ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00944.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Geological aspects of the cap‐rock problem were investigated on a worldwide scale in order to provide guide‐lines for assessing the sealing and retention risk in exploration ventures. The most common caprock lithologies are shales and evaporites, which have typical thicknesses of tens to hundreds of meters. Regional seals are often provided by evaporitic sabkha environments and transgressive and regressive shales. Cap‐rocks must be placed in the frame of a hydrocarbon habitat which evolves with time to judge properly the retention risk. Important parameters are rate of diffusion of hydrocarbons through cap‐rocks, and fracture development as a function of the intensity of geomechanical deformation. When losses due to seal failure and diflusion occur, replenishment from an active generation‐migration system may counter‐balance the loss. “Giant” oil‐ and gasfields serve as a yardstick for measuring shale—evaporite ratios and seal depths. Surface seepages can provide a measure of seal failure. As the cap‐rock problem is in an initial stage of research, many uncertainties affect the reliability of semi‐quantitative statements on risks o

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00945.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Petrographic and petrophysical studies were completed on cores from Atokan (Pennsylvanian) carbonate gas reservoirs at depths in excess of 4,000 m in theChapman Deepfield, Delaware Basin, Texas. Porosity concentration is in pure carbonate microfaciesof Donezellaalgal mound, upper inner slope, oolitic shoal and lagoon of a platform depositional model, which are characterized by sutured, medium‐ to high‐amplitude stylolites. The porosity is predominantly stylolitic, enlarged and surrounded by halos of oomoldic, biomoldic, cement‐moldic and vuggy types. Non‐sutured, low‐amplitude stylolites, confined to argillaceous carbonate microfacies, have no influence on porosity development.The distribution of sutured stylolitization, being microfacies‐controlled, allows the use of a depositional model as a prediction tool for locating reservoir microfacies. Under deep‐burial conditions, sutured stylolite systems are of critical importance. They permit circulation of undersaturated fluids, become themselves reservoirs together with associated types of secondary porosity, and therefore allow deep commercial g

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00946.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Lithostratigraphic interpretations are here presented of a carbonate body which rims the exposed basement on the SE hinge zone of the Niger delta, and which thickens to over 450 m on a nearby subsurface basement horst. This faulted margin, which is known as the Calabar Flank, was occupied by carboqate platforms similar to those in the Gabon and Angola Basins, during the pronounced South Atlantic Albian transgression. Stromatolitic, oncolitic/pisolitic, oolitic and fossiliferous coralline algal lithofacies are well displayed both in outcrop and in the subsuface of the carbonate body (the Mfamosing Limestone). These lithofacies suggest a facies progression from tidal flats, through restricted marine bays and lagoons to a possible reef front, with ooid bars and encrusting and ramose coralline algae. In the subsurface, the Mfamosing Limestone, which is gas‐bearing and oil‐impregnated, exhibits fair to good porosities in which calcarenitic bars and chalkiped lagoonal, calcarenitic and extensively dolomitized limestones are the potential reservo

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00947.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The lithostratigraphy and petrography of the Ras Malaab Group were investigated in order to define the physiography and structure of the depositional basin. The Ras Malaab Group consists, from the top, of the Zeit, South Gharib and Belayim Formations.The basal Belayim Formation consists of carbonate barrier (reefal, lagoonal and marine tidal‐flat carbonates, located from east to west respectively in the basin. Thus. reefal limestones and evaporites are associated within the succession of the Belayim Formation.The overlying South Gharib Formation is composed of thick evaporite sediments that were deposited in a restricted, subsiding salina basin. Intense subsidence in the western part of the basin is related to faulting.The Zeit Formation consists of evaporites and fine clastics derived from surrounding land‐masses. The Zeit sequence indicates relatively deeper, semi‐restricted, lagoonal condi

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00948.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

A study of microfossils contained in the hydrocarbon fluids derived from four oil‐ and gas‐bearing formations in Western Siberia (of Paleozoic, Jurassic, Neocomian and Albian—Cenomanian ages) has shown the importance of processes of vertical migration in local hydrocarbon accumulations. These processes were found to be concentrated in regions of geological disturbance or intense fracturing of the reservoir

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00949.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The hydrocarbons accumulated in the Huanghua Basin, China, show a remarkably complete evolutionary pattern, from immature heavy oils to highly‐mature condensates, and from biogenic to dry gases. This paper presents GC, GC/MS and IR analytical data for n‐alkanes, branched alkanes, steranes and terpanes; and data concerning the physical and chemical properties of these oils and gases, and their carbon isotopic compositi

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00950.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Eight clastic and carbonate lithofacies of Lower and Middle Jurassic age (the Marrat and Dhruma Formations respectively) have been identified. These lithofacies are mainly shales, shales‐and‐siltstones, siltstones‐and‐shales, sandstones, argillaceous limestones, calcarenitic limestones, calcarenites and dolomites. Intraclasts, pellets, oolites, gypsum, algae, and coral reefs were also found to be dominant among these lithofacies. Furthermore, these beds contained either restricted or diversifed biota, with a few sedimentary structures such as lamination, cross‐bedding and common bioturbation. Thus, it is presumed that the Lower and Middle Jurassic rocks in Central Saudi Arabia were deposited in very shallow (i.e. tidal flat and lagoon), shallow‐neritic, and deep‐marine conditions of the Tethys Sea.During Toarcian (Lower Jurassic) time, the Tethys Sea extended towards Arabia, forming an arcuate shoreline around the Pre‐Jurassic sediments. The greater part of the Arabian Peninsula was under very shallow marine (Tethys) water as is shown by the presence of tidal‐flat and lagoon deposits in northern Oman, Rub al‐Khali, parts of the Aden Protectorate and Yemen, central, eastern and NNW Saudi Arabia, the northern edge of Sinai, NW Jordan, Lebanon, central and northern Syria, and west, central and eastern Iraq and Iran (Fig. 5). On the other hand, east and north of this area, very shallow marine deposits overlaid the shallow‐neritic Tethys deposits.Further expansion of the Tethys Sea transgression occurred during Bajocian‐Bathonian (Middle Jurassic) time, when major parts of the Arabian Peninsula and its neighbouring regions were submerged below shallow‐neritic and deepmarine Tethys conditions (Fig. 6). During this time, shallow‐nentic Tethys conditions extended to include the Oman Mountains, as far west as western Rub al‐Khali, north to include Central Saudi Arabia, running through parts of its northern area and passing under the Saudi Arabia‐Iraq Neutral Zone and reaching SW Iraq, turning west to include part of the area of NW Arabia and reaching NW Jordan. Northern Oman, most of central Rub al‐Khali, eastern Saudi Arabia, western Iran, central and eastern Iraq, and eastern and northern Jordan, were covered by deepmarine Tethys waters (F&. 6). However, simultaneously, SW Arabia, Yemen and the Aden Protectorate display a marked continuous sedimentation of continental and neritic conditions, as neritic

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00951.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00952.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00954.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY