Recent Advances in Burial and Thermal Geohistory Analysis

Falvey, David A.; Deighton, I.

doi:10.1071/aj81004

Cited by 22 publications

(13 citation statements)

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“…4for details. Maturity zones are determined from the shape of the curve and from the sterane and triterpane oil-source rock extract correlations (see text)time and temperature on the maturation process(Waples 1980;Falvey & Deighton 1982; …”

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confidence: 71%

Some Geological Controls on Oil Composition in the U.K. North Sea

Cornford¹,

Morrow²,

Turrington³

et al. 1983

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Summary The U.K. North Sea contains a wide variety of reservoired oils, ranging from the biodegraded heavy oils, via mid-gravity crudes to light oils and condensates. Statistical data from a suite of U.K. North Sea oils gives an average API gravity of 36°, an average asphaltene content of 1.4% and an average saturate/aromatic ratio of 2.02. Averages for pristane/phytane, pristane/n-C 17 and phytane/n-C 18 are 1.24, 0.63 and 0.56 respectively. It is possible to explain the ocurrence of the vast majority of the U.K. North Sea crudes in terms of generation over a range of maturities from single source rock horizons (the Kimmeridge Clay Formation hot shales), followed by alteration during migration or within the reservoir. The source rocks are shown to be immature below 175°F (80°C); early mature between 175–225°F (80–107°C); mid-mature between 225–265°F (107–130°C) and late mature above 265°F (130°C). Early mature, full maturity spectrum and late mature oils are identified using maturity-controlled sterane and triterpane ratios established from the source rock studies, and are related to bulk properties such as API gravity and saturate/aromatic ratios. Bacterial degradation in shallow cool reservoirs (less than 6000 ft; below 140°F (60°C)) is responsible for the majority of the heavy oil in the U.K. North Sea, while asphaltene enrichment is another mechanism for producing heavy oils. Though the Kimmeridge Clay Formation hot shales are fairly homogeneous over the U.K. North Sea, molecular ratios such as the pristane/phytane ratio, the abundance of a C 28 hopane and a C 27 moretane can be used to correlate oils with specific facies of the generally homogeneous source rock.

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confidence: 71%

Some Geological Controls on Oil Composition in the U.K. North Sea

Cornford¹,

Morrow²,

Turrington³

et al. 1983

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“…Sclater & Christie 1980;Falvey & Deighton 1982). In order to restore the original thickness of a stratigraphic unit, its normal porosity/depth relationship must be determined.…”

Section: Sediment Decompactionmentioning

confidence: 99%

“…The source rock thermal history required to model observed maturity parameters is generally determined from burial history and palaeogeothermal gradient(s) or palaeoheatflow/thermal conductivity (e.g. Falvey & Deighton 1982;Bray et al 1992). A parameter frequently used to express the maturity of source rocks is the quantitatively determined extent to which the kerogen maceral, vitrinite, reflects visible light (vitrinite reflectance).…”

Section: Source Rock Maturitymentioning

confidence: 99%

Regional Tertiary Exhumation in and around the United Kingdom

Hillis¹

1995

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Sonic velocities in the Upper and Middle Chalk, the Bunter Sandstone and the Bunter Shale were used independently to quantify apparent exhumation (amount of missing section) in the UK Southern North Sea (SNS). Apparent exhumation results derived from these units are statistically similar. The consistency of results from chalks, shales, and sandstones in the UK SNS, and in other areas (Inner Moray Firth and Celtic Sea/South-Western Approaches), suggests that, at a formation and regional scale, burial-depth is the primary control on velocity (and porosity) in these units, and validates the use of lithologies other than shale in maximum burial-depth determination. The consistency of apparent exhumation results from units of Early Triassic to Late Cretaceous age suggests that Tertiary exhumation was of sufficiently great magnitude to mask any earlier Mesozoic periods of exhumation, and that maximum Mesozoic-Cenozoic burial-depth was attained prior to Tertiary exhumation.The analysis of sonic velocities, apatite fission tracks, vitrinite reflectance, normalized drilling rate and clay mineral diagenesis all suggest that there was a regional component of approximately I km of exhumation during Tertiary times, which affected structurally uninverted areas in and around the UK. The widely-recognized inversion-related exhumation is superimposed on regional Tertiary exhumation. Regional Tertiary exhumation need not have been contemporaneous with structural inversion. Further refinement beyond Tertiary age is not possible from the sonic velocity data. Regional exhumation, however, is most likely to be associated with regional Palaeocene or Oligocene/Miocene unconformities.The evidence for regional exhumation implies that there was a pre-exhumational phase of burial (during which the eroded sedimentary rocks were deposited). Exhumation and prior burial associated with the regional Tertiary event need to be incorporated in aspects of basin analysis such as sediment decompaction and diagenetic and maturation modelling, and can, for example, account for the maturity of the Carboniferous of the onshore East Midlands Shelf, and the Lias exposed on the north coast of Somerset. The regional, Tertiary tectonic uplift associated with exhumation must have had a thick-skinned origin, and, in areas where there is no evidence for significant Tertiary igneous activity, a decoupled, two-layer model of lithospheric compression is invoked to account for the subsidence/uplift patterns of both inverted and uninverted areas.

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“…The source rock thermal history required to model observed maturity is generally determined from burial history and palaeogeothermal gradients or palaeo-heatflow/thermal conductivity (e.g., Falvey and Deighton, 1982). To assess the influence of Late Triassic -Early Jurassic and Late CretaceousTertiary exhumation on source rock maturity, vitrinite reflectance levels have Figure 11.…”

Section: Influence Of Exhumation On Source Rock Maturitymentioning

confidence: 99%

Quantification of Exhumation from Sonic Velocity Data, Cooper Basin, Australia, and Implications for Hydrocarbon Exploration

Mavromatidis¹

2006

Surv Geophys

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Exhumation (defined as rock uplift minus surface uplift) in the Cooper Basin of South Australia and Queensland has been quantified using the compaction methodology. The sonic log, which is strongly controlled by the amount of porosity, is an appropriate indicator of compaction, and hence is used for quantifying exhumation from compaction. The traditional way of estimating exhumation based on the degree of overcompaction of a single shale unit has been modified and five units ranging in age from Permian to Triassic have been analysed. The results reveal that exhumation increases eastwards from the South Australia into the Queensland sector of the basin. The results show that exhumation in Late Triassic -Early Jurassic times, after the Cooper Basin deposition, seems to be 200-400 m higher than exhumation in Late Cretaceous -Tertiary times, after the Eromanga Basin deposition. This study has major implications for hydrocarbon exploration. Maturation of source rocks will be greater for any given geothermal history if exhumation is incorporated in maturation modelling. Exhumation values can also be used to improve porosity predictions of reservoir units in undrilled targets.

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Recent Advances in Burial and Thermal Geohistory Analysis

Cited by 22 publications

References 0 publications

Some Geological Controls on Oil Composition in the U.K. North Sea

Some Geological Controls on Oil Composition in the U.K. North Sea

Regional Tertiary Exhumation in and around the United Kingdom

Quantification of Exhumation from Sonic Velocity Data, Cooper Basin, Australia, and Implications for Hydrocarbon Exploration

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