摘要:

Source‐rock richness, timing of hydrocarbon generation, and thicknesses of potential source shales of the Upper Jurassic/Lower Cretaceous section of the Australian NW Shelf have been examined in order to make predictions as to the hydrocarbon productive of liquid hydrocarbons: the Brows Basin, the Malita Graben/NW Bonaparte Gulf Basin, the Rowley Sub‐basin, and the Vulcan Sub‐basin/Sahul Syncline, respectively.Recent liquid hydrocarbon discorveries in the Vulcan Sub‐basin, probably source by the Upper Jurassic shales, upgrade all four of these areas, and lead to the conclusion that overall, drilling results on the NW Shelf have to date not been indicative the timing of generation as delineated in this study with the timing of structural development in order to improve chances of success, rather than relying on the size of Structures alone.A new method of presenting timing of generation, in the form of a “timing‐of‐generation map”, is introduced, where the timing of the progress of significant hydrocarbon generation is contoured over the NW Shelf for each sour

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1988.tb00808.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Lower Permian palaeoaplysinid build‐ups, inter‐bedded with inter‐build‐up logoonal sediments occur both on Bjornoya † and in the subsurface of the Barents Sea. They formed on a low‐energy, broad and shallow shelf, and show a cyclic development which was probably related to minor eustic sea‐level changes. During periodic lowering of sea level, build‐ups were subaerially exposed, meteoric diagenesis with Karstification took place within the build‐ups, and hypersaline conditions prevailed in the lagoons.Most diagenetic changes took place early and include fresh‐water dissolution, dolomitization, evaporite precipitation, and pseudomorphic replacement of evaporites. Fracturing and associated hydrothermal calcite, barite and galena cementation occured during the Early Tertiary opening of the Norwegain‐Greenland Sea, and affected the entire western part of the Barents Shelf.In the Barents Sea, the palaeoplysinid build‐ups have composite thickness on the order of several hundred metres and are restricted to positive structural elements. They are regarded as potential reservior rocks in this area, partly because of the high porosity of similar build‐ups in Central Spitsbergen. The reservoir quality of the build‐ups on Bjornoya and from the single cored build‐up complex in the Barents Sea is, however, relatively poor. Early Tertiary fracturing increased the permeability of the bulk rock, but also caused leakag

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1988.tb00809.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The tectonic‐sedimentary evolution of SW and central Somalia is characterized by two main depositional cycles. The first cycle (Triassic to Early Cretaceous) is characterized by subsiding basins related to a process of crustal thinning, and is associated with the separation of Madagascar from Africa, between 165 and 121 Ma*. The second cycle, starting in the Late Cretaceous with a regional unconformity, is related to the separation and NEward drift of India, at approximately 80 Ma. The folds that affect the Jurassic and Early Cretaceous formations of the Lugh‐Mandera basin in SW Somalia are the result of a compressive phase connected with dextral transcurrent movements along NE‐S W trending fracture zones. These zones are developed parallel to the oceanic system of transform faults, in connection with the change in the stress regime intervening at the shift of the direction of spreading between the first and the second stages of evolution of the Indian

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1988.tb00810.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Source‐rock quality and organic matter maturity of coals and sediments from several Tanzanian Karoo basins (Permian‐Triassic) have been evaluated by microscopic, pyrolytic and geochemical methods. The intracratonic Ruhuhu Basin (SW Tanzania) differs from two peripheral cratogene basins (Mikumi and Rufiji) with respect to the composition of organic matter, thermal evolution and probable hydrocarbon generation in a tensional tectonic stress field of the East African craton at the Palaeozoic/Mesozoic boundary.The Lower Permian sediments and coals and the Upper Permian sediments of the Ruhuhu Basin exhibit moderate source‐rock properties. They were not subjected to significant subsidence and are moderately mature source rocks. They possibly experienced temperatures in the range 60–110d̀ and vitrinite reflectance values of 0.5—0.8 were attained, thus placing them within the “oil window”. Kerogen Type III is typical for all the basins, and productivity indices indicate moderate to advanced stages of evolution.The coastal basins differ in most parameters. The sediments do not have source‐rock properties. High vitrinite reflectance values (1.0–2.0%) imply a higher degree of thermal maturation, and geochemical results confirm that organic matter in these sediments is postmature, and that hydrocarbon generation, if it occurred at all, ceased some time ago. The assumption of a stable geothermal gradient from Late Palaeozoic to recent times, combined with field observations, leads to the conclusion that no significant overburden has covered the Ruhuhu Basin. A mean subsidence of 1, 5OO‐3,000 m, depending on basin type and stratigraphic position, seems realistic, and this overburden is provided by the sediments of the “younger Karoo cycle” (Triassic). No post‐Karoo sedimentary cover was deposited in the Ruhuhu Basin. Migration probably occurred in Jurassic times, shortly after the end of the Karoo sedimentary cycle, and it is presumed that no significant tectonic activity during the Cenozoic affected pre‐existing accumulations. The chances that commercial volumes of hydrocarbons (mainly

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1988.tb00811.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Coal‐rank measurements and heat‐flow data from three rhomb‐shaped grabens along the continental portion of the Dead Sea Transform—the Hula Depression, the Sea of Galilee and the Dead Sea Graben—reveal contrasting thermal regimes. The coalification profile the Hula Depression indicates a relatively high thermal gradient, averaging 40d̀C/km, throughout the Late Cenozoic. Similarly, a relatively high heat flow, approx 1.77 HFU, was reported in the Sea of Galilee, 35 km to the south. Coalfieation profile, heat flow data and BHT measurements on the Dead Sea Graben (200 km to the south) reveal a considerably lower thermal regime (approx 0.7 HFU, 2Od̀C/km) that has prevailed since the mid‐Miocene.However, the differences in the thermal regime do not represent different mechanisms of basin formation. With the corroboration of hydrological and geophysical data, it is suggested that the high thermal regime in the two northern basins reflects a regional phenomenon associated with the nearby extensive Golan‐Jeble Druze young volcanic terrain. Therefore, it has no relationship to the mechanism of rhomb‐shaped graben formation, and should not be cited in support of kinematic models requiring a hi

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1988.tb00812.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The attention paid to rock fracturing in recent years is a result of the discovery of large volumes of hydrocarbons in fractured rock reservoirs. This regional study was conducted in order to facilitate a better understanding of the performance of fractured reservoirs, and to select the proper procedures and well intervals for artificial fracturing.Five classification schemes are proposed for fracture, breccia, porosity and permeability developments, as revealed by mega‐ and microscopic examination of cores, thin‐sections and outcrop samples. A composite classification combines the attributes of the other schemes in an attempt to predict residual porosity and permeability on a reservoir scale. Various genetic types of breccia were encountered in this study, but those of tectonic origin predominate and control hydrocarbon production.At the initial time of fracturing, porosities range from low in crackle breccia, to very high in random and pheno‐breccias. With moderate cementation, random and pheno‐breccias remain the most porous and permeable structures, However, with a high degree of cementation, porosity and permeability become negligible in crackle breccia, and very low or absent in pheno‐breccia. The degree of cementation which controls residual porosity depends on the availability of mineral‐lade

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1988.tb00813.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The high degree of thermal maturity observed in shallow sediments in the western part of the Sirte Basin, Libya, requires higher geothermal gradients and/or thicker overburden in the past than exist today.The degree of thermal maturity of the Upper Cretaceous shales, the regional structure, and the subsidence history of the basin all indicate that over 3,000 m of section was removed from the western flank of the basin by uplift and erosion in the mid‐Tertiary. Vitrinite reflectance values in wells suggest that gradients of 1.6d̀FC/100 ft to 1.8d̀FC/100 ft existed in the western region at the time of peak thermal activity, in contrast with a general basin average of 1.2 d̀F/

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1988.tb00814.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The region under discussion is that part of Indochina which includes Vietnam, Laos, Kampuchea and eastern Thailand. The Kontum Massif composed of a metamorphosed basement complex, is the core of the Indochina region, and crops out from eastern Vietnam to Laos and Kampuchea. The concept of concentric growth of orogenic belts along the periphery of this massif seems to have been accepted as being within the scope of the classic theory of orogeny. The application of a modem plate‐tectonic hypothesis with the aid of Landsat image analysis, has, however, enabled a new interpretation of the tectonic development of the area to be made.The hydrocarbon potential of Indochina is here investigated, based on this interpretation of the region's tectonic development, and taking account of the morphological and textural characteristics detected from Landsat imagery. Three areas: (1) the Mekong Delta. (2) the Khorat Plateau, and (3) the Hanoi Basin‐gulf of Tonkin, are selected for detailed discussion of their hydrocarbon potent

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1988.tb00815.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1988.tb00816.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Book reviewed in this article:“At the time of writing, v e y significant shows of gas have been detected on the way down at depths below three kilometres in the granite making clear that gas is indeed streaming up through the broken rock”.“Slowly, I came to understand that all these belifs had arisen in reverse. The presence of large petroleum deposits had merely suggested that the, province must have been favoured in these ways. As for actual documentation, there was nothing that indicated these enormously favourable circumstances”“Power from the Earth”: by T Gold.“Future petroleum provinces of the world': edited by M.T. Halbouty.“World sedimentary basins map”: 1st edition,Petroleum Operations in Nigeria”, by T. Oremade.“Deposits of oil and natural gas in Central Europe”, by D. Durica et a1”The oil and gas directory, 1987‐88”.“Reservoir characterfzation”, edi

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1988.tb00817.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY