RELATIONS BETWEEN DEPTH OF BURIAL, VITRINITE REFLECTANCE AND GEOTHERMAL GRADIENT: THE LONE STAR BERTHA ROGERS BOREHOLE, ANADARKO BASIN, OKLAHOMA, USA - THE WORLD'S DEEPEST EXPLORATION BOREHOLE

Sediments from the Permian Pedirka Basin and the overlying Triassic Simpson Desert Basin have been studied to determine their potentials as source rocks for hydrocarbons. Principal techniques used are reflected light microscopy, including vitrinite reflectance, solvent extraction and kerogen isolation.Dispersed organic matter (DOM) occurs through the Permian and Triassic sequences, and is most abundant near the top of the Triassic, constituting up to 2 per cent of the sediments by volume. Of this DOM, 30 to 50 per cent is vitrinite plus exinite. The Permian and Triassic coals have vitrinite reflectivities of up to 0.9 per cent. The geothermal gradient in the vicinity of Poolowanna 1 is probably sufficient to cause the cutinite within the Triassic sediments to break down into petroleum hydrocarbons. In the case of the Poolowanna Jurassic oil show, migration up faults and accumulation in high-temperature reservoirs have been accompanied by the loss of volatile hydrocarbons.

Download Full-text

Thermal Maturation by Vitrinite Reflectance of Woodford Shale, Anadarko Basin, Oklahoma: REPLY

AAPG Bulletin ◽

10.1306/948878de-1704-11d7-8645000102c1865d ◽

1987 ◽

Vol 71 ◽

Author(s):

Brian J. Cardott (2), Michael W. La

Keyword(s):

Vitrinite Reflectance ◽

Woodford Shale ◽

Anadarko Basin ◽

Thermal Maturation

Download Full-text

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

The APPEA Journal ◽

10.1071/aj96030 ◽

1997 ◽

Vol 37 (1) ◽

pp. 505 ◽

Cited By ~ 2

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.

Download Full-text

Comparison of Maturation Data and Fluid-Inclusion Homogenization Temperatures to Simple Thermal Models

Current Research in Earth Sciences ◽

10.17161/cres.v0i240.11847 ◽

1997 ◽

pp. 13-27

Author(s):

K. David Newell

Keyword(s):

Fluid Inclusion ◽

Vitrinite Reflectance ◽

Geothermal Gradient ◽

Upper Ordovician ◽

Thermal Event ◽

Geothermal Gradients ◽

Thermal Maturation ◽

Tectonic History ◽

History Of ◽

Homogenization Temperatures

Time-temperature index (TTI) modeling is used to establish a simple theoretical thermal maturity for Paleozoic strata in central Kansas. These thermal maturation calculations are based on estimates of likely geothermal gradients and best knowledge of the tectonic history of the region, as derived from stratigraphic thicknesses and estimates of erosion at unconformities. Major uncertainties in the data for the TTI modeling are burial during Cretaceous time and geothermal gradient, thus several models were calculated in which ranges of these two variables were considered. Results of the thermal modeling are then compared to available data on the thermal maturation. These data are principally derived from subsurface samples, on which vitrinite-reflectance, pyrolysis, and fluid-inclusion analyses have been performed. Vitrinite-reflectance and Rock-Eval maturation measurements indicate that Middle and Upper Ordovician strata (i.e., Simpson, Viola, and Maquoketa formations) in the study area are in initial phases of oil generation. Maturation modeling can match the results of the organic analyses, but geothermal gradients and burial during the Cretaceous have to be maximized. Although the TTI modeling utilizing very high geothermal gradients and near-excessive thicknesses of Cretaceous strata can match the observed maturation, the modeled results are probably not correct because fluid-inclusion data from saddle dolomites from the Upper Ordovician Viola Limestone indicate this unit reached temperatures 50° C higher than the maximum modeled temperature. A thermal event is inferred to account for the excess maturation and elevated fluid-inclusion homogenization temperatures. This thermal event may be manifested in the erratic increase of vitrinite-reflectance with depth for post-Devonian strata, as well as for pyrolysis measurements in wells for which maturation profiles are available. Flow of heated water onto the cratonic shelf out of the Anadarko basin during the late Paleozoic Ouachita orogeny may be responsible for the maturation anomalies.

Download Full-text

Thermal maturity of the accretionary wedge

10.5194/egusphere-egu2020-6446 ◽

2020 ◽

Author(s):

Utsav Mannu ◽

David Fernández-Blanco ◽

Ayumu Miyakawa ◽

Taras Gerya ◽

Masataka Kinoshita

Keyword(s):

Thermal Conductivity ◽

Phase Transitions ◽

Vitrinite Reflectance ◽

Geothermal Gradient ◽

Accretionary Wedge ◽

Thermal Maturity ◽

Thermomechanical Model ◽

Borehole Data ◽

Different Temperatures ◽

The Impact

<p>Records of thermal maturities in boreholes have led to a better understanding of the formation of geological structures, especially the duration of thrusting during the evolution of accretionary wedges.&#160;The temporal extent of thrusting is controlled by a host of factors such as the nature of sedimentation, the topography of the incoming plate and so on. As a result, estimating the peak heating through the thermal maturity of organic material can help elucidate which mechanism has played a prominent role in wedge evolution. However, the thermal maturity value expressed as the distribution of vitrinite reflectance is the combined effect of two factors: the geothermal gradient and the time the sediments were exposed to different temperatures. Thus, the distribution of vitrinite reflectance in accretionary wedges does not necessarily reveal the deformational pathway of individual thrusts. Moreover, since the conductivity of the sediments close to the surface (<10 km) is most accessible in borehole data and predominantly controlled by porosity, models of accretionary wedge simulating thermal maturity ought to incorporate the impact of porosity on thermal conductivity. Additionally, phase transitions of the sediments in the wedge, such as smectite-illite transition and the formation of zeolite facies, that lead to increased thermal conductivity and internal angle of friction for sediments at structurally deeper locations within the wedge, must be accounted for in modeling studies. Therefore, we use a 2D thermomechanical model of subduction with empirical porosity values form the Nankai subduction margin and incorporate the effect of phase transitions to simulate the formation of the accretionary wedge under several sedimentary conditions and track the evolution of the vitrinite reflectance. As a result, we gain a holistic picture of deformation in accretionary wedges exploring different scenarios using geodynamic modeling alongside field data.</p>

Download Full-text