SOURCE, MATURITY AND GAS COMPOSITION RELATIONSHIPS IN THE SOUTHERN COOPER BASIN

1980 ◽  
Vol 20 (1) ◽  
pp. 191
Author(s):  
D.A. Schwebel ◽  
S.B. Devine ◽  
M. Riley
Keyword(s):  
Vitrinite Reflectance ◽  
Sedimentary Basins ◽  
Geothermal Gradient ◽  
Temperature Gradients ◽  
Land Plants ◽  
Hydrocarbon Generation ◽  
Gas Composition ◽  
Wet Gas ◽  
Structural Zones ◽  
Cooper Basin

In the Permian sedimentary sequence of the Cooper Basin, land plants contributed the bulk of the organic matter to the sediments. Inertinite, vitrinite and exinite are common kerogen types present in the organic-rich shales. Coal thickness varies areally.The geothermal gradient, though varying (from area to area), is everywhere higher than normal for sedimentary basins. The whole of the Permian sequence is mature for hydrocarbon generation. The highest temperature gradients of up to 3.19°F/100’ are measured in the Nappamerrie Trough and are associated with areas of granitic basement. Vitrinite reflectance profiles confirm that the sediments are thermally mature.Trends of gas composition indicate three distinct regions with gases trapped in:the Patchawarra Trough tend to be high in CO2 and wet gas;the Nappamerri Trough tend to be high in CO2 and low in wet gas; andthe Tennapera Trough tend to be low in CO2 and moderately high in wet gas.These differences in gas composition are accounted for by differences in thermal history within structural zones.

LATERAL AND VERTICAL RANK VARIATION: IMPLICATIONS FOR HYDROCARBON EXPLORATION

1978 ◽  
Vol 18 (1) ◽  
pp. 143 ◽  
Author(s):  
A.J Kantsler ◽  
G. C. Smith ◽  
A. C. Cook
Keyword(s):  
Vitrinite Reflectance ◽  
Sedimentary Basins ◽  
Hydrocarbon Exploration ◽  
Hydrocarbon Generation ◽  
Marked Rise ◽  
Canning Basin ◽  
Early Maturation ◽  
Late Tertiary ◽  
Uplift And Erosion ◽  
Gas Fields

Vitrinite reflectance measurements are used to determine the vertical and lateral patterns of rank variation within four Australian sedimentary basins. They are also used to estimate palaeotemperatures which, in conjunction with present well temperatures, allow an appraisal of the timing of coalification and of hydrocarbon generation and distribution.The Canning Basin has a pattern of significant pre-Jurassic coalification which was interrupted by widespread uplift and erosion in the Triassic. Mesozoic and Tertiary coalification is generally weak, resulting in a pattern of rank distribution unfavourable to oil occurrence but indicating some potential for gas. The Cooper Basin also has a depositional break in the Triassic, but the post-Triassic coalification is much more significant than in the Canning Basin. The major gas fields are in, or peripheral to, areas which underwent strong, early, telemagmatic coalification whereas the oil-prone Tirrawarra area is characterized by a marked rise in temperature in the late Tertiary. The deeper parts of the Bass Basin underwent early coalification and are in the zone of oil generation, while most of the remaining area is immature. Inshore areas of the Gippsland Basin are also characterized by early coalification. Areas which are further offshore are less affected by this phase of early maturation, but underwent rapid burial and a sharp rise in temperature in the late Tertiary.

ELEVATED MID-CRETACEOUS PALAEOTEMPERATURES IN THE WESTERN OTWAY BASIN: CONSEQUENCES FOR HYDROCARBON GENERATION MODELS

1997 ◽  
Vol 37 (1) ◽  
pp. 505 ◽  
Author(s):  
M.M. Mitchell
Keyword(s):  
Upper Cretaceous ◽  
Vitrinite Reflectance ◽  
Geothermal Gradient ◽  
Hydrocarbon Generation ◽  
Key Factors ◽  
Factors Affecting ◽  
Early Maturation ◽  
Maximum Temperatures ◽  
Hydrocarbon Preservation ◽  
Uplift And Erosion

The Otway Basin formed during the Mesozoic separation of Antarctica and Australia. A study of apatite fission track (FT) analysis and vitrinite reflectance (VR) data from borehole samples in the western Otway Basin was initiated to elucidate some of the thermal and structural complexities of this region.Interpretation of results suggest that some areas experienced regionally elevated palaeotemperatures, however, much of the region is at present-day maximum temperatures. Where cooling from maximum palaeotemperatures is observed, the timing may be grouped over three main intervals as follows; mid-Cretaceous, Late Cretaceous to Early Tertiary, and Tertiary. Cooling was facilitated by a decline in geothermal gradient, uplift and erosion, or both. Evidence for a decline in geothermal gradient from values >55°C/km in the mid- Cretaceous is recognised in several wells. Elevated mid- Cretaceous palaeogeothermal gradients (50−60°C/km) have been reported for the eastern Otway Basin, suggesting that these high temperatures were a regional phenomena. Cooling by uplift and erosion at this time was minimal throughout the western Otway Basin in contrast to the kilometre scale uplift and erosion reported for the eastern Otway Basin and adjacent basement inland of this section of the rift.The relative early maturation of the Otway Supergroup during mid-Cretaceous regionally elevated geothermal gradients, and subsequent basin restructuring, are key factors affecting hydrocarbon preservation in the western Otway Basin. Strategies for identification of prospective areas include identification of regions that have remained at moderate temperatures during the Early Cretaceous, and have not undergone burial under a thick Upper Cretaceous to Tertiary section.

HYDROCARBON GENERATION IN THE FLY LAKE—BROLGA AREA OF THE COOPER BASIN

1979 ◽  
Vol 19 (1) ◽  
pp. 108
Author(s):  
Michelle Smyth
Keyword(s):  
Organic Matter ◽  
Sedimentary Basins ◽  
Depositional Environments ◽  
Fluorescent Light ◽  
Hydrocarbon Generation ◽  
Coal Seams ◽  
Clastic Sediments ◽  
Permian Coal ◽  
Coal Measures ◽  
Cooper Basin

The Cooper Basin is a major gas producing basin in Australia. Organic material in sediments from its Permian coal measures has been studied using transmitted, reflected and fluorescent light microscope techniques of analysis. In the Fly Lake—Brolga area, of the Patchawarra Trough, Cooper Basin, the interseam sediments of the Patchawarra Formation contain three types of kerogen or dispersed organic matter (d.o.m.): exinitic, vitrinitic and inertinitic. Exinitic d.o.m. is most abundant near the top of the Formation, vitrinitic d.o.m. is more abundant in the middle and lower parts of it, and inertinitic d.o.m. occurs throughout.A correlation between the type of d.o.m. in the sediments and the petrography of associated coals is emerging. Exinitic d.o.m. appears to be associated with coals that have high vitrite-plus-clarite contents, whereas vitrinitic d.o.m. is associated with high "intermediates" coals. Further examples are needed to establish these relationships more firmly.On the basis of results of coal petrographic studies in other Australian Permian sedimentary basins, depositional environments have been proposed for the coal seams in the Fly Lake—Brolga area. These environments are compared with those proposed by Thornton (1978) using the clastic sediments of the Patchawarra Formation.

FOCUSSING EXPLORATION IN THE OTWAY BASIN: UNDERSTANDING TIMING OF SOURCE ROCK MATURATION

1997 ◽  
Vol 37 (1) ◽  
pp. 178 ◽  
Author(s):  
I.R. Duddy
Keyword(s):  
Late Cretaceous ◽  
Vitrinite Reflectance ◽  
Integrated Approach ◽  
Geothermal Gradient ◽  
High Heat ◽  
Source Rocks ◽  
Hydrocarbon Generation ◽  
Top Down ◽  
Early Maturation ◽  
Hydrocarbon Preservation

Quantitative reconstruction of the thermal and structural histories at key locations in the Otway Basin using an integrated approach based on AFTA® and vitrinite reflectance data reveals a regional pattern of elevated geothermal gradient prior to mid-Cretaceous cooling. Paleogeothermal gradients declined from −50 to 70°C/ km at −95 Ma to present day levels in the range −30 to 40°C/km by around 80 Ma. As a result, significant hydrocarbon generation must have occurred from the thick Late Jurassic to Early Cretaceous Otway Group section during the rapid rift-burial phase that preceded major mid-Cretaceous cooling.Regional decline in geothermal gradient in the Late Cretaceous leads to a 'two-stage' generation history for Otway Group source rocks because subsequent hydrocarbon generation did not recommence until the early maturation effects were overcome by greater Late Cretaceous and Tertiary burial. Such early, high heat flow is regarded as a feature of rift basins, and this results in an inverted pattern of hydrocarbon generation from rift source rocks that is here referred to as 'top-down generation', and which has a key influence on hydrocarbon prospectivity.Analysis of key hydrocarbon discoveries in the basin leads to the conclusion that all significant accumulations can reasonably be inferred to be sourced from the Otway Group, due to 'top-down generation5 delayed until the mid-Tertiary to present-day burial phase. This situation clearly favours hydrocarbon preservation in traps of a range of ages and has the added advantage of limiting the time available for traps to be breached in subsequent structuring episodes.This understanding of the decoupled relationship between the burial and thermal histories provides a sharp focus for further exploration of Otway Group-sourced accumulations, by defining areas with suitable thicknesses of the Late Cretaceous and Tertiary depositional packages which maximise the amount of re-generation since the mid-Tertiary.

