摘要:

The Golden Lane oilfields of Mexico will always hold a place of prominence in the annals of petroleum geology. The most prolific oil‐well ever drilled, Cerro Azul No. 4, was one of a string of wildcats which defined a Cretaceous carbonate ridge that lay buried below gently‐dipping Neogene clastics on the Tampico coastal plain. Continued drilling showed that the buried ridge had an arcuate shape, and this led to the interpretation that the feature was a Lower Cretaceous reef. When the Poza Rica “giant” was discovered in detrital Cretaceous limestones west of the ridge, these were naturally considered to be forereef talus. Later drilling offshore discovered another string of Cretaceous carbonate traps which joined the onshore fields to complete the circlet that became renowned as the “Golden Lane atoll.”An abundance of rudists in Cretaceous reservoirs of the Golden Lane and Poza Rica gave rise to the concept of the rudist reef build‐up. A presumed analogue for the rudist reef of the Golden Lane was discovered in Lower Cretaceous rudistid limestones exposed at Sierra El Abra, NW of the oilfields. The foregoing interpretation has become entrenched in geological literature, even though an integrated structural‐stratigraphic synthesis of the Golden Lane is lacking.Time‐stratigraphic control of Cretaceous formations in the Tampico embayment is complicated by scarcity of documented marker fossils, and confused by the common occurrence of reworked detritus. It is ussumed herein that Cretaceous volcanicity in the Tampico embayment, as in the Gulf of Mexico generally, commenced in the Late Cenomanian. From this, it is concluded that much of the Golden Lane and Poza Rica reservoir sequences in which bentonite layers occur are of Late Cretaceous age. The El Abra outcrops, on the other hand, are undoubtedly Early Cretaceous. Structural analyses show that the Golden Lane area has an active and complex structural history. Strong faulting along NE‐SW trends was active in Late Cretaceous time, giving rise to syntectonic débris flows. At the same time, a major positive feature developed to the east in the Gulf of Mexico.By Middle Eocene time, the Gurf of Mexico positive was stripped‐down to metaphoric basement and subsequently collapsed as regional extension sundered the basement and allowed the injection of oceanic crust. A salt basin formed during the Oligocene eustatic low‐stand. Cretaceous carbonates of the Golden Lane were incorporated in a westward‐plunging synform in pre‐Oligocene time, but thereafter were rotated by regional downwarping into the Gurf of Mexico. In Holocene time, the synform was inverted, and these latest stresses were accompanied by injection of numerous dykes and plugs that cut the Golden Lane.From, this structural and stratigraphic synthesis, it is concluded that the Golden Lane anomaly is the product of a complex sequence of post‐Lower Cretaceous structural events. It is bounded on the west by a buried Middle Eocene fault, and on the east by a Neogene growth fault, and is not a Lower

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00994.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Subaerial, and in some case submarine, erosional processes sometimes leave a depositional surface which is not plane. During any subsequent transgression and sedimentation, remnant relief on the old surface may be preserved, particularly where depositional rates during the early period of the transgression are high, and the environment energy of deposition is relatively low. As well as in circumstances involving normal clatic sediments, similar situtions can arise in the inundation of a volcanic surface including relief features like vents, fissures and mounds, or of a karstified surface‐carbonate unit.Apparent, or “false” buried topography can be produced by a wide range of geological processes. The difference between such features and those of true buried topography is that at the time of transgression, the latter formed part of the contempory Earth surface, whilst in the case of the false features, the surface at which they were formed was already buried beneath varying depths of sediment.Attention has been directed in recent years to the potential importance of buried topographic features in hydrocarbon exploration. From this viewpoint, the difference between true and false features of this type may be trivial in some cases, but important in others, usually because of the details of the sedimentological processes inv

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00995.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The Porcupine Seabight appears to have been formed in three distinct episodes, each reflecting somewhat different structural controls. The oldest episode was rifting and selective crustal thinning associated with Permo‐Triassic taphrogenes, during which there was some dextral movement on NW‐trending faults. The important second episode was probably Mid‐Jurassic to Mid‐Cretaceous, and involved major crustal thinning related to nearby oceanic crust spreading, which initially reactivated and exploited structures in the continental crust while later imposing structural trends more related to the newly‐developing oceanic crust rift‐transform orientations. The last significant phase was one of minor adjustment, mainly by normal faulting of a down‐to‐basin character. Later, minor compression with some folding associated with reactivation along structural lines took place during Tertiary, probably Alpine times, but did not much affect the pattern of sedimentation within the Porcupine Seabight.A speculative model as to the character of sediments and local sediment distribution related to the structural episo

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00996.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Despite suggestions by some workers that most, if not all, the calcium sulphate in natural evaporites was originally deposited as gypsum, controversy concerning the origin of anhydrite has arisen, both because bedded anhydrite is common throughout much of the geologic record, and also as a result of the discovery of the recent anhydrite formations in the UAE, Persian/Arabian Gulf, and other areas. In addition, an inability to synthesize anhydrite in the laboratory under geologically reasonable conditions has caused the reliability of previous experimental methods to be doubted. However, new evidence from studies of chemical kinetics indicates that supersaturation and surface energies in the CaSO4— H2O system may regulate primary anhydrite precipitation. Arguments for and against the universality of gypsum as the sole origin of anhydrite are here related to specific facts and relevant observations from the fields of petrology, geology, and geochemistr

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00997.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Reliable estimates of the oil and gas potentials of frontier areas can be made by combining statistical analyses of petroleum data from well‐explored basins world‐wide with models of hydrocarbon‐generation processes. The combined techniques, together with the data collected, have to be guided by a systematic approach in order to produce statistically‐regular results.The hydrocarbon‐generation models here proposed express geochemical factors and organic matter maturity in terms of available geological parameters (lithology, depth‐distribution and age of rocks, heat‐activation temperatures, etc.). This type of model is applicable to both poorly‐explored and well‐explored basins. The study of the correlation of yield with each geological parameter leads to the expression of hydrocarbon‐generating processes by a set of multiple‐regression models which are of increasing complexity and accuracy, ranging from a simple bulk‐statistical model for unexplored basins, to a sophisticated non‐linear genetic‐statistical model for well‐explored basins.The coefficient of variation associated with each model allows calculation of the confidence interval for estimates of ultimate petroleum potential in terms of physical probability, and is more reliable than the conventional Monte‐Carlo technique.Based on the same world‐wide petroleum statistics, non‐linear predictive models for the gas/oil ratio and risk exploration factor for unexplored basins have been constructed. The technique of genetic‐statistical modelling (GSM) has then been applied to some well‐explored basins, on the assumption that only early exploration information was available. All the results obtained agree well with later assessments, based

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00998.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Mineralogical and chemical studies have been made of shale cuttings from the Akiri‐1 well in Oligocene — Miocene sediments of the Niger Delta. The<2μm fraction from the 2,183 to 3,720m stratigraphic interval was analyzed by X‐ray diffraction. Kaolinite and chlorite are more abundant than other clay minerals. The illiteh mectite composition changes from a phase with 32% illite layers, to one with 82% illite layers over the 3,250 to 3,720m stratigraphic interval. Kaolinite decreased in shallow shales from 22 to 16% and increases to 29% in deep shales. Quartz increases in abundance with depth, while chlorite and plagioclase feldspar show no systematic trend with depth. Calcite is present in small amounts in all the samples.Variations in the bulk chemical composition of true shale with depth only show significant changes in the K2O and Fe2O3content: other major chemical constituents show no systematic variations. The potassium appears to be derived from the pore water. The loss of smectite and abundance of Fe coincided with hydrocarbon occurrence. On the basis of the apparent systematic transformation of smectites to illites through mixed layers, the illite/smectite reference interval in the subsurface has been established: this interval coincided with hydrocarbon occurrence.Mineralogical and chemical changes observed are dependent on the pore system chemistry, the temperature, and possibly compaction e

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00999.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.tb01000.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Book reviewed in this article:“USSR Energy Atlas”, compiled by the US Central Intelligence Agency.“Atlas of selected oil and gas reservoir rocks from North America”, by E.J. Biederman Jr.“International Petroleum Encyclopedia 1986”.“Oil and gas directory: 1986–87”.“Oil and Gas Journal Databook: 1986”.“An introduction to carbonate sediments and rocks”, by T.P. Scoffin.“Petroleum geochemistry and source‐rock potential of carbonate r

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb01001.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.tb01002.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY