ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1991.tb00294.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Six basinal elements have been recognized in the Baluchistan Basin on the basis of plate‐tectonic considerations. The Makran forms part of the southernmost coastal accretionary fore‐arc basin, where a more than six‐kms thick, relatively undeformed succession of neritic sediment overlies the turbidites. A reported oil seepage in the north, several gas seepages along the coast, abundant “bright spots” in the seismic profiles offshore, and the occurrence of hydrocarbons in similar geologic settings elsewhere, all support the recently‐emerging impression amongst the petroleum geologists involved in the area that the Makran region may provide a uniquely instructive setting in which to study petroleum occurrence in cool basin environments.Results of recent stratigraphic, sedimentological, tectonic and organicgeochemical studies in the Makran area are presented in this paper, in order better to understand the petroleum geology of the region and its implications for hydrocarbon ac

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1991.tb00295.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Using an inversion technique, we show that pollen translucency with depth can be used as a quantitative tool to estimate the thermal history of sedimentary sequences. The overall trend of translucency is a decrease with increasing depth.In this study, three wells in southern Louisiana were examined, each havingCarya (a pollen genus including present‐day Pecans and Hickories) translucency measurements with depth, and one of the wells containing measurements of vitrinite reflectance with depth. High sedimentation rates (>250 ft/MM yrs of shale) require the use of a fluid flow/compaction burial history program linked with theCaryainversion algorithm. Thermal history is estimated by the interaction of a heat flux taken to be linear in time, and a time‐temperature integral for the inversion ofCaryatranslucency. The former involves β, a linear heat‐flux coefficient to be determined, while the latter involves two previously unknown constants: TC, a critical temperature, below which the translucency is stable (no carbonization), and TD,a scaling constant, roughly analogous to a doubling temperature. TDand Tcare chemical constants, and should be consistent in the three wells, while β should be consistent when determined independently by vitrinite reflectance andCaryatranslucency inversions. Grid searches for an acceptable solution in TCvs.TDvs. βspace were carried out for each of the three wells to determine the best TDTCand β for each well. A goodness‐of‐fit criterion, contoured in TDvs.TCvs. βspace, defines a volume of solutions within fixed error limits. Estimates of TD= 75 ± 30°K and TC= 290 + 20°K, for the genusCarya,are consistent for all of the wells. Acceptable β ranges, determined by theCaryainversion, overlap for the neighbouring wells. and the ranges are also consistent with β determined by the independent inversion of vitrinite reflectance in one of the wells.We conclude thatCaryatranslucency can be used as a quantitative thermal indicator. Application of the inverse method to translucency measurements on other palynomorphs having longer. or different, age ranges than the Eocene‐Recent lifetime f

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1991.tb00296.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Primary oil migration from a source rock has been simulated using a computer. The simulation model is based on a finite difference solution of one‐dimensional fluid‐flow differential equations. Oil generation is simulated by the time‐temperature index. Shale porosity is reduced by compaction. Oil saturation rises as organic matter is conversed to oil, and the source‐rock porosity decreases during burial. When oil saturation reaches an irreducible level, surplus oil is expelled by capillary and excess pore fluid pressure.The model is applied to an actual case. Oil generation and migration from a possible source rock in Kuwait is simulated. A reasonable estimate of the time of oil expulsion is obtained. even though values of several parameters had to be assumed. The results confirm the validity of the model and point to the possible use of such computer simulation models in oil expl

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1991.tb00297.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The results are outlined of a detailed sedimentological study made of the Jurassic succession presented in northern Egypt at surface and in the subsurface, largely on the basis of material from over 80 wells. With the benefit of a detailed stratigraphical scheme, it has become possible to map the distribution of fluvio‐deltaic, shelf and open‐marine facies belts. Changes in distribution of facies are attributed to the eustatic interaction between Nubian and Tethyan influences, and to the repeated movement of local faults. Active basins are identified on the basis of static facies. and stacked thick sequences. The pattern of syn‐depositional tectonic activity thus assembled is compatible with existing tectonic models for the Eastern Mediterranean region: indeed, it is used to improve them. The present continental margin to Egypt is shown to have formed during a period of westward‐propagating crustal rifting, over the late Pliensbachian‐Bathonian interval. Evidence is presented for a link between movements within the central/southern African craton, and the sequence of extensional and transtensional activity observed in Egypt during the Jurassic and the “Cimmerian” event. Faults accommodating this strain were mostly orientated NE‐SW, that is, contiguous with t

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1991.tb00298.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Carboniferous successions may have hydrocarbon source‐rock potential in several districts of Northern Ireland. They have been buried to depths required for hydrocarbon generation beneath younger Carboniferous rocks in the west, and beneath Permo‐Triassic basins in the east. Samples of coals and shales collected from outcrop and boreholes have been less‐deeply buried and are consequently less mature, but upon pyrolysis give good hydrocarbon yielak, which suggests that hydrocarbon generation is likely to have occurred in the basinal districts. Carboniferous rocks in the west, and in adjacent parts of the Republic of Ireland, include numerous shows of solid bitumen, which represent degraded oil residues. However, the coaly nature of much of the carbonaceous sediment suggests that the predominant hydrocarbon product would probably b

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1991.tb00299.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The role played since the Early Jurassic by the Marda Fault Zone (MFZ) in the geodynamic evolution of the Horn of Africa is examined. Three main stages of evolution have been recognized: (a) a Tethyan stage (Jurassic/Early Cretaceous): (b) an Indian stage (Late Cretaceous/Eocene); and (c) an Arabian stage (Oligo‐Miocene/Resent).During the Tethyan stage (which is characterized by the distribution of fauna with a Tethyan affinity), the MFZ probably acted as a major deep‐ rooted transfer fault, connecting overstepping segments of en‐éhelon east‐west strike‐slip faults. Crustal stretching, caused by the southwards drift of Madagascar, was active in the SW region of the Horn of Africa. but was relatively negligible in the NE region.During the Indian stage (involving the NEwards drift of India), the MFZ was still aligned, in the Late Cretaceous, with the paleo‐margins of the Red Sea — bgore the rotation of Arabia away from Africa — and with the oceanic spreading ridges developed in the Mascarene Basin of the Indian Ocean. It was in this stage that the MFZ is interpreted as having acted as an incipient aborted rift, causing the rapid subsidence of the NE region of the Horn of Africa, and consequently the onset of a new depositional cycle.During the Arabian stage (separation of Arabia from Africa), there was a sudden change in the geodynamics of the Horn of Africa: crustal stretching of the Red Sea — Gulf of Aden —Ethiopian Rift Valley triple junction occurred, leaving the segment of the MFZ in the Horn of Africa inactive.These three stages correspond with three important tectonic changes in the Indian Ocean and the Western

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1991.tb00300.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The Sirte Basin of Libya has a history of faulting and differential subsidence brought about by lithospheric extension during a 25 MM (million) year period beginning in the Late Cretaceous. The first phase of extension and initial subsidence, with faulting and graben formation, occurred from Cenomanian to Campanian times. Following extension. there occurred widespread thermally‐driven subsidence from Maastrichtian through Eocene and Oligocene times, accounting for about half of the total subsidence.Details of basin subsidence, sediment accumulation rates. and facies variations have been reconstructed for the northern Sirte Basin from a suite of approximately 100 completion well logs and numerous seismic lines. These show that at various times in the Late Cretaceous and Paleocene‐Eocene, renewed differential subsidence followed fault reactivation. Tectonic subsidence maps show a sysrematic SE to NW shift in the loci of maximum and minimum subsidence, which parallels the structural trend of the basin. The greatest subsidence observed in the Sirte Trough is 2,085 meters, whereas subsidence of the horsts is generally less than 1,000 meters.The stretching factor (β: in the range of 1.1 to 1.75). corresponds to an extension of 10–75%. with an average of less than 50%. The greatest stretching is associated with the central

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1991.tb00301.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1991.tb00302.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1991.tb00303.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY