bluuebunny/crossref_metadata_2025_split huggingface dataset:
ORGANIC METAMORPHISM IN THE LOWER MISSISSIPPIAN‐UPPER DEVONIAN BAKKEN SHALES — II: SOXHLET EXTRACTION1
Authors: Price Leigh C. , Ging Tom , Love Alonza , Anders Don 
Published: December 2007

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‐Eva1 pyrolysis 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‐Eval pyrolysis 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 analysis alone.
OIL AND GAS ACCUMULATIONS AND THEIR POSSIBLE SOURCE ROCKS IN SOUTHERN ENGLAND
Authors: Ebukanson E. J. , Kinghorn R. R. F. 
Published: December 2007

A number of commercial hydrocarbon accumulations, which include oil and gas, are now known in southern England. Investigations into the organic maturity and hydrocarbon potentials of sedimentary rocks in the area suggest that the Jurassic Lias, Oxford Clay and Kimmeridge Clay units are the most probable sources for these hydrocarbon accumulations. The Lias on the southern side of the Purbeck‐Isle of Wight Disturbance appears to be the main source of the Dorset oils (Wytch Farm and Kimmeridge Bay) on the bases of adequate maturity, n‐alkane distribution, alkane ratios and stable carbon and hydrogen isotope ratios. On the basis of organic maturity, the oil accumulations in the Weald and the adjacent Hampshire areas are considered to be composed of varying contributions of bitumen generated from the three Jurassic source formations.Application of the modified Lopatin method of basin modelling suggests the Lias in the Weald as the probable source for the natural gas deposit at Godley Bridge in Surrey and predicts a possible Liassic sourced wet‐gas field in the Dorset‐Isle of Wight area.
PETROGRAPHICAL AND GEOCHEMICAL STUDIES OF CRETACEOUS CARBONATE ROCKS, AIN ZALAH OILFIELD, NORTH IRAQ
Authors: Ahmed Walid A. , Elzarka M. , AI‐Dabbas Moutaz 
Published: December 2007

Petrographical and geochemical studies of 135 core rock samples from Cretaceous formations at the Ain Zalah oilfield suggests that the carbonate rocks contain different percentages of dolomite and calcite.Dolomitisation, stylolisation and neomorphic processes were observed in these formations. This study suggests that the Upper Cretaceous formations were deposited in a deep‐sea environment under low‐energy conditions, while the Middle and Lower Cretaceous formations were deposited in a shallow‐marine environment associated with tidal conditions far from wave attack.
SUPERPOSITION AND THE LAW OF REGULARITY IN STRATAL ORDER—KEYS TO THE PRACTICE AND THEORY OF GLOBAL STRATIGMPHY
Authors: Patterson J.R. 
Published: December 2007

In petroleum geology, the widespread practice of mapping lateral variations of lithology within the confines of general formations instead of time‐zones inevitably provokes differences of opinion over the scope and definition of stratigraphy. These differences can be traced back to a blending together of the separate concepts of two founders of geology, William Smith and Abraham Gottlob Werner. Werner originated a lithologic definition of rock formations; also, he taught the concept that the relative ages of formations could be determined by fossils. Smith contributed to the development of stratigraphy with his invention of the term ‘stratigraphical’, which referred to the occurrence of specific fossils and rock types within units of strata.The outcome of reconciling these different concepts has been that geologists have used Smith's basic terminology, the principle of superposition, and the formational units of stratigraphy, but have redefined them to accord with Werner's theory of Earth history. These changes in definition have confused the concept of stratigraphy, because they misrepresent its spatial form evident from ‘regularity in stratal order’. This general law was accepted by William Smith as the basis for his stratigraphical arrangement of rocks and fossils, which in the practice of correlating rocks by superposition led to a stratigraphic system of strata and the economy of a single stratigraphic scale.
THE BEJUCO PALEOCANYON (CRETACEOUS‐PALEOCENE) IN THE TAMPICO DISTRICT, MEXICO
Authors: Cantu‐chapa A. 
Published: December 2007

