Z.X., Zou, H.Y., Duan, J.B., 2010. Influence factor analysis for evolution of Feixianguan Formation carbonate platform in Yuanba area, northeast Sichuan basin. Oil Geophys. Prospect. 45, 410e413 (In Chinese with English abstract). Zheng, R.C., Luo, P., Wen, Q.B., Xu, F.B., Li, Y., Gong, W., 2009. Characteristics of sequence-based lithofacies and palaeogeography, and prediction of oolitic shoal of the Feixianguan Formation in the Northeastern Sichuan. Acta Sedimentol. Sin. 27, 1e8 (in Chinese with English abstract). Zou, C.N., Xu, C.C., Wang, Z.C., Hu, S.Y., Yang, G., Li, J., Yang, W., Yang, Y., 2011. Geological characteristics and forming conditions of the platform margin large reef-shoal gas province in the Sichuan Basin. Petroleum Explor. Dev. 38, 641e651 (in Chinese with English abstract).
Contents lists available at ScienceDirect
Marine and Petroleum Geology journal homepage: www.elsevier.com/locate/marpetgeo
Research paper
Oolitic shoal complexes characterization of the Lower Triassic Feixianguan Formation in the Yuanba Gas Field, Northeast Sichuan Basin, China Lei Chen a, b, Yongchao Lu b, *, Xiaoyue Fu c, Fengcun Xing d, Chao Wang b, e, Chan Luo a a
School of Geoscience and Technology, Southwest Petroleum University, Chengdu, 610500, China Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education, China University of Geosciences(Wuhan), Wuhan, 430074, China Southern Exploration and Development Division Company of SINOPEC, Chengdu, 610041, China d Chengdu University of Technology, Chengdu, 610059, China e Jianghan Oil Field Branch Company of SINOPEC, Qianjiang, 433124, China b c
a r t i c l e i n f o
a b s t r a c t
Article history: Received 14 July 2016 Received in revised form 15 February 2017 Accepted 9 March 2017 Available online 10 March 2017
The Yuanba Gas Field is the second largest natural gas reservoir in the Sichuan Basin, southwest China. The vast majority of the natural gas reserve is from the Permian Changhsingian reef complexes and Lower Triassic Feixianguan oolitic shoal complexes. To better understand this reservoir system, this study characterizes geological and geophysical properties, spatial and temporal distribution of the oolitic shoal complexes and factors that control the oolitic shoals character for the Lower Triassic Feixianguan Formation in the Yuanba Gas Field. Facies analysis, well-seismic tie, well logs, seismic character, impedance inversion, and root mean square (RMS) seismic attributes distinguish two oolitic shoal complex facies e FA-A and FA-B that occur in the study area. FA-A, located in the middle of oolitic shoal complex, is composed of well-sorted ooids with rounded shape. This facies is interpreted to have been deposited in shallow water with relatively high energy. In contrast, FA-B is located in flanks of the oolitic shoal complex, and consists of poorly sorted grains with various shape (rounded, subrounded and subangular). The oolitic shoal complexes were mainly deposited along the platform margin. From the early Fei 2 Member period to the late Fei 2 Member period, the oolitic shoals complexes on the platform margin gradually migrated from the southwest to the northeast with an extent ranging from less than 100 km2 e150 km2 in the Yuanba Gas Field. The migration of oolitic shoals coincided with the development of a series of progradational clinoforms, suggesting that progradational clinoforms caused by sea-level fall maybe are the main reason that lead to the migration of oolitic shoals. Finally, this study provide an integrated method for the researchers to characterize oolitic shoal complexes by using well cores, logs, seismic reflections, impedance inversion, and seismic attribute in other basins of the world. © 2017 Elsevier Ltd. All rights reserved.
Keywords: Oolitic shoal Feixianguan Formation Lower Triassic Northeast Sichuan Basin
1. Introduction Oolitic shoal deposits form prolific reservoirs in North America and other areas, such as Mississippian oolitic reservoir in Oklahoma (Asquith, 1984), Ooids in the Jurassic Smackover Formation of the eastern Gulf of Mexico Basin (Tedesco and Major, 2012), prolific oolitic reservoir in Arab Formation (Upper Jurassic) and Khuff Formation (Upper Permian-Lower Triassic) of Saudi Arabia (Ibe, 1985; Fontana et al., 2010; Zeller et al., 2011; Hasse and Aigner, 2013;
* Corresponding author. E-mail address: [email protected] (Y. Lu). http://dx.doi.org/10.1016/j.marpetgeo.2017.03.009 0264-8172/© 2017 Elsevier Ltd. All rights reserved.
Asadi-Eskandar et al., 2013), Great Oolite Group in the Humbly Grove Oilfield in England (Sellwood, 1985), Oolite Blanche Formation in Paris Basin (France) (Makhloufi et al., 2013). To understand these systems, numerous studies have examined the sedimentology (Rankey and Reeder, 2011; Li et al., 2015; Pomar et al., 2015; Eren et al., 2016; Qiao et al., 2016), geomorphology (Qi et al., 2007; Sparks and Rankey, 2013), stratigraphy (Sparks and Rankey, 2013) and petrology (Amour et al., 2013; Lipinski et al., 2013; Kosakowski and Krajewski, 2014) to understand the factors that control sedimentary environment, geometry, distribution, heterogeneity, and evolution of oolitic deposits in modern and ancient shallow-marine environments (Reeder and Rankey, 2008; Goldstein et al., 2013; Esrafili-Dizaji and Rahimpour-Bonab, 2014; Rankey, 2014).
36
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49
Fig. 1. (A) Paleo depositional environment of the Fei 2 Member of the Triassic Feixianguan Formation in the northeastern Sichuan Basin, China. The east-west cross section across the Yuanba Gas Field in Fig. 12 is also shown. (B) Structural setting and location of the Yuanba Gas Field in the northeast Sichuan Basin (After Duan et al., 2008). Also shown are key wells, 3-D seismic survey and location of cross section shown in Fig. 10.
One geologically interesting time period with abundant ooids was the Early Triassic after the end Permian extinction. During this period, a coincidence of global paleoclimatic, eustatic change, along with the regional tectonic and paleographic conditions, resulted in the widespread deposition of oolitic shoals in South China (Chen, 1995; Hallam and Wignall, 1999; Ma et al., 2005a; Ni et al., 2007; Mei and Tucker, 2007; Mei et al., 2007; Zhang et al., 2009, 2011; Guo, 2010; Zou et al., 2011; He et al., 2012; Wu et al., 2012; Lehrmann et al., 2003, 2012; Tan et al., 2012; Chen et al., 2015). The oolitic shoal of the Lower Triassic Feixianguan Formation in the Northeast Sichuan Basin, due to its great petroleum potential and
considerable scientific importance, has drawn increasing interest for petroleum geologists (He et al., 2012; Tan et al., 2011). Although gas flow was obtained from oolitic shoal reservoirs of the Lower Triassic Feixianguan Formation from Ba 3 well in 1963, there is no breakthrough until Dukouhe Gas Field, Tieshanpo Gas Field and Luojiazai Gas Field discovered during 1996e2000 in the Northeast Sichuan Basin (Wang et al., 2002). Since then, due to a lot of drilling wells and seismic data available, more and more studies were conducted on sedimentary characteristics, reservoir features and formation of the oolitic shoals of the Feixianguan Formation in the Northeast Sichuan Basin (Cai et al., 2004; Wei et al., 2005; He et al.,
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49
37
Fig. 2. Generalized stratigraphic column of the Upper Permian Changxing Formation to the Lower Triassic Feixianguan Formation in Yuanba area, showing the limestone dominated the Feixianguan Formation and the oolitic shoals mainly developed in Fei 2 Member of the Feixianguan Formation.
2007; Yang et al., 2006, 2007), which directly lead to the discovery of the giant Puguang Gas Field in 2003 with a proven original inplace gas volume of 350 109 m3 (Ma et al., 2005b, 2007a, 2007b), Longgang Gas Field in 2006 with a proven original inplace gas volume more than 300 109 m3 and Yuanba Gas Field in 2007 with a proven original in-place gas volume of 159 109 m3. Studies on oolitic reservoirs of the Lower Triassic Feixianguan Formation in the Northeast Sichuan Basin have proved that sedimentary facies and topography control the distribution of the oolitic shoals (Yang et al., 2001, 2002; Wang et al., 2002; Guo, 2011; Zhang et al., 2011; Zou et al., 2011; He et al., 2012; Kang et al., 2012; Tan et al., 2012; Zhang et al., 2012), and dolomization lead to formation of high-quality oolitic reservoirs (Wang et al., 2002; Zhang et al., 2009; Guo, 2010; Tan et al., 2011; He et al., 2012; Zhang et al., 2013; Chen et al., 2014). Understanding the characteristics and distribution of the oolitic shoal is essential for predicting favorable reservoirs. Numerous literature related to oolitic shoal characterization of the Feixianguan Formation in the Northeast Sichuan Basin were published (Guo, 2010; He et al., 2012; Qiao et al., 2016). However, a few researches focused on the detail studies related to the facies, architecture, distribution of the oolitic shoal in the Yuanba area (Zhao et al., 2010; Chen et al., 2010; Guo, 2011; Miu et al., 2014).
This study integrates well-seismic tie, well logs, seismic reflections, impedance inversion, and seismic attribute to characterize the detailed sedimentary properties, spatial and temporal distribution of the oolitic shoal complexes of the Feixianguan Formation in the Yuanba Gas Field. At the same time, this study aims to figure out the factors that control the development of the oolitic shoals in the Feixianguan Formation in the Yuanba area. This study, in one hand, may help researchers to better understand the oolitic shoal complexes of the Feixianguan Formation, in the other hand, can provide an integrated method for the researchers to characterize oolitic shoal complexes by using well cores, logs, seismic reflections, impedance inversion, and seismic attribute in the other area. 2. Geological setting 2.1. Palaeogeographical setting The Yuanba Gas Field, located on the west flank of KaijingLiangping Trough in the northeast Sichuan Basin, is the second largest gas field in China with an area of 3200 km2 (Fig. 1A). It borders on the Jiulongshan anticlinal structural belt to the north and the Tongnanba anticlinal structural belt to the northeast
38
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49
Fig. 3. Synthetic seismogram of yb27 well, T1f1 ¼ the base of the Feixianguan Formation, T1f2 ¼ the base of the Fei 2 Member of the Feixianguan Formation, T1f3 ¼ the base of the Fei3 Member of the Feixianguan Formation, T1f4 ¼ the base of the Fei4 Member of the Feixianguan Formation, T1j1 ¼ the top boundary of the Feixianguan Formation, AC ¼ acoustic, K ¼ density, A-1DSYN ¼ synthetic seismogram.
Fig. 4. Core photograph and thin-section photomicrographs of FA-A in Fei 2 Member of the Feixianguan Formation from yb2 well and yb204 well. (A) Rudstone, in which pisolite grains are well sorted and rounded in shape, yb2 well, 6433.5 m (Porosity ¼ 3.17%, Permeability ¼ 0.4649 103mm2). (B) Rudstone composed of pisolites with concentric laminae, yb2 well, 6434.0 m (Porosity ¼ 3.17%, Permeability ¼ 0.4649 103mm2). (C) Oolitic grainstone showing ooids with concentric structures and moderate sorting, yb2 well, 6433.1 m (Porosity ¼ 2.62%, Permeability ¼ 0.1412 103mm2). (D) Oolitic grainstone with well-sorted ooids, yb204, 6557.2 m (Porosity ¼ 4.97%, Permeability ¼ 30.7782 103mm2).
(Fig. 1B). The northeast Sichuan Basin, as a part of the Upper Yangtze Platform, underwent Caledonian movement (Late Sinian to Silurian), Hercynian movement (Devonian to the Middle Permian), Indosinian movement (Late Permian to Triassic), Yanshan movement (Jurassic) and Himalayan movement (Cretaceous to Neogene) from the Sinian to Neogene. During the Late Permian to the Early Triassic periods, the northeast Sichuan Basin was situated in the eastern part of Tethys and dominated by the marine environment with a suit of carbonate deposited in this area (Chen, 2008; Duan
et al., 2008; Cheng et al., 2010). Under control of the Emei rifting activity (Luo, 1981; Du et al., 1997; Wang et al., 2006), the northwest-southeast trending Kaijiang-Liangping Through and Chengkou-Exi Through were formed in the northeast Sichuan Basin, resulting in carbonate platform and slope occurred on the east and west side of the Kaijiang-Liangping Through during the Late Permian and Early Triassic periods. Although the palaeogeography in the northeast Sichuan Basin did not change notably from the Changxing Formation (Late Permian) to the Feixianguan Formation
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49
39
Fig. 5. Core photograph and thin-section photomicrographs of FA-B in Fei 2 Member of the Feixianguan Formation from yb204, yb27 and yb2 wells. (A) Rudstone with pisolites poorly sorted and diameter more than 2 mm, yb204 well, 6405.1 m. (B) Oolitic grainstone with oolites poorly sorted, yb204 well, 6421.1 m (Porosity ¼ 1.64%, Permeability ¼ 0.0366 103mm2). (C) Rudstone with pisolites, ooids and algae grains developed together, yb27 well, 6128.84 m (Porosity ¼ 3.21%, Permeability ¼ 0.0364 103mm2). (D) Oolitic grainstone with poorly sorted and rounded ooids developed, yb27 well, 6130.65 m (Porosity ¼ 3.43%, Permeability ¼ 0.0221 103mm2). (E) Bioclastic packstone composed of poorly sorted, subangular-subrounded bioclasts, yb2 well, 6460.6 m (Porosity ¼ 1.49%, Permeability ¼ 0.0305 103mm2). (F) Bioclastic packstone made up of moderately sorted, subrounded bioclasts (including Gastropoda), yb2 well, 6460.6 m (Porosity ¼ 1.82%, Permeability ¼ 0.0084 103mm2). P¼Pisolite, B¼Bioclast, G ¼ Gastropoda.
(Early Triassic), the deposit on the platform margin changed from reef complexes in the Late Permian to oolitic shoal complexes in the Early Triassic because of the end-Permian mass extinction (Groves, 2004; Ma et al., 2005c; Ni et al., 2007; Ehrenberg et al., 2008; Zheng et al., 2009; Li et al., 2013) (Fig. 1A).
2.2. Stratigraphy
Fig. 6. The cross-plot between porosity and permeability for FA-A and FA-B of Fei 2 Member in Yuanba Gas Field in the northeast Sichuan Basin.
The Lower Triassic Feixianguan Formation conformably overlies the Changxing Formation (Upper Permian), which is composed of micrite and bioclastic limestone in the Lower Member (Ch1) of Changxing Formation and bioclastic limestone and dolomite in the Upper Member (Ch2) (Chen et al., 2012) (Fig. 2). The fossil assemblage in the Changxing Formation is characterized by abundant fusulinids (Palaeofusulinasinese), brachiopods (Oldhamina sp.), and ammonoids (Pseudotirolitesasiaticus and Pseudogastrioceras sp.), which are typical characteristics of the Changhsingian assemblages in South China (Chen and Liao, 2009). The Feixianguan Formation has been described as a series of oolite dolomitic limestone,
40
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49
Fig. 7. Log responses of FA-A and FA-B of Fei 2 Member of yb27 well in Yuanba Gas Field in the northeast Sichuan Basin. GR ¼ natural gamma-ray, KTH ¼ gamma ray without uranium, DEN ¼ density, CNL ¼ compensated neutron log, RD ¼ deep investigate double lateral resistivity log, RS ¼ shallow investigate double lateral resistivity log, AC ¼ acoustic. See Fig. 1 for well location.
deposited in the shallow-marine platform interior and on the platform margins during high-frequency relative fluctuations of sea level within an overall regression of the Induan Tethys Sea (Yan, 1999; Wang et al., 2002; Xu et al., 2011). According to the lithology, the Feixianguan Formation was divided into four members in the northeast Sichuan Basin: Fei1 (1st) Member, Fei2 (2nd) Member, Fei3 (3rd) Member and Fei4 (4th) Member, from bottom to top (Fig. 2). Fei1 Member was deposited following mass-extinction at the end of the Permian and consists of limestone interbedded with ooid packstone and grainstone in the carbonate platform, and argillaceous limestone and shale in the slope and shelf setting. Fei 2 Member is characterized by abundant ooids packstone and grainstone deposited with dolomite developed on the upper most part of this member. Fei3 Member includes broader platform facies that expanded to occupy nearly the whole Yuanba area, with limited distribution of oolitic shoals. Fei4 Member represents the evaporitic environment and gypsum rock dominates this interval (Fig. 2). Generally, from Fei1 Member to Fei4 Member, the succession gradually shallows upwards, the carbonate platform expanded laterally, and the system evolved from an open-marine platform to an evaporitic platform. The Feixianguan Formation is also conformably overlain by the Middle Triassic Jialingjiang Formation, which includes limestone interbedded with gypsum (Hu et al., 2010). 3. Data and methods A 1102 km2 3-D seismic survey covering the main producing
oolitic shoal reservoirs intervals in the Yuanba Gas Field was interpreted for details in stratigraphic and seismic attributes analyses. Digital well logs from 16 wells including GR (natural gamma ray) logs, KTH (gamma ray without uranium) logs, DEN (density) logs, AC (acoustic) logs, CNL (neutron) logs, RD (deep investigate double lateral resistivity log) and RS (shallow investigate double lateral resistivity log) logs were collected for this study. More than 256 m of core from five wells is available for the core analysis. More than 1000 thin sections from five wells within the seismic survey were also collected for this study. 79 core samples were collected for porosity and permeability measurement. Detailed core studies of five wells and thin section analyses of more than 150 samples provide the basis for describing the facies of the oolitic shoal complexes. The lithologic description follows the classification outlined by Dunham (1962), as modified by Embry and Klovan (1971). Based on the diameter of ooids, we divided ooid grains into two kinds: pisolite (diameter >2 mm) and ooid (diameter <2 mm). To tie the logs to the seismic data, we use acoustic and density logs with wavelet to generate a synthetic seismogram to tie well tops of different members of the Feixianguan Formation to seismic reflections (Fig. 3). Based on the well calibration, oolitic shoals were characterized by their seismic properties from seismic reflections, seismic attributes and impedance inversion. The analysis of a series seismic attributes indicated that the root mean square (RMS) amplitude attribute is the most useful to characterize the oolitic shoals.
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49
41
Fig. 8. Seismic response of oolitic shoals in the Feixianguan Formation in Yuanba Gas Field, T1f3 ¼ the bottom of Fei 3 Member, T1f1 ¼ the bottom of Fei 1 Member, the Fei 2 Member is located between T1f3 and T1f1 (black color-positive high amplitude, red color-negative). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 9. RMS slice in Fei 2 Member of the Feixianguan Formation in 3D seismic area of Yuanba Gas Field, showing the distributions of the oolitic shoals with the characteristics of low RMS (<25) amplitude based on well-seismic tie data.
42 L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49
Fig. 10. Paleo-depositional cross section and stratigraphic cross section of the Feixianguan Formation showing distribution of oolitic shoals in Yuanba Gas Field. See Fig. 1B for location of the cross section.
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49
4. Results 4.1. Facies association of oolitic shoals Based on the core description and thin section observation, two facies were identified. These facies have distinct geologic, petrophysical, and geophysical characteristics. 4.1.1. Facies association A (FA-A) FA-A is composed of rudstone and oolitic grainstone (Fig. 4). Rudstone is characterized by well sorted, rounded to well-rounded pisolites ranging in abundance from 60% to 80% (Fig. 4A and B). The pisolites, 2e3 mm in diameter, show obvious concentric layers. The oolitic grainstone consists of more than 80% ooids with diameters ranging from 0.1 to 0.3 mm and few algae fragment (Fig. 4C and D). The ooids and pisolites in the grainstone display well-developed concentric layers, small size, good sorting. The thickness of FA-A can reached up to about 30 m in maximum in the study area. In general, well-sorted, rounded to well-rounded ooids dominated the FA-A. Good sorting and psephicity of ooids, few bioclasts, large thickness of ooids and sparry calcite cementation indicate high-energy conditions in the shallow water. 4.1.2. Facies association B (FA-B) FA-B consists of rudstone, oolitic grainstone and bioclastic packstone (Fig. 5). The rudstone contains some pisolites more than 2 mm in diameter and is characterized by presence of poorly sorted ooids/pisolites with various sizes and shapes (Fig. 5A and C). Some algae grains can be found in the rudstone, which are ramdon distributed with diameter less than 0.5 mm (Fig. 5C). The oolitic grainstone contains two type of ooids; one type is rounded with the size of less than 2 mm and completely concentric laminae, whereas the other type is subrounded-to-rounded, characterized by a smaller size (diameter<0.25 mm), with faint concentric laminae (Fig. 5B and D). There are also some algae aggregate and algae
43
grains with subrounded shape in the oolitic grainstone, which have much smaller size (diameter<0.25 mm) with faint boundary and no obvious concentric laminae (Fig. 5B and D). Bioclastic packstone is characterized by subangular-subrounded bioclastic grains (eg. algae aggregate and algae grains) with random arrangement (Fig. 5E and F). In general, the ooids, pisolites and some bioclastic grains, with the content ranging between 50 and 80%, dominated the facies. Most of the space between the grains is filled by clay matrix and little is filled by sparry calcite cement. The common size of the grains in FA-B is 0.5e2 mm in diameter and the pisolites represent size greater than 2 mm. FA-B is thinner than FA-A with a range from few meters to 10 m in the study area. The poorly sorted, subrounded-subangular, random distributed grains (including ooids, pisolites and bioclasts) and abundant clay matrix filled in the space between grains suggest that FA-B occurred in the flank of the oolitic shoal complexes with a relatively low hydrodynamic condition. 4.2. Petrophysical and geophysical characteristics of oolitic shoals 4.2.1. Petrophysical properties of oolitic shoals Each Facies Association has a distinct range of porosities and permeabilities in the study area. FA-A have a wider range of porosity and permeability than FA-B (Fig. 6). The average porosity of FA-A is 4.76%, whereas FA-B have an average porosity of 3.70%. The permeability of FA-A measured between 0.02 103mm2 and 103.18 103mm2 and the average permeability is 14.62 103mm2, whereas the permeability of FA-B ranges from 0.01 103mm2 to 110.36 103mm2 with an average permeability of 3.09 103mm2, a little lower than that of FA-A. 4.2.2. Log response of oolitic shoals FA-A: gamma ray (GR) and gamma ray without uranium (KTH) logs display characteristic log patterns in FA-A. The GR log exhibits upward decreasing with low radioactivity ranging between 11 and
Fig. 11. Impedance inversion of a SW-NE oriented seismic section across the study area, showing the development characteristics of oolitic shoals of the Feixianguan Formation in Yuanba area. The Fei 2 Member is located between T1f3 and T1f1. TWT ¼ two-way travel time. Seismic section location is shown in Fig. 9.
44
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49
Fig. 12. Seismic profile across wells yb2-yb1-yb5-yb4, showing the oolitic shoals' progradational development characteristics in the Yuanba Gas Field. TWT ¼ two-way travel time. See Fig. 1A for the location of the seismic profile.
13 API, and the KTH log shows low values ranging from 4.5 to 6.5 API (Fig. 7). Deep investigate double lateral resistivity log (RD) and shallow investigate double lateral resistivity log (RS) almost coincide in the interval of FA-A, and corresponded to low resistivities ranging from 1700 to 4000 U m density (DEN) log reveals that FA-A has a stable density about 2.6 g/cm3 on average (Fig. 7). Acoustic (AC) log and compensated neutron log (CNL) both show increasing upward curve patterns for this association. FA-B: Compared with FA-A, there are almost identical features in GR and KTH logs associated with varied lithofacies of FA-B, including higher radioactivity, ranging from 15 to 18 API in GR log and 5 to 7 API in KTH log (Fig. 7). RD and RS logs show no obvious change patterns (Fig. 7). The DEN log shows that FA-B has stable density just ranging between 2.6 and 2.7 g/cm3. 4.2.3. Seismic response of oolitic shoals The petroleum exploration and exploitation have proved that the “bright spot” on the seismic profiles represents the oolitic shoal complexes in Feixianguan Formation in the northeast Sichuan Basin (Wang et al., 2002; Ma et al., 2005c; Wu et al., 2011). However, because the oolitic shoals interval is thin and the resolution of seismic data is relatively low in Yuanba Gas Field (Guo, 2010, 2011), it is hard to distinguish FA-A from FA-B based on seismic reflections, all of them just show moderate amplitude, low-frequency, mounded to discontinuous reflection in the seismic profiles (Fig. 8).
4.2.4. Spatial distributions of oolitic shoals A lot of studies have confirmed that RMS amplitude attribute is a powerful technique in evaluating the spatial distribution of oolitic shoals (Zeng and Kerans, 2003; Zhang et al., 2009; Lü et al., 2012) (Fig. 9). As such, RMS amplitude attribute can be used to predict the spatial distribution of the oolitic shoals of the Feixianguan Formation in Yuanba Gas Field. In this study, based on well calibration, the interval of oolitic shoals were identified from the seismic section. Then the RMS amplitude attribute of the oolitic shoals interval was extracted. The cut-off value of the oolitic shoals from the RMS amplitude attribute was determined through analysis the RMS amplitude values in the location of the oolitic shoals interval in the drilling wells. Based on the study of 13 wells, the oolitic shoals in the RMS amplitude slice shows values less than 25. Integration of the RMS amplitude attributes, well logs, and sedimentary facies analysis indicates clearly that carbonate platform, platform margin, slope and shelf are distributed from southwest to northeast in the Yuanba area during Fei 2 Member period (Fig. 9). The oolitic shoals are scattered throughout the carbonate platform interior in the southwest and widely distributed along the platform margin in the northeast with a northwestto-southeast-oriented elongated shape parallel to the platform margin (Fig. 9).
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49 Fig. 13. RMS amplitude stratal slice showing the evolution of oolitic shoals in Fei2 Member in the Yuanba area. Stratal slice positions are showed on the left of Fig. 7 (A) Stratal slice showing the distribution of oolitic shoals in the early Fei 2 Member period, (B) Stratal slice showing the distribution of oolitic shoals in the middle Fei 2 Member period, (C)Stratal slice showing the distribution of oolitic shoals in the late Fei 2 Member period.
45
46
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49
Fig. 14. Sedimentary model for oolitic shoals in the Feixianguan Formation in Yuanba Gas Field, northeast Sichuan Basin.
5. Discussion 5.1. Development characteristics of oolitic shoals Unlike the Puguang Gas Field with thick oolitic shoals, oolitic shoals in the Yuanba Gas Field mainly occurred in the Fei2 Member of the Feixianguan Formation as thin layers with pronounced lateral migration (Fig. 10). FA-B deposited on the flanks of the oolitic shoal complexes on the platform margin, whereas FA-A occurred in the middle of the oolitic shoal complexes, forming a moundy shoal with a relatively high hydrodynamic environment (Fig. 10). Many scholars argue that open carbonate platform with gentle slope (carbonate ramp) in the Yuanba area and large-scale regression during the deposition of Fei 2 Member are the key factors that resulted in the thin deposit and lateral migration of the platform margin oolitic shoals of Fei 2 Member in the Yuanba Gas Field (Chen, 1995; Hallam and Wignall, 1999; Deng et al., 2004; Ma et al., 2006; Mei and Tucker, 2007; Mei et al., 2007; Ni et al., 2007; Zhang et al., 2009; Guo, 2010; Wu et al., 2012). Based on the oolitic shoals facies identification and well log correlations, a paleo depositional cross section through the Yuanba Gas Field was reconstructed (Fig. 10), it can be seen that carbonate platform, slope and shelf developed during the time of the Fei 1 Member's development. During the Fei 2 Member, the carbonate platform quickly expanded toward the basin and the oolitic shoals formed. The shoals exhibit obvious lateral progradational migration toward basin in Fei 2 Member period. With the migration of platform margin, oolitic shoals migrated to the northeast part of the study area and are
scattered along the platform margin during the Fei 3 Member. Evaporites dominate the whole Fei 4 Member, no oolitic shoals developed during this period (Fig. 10). In general, based on the correlation between wells, oolitic shoals were mainly deposited in Fei 2 Member. Lateral progradation of the oolitic shoals also can be observed from the impedance inversion seismic section and well-to-seismic tie data (Fig. 11, Fig. 12). Several progradational clinoforms developed and the oolitic shoals were deposited on the top of progradational clinoforms. The lateral migration of oolitic shoals appears to be associated with development of the progradational clinoforms. Many scholars have confirmed that sea-level fall happened during the Fei 2 Member in the northeast Sichuan Basin (Ma et al., 2006; Ni et al., 2007; Zhang et al., 2009; Guo, 2010; Wu et al., 2012), so the see-level fall led to the development of the progradational clinoforms, which maybe the main reason that lead to the migration of oolitic shoals during Feixianguan Formation period in the study area.
5.2. Spatial and temporal distribution of oolitic shoals in Feixianguan Formation Based on a stratal slice extracted from 3D seismic data, the spatial and temporal distribution of oolitic shoal complexes in different time during the Fei 2 Member in Yuanba Gas Field were revealed. In the early stage of the Fei 2 Member, the extent of oolitic shoals is limited to local areas, scattered throughout the carbonate platform interior in the south and extensively distributed along the platform margin in the north part of the study area (Fig. 13A). In the
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49
middle stage of the Fei 2 Member, the significant change is that the oolitic shoals migrated northeastward up to about 150 km2 into the platform margin (Fig. 13B). Meanwhile, the carbonate platform, slope and shelf all showed NE-trending migration during this time. When it comes to late period of the Fei 2 Member, the oolitic shoals continued to migrate toward the northeast covering an areas less than 100 km2, while the carbonate platform occupied the rest of the study area (Fig. 13C). Based on the distributions of oolitic shoals through different Fei 2 Member periods, it can be seen that the oolitic shoals displayed obvious migrations. 5.3. Depositional model of oolitic shoals in Feixianguan Formation The comprehensive interpretation and analysis of petrography, seismic reflections, impedance inversion and seismic attribute suggest a depositional model for the oolitic shoals of Feixianguan Formation in the Yuanba Gas Field (Fig. 14). During the Feixianguan Formation period, the oolitic shoals were mainly deposited as a belt along the platform margin and scattered throughout the carbonate platform interior. FA-A were located on the middle of the oolitic shoal complexes, while FA-B were deposited on the flanks of the oolitic shoal complexes, forming a moundy shoals. As a response to sea-level fall, a series of progradational clinoforms developed, and the oolitic shoals, which developed on the top of the progradational clinoforms, followed this migration towards the basin. Northeastward migration of oolitic shoals in Feixianguan Formation coincided with the development of progradational clinoforms in the Yuanba Gas Field, suggesting that progradational clinoforms caused by sea-level fall maybe are the main reason that lead to the migration of oolitic shoals. 6. Conclusions 1 Two facies associations, Facies Associations A (FA-A) and Facies Associations B (FA-B), were identified for the oolitic shoal complexes in the Feixianguan Formation in the Yuanba Gas Field in the northeast Sichuan Basin. FA-A mainly occurred in highenergy conditions in the shallow water and was located in the middle part of the oolitic shoal complexes, while FA-B occurred on the flanks of the oolitic shoal complexes. 2 FA-A has a wider range of porosity and permeability than FA-B. The average values of porosity and permeability in FA-A are a little higher than that in FA-B. FA-A exhibits relatively lower radioactivity and resistivity in well logs with an upward decreasing pattern. In contrast, FA-B shows relatively higher radioactivity and resistivity in well logs with an upward increasing pattern. 3 The oolitic shoals of Feixianguan Formation show lateral migration toward the shelf from the southwest to the northeast and were mainly deposited along the platform margin in Yuanba Gas Field. The spatial and temporal distribution of oolitic shoals shows that the oolitic shoals migrated through time toward the basin. In the early stage of the Fei 2 Member, the extent of oolitic shoals is limited to local areas. In the middle stage of the Fei 2 Member, the oolitic shoals extend to 150 km2 on the platform margin and migrated northeastward. When it comes to late period of the Fei 2 Member, the oolitic shoals continued to migrate toward the northeast covering an areas less than 100 km2 on the platform margin. 4 Northeastward migration of oolitic shoals in Feixianguan Formation coincided with the development of progradational clinoforms in the Yuanba Gas Field, suggesting that progradational clinoforms caused by sea-level fall maybe are the main reason that lead to the migration of oolitic shoals. .
47
Acknowledgments This study was supported by the Young scholars development fund of Southwest Petroleum University (SWPU) (No. 201599010078) and the National Natural Science Foundation of China (NSFC) programs (No. 41302089 and No. 41202086). We thank Eugene C. Rankey of the University of Kansas and Stacy L Reeder of the Schlumberger for their constructive suggestions and language help. Thanks to Hui Rong for his earlier work about the thin section analysis and core study. The authors wish to thank Zebulon Pischnotte, University of Utah at Salt Lake City, for providing language help. References s, S., Amour, F., Mutti, M., Christ, N., Immenhauser, A., Benson, G.S., Agar, S.M., Toma Kabir, L., 2013. Outcrop analog for an oolitic carbonate ramp reservoir: a scaledependent geologic modeling approach based on stratigraphic hierarchy. AAPG Bull. 97, 845e871. Asadi-Eskandar, A., Rahimpour-Bonab, H., Hejri, S., Afsari, K., Mardani, A., 2013. Consistent geological-simulation modeling in carbonate reservoirs, a case study from the Khuff formation, Persian Gulf. J. Petroleum Sci. Eng. 109, 260e279. Asquith, G.B., 1984. Depositional and Diagenetic History of the Upper Chester (Mississippian) Oolitic Reservoirs, North-Central Beaver County, Oklahoma. In: Hyne, N.J. (Ed.), Limestones of the Mid e Continent. Tulsa Geological Society, Tulsa, pp. 87e92. Cai, C.F., Xie, Z.Y., Worden, R.H., Hu, G.Y., Wang, L.S., He, H., 2004. Methane-dominated thermochemical sulphate reduction in the triassic Feixianguan Formation east Sichuan basin, China: towards prediction of fatal H2S concentrations. Mar. Petroleum Geol. 21, 1265e1279. Chen, J.X., Tan, Q.Y., Guo, T.L., Deng, P., Wang, R.H., Wang, Z.H., 2010. Sedimentary characteristics and evolution of the carbonate platform-margins in the Changxing Formation-Feixianguan Formation in Yuanba, northeastern sichuan. Sediment. Geol. Tethyan Geol. 30, 29e36 (In Chinese with English abstract). Chen, L., Lu, Y.C., Guo, T.L., Deng, L.S., 2012. Growth characteristics of changhsingian (late permian) carbonate platform margin reef complexes in Yuanba gas field, northeastern Sichuan Basin, China. Geol. J. 47, 524e536. Chen, P.Y., Tan, X.C., Liu, H., Ma, T., Luo, B., Jiang, X.F., Yu, Y., Jin, X.J., 2014. Formation Mechanism of Reservoir Oolitic Dolomite in Lower Triassic Feixianguan Formation, Northeastern Sichuan Basin, Southwest China, vol. 21. Journal of Central South University, pp. 3263e3274. Chen, P.Y., Tan, X.C., Yang, H.T., Jiang, Y.W., Jin, X.J., Yu, Y., 2015. Characteristics and genesis of the Feixianguan Formation oolitic shoal reservoir, Puguang gas field, Sichuan Basin, China. Front. Earth Sci. 9, 26e39. Chen, Z.Q., 1995. The globally drowning events at the end of Permian. Sediment. Facies Paleogeogr. 15, 34e39. Chen, Z.Q., 2008. Changxing Formation biohermal gas pools and natural gas exploration, Sichuan Basin, China. Petroleum Explor. Dev. 35, 148e156, 163 (in Chinese with English abstract). Chen, Z.Q., Liao, Z.T., 2009. Brachiopod faunas across the wuchiapingian changhsingian (late permian) boundary at the stratotype section and subsur€ontologie Abh. face of changxing area, south China. Neues Jahrb. für Geol. Pala 254, 315e335. Cheng, J.X., Tan, Q.Y., Guo, T.L., Deng, P., Wang, R.H., Wang, Z.H., 2010. Sedimentary characteristics and evolution of the carbonate platform-margins in the Changxing FormationeFeixianguan Formation in Yuanba, northeastern sichuan. Sediment. Geol. Tethyan Geol. 30, 29e38 (in Chinese with English abstract). Deng, Y., Zhang, Y.C., Li, Z., Wang, Q.G., Cao, M., Yu, F.R., Zhang, C.L., Wang, Y.H., 2004. Study of sedimentary facies of the lower triassic Feixianguan Formation in eastern Sichuan Basin. Prog. Explor. Geophys. 27, 371e375. Duan, J.B., Huang, R.C., Cheng, S.R., Zeng, T., Zhu, X., 2008. Depositional system and the evolution of carbonate rock platform of Changxing-Feixianguan period in Yuanba area of Northeast Sichuan, China. J. Chengdu Univ. Technol. Sci. Technol. Ed. 35, 663e668 (in Chinese with English abstract). Dunham, R.J., 1962. Classification Chineseon of Carbonate Rocks According to Depositional Texture. In: Ham, W.E. (Ed.), Classification of Carbonate Rocks. American Association of Petroleum Geologists Memoir 1, Tulsa, pp. 108e121. Du, Y.S., Yin, H.F., Wang, Z.P., 1997. The late Caledonian-early Hercynian basin's framework and tectonic evolution of Qinling orogenic belt (in Chinese with English abstract). Earth Sci. 22, 401e405. Ehrenberg, S.N., Svånå, T.A., Swart, P.K., 2008. Uranium depletion across the Permian-Triassic boundary in Middle East carbonates: signature of oceanic anoxia. AAPG Bull. 92, 691e707. Embry, A.F., Kelovan, J.E., 1971. A late devonian reef tract on northeastern banks island, northwest territories. Can. Pet. Geol. Bull. 19, 730e781. Eren, M., Güler, C., Kadir, S., Wanas, H., 2016. Sedimentological, mineralogical and € kova Bay, geochemical characteristics of the ooids in Cleopatra (Sedir Island, Go SW Turkey) and Alexandria (NW Egypt) Beach sediments: a comparison and reality of myth of the love. Chem. Erde 76, 157e169. Esrafili-Dizaji, B., Rahimpour-Bonab, H., 2014. Generation and evolution of oolitic
48
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49
shoal reservoirs in the Permo-Triassic carbonates, the South Pars Field, Iran. Facies 60, 921e940. Fontana, S., Nader, F.H., Morad, S., Ceriani, A., Al-Aasm, I.S., 2010. Diagenesis of the Khuff Formation (PermianeTriassic),northern United Arab Emirates. Arabian J. Geosciences 3, 351e368. Goldstein, R.H., Franseen, E.K., Lipinski, C.J., 2013. Topographic and sea-level controls on oolite-microbialite-coralgal reef sequences: the terminal carbonate complex of southeast Spain. AAPG Bull. 97, 1997e2034. Groves, J.R., 2004. Lower Triassic Oolites in Tethys: a Sedimentologic Response to the End-Permian Mass Extinction. 2004 Denver Annual Meeting. Guo, T.L., 2010. Diagenesis of the feixianguan oolitic shoal reservoirs in the northeastern Sichuan Basin-examples from xuanhan-daxian and Yuanba areas. Oil Gas Geol. 31, 620e631 (in Chinese with English abstract). Guo, T.L., 2011. Sequence strata of the platform edge in the Changxing and Feixianguan formations in the Yuanba area, northeastern Sichuan Basin and their control on reservoirs. Acta Pet. Sin. 32, 387e396 (in Chinese with English abstract). Hallam, A., Wignall, P.G., 1999. Mass extinction and sea-level changes. Earth-Science Rev. 48, 217e250. Hasse, M.M., Aigner, T., 2013. High-resolution anatomy of a grainstone package in Khuff sequence KS4, Oman mountains, sultanate of Oman. Geo Arab. 18, 17e44. He, Y., Guo, X.S., Zhang, K.Y., Zhao, X., Bian, S.T., 2007. Diagenesis of excellent reservoirs in Feixianguan formation in northeastern Sichuan basin. Nat. Gas. Ind. 27, 12e16. He, Y.L., Fu, X.Y., Liu, B., Hou, M.H., Zhang, X.F., Gao, J.X., Yang, Y.K., Shi, K.B., 2012. Control of oolitic beaches sedimentation and diagenesis on the reservoirs in Feixianguan Formation, northeastern Sichuan Basin. Petroleum Explor. Dev. 39, 466e475. Hu, M.Y., Wei, G.Q., Li, S.T., Yang, W., Zhu, L., Yang, Y.H., 2010. Characteristics of sequence-based lithofacies and paleogeography, and reservoir prediction of the Jialingjiang Formation in Sichuan Basin. Acta Sedimentol. Sin. 28, 1145e1152 (in Chinese with English abstract). Ibe, A.C., 1985. In situ formation of petroleum in oolites -Ⅱ: a case study of the Arab Formation oolite reservoirs. J. Petroleum Geol. 8, 331e341. Kang, S.W., Liu, H., Luo, B., Qiao, L., Jiang, X.F., 2012. Sedimentary characteristics and distribution regularity of oolitic beach reservoirs in Feixianguan formation in Tieshan-Huang Nitang area of Northeast Sichuan Basin. Petroleum Geol. Eng. 26, 20e24 (in Chinese with English abstract). Kosakowski, P., Krajewski, M., 2014. Hydrocarbon potential of the Zechstein Main Dolomite in the western part of the Wielkopolska platform, SW Poland: new sedimentological and geochemical data. Mar. Petroleum Geol. 49, 99e120. Lehrmann, D.J., Payne, J.L., Felix, S.V., Dillett, P.M., Wang, H., Yu, Y., Wei, J., 2003. Permian-Triassic boundary sections from shallow-marine carbonate platforms of the Nanpanjiang Basin, South China. Palaios 18, 138e152. Lehrmann, D.J., Minzoni, M., Li, X.W., Yu, M.Y., Payne, J.L., Kelley, B.M., Schaal, E.K., Enos, p., 2012. Lower Triassic oolites of the Nanpanjiang Basin, south China: facies architecture, giant ooids, and diagenesis-Implications for hydrocarbon reservoirs. AAPG Bull. 96, 1389e1414. Li, F., Yan, J.X., Chen, Z.Q., Ogg, J.G., Tian, L., Korngreen, D., Liu, K., Ma, Z.L., Woods, A.D., 2015. Global oolite deposits across the PermianeTriassic boundary: a synthesis and implications for palaeoceanography immediately after the end-Permian biocrisis. Earth-Science Rev. 149, 163e180. Li, F.N., Yan, J.X., Thomas, J., Wu, X., 2013. Paleoceanographic conditions following the end-Permian mass extinction recorded by giant ooids (Moyang, south China). Glob. Planet. Change 105, 102e120. Lipinski, C.J., Franseen, E.K., Goldstein, R.H., 2013. Reservoir analog model for oolitemicrobialite sequences, Miocene terminal carbonate complex, Spain. AAPG Bull. 97, 2035e2057. Luo, Z.L., 1981. Taphrogensis since Late Paleozoic and its influence on forming minerals as hydrocarbon et al. in Southwest China (in Chinese with English abstract). Acta Geol. Sichuan 2, 1e17. Lü, X.J., Shou, J.F., Xu, M.R., Yang, Y., Zhou, J.G., Li, C., Liu, J.L., Pan, L.Y., 2012. Integrated seismic-geological prediction of oolitic beach microfacies in the Feixianguan Formation, Longgang area. Nat. Gas. Ind. 32, 21e23 (in Chinese with English abstract). Ma, Y.S., Mu, C.L., Guo, T.L., Tan, Q.Y., Yu, Q., 2005a. Sequence stratigraphy and reservoir distribution of Feixianguan Formation in northeastern sichuan. J. Mineralogy Petrology 25, 73e79. Ma, Y.S., Guo, X.S., Guo, T.L., Huang, R., Li, G.X., 2005b. Discovery of the large-scale Puguang gas field in the Sichuan Basin and its enlightenment for hydrocarbon prospecting. Geol. Rev. 51, 477e450 (in Chinese with English abstract). Ma, Y.S., Guo, X.S., Fan, R., 2005c. Reservoir prediction of Feixianguan Formation in Puguang gas field, northeast Sichuan province. Petroleum Explor. Dev. 32, 60e64. Ma, Y.S., Mou, C.L., Tan, Q.Y., Yu, Q., 2006. A discussion on Kaijiang-Liangping ocean trough. Oil Gas Geol. 27, 326e331 (in Chinese with English abstract). Ma, Y.S., Guo, X.S., Guo, T.L., Huang, R., Cai, X.Y., Li, G.X., 2007a. The Puguang gas field: new giant discovery in the mature Sichuan Basin, southwest China. AAPG Bull. 91, 627e643. Ma, Y.S., Mou, C.L., Tan, Q.Y., Yu, Q., Wang, R.H., 2007b. Reef-bank features and their constraint to reservoirs of natural gas, from permian Changxing Formation to triassic Feixianguan Formation in daxian-xuanhan area of sichuan province, south China. Earth Sci. Front. 14, 182e192. Makhloufi, Y., Collin, P.Y., Bergerat, F., Casteleyn, L., Claes, S., David, C., Menendez, B., Monna, F., Robion, P., Sizun, J.P., Swennen, R., Rigollet, C., 2013. Impact of
sedimentology and diagenesis on the petrophysical properties of a tight oolitic carbonate reservoir. The case of the Oolite Blanche Formation (Bathonian, Paris Basin, France). Mar. Petroleum Geol. 48, 323e340. Mei, M.X., Ma, Y.S., Deng, J., Chen, H.J., 2007. Sequence-stratigraphic frameworks and their palaeogeographic patterns for the Permian Lopingian of the Dianqiangui Basin and its adjacent areas of southwestern China. Sci. China (Series D) 50, 869e885. Mei, M.X., Tucker, M.E., 2007. Sequence-stratigraphic frameworks and sea-level changes for the late paleozoic of the dianqiangui basin and its adjacent areas of southwestern China. In: Wong, ThE. (Ed.), Proceedings of the XVth International Congress on Carboniferous and Permian Stratigraphy. Royal Netherlands Academy of Artsand Sciences, Amsterdam, pp. 417e430. Miu, Z.W., Bie, J., Ji, C.H., 2014. Reservoir prediction on the section of Feixianguan Formation in Yuanba area, northeast Sichuan. Oil Geophys. Prospect. 49, 329e337 (In Chinese with English abstract). Ni, X.F., Chen, H.D., Tian, J.C., Wei, D.X., 2007. Sedimentary framework of Changxing -Feixianguan Formations and its control on reservoiring in northeastern Sichuan basin. Oil Gas Geol. 28, 458e465 (in Chinese with English abstract). denas, B., Morsilli, M., Al-Awwad, S.F., 2015. Depositional Pomar, L., Aurell, M., Ba model for a prograding oolitic wedge, Upper Jurassic, Iberian basin. Mar. Petroleum Geol. 67, 556e582. Qi, L.S., Carr, T.R., Goldstein, R.T., 2007. Geostatistical three-dimensional modeling of oolite shoals, St. Louis Limestone, southwest Kansas. AAPG Bull. 91, 69e96. Qiao, Z.F., Janson, X., Shen, A.J., Zheng, J.F., Zeng, H.L., Wang, X.F., 2016. Lithofacies, architecture, and reservoir heterogeneity of tidal-dominated platform marginal oolitic shoal: an analogue of oolitic reservoirs of Lower Triassic Feixianguan Formation, Sichuan Basin, SW China. Mar. Petroleum Geol. 76, 290e309. Rankey, E.C., Reeder, S.L., 2011. Holocene oolitic marine sand complexes of the Bahamas. J. Sediment. Res. 81, 97e117. Rankey, E.C., 2014. Contrasts between wave-and tide-dominated oolitic systems: holocene of CrookedeAcklins Platform, southern Bahamas. Facies 60, 405e428. Reeder, S.L., Rankey, E.C., 2008. Relations between sediments and tidal flows in ooid shoals, Bahamas. J. Sediment. Res. 78, 175e186. Sellwood, B.W., 1985. Stratigraphy and sedimentology of the great oolite group in the humbly Grove Oilfield, hampshire. Mar. Petroleum Geol. 2, 44e55. Sparks, A.S., Rankey, E.R., 2013. Relations between geomorphic form and sedimentologic -stratigraphic variability: holocene ooid sand shoal, Lily Bank, Bahamas. AAPG Bull. 97, 61e85. Tan, X.C., Liu, H., Li, L., Luo, B., Liu, X.G., Mou, X.H., Nie, Y., Xi, W.Y., 2011. Primary intergranular pores in oolitic shoal reservoir of Lower Triassic Feixianguan Formation, Sichuan Basin, Southwest China: fundamental for reservoir formation and retention diagenesis. J. Earth Sci. 22, 101e114. Tan, X.C., Zhao, L.Z., Luo, B., Jiang, X.F., Cao, J., Liu, H., Li, L., Wu, X.B., Nie, Y., 2012. Comparison of basic features and origins of oolitic shoal reservoirs between carbonate platform interior and platform margin locations in the Lower Triassic Feixianguan Formation of the Sichuan Basin, southwest China. Petroleum Sci. 9, 417e428. Tedesco, W.A., Major, R.P., 2012. Influence of primary ooid mineralogy on porosity evolution in limestone and dolomite reservoirs: an example from the Eastern Gulf of Mexico Basin. Gulf Coast Assoc. Geol. Soc. Trans. 62, 461e469. Wang, X.Z., Zhang, F., Ma, Q., Yang, M.P., Wang, Y.G., Wen, Y.C., Yang, Y., Zhang, J., 2002. The characteristics of reef and bank and the fluctuation of sea-level in feixianguan period of late permian e early triassic, east Sichuan basin. Acta Sedimentol. Sin. 20, 249e254 (in Chinese with English abstract). Wang, Y.G., Liu, H.Y., Wen, Y.C., Yang, Y., Zhang, J., 2002. Distribution law, exploration method and prospectiveness prediction of the oolitic beach reservoirs in Feixianguan Formation in northeast Sichuan Basin. Nat. Gas. Ind. 22 (supplementary issue), 14e18 (in Chinese with English abstract). Wang, Y.G., Wen, Y.C., Hong, H.T., Xia, M.L., Zhan, J., Song, S.Y., Liu, H.Y., 2006. Petroleum geological characteristics of deep water deposits in upper PermianLower Triassic trough in Sichuan Basin and adjacent areas (in Chinese with English abstract). Oil Gas. Geol. 27, 702e714. Wei, G.Q., Yang, W., Zhang, L., Jin, H., Wu, S.X., Shen, J.H., 2005. Dolomization genetic model of Feixianguan Group oolitic beach reservoir in northeast Sichuan Basin. Nat. Gas. Geosci. 16, 162e166 (in Chinese with English abstract). Wu, B., Wang, X.Z., Zhang, F., Yang, Y.M., Li, P., 2012. Reservoir characteristics and control factor of Feixianguan Formation in northern sichuan. Geoscience 26, 168e174 (in Chinese with English abstract). Wu, L., Zhang, Y.G., Jiang, D.J., Zhao, Y.P., 2011. Reservoir prediction based on isochronous stratigraphic framework: an example of Feixianguan formation in Tongnanba Structural Belt. Oil Geophys. Prospect. 46, 944e951 (in Chinese with English abstract). Xu, L.S., Chen, J.F., Zhao, J., 2011. Trace element and sea-level change of Changxing Feixianguan Formations in Puguang gas reservoir. Nat. Gas Explor. Dev. 34, 17e22 (in Chinese with English abstract). Yan, J.X., 1999. Permian e Triassic Paleoclimate of Eastern Tethys and its Paleogeographic Implication. Earth Science-Journal of China University of Geosciences 24, pp. 13e20 (in Chinese with English abstract). Yang, Y., Wang, Y.G., Wen, Y.C., Liu, H.Y., 2001. Sedimentary facies of Feixianguan Formation and distribution of the oolitic shoals reservoir in the East Sichuan Basin. Nat. Gas Explor. Dev. 24, 18e21 (in Chinese). Yang, Y., Zeng, Y.X., Liu, W., 2002. The influence of sedimentary facies on oolitic shoals reservoir distribution of the Feixianguan Formation in the Northeast Sichuan Basin. Nat. Gas Explor. Dev. 25, 1e9 (in Chinese). Yang, W., Wei, G.Q., Jin, H., Zhang, L., Shen, J.H., Wu, S.X., 2007. Master controlling
L. Chen et al. / Marine and Petroleum Geology 83 (2017) 35e49 factors and genetic mode of oolitic shoal reservoir development in Feixianguan Formation, northeastern Sichuan Basin. Nat. Gas. Geosci. 18, 192e196 (in Chinese with English abstract). Yang, X.P., Zhao, W.Z., Cao, H., Yang, Y., Zhang, B.M., Tao, S.Z., 2006. Formation and distribution of Triassic Feixianguan oolitic bank favorable reservoir in the NE Sichuan Basin. Petroleum Explor. Dev. 33, 17e21 (in Chinese with English abstract). €ppelreiter, M., Aigner, T., 2011. Near well-scale Zeller, M., Koehrer, B., Adams, E.W., Po heterogeneities in a Khuff outcrop equivalent (saiq plateau, Al jabal Al akhdar, sultanate of Oman). J. Petroleum Geol. 34, 241e260. Zeng, H.L., Kerans, C., 2003. Seismic frequency control on carbonate seismic stratigraphy. A case study of the Kingdom Abo sequence, west Texas. AAPG Bull. 87, 273e293. Zhang, J.Y., Zhou, J.G., Pan, L.Y., Wang, X.F., Wang, F., Hao, Y., Gu, M.F., Zhang, R.H., Chen, W., Lv, Y.Z., 2013. The main origins of high quality reservoir in Feixianguan Formation in northeast Sichuan basin: atmospheric water eluviation and seepage-reflux dolomitization. Nat. Gas. Geosci. 24, 9e18 (in Chinese with English abstract). Zhang, T.F., Shou, J.F., Zheng, X.P., She, M., Pan, L.Y., 2012. Spatial distribution and characterization of pore and throat of oolitic dolostone of the Lower Triassic Feixianguan Formation in northeastern Sichuan Province. J. Palaeogeogr. 14,
49
187e196 (in Chinese with English abstract). Zhang, X.F., He, Y.L., Ma, Y.S., Liu, B., Zhao, P.R., Gao, J.X., Yang, Y.K., 2011. Controls of sedimentation on reservoir Formation in lower triassic Feixianguan Formation, northeastern Sichuan Basin. Earth Sci. Front. 18, 224e235 (in Chinese with English abstract). Zhang, X.H., He, Z.H., Zhao, S.W., 2009. Seismic recognition technology on oolitic beach in the northeast of Sichuan Feixianguan. Pet. Geophys. 7, 13e17 (in Chinese with English abstract). Zhao, W.G., Cai, Z.X., Zou, H.Y., Duan, J.B., 2010. Influence factor analysis for evolution of Feixianguan Formation carbonate platform in Yuanba area, northeast Sichuan basin. Oil Geophys. Prospect. 45, 410e413 (In Chinese with English abstract). Zheng, R.C., Luo, P., Wen, Q.B., Xu, F.B., Li, Y., Gong, W., 2009. Characteristics of sequence-based lithofacies and palaeogeography, and prediction of oolitic shoal of the Feixianguan Formation in the Northeastern Sichuan. Acta Sedimentol. Sin. 27, 1e8 (in Chinese with English abstract). Zou, C.N., Xu, C.C., Wang, Z.C., Hu, S.Y., Yang, G., Li, J., Yang, W., Yang, Y., 2011. Geological characteristics and forming conditions of the platform margin large reef-shoal gas province in the Sichuan Basin. Petroleum Explor. Dev. 38, 641e651 (in Chinese with English abstract).