ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1986.tb00387.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Subsurface geothermal gradients play a significant role in oil exploration. Based on a synthesis of bottom‐hole temperatures recorded in electric logs from 74 exploratory and development wells in various parts of Pakistan, a study of geothermal gradients was undertaken to delineate the temperature regimes and to identify the oil window in various areas. Case‐histories of known accumulations are given to substantiate the results. The first‐ever iso‐geothermal gradient map of Pakistan is presented. A regional correlation of the oil window, superimposed with stratigraphy, is attempted for the first time, providing a unique exploration tool. Several indications, based on geothermal gradients, are given for the regional prospects of oil

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1986.tb00388.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

An investigation of the maturity levels of organic matter in the major potential Jurassic hydrocarbon source rock units in Southern England (i.e. the Lower Lias, Oxford Clay and Kimmeridge Clay) using sporomorph colouration and alkane distribution patterns shows that the Oxford Clay and the Kimmeridge Clay organic materials are immature in most parts of the area. They are mature only in the central parts of the Mesozoic Wealden Basin.The distribution of mature Lower Lias sections is found to be more extensive. Attempted reconstruction of the burial histories of Jurassic sections across Southern England, and the application of the Lopatin method of theoretical organic maturity prediction, seem to support the observed maturity trends and suggest that the present maturity levels of Jurassic organic matter at any given locality are dependent on the structural development of that area through time.

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1986.tb00389.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

A clastic dominated Lower‐Middle Jurassic sequence, known as the Shemshak Formation, is extensively exposed in the Eastern Alborz area, NE Iran. The unit represents a deltaic complex sandwiched between carbonate rocks. Sedimentological study of the formation outcrops has revealed that it was deposited in environments ranging from subaerial to subaqueous delta plains.Potential source, reservoir and cap rocks are present within the Shemshak Formation; under favourable conditions, generation and accumulation of hydrocarbons in significant quantities can be envisaged. It is suggested that the Shemshak delta, buried under the thick Neogene sediments in the Eastern Alborz area, is a highly prospective exploration target with potential for a multipay sectio

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1986.tb00390.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The mineralogical composition of the Miocene Gharandal group has been studied petrographically, and has been confirmed by chemical analyses and Differential Thermal and X‐Ray Diffraction analyses (DTA andXRDA). These investigations have been supplemented by geological mapping, which has revealed the geological setting and paleoenvironmental conditions of the Lower Miocene Gharandal group at the South Bakroilfield.The lithic association of the Nukhul and Rudeis formations indicates that deposition took place in a shallow‐marine environment in the sublittoral zone. The mineral association of the rocks of the Kareem Formation suggests a semirestricted environment, where the chemical conditions changed from weakly‐oxidising to slightly reducing during the deposition of these sediments. The lithic association of the rocks of the Kareem Formation indicates that their deposition occurred in a barred basin. The basin was affected by gentle subsidence, which might be associated with post Early Miocene growth‐faulting in its western section.The rocks of the Gharandal group represent the lower section of an evaporite cycle of deposition.The structure and variation of the thickness and facies has led the Authors to present some deductions concerning the paleoenvironmental conditions under which the investigated rocks were

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1986.tb00391.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

In this paper, we report on Soxhlet extraction (and subsequent related analyses) of 39 Lower Mississippian‐Upper Devonian Bakken shales from the North Dakota portion of the Williston Basin, and analyses of 28 oils from the Basin. Because of the influence of primary petroleum migration, no increase in the relative or absolute concentrations of hydrocarbons or bitumen was observed at the threshold of intense hydrocarbon generation (TIHG), or during mainstage hydrocarbon generation in the Bakken shales. Thus, the maturation indices that have been so useful in delineating the TIHG and mainstage hydrocarbon generation in other studies were of no use in this study, where these events could clearly be identified only by Rock‐Eva1pyrolysis data.The type of primary petroleum migration operative in the Bakken shales led to the selective concentration of certain compound types in the oils of the basin, as well as the selective concentration of certain compound types in the shale extracts. The compositional differences between the crude oils and shale extracts provide evidence of the primary migration mechanism operative in this case, which is believed to have been gaseous solution, although the actual expulsion of oil from the rock, if observed, would probably have appeared to be bulk phase migration. Gaseous‐solution bulk‐phase primary petroleum migration also left organic‐geochemical imprints on the Bakken shales, observable by Soxhlet extraction and to a lesser extent by pyrolysis. The data of this study demonstrate that primary petroleum migration is a very efficient process.Four distinctive classes of saturated hydrocarbon gas chromatograms from the Bakken shales arose from facies, maturation, and primary migration controls. As a consequence of maturation, the percentage of saturated hydrocarbons increased in the shale extract at the expense of decreases in the resins and asphaltenes. Measurements involving resins and asphaltenes appear to be excellent maturation indices in the Bakken shales. Two different and distinct organic facies were present in immature Bakken shales.Rock‐Evalpyrolysis analysis was a critical research tool in this study; however, combined use of pyrolysis and Soxhlet extraction allowed organic‐geochemical features to be distinguished which would not have been possible by using either a

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1986.tb00392.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Devonian dolomites are described, in which broken grains and internal crystal silts are associated with stylolites and pressure‐solution seams. These features are interpreted as resulting from a progressive mechanical collapse, following dissolution of anhydrite. The transfer of loading by failure within the rock unit was responsible for stress concentrations, which led to the initiation of the stylolites with fluids driven out by compaction. The evidence suggests occlusion of a formerly extensive, vuggy, porosit

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1986.tb00393.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1986.tb00394.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1986.tb00395.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1986.tb00396.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY