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The 1-D burial and thermal history of the Korotaikha depression in the Timan–Pechora basin was numerically simulated for the sedimentary sequences of three wells: Korotaikhinskaya 1, Labogeyskaya 15, and Khavdeiskaya 1. This made it possible to numerically assess the conversion history of the hydrocarbon (HC) potential of source rocks in the southwestern flank of the Korotaikha depression in the northeastern Timan−Pechora basin. The modern modified kinetic spectrum of vitrinite maturation was used in calculations of the vitrinite reflectance to clarify the thermal history of the sedimentary cover of the study area. The occurrence of episodes of hydrothermal activity follows from comparison of the calculated and measured values of the vitrinite reflectance and explains the jumps in the maturity of organic matter at the boundaries of the unconformity of Quaternary and Triassic sediments, as well as the Permian and Carboniferous sediments. The simulations suggest a high conversion of the initial HC potential of the source rocks of the Silurian and Domanic horizons, Tournaisian, and Visean ages in the Korotaikhinskaya and Labogeiskaya areas and moderate generation in the Havdeyskaya area. The simulation shows that the high grades of the catagenesis (MC5 and higher) of the main source rocks and the significant role of secondary cracking of liquid HC fractions in the central part of the Korotaikha depression (wells Korotaikhinskaya 1 and Labogeyskaya 15) suggest that the possible HC accumulations should contain only gas. Accumulations in the southern part of the depression (Khavdeiskaya area), where secondary cracking was minimal and source rocks occur within the oil window, should contain both oil and gas (due to Permian rocks with terrigenous organic matter). [ABSTRACT FROM AUTHOR]

Based on the systematic analyses of samples collected from the western Qaidam basin, the organic geochemical characteristics of representative Paleogene saline lacustrine carbonate source rocks were synthetically studied. The results show that the carbonate source rocks are characterized by total organic carbon (TOC) content varied in the range of 0.07 to 1.57%, with an average of 1%, and hydrocarbon generation potential (S1 + S2) is range from 0.2 to 9.61 mg HC/g rock with an average of 4.6 mg HC/g rock, and organic matters of Types II1 and Type I, which indicated that it belongs to high-quality carbonate source rocks. Meanwhile, the Tmax of source rock range from 409 to 438°C and productivity index (PI) varied in the range of 0.09 to 0.38, which imply that the source rock in immaturity to low-maturity phase. The biomarker compositions are characterized by the Pr/Ph ratio of the source rocks is 0.36, and the gammacerane/αβ-C30 hopane ratio up to 1.25, these data reflect that the presence of a highly reducing saline environment. Meanwhile, a high abundance of C27 sterane and bicyclic terpane indicates that aquatic algae are the main organic parent material. The identification of microscopic organic components of samples also reveals an abundance of the Botryococcus braunii fossil of up to 30% with strong yellow fluorescence. These results, together with comparison research of crude oil and source rocks, show that the saline lacustrine carbonate source rocks from the Yingxi area deposited under an anoxic and saline environment at the stage of low maturity. This study provides guidance for predicting the distributions of high-quality source rocks in the western Qaidam basin. [ABSTRACT FROM AUTHOR]

This paper reports the results of numerical estimation of the degree of organic matter maturity and hydrocarbon generation in the rocks of the Bremer 1–6 formations during the burial of the sedimentary basin of the Mawson Sea on the passive margin of East Antarctica. Numerical simulation of basins was conduced for 15 areas along two profiles, 5903 and 5909, in the eastern and western parts of the Mawson Sea. The calculations revealed correlations between the yield of various hydrocarbon fractions and vitrinite reflectance in the supposed source rocks of the basin. Using these correlations, the generation characteristics of the rocks of the Bremer formations in the eastern and western Mawson Sea were compared. It was shown that the rocks of the Bremer 1–4 formations are mainly gas-prone in the eastern part of the basin, but could generate heavy and light oil in the western part of the basin. On the other hand, it was suggested on the basis of modeling that the rocks of the least buried Bremer formations (Bremer 5 and 6) produce mainly heavy oil in the western part of the Mawson Sea and light oil in its eastern part. [ABSTRACT FROM AUTHOR]

This paper analyzes differences in the history of hydrocarbon (HC) generation by the rocks of the Bremer 1-6 formations in adjacent areas of the nonvolcanic passive continental margins of Australia and Antarctica. The problem is examined by the example of the numerical reconstruction of the burial and thermal history of two sedimentary sequences of approximately equal thicknesses: the section of well 19-2012 in the Bremer sub-basin of the southwestern margin of Australia and the section of pseudowell 2 in the adjacent area of the passive margin of Antarctica on seismic profile 5909 across the Mawson Sea. The asymmetry of Gondwana rifting in the region of interest resulted in asymmetry in the tectonic structure and development of adjacent areas of passive margins and, as a consequence, significantly different histories of HC generation by the rocks of the Bremer 1-6 formations in these areas. Modeling indicates that the rocks of the Bremer 1 and 2 formations are mainly gas-prone in the Bremer basin and can become oil-prone in the Mawson Sea region of the Antarctic margin. In contrast, according to modeling, the rocks of the Bremer 4 and 5 formations generate a minor amount of HC in the well 19-2012 area of the Bremer sub-basin and considerable amounts of heavy and light oil in the adjacent Antarctic margin area at pseudowell 2 in the Mawson Sea. [ABSTRACT FROM AUTHOR]

The thermal history of the Sirt Basin and realization of its hydrocarbon potential were modeled using the GALO numerical simulation system and a refined database of temperatures measured at various depths, vitrinite reflectance, and detailed data on vertical sections of the basin. These models are more accurate than preexisting basin models, which were underlain by the assumption that the temperature gradient remained unchanging throughout the whole evolutionary history of the basin. The burial history, temperature variations, and the maturity of organic matter in the sedimentary rocks of major tectonic structures in the Sirt Basin were numerically simulated with regard for multiple tectonic (stretching) and thermal reactivation of the lithosphere beneath the basin. The modeling was conducted for eight seismic sections arranged along a profile trending from east to west, from the Cyrenaica Platform in the eastern flank of the basin to the Hun graben in its western flank. Along with the traditionally analyzed Sirt source rocks of Campanian age, we analyze the outlooks of hydrocarbon generation in the pre-Campanian rocks. Our modeling results suggest that organic matter (OM) of Lower Cretaceous rocks in the Hameimat, Ajdabiya, and Maradah troughs was highly mature when some hydrocarbons (HC) could decompose into gas and coke in the course of their secondary cracking. The rocks of the Upper Cretaceous formations (95-65 Ma), including the widely known source rocks of the Sirt Shale, Formation, can be viewed as intensely generating oil within all modeled areas of the basin, except only the Hun graben and the Zelten and Dahra platforms. [ABSTRACT FROM AUTHOR]

Burial history, temperature variations, and organic matter maturation in the sedimentary rocks in the Ghadames Basin were numerically reconstructed using the GALO system for basin modeling taking into account repeated tectonic (stretching) and thermal activation events in the basin lithosphere. The modeling improved the reconstruction of the thermal history of the basin and hydrocarbon generation potential compared with previous model estimates based on the assumption of a constant temperature gradient during the whole period of basin development. In particular, the results of modeling suggest that the amplitude of Cenozoic erosion was smaller than that proposed in previous studies. The central part of the Ghadames Basin, which was considered in this study, is the western part of the Libyan sector of the basin, which underwent intense subsidence reaching 4000 m already in the Carboniferous. Given the relatively active thermal history of the basin, the modeling suggests high degrees of organic maturity in the source rocks of the Lower Silurian in the modern section of the basin and confirms the high generation potential of liquid and gaseous hydrocarbons in these formations. Significant hydrocarbon generation has occurred there since the Late Carboniferous. On the other hand, the generation potential of the Late Devonian (Frasnian) sequences is limited and strongly dependent on burial depth. The main stage of hydrocarbon generation in these rocks coincided with the Cenozoic thermal activation of the basin lithosphere. In all the areas considered, the oil window overlaps a significant portion of the modern sedimentary section of the Ghadames Basin. [ABSTRACT FROM AUTHOR]

Temperature and catagenetic history of the South Sumatra Basin in Indonesia is considered by the example of the sedimentary sequence of the Limau graben during its subsidence from the Oligocene to the present time. GALO system for basin modeling was applied for numerical reconstruction of six sedimentary successions in the area of holes Pandan-81, Petanang-1, Tepus-2, Tepus-1, Gambir-1, and Lembak-8 located along the profile cutting across the Limau graben. Modeling suggests significant cooling of the basemen for the last 15-20 Ma from the high initial heat flow of 105 mW/m, which is typical of axial zones of continental rifting, and significant heating of the basin lithosphere during the last 2-5 Ma. Examination of variations in tectonic subsidence of the basin confirms the possible extension of the lithosphere in the Oligocene-Miocene with an amplitude β increasing from 1.12 on the flanks of the Limau graben (Hole Lembak-8) to 1.32 in the central part of the graben (Tepus-1 and 2), Tectonic analysis indicates also the notable thermal activation of the basin in the Pliocene, Pleistocene, and Holocene. This activation is consistent with the high temperature gradient typical of the present-day sedimentary cover of the basin. Numerical modeling of the evolution of the organic matter maturity and hydrocarbon generation by main source formations of the basin confirms good prospects of the inferred source formations (Lemat, Talang Akar, and Gumai) of the South Sumatra basin for the generation of liquid hydrocarbons (HC) in the Limau Graben. It is also demonstrated that the source rocks of the Lemat Formation are ore-generating rocks in the main part of the Limau graben and are gas-generating rocks only in the deepest portions of the graben. The rocks at the base and roof of the Talang Akar Formation could be considered as highly oil-generating rocks, probably except for the upper horizons of the formation in the shallowest portions of the graben (Hole Lembak-8). Oil generation reached peak in the last 5-10 Ma. Modeling showed that intense oil generation by the Gumai Formation may be significant in the most part of the Limau graben and negligible only in the distant flanks of the graben (Hole Lembak-8). [ABSTRACT FROM AUTHOR]

The history of burial, temperature variations, and organic maturation in the sedimentary rocks of the Murzuq Basin in southwestern Libya was numerically reconstructed for eight wells and one pseudowell along northeast-southwest and northwest-southeast profiles across the basin. The reconstruction was performed using the GALO system for basin modeling taking into account that the basin lithosphere underwent repeated tectonic and thermal activation. The modeling allowed us to refine the reconstructions of the thermal history of the basin and assessment of its hydrocarbon potential obtained by previous models, which assumed a constant temperature gradient during the whole period of basin development. The Murzuq Basin is characterized by moderate basement subsidence (2200-2800 m), which would have corresponded in an ordinary basin to immature or early mature organic matter. However, the history of the basin included several periods of extensive uplift and subsidence, which were accompanied by the erosion of the sedimentary cover and thermal activation of the lithosphere. This resulted in variations in organic matter maturity reached in different segments of the basin and a peculiar distribution of the degree of maturation, which is higher at the flanks of the Murzuq Basin compared with the same rocks from deeper buried zones. Our modeling indicated that the rocks of the Tanezzuft Formation could generate significant volumes of liquid hydrocarbons at some areas of the basin, but the situation is strongly dependent on the depth of rock burial and amplitude of erosion of the sedimentary cover at various areas of the basin. [ABSTRACT FROM AUTHOR]