THE SIGNIFICANCE OF HYDROCARBON SHOWS AND OIL RECOVERIES IN THE LONGREACH AREA, CENTRAL QUEENSLAND

1989 ◽  
Vol 29 (1) ◽  
pp. 157
Author(s):  
C.C. Hodge ◽  
N.J. Russell ◽  
M. Smyth
Keyword(s):  
Joint Venture ◽  
Oil And Gas ◽  
Vitrinite Reflectance ◽  
Source Rocks ◽  
Hydrocarbon Generation ◽  
Variable Nature ◽  
Water Well ◽  
Reflectance Measurements ◽  
Cooper Basin ◽  
Commercial Oil

In 1925, over 40 gallons of oil were recovered from the Longreach town- water well. More recently, Corona 1, drilled by the ATP 271P Joint Venture in 1984, recovered 9 m (0.5 bbls) of oil in the drill pipe.These oil recoveries, along with several water- bore oil and gas occurrences, are all located in the Longreach area, Central Queensland, over 100 km north- northeast of the Cooper Basin zero edge. The oil recoveries and shows are therefore considered to be the product of source rocks other than those of the Cooper Basin.The Birkhead Formation, the unit considered most likely to source the Longreach and Corona oils, has been studied with a view to understanding the nature of hydrocarbon generation in the vicinity of the Maneroo Platform. The variables measured include (1) thickness of the shale units, (2) volume and type of dispersed organic matter (DOM) and (3) maturity (vitrinite reflectance). Measurements were taken from 10 exploration wells through the whole formation to provide uniform comparative assessment.The Birkhead Formation in the Maneroo Platform area is shown to have an anomalously low sandstone- to- shale ratio, vitrinite reflectance values (Rm(o)) consistently greater than 0.7 per cent and a favourable petroleum generative geochemistry.These results emphasise the highly variable nature of the Eromanga Basin sequence, and therefore its diverse generative potential, and highlight the encouraging prospectivity of the Maneroo Platform area despite the present lack of commercial oil discoveries.

ORIGIN OF GILMORE GAS AND OIL, ADAVALE BASIN, CENTRAL QUEENSLAND

1998 ◽  
Vol 38 (1) ◽  
pp. 399 ◽  
Author(s):  
C.J. Boreham ◽  
R.A. de Boer
Keyword(s):  
Oil And Gas ◽  
Isotope Composition ◽  
Vitrinite Reflectance ◽  
Sedimentary Basins ◽  
Source Rocks ◽  
Gas Generation ◽  
Migration Pathway ◽  
Wet Gas ◽  
Modelling Studies ◽  
High Maturity

Dry gas in the Gilmore Field of the Adavale Basin has been sourced from both wet gas associated with oil generation, together with methane from a deep, overmature source. The latter gas input is further characterised by a high nitrogen content co-generated with isotopically heavy methane and carbon dioxide. The eastern margin of the Lissoy Sandstone principal reservoir unit contains the higher content of overmature dry gas supporting reservoir compiirtmenmlisalion and a more favourable migration pathway to this region. The combination of a molecular and multi-element isotopic approach is an effective tool for the recognition of an overmature, dry gas source. This deep source represents a play concept that previously has been undervalued and may be more widespread within Australian sedimentary basins.The maturity level of the wet gas and associated oil are identical, having reached an equivalent vitrinite reflectance of 1.4−1.6 per cent. Modelling studies support the concept of local Devonian source rocks for the wet gas and oil. Reservoir filling from late stage, high maturity oil and gas generation and expulsion, was a result of reactivation of petroleum generation from Devonian source rocks during the Early Cretaceous. The large input of dry gas from a deeper and highly overmature source is a more recent event. This gas can fractionally displace condensable C2+ liquids already in the reservoir possibly allowing tertiary migration into younger reservoirs, or adjacent structures.Oil recovered from Gilmore-2 has been sourced from Devonian marine organic matter, deposited under mildly evaporitic, restricted marine conditions. The most likely source rocks in the Adavale Basin are the basal marine shale of the Log Creek Formation, algal shales at the top of the Lissoy Sandstone, and the Cooladdi Dolomite. Source-sensitive biomarkers and carbon isotope composition of the Gilmore-2 oil have much in common with other Devonian-sourced oils from the Bonaparte and Canning basins. The chemical link between western and eastern Australian Devonian oils may suggest diachronous development of source rocks over a wide extent. This implies that the source element of the Devonian Petroleum Supersystem may be present in other sedimentary basins.

scholarly journals Thermal history and organic matter maturation modeling of the East Siberian Sea sedimentary basins

2017 ◽  
pp. 15-27
Author(s):  
M. D. Lineva ◽  
N. A. Malyshev ◽  
A. M. Nikishin
Keyword(s):  
Organic Matter ◽  
Cross Sections ◽  
Thermal History ◽  
Vitrinite Reflectance ◽  
Sedimentary Basins ◽  
Source Rocks ◽  
Hydrocarbon Generation ◽  
Seismic Line ◽  
East Siberian Sea ◽  
Temperature Maps

2D and 3D thermal history and organic matter maturity modeling of East Siberian Sea sedimentary basinsare performed in this study. We present cross-sections with temperature and vitrinite reflectance distribution along composite seismic line, temperature maps ofmain horizons fordifferent time stages. Vitrinite reflectance maps of source rocks fordifferent time stages and transformation ratio maps of source rocks for present time are also presented. Maturation history and possibilities of hydrocarbon generation were analyzed using modeling results.

Burial History Reconstruction of the Appalachian Basin in Kentucky, West Virginia, Pennsylvania, and New York, Using 1D Petroleum System Models

2019 ◽  
Vol 56 (4) ◽  
pp. 365-396
Author(s):  
Debra Higley ◽  
Catherine Enomoto
Keyword(s):  
New York ◽  
Vitrinite Reflectance ◽  
Structural Complexity ◽  
Appalachian Basin ◽  
Source Rocks ◽  
Burial History ◽  
Gas Generation ◽  
Deep Basin ◽  
Utica Shale ◽  
Wet Gas

Nine 1D burial history models were built across the Appalachian basin to reconstruct the burial, erosional, and thermal maturation histories of contained petroleum source rocks. Models were calibrated to measured downhole temperatures, and to vitrinite reflectance (% Ro) data for Devonian through Pennsylvanian source rocks. The highest levels of thermal maturity in petroleum source rocks are within and proximal to the Rome trough in the deep basin, which are also within the confluence of increased structural complexity and associated faulting, overpressured Devonian shales, and thick intervals of salt in the underlying Silurian Salina Group. Models incorporate minor erosion from 260 to 140 million years ago (Ma) that allows for extended burial and heating of underlying strata. Two modeled times of increased erosion, from 140 to 90 Ma and 23 to 5.3 Ma, are followed by lesser erosion from 5.3 Ma to Present. Absent strata are mainly Permian shales and sandstone; thickness of these removed layers increased from about 6200 ft (1890 m) west of the Rome trough to as much as 9650 ft (2940 m) within the trough. The onset of oil generation based on 0.6% Ro ranges from 387 to 306 Ma for the Utica Shale, and 359 to 282 Ma for Middle Devonian to basal Mississippian shales. The ~1.2% Ro onset of wet gas generation ranges from 360 to 281 Ma in the Utica Shale, and 298 to 150 Ma for Devonian to lowermost Mississippian shales.

scholarly journals Thermal Maturation Regime Revisited in the Dongying Depression, Bohai Bay Basin, East China

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Haiping Huang ◽  
Hong Zhang ◽  
Zheng Li ◽  
Mei Liu
Keyword(s):  
Organic Geochemistry ◽  
Vitrinite Reflectance ◽  
Source Rocks ◽  
East China ◽  
Burial Depth ◽  
Bohai Bay ◽  
Hydrocarbon Generation ◽  
Bohai Bay Basin ◽  
Dongying Depression ◽  
Hydrocarbon Maturation

To the accurate reconstruction of the hydrocarbon generation history in the Dongying Depression, Bohai Bay Basin, East China, core samples of the Eocene Shahejie Formation from 3 shale oil boreholes were analyzed using organic petrology and organic geochemistry methods. The shales are enriched in organic matter with good to excellent hydrocarbon generation potential. The maturity indicated by measured vitrinite reflectance (%Ro) falls in the range of 0.5–0.9% and increases with burial depth in each well. Changes in biomarker and aromatic hydrocarbon isomer distributions and biomarker concentrations are also unequivocally correlated with the thermal maturity of the source rocks. Maturity/depth relationships for hopanes, steranes, and aromatic hydrocarbons, constructed from core data indicate different well locations, have different thermal regimes. A systematic variability of maturity with geographical position along the depression has been illustrated, which is a dependence on the distance to the Tanlu Fault. Higher thermal gradient at the southern side of the Dongying Depression results in the same maturity level at shallower depth compared to the northern side. The significant regional thermal regime change from south to north in the Dongying Depression may exert an important impact on the timing of hydrocarbon maturation and expulsion at different locations. Different exploration strategies should be employed accordingly.

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