New seismic reflection results in the central Eromanga Basin, Queensland, Australia: The key to understanding its tectonic evolution

~~~j~~~~~~~~c~, 100 (1983) 147-162 Eisevier Science Publishers B.V.. Amsterdam - Printed in The Netherlands

147

NEW SEISMIC REFLECTION RESULTS IN THE CENTRAL EROMANGA BASIN, QUEENSLAND, AUS~LI~ THE KEY TO UNDERSTANDING ITS TECTONIC EVOLUTION

K.D. WAKE-DYSTER, F.Y. MOSS and M.J. SEXTON Bureau of Mineral Resources, Geology and Geophysics, Canberm, A. C. K (Australia)

(Received by Publisher September 24, 1983)

ABSTRACT Wake-Ryster, KD,, Moss, F.J. and Sexton, M.J., 1983. New seismic reflection results in the central Eromanga Basin, Queensland, Australia: the key to understanding its tectonic evolution. In: M. Friedman and M.N.Toksoz (Editors), Continental Tectonics: Structure, Kinematics and Dynamics. ~~c~o~5~h~~jc~.t Of): 147- 162. Regionat seismic traverses were recorded from 1980 to 1982 by the Bureau of Mineral Resources, Geology and Geophysics as part of a major multidisciplinary program aimed at studying the geological evolution of the central Eromanga Basin area and its petroleum potential. Six-fold CDP reflection data were obtained to 20 s reflection time on 1400 km of traverses, up to 400 km long, crossing the main structural features of the area. Additional seismic reflection information to complement the study was obtained from 2300 km of older, mainly single coverage analogue data, which was transcribed to digital format and reprocessed. The central Eromanga Basin area has a complex history and contains four Phanerozoic potentially hydrocarbon-bearing basins each separated by u~~nformities, i.e. the Devonian Adavale Basin, the Late Carboniferous to Triassic Cooper and Galilee basins, and the Jurassic-Cretaceous Eromanga Basin. The seismic results are being interpreted, with the aid of synthetic seismograms from key wells, to provide information on the extent, nature and relationship of these basins. The quality of the reflection data from the Devonian sequence is generally very good and these data are proving to be most useful in the study. Thick Devonian sediments were deposited over a wide area weI1 beyond the present confines of the Adavale Basin and its associated trot&s. ‘Intensive folding and faulting accompanied by major basement uplift, including the Canaway Ridge in the centre of the area, took place during the mid-Carboniferous Kanimblan Orogeny. This was folfowed by a period of erosion which truncated the Devonian sequence and resulted in separation of the Adavale Basin from the other Devonian Troughs in the area. The preIi~na~ seismic results give some indicatjon also of the extent and nature of the Cooper and Galilee basins sediments. These are generatly thin in the central area and thicken to the west and east respectively where coal measures produce good lithologic and seismic markers. Gentle folding and minor faulting apparent in the seismic reflection sections fromthe overlying Eromanga Basin sequence have resulted mainly from basement uplift and minor movements along pre-existing fat&s continuing into the fate mid-Tertiary, and possibly from some compaction of the thick sedimentary se&on. The seismic information is also assisting in studies of the petroleum potential of the area, providing information particularly on structuring, timing and depth of burial of the prospective sediments.

14x

Further obtained clearer

more detailed

in the central understanding

interpretation

Eromanga

of the seismic reflection

Basin project.

of the basin relationships

results, integrated

which is currently

in progress,

with other information

will add sigmficantly

to a

and their history.

INTRODUCTION

the

Seismic reflection studies play a key role in the multidisciplinary project which Bureau of Mineral Resources, Geology and Geophysics (BMR) has been

0

0)

GALILEE

h

BarrolkaC) Durham

\

0

0

Owareene

g 0

Downso~,

BASIN

,/

TROUGH

0

,O

RIOGE OYNEVOR SHELF

km

0

Fig.

1. Geological

exploration al. (1978).

BMR survey f 1980-82)

-

Concealed truncated margin of Cooper and Galilee Basins

Exploration

---_

Concealed margin of Adwale Basin and equiva/enr troughs

well

Major fault

setting

of the central

Etomanga

wells and the new BMR seismic refkction

Basin

area

traverses.

showing

The geology

the location

of petroleum

is modified

from Senior et

conducting since 1980 in the central Eromanga Basin, Queensland, with the cooperation of the Geological Survey of Queensland. The project involves geological and geophysical investigations of the Eromanga Basin and its infra-basins; its main objectives are to determine the structural and depositional history of the area and to contribute to a better understanding of its petroleum resource potential (Moss and Wake-Dyster, 1983). The geophysical program included 1400 km of mainly six-fold CDP reflection traverses, with recordings to 20 s (Fig. 1); crustal seismic refraction traverses mainly with recordings along two major east-west and north-south reflection traverses; gravity measurement along all new BMR reflection traverses; and magnetotelluric recordings along the same east-west traverse as for the refraction work. The seismic reflection traverses were positioned to cross major structural features and to tie to a number of logged petroleum exploration wells to provide geological control. The new seismic reflection survey results are being integrated with the results from previous seismic surveys, some of which have been reprocessed using modem digital techniques, to provide comprehensive structure and isopach maps of the area which will include information on depositional environment obtained from geological and seismic studies. A comprehensive account of the geological evolution of the area is being unravelled from these results and other geophysical and geological information. The basic information from the seismic reflection surveys has been publicly released to aid petroleum exploration programs. Although the analysis and interpretation of the reflection data are at an early stage, preliminary results presented in this paper indicate that the reflection information is making a major contribution towards a better understanding of the area and its history. GEOLOGY

A brief intr~uction to the geology of the central Eromanga Basin area is given by Moss and Wake-Dyster (1983). For more detailed accounts of the geology of the four potentially hydrocarbon-bearing basins which underlie the area reference should be made to the following: Devonian Adavale Basin (Paten, 1977); Late Carboniferous-Triassic Galilee Basin (Hawkins, 1977); Late Carboniferous-Triassic Cooper Basin (Laws, 1977); and Jurassic-Cretaceous Eromanga Basin (Senior et al., 1978). These authors discuss the structure and stratigraphy of the basins but do not give comprehensive accounts of their evolution. The basement complex is considered by Murray and Kirkegaard (1978) to consist of low-grade metamorphic, volcanic and granitoid rocks of the early Palaeozoic Thomson Fold Belt. Basement rock types penetrated by some petroleum exploration wells include schist, quartzite, strongly folded elastics, granite, porphyry and basalt. In general the basement rocks are poorly known and their inter-relationships are poorly understood.

The basins underlying the Eromanga Basin are not exposed in the study area or elsewhere, except for the Galilee Basin which is exposed in the north--east. Information on the sedimentary sequences has been obtained primarily from the sparsely lucated petroleum exploration wells and from seismic reflection and refraction surveys. information on the Eromanga Basin sequence has been obtained mainly from surface geoiogy and from a large number of shallow water bores. Some of the early petroleum exploration wells, drilled to test the underlying Cooper Basin sequence, provided poor information on the Eromanga Basin sequence. The main structural trend as seen on the surface is northeast, modified in places by a northerly component. Minor faulting and folding in the Eromanga Basin sequence reflects stronger defo~at~o~ either in underlying basins or in the basement. However, it is not possible to define the extent and nature of pre-Eromanga Basin structuring from the available geological information oniy, GEOPHYSICS

The app~~caijo~ of ~eophys~ea~ techniques has been particularly useful in complementing geological studies of the Eromanga Basin and its unexposed infra-basins. Preuious surveys

The central Eromanga Basin bas been covered on a regional sc.ale by aeromagnetic and gravity surveys. The extent of these regional surveys is discussed by Harrison et al. (1980) and Moss (1980). The usefulness of the magnetic information obtained from a number of independent surveys is limited mainly because of the widely separated flight lines and the use of different datum% The regional gravity coverage on a II-km grid spacing has proved to be extremely useful particularly because of the close correlation between gravity lows and areas since proven to contain substantial thicknesses of sediments. The wide spacing of the gravity observations precludes their use for detailed analysis of basin structures. From 1959 to 1980 about 80 seismic reflection surveys have been made in the search for hydrocarbons (Harrison et at., 1980). Some of the surveys incfuded shallow seismic refraction and gravity observations along the reflection lines. The quality of the reflection data was generally fair to good; the use of CDP techniques and digital recording in the more recent surveys gives better resolution than earlier sing&e-fold andogue surveys, The surveys have generally been d&t&d surveys to outline particular petrooleum prospects rather than reborn. They have provided some ~~fo~a~io~ on the subsurface but leave many gaps in our knowledge of the basins and their history.

151

New programs

Moss and Wake-Dyster (1983) summa~se the various geophysical and other programs involved in the central Eromanga Basin project. The most significant new program has been the 1400 km of regional, mainly six-fold CDP seismic reflection traverses recorded in 1980-1982 along lines up to 400 km long crossing the region. Reviews of the geology and geophysics prior to the main reflection program were provided by Pinchin (1980) and Mathur and Sexton (1981), and operational reports on the surveys are given by Wake-Dyster and Pinchin (1981) and Sexton and Taylor (1983, 1984). The preliminary results of the reflection work in the sedimentary basins are discussed in detail later in this paper. Preliminary results from the deep crustal reflection recordings, which were made to 20 s along all traverses, are discussed by Mathur (1983). Seismic refraction recordings made along two lines, parts of which include east-west reflection Traverses l-9 and north-south Traverse 10 (Fig. l), provide some information on basement velocities and structure where interpreted with the aid of the reflection information. Collins and Lock (1983) and Lock et al. (1984) discuss the shallow refraction results. Finlayson (1983) and Finlayson et al. (1983) discuss the deep crustal refraction results. The analysis of gravity observations made along all new BMR seismic traverses has been particularly useful in providing constraints on the seismic reflection interpretation. Anfiloff (1984) has incorporated these detailed gravity results in studies of the gravity field over the entire area. Magnetotelluric (MT) soundings made at twelve sites along Traverse 1 provide resistivity information on the crust and upper mantle (Spence and Finlayson, 1983). NEW SEISMIC REFLECTION

INFORMATION

The locations of all new seismic traverses are shown in Fig. 1. The traverses were interconnected with each other or with good quality petroleum exploration company data to provide a network of good quality regional lines to which new and older, poorer quality seismic traverses can be tied for interpretation purposes. Parts of sections showing some important structural features in the main Devonian troughs are shown in Fig. 2. Traverse 1 was recorded mainly to investigate the nature and extent of Devonian sediments in the Warrabin Trough, and the nature and limits of the Cooper Basin sequence. Traverses 3-8 were planned to study the Cooper and Thomson Synclines and underlying Devonian troughs. Traverses 6 and 8 were located to cross the Canaway Ridge, and together with Traverse 1 provide links to Traverses 2,ll and 9, which investigate the Adavale Basin and its associated Quilpie and Cooladdi troughs. Traverse 10 was recorded to tie between the main east-west traverses in the Adavale Basin, through key exploration wells, to the Quilpie Trough. Traverse 12,

linked

through

Syncline,

petroleum

provided

exploration

company

a well tie to shallow

area. Traverse

13 was recorded

on the eastern

flank of the Pleasant

to investigate

5 in the Thomson

in the northwestern

the nature

part of the

of the sedimentary

Creek Arch. This traverse

by a modern good quality seismic tine recorded In addition to the normal CDP reflection attempts Traverse

lines to Traverse

basement

sequence

is tied to Traverse

2

by an exploration company. traverses with recordings to 20 s,

were made to record wide-angle reflections from refraction shots on 1 and two expanded spreads were recorded on Traverse 9 on the eastern

W

Quilpie

Warrabin

Trough

Trough

Earcoo Trouah

Fig. 2. Representative The strongly faulted

seismic reflection

folded and faulted

younger

sequences

sections over parts of the Quilpie,

Devonian

sequence

by a major angular

is separated

unconformity.

Warrabin

from the overlying

and Barcoo gently

troughs.

folded

and

153

margin of the Quilpie Trough and on Traverse 10 in the central part of the Adavale Basin. To aid the interpretation of the seismic data synthetic reflection seismograms were produced from sonic logs in most of the exploration wells in the area. An example is shown in Fig. 3. About 2300 km of mainly single coverage, old analogue seismic data from company surveys were transcribed to digital format and processed (Sexton et al., 1983). This treatment improved the quality of the older data and provided additional seismic information to extend interpretation throughout the area. The main seismic reflection events which can be readily identified are indicated by reference to the stratigraphic table in Moss and Wake-Dyster (1983) and referred to later in discussion of results.

BARCOO Interval

JUNCTION

Sonic tog velocity (m/s)

Seismic

1 synthetic

Seismic

section

1.15

ZS-

I----CoOladdi

Fig. 3. Synthetic example

reflection

seismogram

of the use of synthetics

Oo,omite

--$

from the Barcoo

Junction

to aid the seismic interpretation.

1 well and BMR seismic section.

An

DISCUSSION

OF RESUL’TS

Basemenr rnappir~~~

Although no clearly defined basement reflections were recorded anywhere in the area, the basement depth and configuration can be inferred in most places from the available reflection data. Gravity is proving to be a useful tool in defining basement in some places where there is poor seismic penetration because of strong reflectors associated with Permian coals (Fig. 4) higher in the section (Anfiloff, 1984). There are two main reasons for the lack of refLections from basement. Firstly there is little or no change in acoustic impedance between the basement rocks and the immediate overlying sediments. Velocities of the order of 5.0-5.5 km/s were obtained from both the analysis of the deep sedimentary CDP and expanded spread data and by Collins and Lock (1983) from basement refraction studies. Secondly the various basement rocks penetrated in petroleum exploration wells are highly deformed in places.

The quality of the reflection data from the Devonian sequence is generally very good and these data are proving to be most useful in studying this complex region. Devonian rocks have been penetrated in wells in the Adavale Basin which lies to the east of the faulted Canaway Ridge. Distinctive reflection events can be identified with particular formations as discussed earlier (Fig. 5). The sequence is strongly folded and faulted and its upper boundary is a clearly defined major erosional

w

E

Datum Fig.

4.

measures

1831~

Seismic

masking

section

10 ire t

0 L

A.S.L.

east of Mount

possible

deeper section.

Howitt

1 well showing

strong

reflections

from

Permian

coai

155

w

Warrabin

E

Quilpie Trough

Trough

10

Fig. 5. Parts of seismic sections sections aiding

illustrate interpretation

the distinctive

5 km

O-

Datum 183m A.S.L. from the Devonian character

sequence

of reflections

26/O/,44

in the Quilpie and Warrabin

associated

with particular

troughs.

Devonian

These

formations

in areas which have not been drilled.

angular unconformity which can be readily identified on seismic reflection sections throughout the area. A mid-Devonian unconformity is also recognized. South of the Adavale Basin, the reflection data show that the Quilpie and Cooladdi troughs are separated from the basin by major faults and uplifted basement blocks. Dixon (1984) discusses the Quilpie Trough, and its relationship to the Adavale Basin, and other Devonian troughs in the area. The Devonian sequence in these troughs has not been penetrated entirely but the seismic sections can be readily interpreted because of the distinctive nature of the reflection events (Fig. 5). Another major Devonian trough, the Westgate Trough, lies to the southeast and there is a possibility of additional minor, isolated troughs to the east of the main basin. The seismic reflection program has added significantly to understanding the extent and nature of Devonian sedimentation west of the Canaway Ridge. Pinchin and Senior (1982) have interpreted the seismic info~ation in the Warrabin Trough, which contains up to 3000 m of Devonian sediments, and Wake-Dyster (1984) discusses the Barcoo Trough, which contains up to about 1600 m. The Barcoo Trough, named by Pinchin and Senior (1982), lies to the northwest of the Warrabin Trough and is connected to that trough by a thin veneer of Devonian sediments. Another Devonian Trough may also be present further to the west about the axis of the Cooper Syncline. This has been postulated from the gravity results (Anfiloff, 1984) but is not confirmed from the seismic results. As discussed earlier, strong reflections associated with coals in this area appear to mask effective seismic

CANAWAY

FAULT

L

I

0,

Datum 183m A.&L.

.___._ ------

__ -----

--___--

- __-__

l,Okm

.-._

__

26’0/145 Fig.

6.

Seismic

and Anfiloff,

section and schematic 1982).

interpretation

of the structure

penetration. Other Devonian troughs may be present Cooper Basin outside the main study area. Major

faults

can be seen on the seismic

Some of these faults can be traced fault displacements

are evident

faults have not apparently long structural separates

feature,

the Adavaie

Basin

margin

its associated

also in the deeper part of the

sedimentary

sequence.

section;

smaller

of the major fault systems.

later sediments.

the eastern from

Ridge cafter Pinchin

from the Devonian

into the overlying

from reactivation

affected forming

sections

of the Canaway

The Canaway

of the Canaway western

Other

Fault is a 250-km

troughs.

Ridge which Pinchin

Anfiloff (1984) have interpreted the new seismic and gravity information with previous data (Fig. 6) to study the structure and timing of this fault.

and

together

The Cooper and Galilee Basins The Cooper Basin extends over much of the western part of the area and overlies parts of the Warrabin and Barcoo troughs. The sequence is thin over these troughs and consists of unnamed thin Permian coal measures, which have poor reflection characteristics making the boundary difficult to interpret from the seismic data. The unconformity between the Cooper Basin sequence and the overlying Jurassic rocks of the Eromanga Basin is also difficult to interpret in the seismic sections.

157

To the west, over the Cooper coal measures

(Fig. 4). The depositional by distinctive Pinchin

Syncline,

the Permian

which give rise to the prominent edge of the Triassic

section

reflection

consists

marker

is characterised

of thicker

referred

to earlier

on the seismic sections

prograding.

and Senior (1982) interpreted

sediments

in the Warrabin

of Cooper

Basin sedimentation

Trough

the boundaries

of the Permian

area and Wake-Dyster

in the Barcoo Trough.

and Triassic

(1984) discusses Wake-Dyster

the extent

also points

out

that the BMR seismic data showed that a previously interpreted thick section of Permian in the Thomson Syncline is in fact Devonian sediments of the Barcoo Trough (Figs. 2 and 3). The Galilee Basin sequence

is partly

contemporaneous

with the Cooper

Basin

sequence and these sequences may be contiguous across the northern-most part of the Canaway Ridge. The Galilee Basin sequence lies east of the Canaway Ridge and is relatively

thin over most of the area, making

it difficult

to define

information. Preliminary seismic results show a depression Creek Arch containing a substantial thickness of sediments; belong earlier.

to the Galilee

Basin

sequence

or alternatively

be Devonian

as discussed

E

W

EROMANGA

using seismic

east of the Pleasant these sediments may

WINTON FORMATION - Coal measures

BASIN

TOOLEBUC

FORMATION

CAONA-OWIE FORMATION HUTTON

COOPER

BASIN

Fig. 7. Prominent seismic reflections is associated

showing channelling are associated

in the Eromanga

with coal measures;

and shoaling; reflections

2 2 km

0

Datum 183m A.S.L.

Formation

SANDSTONE

26/W, 46

I

Basin sequence. The reflection from the Winton

the Toolebuc

Formation

from the Cadna-Owie

gives fair to good reflections

Formation

with sudden increases in velocity in the section. (Reflection

and Hutton Sandstone

time in seconds.)

Inte~retatjon of the data east of the Canaway Ridge is at an early stage and further information on the nature and extent of the Galilee Basin sediments will be forthcoming as interpretation proceeds. The Eromanga

Busin

Prominent seismic reflections in the Eromanga Basin sequence are identified with the Winton Formation, Toolebuc Formation and the Cadna-Qwie Formation (Fig. 7) (Moss and Wake-Dyster, 1983). There appears to be little acoustic impedance difference between most formations in the Jurassic, consequently the Jurassic section lacks distinctive reflections other than from the Hutton Sandstone (Fig. 7). The Eromanga Basin consists of an essentially conformable sequence of Early Jurassic to Late Cretaceous age. It is gently folded and faulted compared with the Devonian sequence. The seismic results indicate that most faults in the section were caused by reactivation of the major faults in the Devonian section. Displacement of the sediments may also be caused by compaction of sediments. The stratigraphy and structure of the Eromanga Basin are summarised by Senior et al. (1978). However, the seismic results are adding significant new information on the extent and nature of the particular formations and on the extent of faults and other structures not readily apparent in the surface geology, which is affected by major episodes of weathering.

Devonian sedimentation was once widespread over a large area on the western edge of the Tasman Geosyncline in eastern Australia, well beyond the present confines of the Adavale Basin and its associated troughs, Although the nature and structure of the basement is not clearly defined there is seismic evidence, in some pfaces, of Early Devonian sediments onlapping basement palaeo-highs, e.g. on the western flank of the Canaway Ridge (Fig. 6). in some areas the seismic results indicate that part of the Early Devonian section is absent, confirming that these areas were structurally high during deposition, e.g. Barcoo Trough. A mid-Devonian unconformity seen on the seismic sections indicates that a minor orogeny took place, resulting in minor folding and faulting and tilting of basement blocks. Minor erosion foilowed prior to widespread deposition of the Coogaddi Dolomite, a prominent lithologic and seismic marker. Late ad-Devonian continents and shallow marine sediments including evaporites were laid down over most of the area. This was followed by infili of the basin with continental red beds. The seismic results indicate that the post-Cooladdi Dolomite sequence is about the same thickness over much of the main basin and its troughs. In some areas seismic evidence indicates onlap of this part of the Devonian sequence onto basement highs, e.g. Windorah Anticline.

159

Intensive fotding and faulting, in~l~di~8 displacement of the C~naway Fault and uplift and westwards tilting of the Canaway Ridge, took place during the midCatboniferous Kanimblan Orogeny. A major period of erosion followed, causing widespread peneplanatio~ oF the area and separation of the Adavale Basin from its associated troughs. The erosion truncated the Devonian sequence and resulted in major angular unconformities in most areas containing the Devonian sediments. There is no clear seismic evidence now of the depositional edge of the Devonian sedimental section. In the period of continued subsidence which followed, Cooper and Galilee Basin sediments were deposited in the low-lying areas surrounding the elevated central region about the Canaway Ridge. Analysis of the seismic data gives some indication of the extent of the Late Carbonife~o~s to Triassic sediments. Their presence is cIearIy shown, parti~ulariy where considerable thicknesses of coaf seams produced in the swamp conditions give rise to prominent reflections. The Eromanga Basin sequence was deposited fairly unifo~mIy throughout the area as a blanket cover during the Jurassic-Cret~c~ous period. The gentle folding and minor faults, apparent in the seismic sections and refIected in the surface geology, have resulted mainly from basement uplifts and minor movements associated with pre-e~s~~8 faults continuing into the late mid-Tertiary and from compaction of the sediments. Further, detailed inte~retation of the seismic reffection and other information obtained on the central Eromanga Basin project, currently in progress, will add signific~tIy to clarifying the basin relationships and their history.

Although a discussion of the petroleum potential of the basins is not the main topie of this paper it is appropriate to comment briefly on the contribution the seismic reflection results are making to a better understanding of the prospecti~ty of the central Eromanga Basin area. Analysis of the seismic reflection data in the Eromanga Basin sequence, partieuIarly those associated with faulting, indieates that appro~mately two-thirds of the total basin sediments were deposited during the Cretaceous, at a much faster rate than for the Jurassic, Most of the subsidence and deposition was shown by the seismic results to have occurred in the Ed-Creta~eous corresponding to a period of major fault movements. Passmore and Boreham (1984), in studies of source rock and maturation history of the area, indicate that areas of bigb organic maturation coincided with areas of thick Cretaeeous sediments. Vitrinite reflectance and headspace gas analyses indicate that a m~mum depth of around 1200 m is required for source rocks in the basin to reach the main threshoId for oil generation: a lateral change in g~therma1 gradient across the region complicates the maturation pattern. The relativefy thin sedimentary section and low geothermal gradients suggest that

i60

source rocks generally in the Eromanga Basin would be unlikely to have reached the oil window except in the western part of the area, although good source rocks are present

in most of the basin. The discovery

stimulated

renewed

Seismic faulting

interest

information

indicates

in the Eromanga

previous

wells. Many

Habermehl protected worthy

fat&s were shown

structures

associated

to have minor

by groundwater

movement

with folding

or not completely displacements:

that such faults may have resulted

Senior

in stagnation

in the basin,

and

tested in and zones

and are therefore

of attention.