The Bejuco area (4,200 sq. km) is in Eastern Mexico, south of the Tampico District. Ammonites, gumma‐neutron logs, and lithologic samples of 65 exploratory wells were studied in order to construct structural maps at several levels within the Neocomian and Upper Jurassic. The purpose of this work was to study the stratigraphy, paleogeography, erosional unconformities, and also the occurrences of hydrocarbons of Late Jurassic‐Neocomian age.In most of the area, the Huasteca series of Middle‐Late Jurassic age lies discordantly on rocks of continental facies. In a few places in the NW, south, SE and centre, the Huasteca overlies intrusive rocks, and in the NW, the Huasteca also overlies metamorphic rocks in a few localities.Marine sedimentation commenced at the beginning of middle Callovian time in the eastern part of the region. Several successive periods of transgression took place: (1) during the early Kimmeridgian (central and western area); (2) the late Tithonian (north); and (3) the late Hauterivian (southern part).An important geological phenomenon is the submarine erosional unconformity which represents the Neocomian‐Eocene time‐interval. The area underlain by this unconformity has a delta shape and extends from the SW to the east. This is the precise area of the Bejuco paleocanyon. The unconformity today lies at a depth of between 1,200 and 2,900 m.The presence of hydrocarbons in either Tithonian or Neocomian rocks is controlled by structural traps, and in some places by combination traps.
A MODEL TO EXPLAIN THE EARTH'S MAGNETIC FIELD AND OTHER GEODYNAMIC PHENOMENA
Authors: Melton Charles E. , Giardini A.A. 
Published: December 2007

Paleomagnetism and other geodynamic processes, such as mantle convection and sea‐floor spreading, are of basic importance to petroleum geology. We present a model that explains the cause of these phenomena. The model is founded on the fact that the core‐mantle interface is a super‐conducting region, and on the concept that the gravitational interaction between the Moon and the Earth's solid inner core decouples the angular velocities of the solid inner core, liquid outer core and mantle. The decoupling is analogous to the crust‐ocean decoupling that produces ocean tides. The continuous decoupling and resultant frictional heat produce a rotating equatorial “hot spot” on the outer surface of the liquid core. The “hot spot” generates a thermal power of up to 10
13
watts and an equatorial current of about 10
9
amperes. The current is held to a narrow equatorial path by the well‐known “pinch effect”. The total resistance of the equatorial circuit is no greater than 10
‐10
ohms. The 10
9
ampere current creates the “polar” magnetic field. The secondary “non‐polar” fields are induction effects due to minor fluctuations (ripples) in the equatorial current. Paleomagnetic polarity reversals are initiated by turbulence, and by imbalances in kinetic pressure (nkT) and magnetic pressure (B
2
/2μ0). Westward drift is explained by the common direction of rotation and the differential angular velocities of the Earth's core and the Moon. The heat generated by the model explains the persistent molten state of the Earths core over a long geologic time, the nature of the deeper part of the geothermal gradient, and the non radiogenic heat emitted by the Earth. This heat is sufficient to drive all thermally‐driven geodynamic processes that are of deep origin.The model is consistent in general with planetary magnetism, in that those planets that are known to have significant magnetic fields also have moons.
THE SEISMIC EXPRESSION OF REAL AND APPARENT BURIED TOPOGRAPHY
Authors: Jenyon M.K. 
Published: December 2007

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 involved.
STRATIGRAPHY AND ROCK UNIT NOMENCLATURE IN THE OIL‐PRODUCING AREA OF INTERIOR OMAN
Authors: Clarke Michael W. Hughes 
Published: December 2007

The sedimentary rock sequence in the oilfield areas of Interior Oman ranges from the Late Proterozoic through Paleozoic, Mesozoic and Tertiary. A number of major gaps or changes in sedimentation are recognised, and these punctuate a subdivision into major rock units ranked as groups. Eleven named groups are recognised: in stratigraphic order from oldest, Huaf (Upper Proterozoic), through Haima (Lower Paleozoic), Misfar (Devonian), Haushi and Akhdar (Carboniferous to Triassic), Sahtan (Jurassic), Kahmah (Lower Cretaceous), Wasia (“Middle Cretaceous”), Aruma (Upper Cretaceous), Hadhramaut (Paleogene) to Fars (Neogene). Most of these groups are further subdivided and 35 named formations are described giving lithologic characteristics, boundaries, inferred age span and variability. These descriptions, together with reference well sections indicating wire‐line log characteristics, provide a sufficient basis for consistent future use of the rock units.Hydrocarbon occurrence within this sedimentary sequence is primarily controlled by the presence of good impermeable sealing units, particularly those of sufficient thickness to be least breached by faulting. Seven important sealing units are recognised, ranging from the evaporites of the Huaf Group to the basal shale of the Hadhramaut Group.Commercial hydrocarbon accumulations are retained by all these seals. Reservoirs are in both carbonate and clastic units, and in South Oman are commonly in much older units than the seal, which overlines unconformably.
GEOLOGY, GEOMORPHOLOGY, AND PETEROLEUM POSSIBILITES OF THE EL GODO AREA, IQUIQUE, CHILE
Authors: Cecioni G. , Meyerhoff A.A. , Teitz H.H. 
Published: December 2007

The presence of solid bitumen in the EI Godo area of Tarapacá province, northern Chile, has been known for centuries but, from a petroleum viewpoint, the region has been little studied. A major deterrent to exploration has been the presence of volcanic accumulations in the objective section, a marine Jurassic sequence more than 3, 000 m thick, which has been intruded by some younger silicic plutons. Objectives older than the Jurassic are unknown but may be present, especially in the deep part of the Jurassic basins and in the offshore.Two basins are present with a total prospective area of about 20,000 sq. kms. They contain shale and carbonate source rocks, shale and evaporite seals, and probable reservoir rocks (carbonates, terrigenous clastics, breccias). Anticlines, formed during the Nevadan orogeny, are present. The widespread presence of bitumen in outcrops indicates that oil has been generated. The western basin has thick syndepositional volcanics, and is the less attractive of the two basins. The eastern basin is nearly free of volcanic rocks and is a prime prospect.An ancient. deeply‐weathered, igneous rock mass forms a basement ridge that separates the two basins. This ridge apparently is an extension of the Precambrian Arequipa massif of southern coastal Peru. Possibly this massif was exposed at times during the Jurassic, supplying quartz detritus at least to the coastal and offshore basins.Karst phenomena, unrecognised before 1957 and almost unnoticed in the literature of this huge desert region, are widespread. The landforms are mature in the west. where poljes dominate, and very youthful in the east, where dolines (sinkholes) are dominant. The landscape east of the Coastal Range at Iquique has a fossil, inactive karst, but north of there, karst development is still active. The karst phenomena are related in only a general way to the structures known to underlie the area.
SOME DEFORMATION EFFECTS IN A CLASTIC OVERBURDEN RESULTING FROM SALT MOBILITY
Authors: Jenyon M. K. 
Published: December 2007

In a basin containing an evaporite sequence that includes salt rock, should the salt become mobile and deform plastically, it will produce important structural effects in overlying sediments. These effects may include folding, faulting, slumping, and in some cases where dissolution of the salt also occurs, collapse structures. The movement of the salt/overburden system during plastic deformation of the salt may be syndepositional, in which case rim syncline sedimentation will take place at the surface. The form taken by the rim syncline deposits will be related to the stage of development of the salt structures with which they are associated.An understanding of the mechanisms involved is important, particularly in a basin containing hydrocarbons. Also, study of the behaviour at depth of sediments which are subject to deformational stress may assist in solving structural problems on the Larger, regional scale. Selected examples of various effects seen in the North Sea Zechstein salt basin are discussed and illustrated with recently‐acquired seismic data.
SOME PROBLEMS IN PETROLEUM GEOCHEMISTRY
Authors: Stannage W. 
Published: December 2007

Limited geological events are occasionally observable, but petroleum geochemistry is inevitably a wholly inferential science. It can only be simulated in the laboratory, with occasional help from industrial‐scale work, by using the Arrhenius equation to convert observations in human time to geotime by means of temperature change.There are difficulties here. First, the Arrhenius equation is purely empirical. The analogy with the theoretically rigorous van't Hoff isochore cannot give the Arrhenius equation any more than empirical status. A departure from linearity unobservable in human time could well make the extrapolation to geotime subject to significant errors.Secondly, the inability to define petroleum generation in terms of specific molecules prevents the assignment of specific activation energies to specific reactions. Energies of activation can vary significantly between even similar reactions.Thirdly, catalysis can accelerate a reaction by ten or twenty powers of ten, and even variations in natural clays can alter reaction rates almost a thousandfold.Each of these three factors could easily introduce errors of two powers of ten in translating laboratory simulation to geotime.From equilibrium considerations, petroleum generation and degeneration belong to a continuous spectrum of reactions in which very large molecules are broken down into smaller ones, and ultimately methane. Pressure inhibits the equilibrium of such reactions to such an extent, especially as the molecules become smaller, that there can be no validity to simulation experiments which are not carried out at geopressures.Altogether. it seems unlikely that the age of oil can be limited by thermodynamic considerations.Finally, an inorganic origin for some petroleum ought not to be completely ignored.
PETROLEUM GEOLOGY OF THE UNITED ARAB EMIRATES
Authors: Alsharhan A. S. 
Published: December 2007

The Permain to Holocene sediments of the United Arab Emirates consist mainly of epeiric shelf carbonates, associated with minor clastics and evaporites, reflecting major cycles of transgression and regression. These were deposited on the eastern margin of the Arabian Sheild, which lay along the southern margin of the Tethys Ocean during the Mesozoic‐Cenozoic eras. Sedimentation patterns were controlled by prominent regional structural features, epeirogenic movements and/or sea‐level fluctuations.The tectonic history of the UAE in the Mesozoic‐Cenozoic is connected with the opening (Triassic) and closure (Upper Cretaceous‐Paleogene) of the southern Neo‐Tethys Ocean.The distinctive structural style, together with the tripartite development of source‐reservoir‐seal, has produced in the UAE one of the world's richest Jurassic ‐ Cretaceous oil habitats. Significant oil discoveries have also been made in the Permian; Middle and Upper Jurassic; Lower‐Middle‐Upper Cretaceous and Oligo‐Miocene carbonates.Two main source rocks have been identified. One is the Upper Jurassic Diyab/Dukhan Formation, which supplies the most prolific reservoirs in the Upper Jurassic (Arab Formation) and Lower Cretaceous (Thamama Group). The other is the Middle Cretaceous Shilaif/Khatiyah Formation, which feeds both Mishrif and Simsima reservoirs. Other minor potential source rocks have also been identified in the study area.There are two principal sealing formations ‐ the Hith Anhydrite and the Nahr Umr shale; these are the main seals for the oil and gas accumulations in the underlying Arab Formation and Thamama Group, respectively. Secondary seals and barriers also exist in the stratigraphic sequence.
LA PENA FORMATION (APTIAN): A CONDENSED LIMESTONE‐SHALE SEQUENCE FROM THE SUBSURFACE OF NE MEXICO
Authors: Cantü‐Chapa A. 
Published: December 2007

An integrated stratigraphic study was made of the La Peña Formation, which is penetrated by a number of wells in NE Mexico. the study was conducted with the aid of ammonites (Cheloniceratidae, Deshayestidae, Acanthohoplitidae), microfossils (Colomiella, Nannoconus), and radioactivity logs to investigate the age of the unit ‐ late Aptian.A series of wells extending 400 Km NW ‐ SE were studied. The results show that the stratigraphic ranges of Colomiella recta, C. mexicana, and certain Nannoconus species are greater than currently believed. In contrast, the ammonite groups mentioned above are present only in the La Peña Formation.The formation is composed of a condensed section of limestone and shale in this area. The La peña and the units below it are cut by normal faults, in particular the Paras Fault System, which is described here for the first time.
PETROLEUM EXPLORATION IN THE ETHIOPIAN RED SEA
Authors: Savoyat E. , Shiferaw A. , Balcha T. 
Published: December 2007

The Red Sea is a pericratonic Upper Tertiary basin which developed on the continental margin of Africa during the separation of Arabia from Africa, and is characterized by halokinetic tectonics in the upper stuctual stage and block‐rifting in the lower strctual stage. The margin is overprinted on a pre‐rift Mesozoic platform.Hydrocarbon exploration interest in the Ethiopian Red Sea area is based on three objectives, which correspond to stages in geotectonic evolution: Mesozic pre‐rift targets; Miocene rift presalt targets; and upper Miocene‐Pliocene post‐rift drift sequences.Reservoirs with appropriate sealing units (salt or shale) have been recorded. Models of sourcerock maturation using observed geothermal gradients are consistent with anaytical resuits, and prove that oil generation and preservation is to be xpected in the Ethiopian Red Sea.
FAULT‐BLOCK TECTONISM IN THE DEVONIAN SUBSURFACE, WESTERN CANADA BASIN
Authors: Greggs R. G. , Greggs D. H. 
Published: December 2007

An alternative model for the formation of Devonian carbonate reefs in the Western Canada Basin is proposed. This model is based on the epeiric clear‐water sedimentation model of Irwin (1965), with structural modfication throughout the Phanerozoic by repeated PreCambrian basement tectonism.The cratonic structural pattern is dominantly controlled by the global regmatic fracture‐system, which comprises a series of NW ‐ SE and NE ‐ SW vertical faults. These faults delineate a mosaic of fault blocks across the entire Western Canada Basin. Wrench faulting and vertical epeirogenic movements throughout the Paleozoic. Mesozoic, and Cenozoic subjected these blocks to further tectonic effects ‐ structural deformation and hydrothermal diagenesis. Preservation of down‐faulted carbonate blocks, and their subsequent isostatic recovery into overlying anhydrite or shale sequences, has led to the formation of carbonate complexes generally referred to as “organic reefs”.In addition, repeated emergence and submergence of the cratonic platform, particularly throughout the Middle and Upper Paleozoic, produced numerous regional and inter‐regional unconformities. These periods of erosion contributed to the leaching, and partial dolomitization, of the Devonian carbonates formed during periods of cratonic submergence. Repeated faulting is considered to have been a major factor in the diagenetic alteration of Devonian carbonates through associated hydrothermal activity, and a dominant control in the migration of hydrocarbons.