Source rocks in the Cooper found

numerous

1 well in t9Xf has

Basin prospects.

Basin which are either untested

(1980) proposed from flushing

of oil in the Jackson

in the Eromanga

Basin in the central

Eromanga

to be much richer than those in the Eromanga

Basin area have been

Basin and range from mature

to overmature (V.L. Passmore, pers, commun., 1983). The sequence is generally shown by the seismic data to be thin in the northeastern part of the Cooper Basin and it is considered to be unlikely to yield substantial quantities of hydrocarbon. However, in the southwest of the study area, where the Cooper Basin sequence thickens, gas has been found in Durham Downs I, Barrolka 1. Wareena 1 and Tart&a 1. Traces of oil were found in Chandos 1, Kyabra 1 and Cumbroo 1. V.L. Passmore (pers. commun., 1983) also considers that source rocks in the deeper part of the Gahlee Basin have reached or are reaching a levef of maturity sufficient

to generate

hydrocarbons,

seismic data to be largely absent The discovery in elastics petroleum

of gas. albeit non-commercial

of mid-Devonian

seismic evidence

prospective,

of the Adavale

further

detailed

Basin

the Adavale

I well in the Adavale untested

and

structures

its associated

troughs

of the main producing before any conclusions

potential

sequence.

by the

Basin. in 1964,

Basin,

suggest

studies of source rocks and maturation,

structure and stratigraphy niques, will be necessary of the Devonian

rocks are shown

at the time of its discovery

age in the Gilmore

of large, possibly

potential

highly. However,

but the best source

from the section overlying

and

that the must

rate

and of the

formation, using seismic techcan be reached on the overall

The preli~na~y seismic reflection results discussed here are the colective efforts of a number of scientists involved in the seismic reflection program in the central Eromanga Basin. In particular the efforts of the BMR seismic party on field surveys during 1980-1982 under the leadership of Ms. J.A. Bauer, Messrs. J. Pinchin, M.J. Sexton, F.J. Taylor and also 0. Dixon (Geological Survey of Queensland) are gratefully acknowledged. J.C. Dooley and Ms. V.L. Passmore criticalty reviewed the Thanks are also due to petroleum manuscript and provided useful comments. exploration leaseholders in the survey area who are making co~fidenti~ company information freely available to the project team. This paper is published with the

161

permission of the Director, Bureau of Mineral Resources, Geology and Geophysics, Canberra, A.C.T., Australia,

REFERENCES

Anfiloff,

V., 1984. The gravity

Collins,

C.D.N.

basement

and

Lock,

field of the Eromanga

J., 1983. A seismic

highs, Eromanga

Basin, eastern

Dixon, 0.. 1984. The Quilpie Trough, Finlayson,

D.M.,

1983.

Tectonophysics, Finlayson,

The

Basin,

eastern

Hawkins,

program

Australia,

including

the

Eromanga

Symposium.

Future,

1980-1982.

Pet. Explor.

Symposium.

J. and

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Collins,

S.P.,

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C.D.N.,

C.D.N.

1983.

Prelimina~

Moss, F.J. (Coordinator), Bur. Miner. Resour.,

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A Stocktake

for The

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and

Tectonophysics, structure

under

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data

100: 175-184. the central

Eromanga

results

from

the central

Eromanga

Basin,

Eromanga

Basin seismic survey, Queensland,

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Jan-June

1980. Aust.

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A.G., 1978. The Thomson

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Structure

Orogen

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Orogenic

Variation

Zone. In: E.

in Tectonic

Style.

48: 299-326. C.J., 1984. Source rock evaluation

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of the central

Basin. J. Geol. Sot. Aust., in press.

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Geol. Geophys.,

J. and Anfiloff,

in Queensland,

A Stocktake

for The

Qld.

Basin seismic survey, Qld., 1980. Preview report.

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Pin&in, J. and Anfiloff, Sot. Aust., in press.

In: Petroleum

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