bluuebunny/crossref_metadata_2025_split huggingface dataset:
IS THERE A CHICONTEPEC PALLEOCANYON IN THE PALEOGENE OF EASTERN MAXICO?
Authors: Chapa A. cantú 
Published: December 2007

The Author studied the sediments in the so‐called Chicontepec paleocanyon of eastern Maxico. With the simultaneous use of planktonic forminifera and electric logs, it was possible to separate the Maastrichtian from the Paleogene, and to subdivide the Paleogene on the basis of paleontologic zones into Paleocene and Lower Eocene. Detailed stratigraphic study made it possible to establish the geographic distribution of the so‐called paleocanyon. The paleocanyon sensu stricto is present only SE of the Poza Rica field. Here, is it present in a plunging synform, in which it has the shape and form of a delta, now at a depth of between 1,800 and 3,600 m below sea‐level.The erosion which formed the paleocanyon cuts beds that range in age from late Tithonian to Maastrichtian; Paleocene is omnipresent. Hence, the erosion that formed the paleocanyon was pre‐Paleocene.Many of the stratigraphic criteria which led to the postulation of the paleocanyon are incorrect and are herein revised. Chronostratigraphy, based on the classic succession of foraminiferal zones, correctly applied together with structural‐contour maps selected zones, makes it possible to explain the hydrocarbon distribution.The high rate of sedimentation during Paleocene and Early Eocene time within the study area is compared with other regions of the world
LITHO‐ AND MICROFACIES OF UPPER JURASSIC CARBONATE ROCKS OUTCROPPING IN CENTRAL SAUDI ARABIA
Authors: Okla Saleh M. 
Published: December 2007

A study of surface sections of Upper Jurassic rock units near the city of Riyadh has revealed a total thickness of 500 m. These rock units are the Tuwaiq Mountain Limestone, Hanifa Formation, Jubaila Limestone, Arab Formation and Hith Anhydrite. The characteristic microfacies of Tuwaiq Mountain Limestone include spicular biomicrites in the lower part of the formation, and corals, stromatoporoids and algal biomicrites in the upper part. The characteristic microfacies of the Hanifa, Jubaila and Arab Formations include spicular biomicrites with some argillaceous shales alternating with pelsparities and oosparites. Conglomeratic micrites, dolomites and breccia are found in the upper Jubaila Limestone and the Arab Formation.The total thickness of these rock units increases in the east to more than 900 m where the Arabian and Gotnia Basins are defined. Central Saudi Arabia is best described as being the site of differential carbonate shelf deposition during Upper Jurassic time. Intra‐shelf basins with euxinic conditions were formed. Over these basins, petroleum source rocks were deposited within each rock unit.
STYLOLITIC POROSITY IN CARBONATES: A CRITICAL FACTOR FOR DEEP HYDROCARBON PRODUCTION
Authors: Carozzi Albert V. , Bergen Donald Von 
Published: December 2007

Petrographic and petrophysical studies were completed on cores from Atokan (Pennsylvanian) carbonate gas reservoirs at depths in excess of 4,000 m in the Chapman Deep field, Delaware Basin, Texas. Porosity concentration is in pure carbonate microfacies of Donezella algal 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 gas production.
SEDIMENTARY HISTORY AND PALEOGEOGRAPHY OF LOWER AND MIDDLE JURASSIC ROCKS, CENTRAL SAUDI ARABIA
Authors: Moshrif Mohamed A. 
Published: December 2007

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 deposits narrow toward the north.
THE THREE‐PHASE DEVELOPMENT OF THE PORCUPINE SEABIGHT: BASIN FORMATION AND THE STRUCTURALLY‐DEPENDENT SEDIMENTARY PATTERN.
Authors: Max M.D. 
Published: December 2007

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 episodes is proposed.
MULTIREGRESSIONAL MODELS FOR RANGED ESTIMATES OF THE PETROLEUM POTENTIAL OF SEDIMENTARY BASINS
Authors: Resnick Victor S. 
Published: December 2007

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 on discovery rate projection techniques.
MINERALOGICAL AND GEOCHEMICAL STUDIES OF TERTIARY SEDIMENTS FROM THE EASTERN NIGER DELTA AND THEIR RELATIONSHIP TO PETROLEUM OCCURRENCE
Authors: Odigi Minapuye I. 
Published: December 2007

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 Fe2O3 content: 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 effects.
HYDROCARBON POTENTIAL OF THE UPPER JURASSIC/LOWER CRETACEOUS OF THE AUSTRALIAN NW SHELF
Authors: Baird R.A. , Philip R.P. 
Published: December 2007

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 source‐rock section.
GAS‐PRONE SOURCE ROCKS FROM CRATOGENE KAROO BASINS IN TANZANIA
Authors: Kreuser T. , Schramedei R. , Rullkotter J. 
Published: December 2007

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 gas) await discovery are fair
THE JURASSIC FACIES IN THE LEVANT
Authors: Hirsch F. , Picard L. 
Published: December 2007

The Triassic‐Liassic contact in the Levant is a distinct sedimentary break expressed by lateritic palaeosols (Mishhor) or volcanics (Asher).A marine platform carbonate regime began in the Pliensbachian (Ardon‐Nirim) and continued in the Toarcian (Qeren‐Nirim). It was interrupted by Toarcian‐Aalenian clastics in the Negev, adjacent Sinai and along a belt crossing Central Israel into South Anti‐Lebanon (Inmar‐Rosh Pinna). In Northern Israel, Lebanon and North Anti‐Lebanon it persisted without interruption through the Oxfordian (Haifa or Kesroaune).Bajocian lithofacies vary from being mixed in the Negev (Daya), to largely marly in Sinai (Maghara), and to monotonous Bajocian‐Oxfordian platform‐carbonates (Haifa) in the north. Bajocian‐Bathonian lithofacies in the Coastal Plain consist of Haifa carbonates, interwedged by oolitic shoals (Sederot) and spiculites (Barnea). Paralic clastics dominate the early Bathonian in the south (Safa‐Sherif), followed by middle‐late Bathonian micrites and marls (Kehailia/Karmon). The latter characteristic body of shales continues to the Callovian, and in the Coastal Plain separates the Bathonian carbonates from the early Callovian calcarenites (Brur).Callovian‐Oxfordian platform micrites are interwedged by marls and biostromes in the Negev (Zohar‐Beersheba) but may consist of bioherms (Nir'Am) in the Coastal Plain. A complete or partial hiatus of the middle‐late Callovian coincides with the extension of the transgressive onlap of early Oxfordian shales (Kidod) from North Sinai to South Anti‐Lebanon, crossing the Coastal Plain and Central Israel.Kimmeridgian oolites, shales and occasionally sands (Halutza) terminate the Jurassic cycle, ending in a regional uplift followed by subaerial denudation or submarine canyons (Gevar‐Am).The palaeotectonic setting of the Jurassic in Israel and adjacent Sinai, prior to Infra‐Cretaceous truncation, consists of the Negev High which extends to the coastal plain area (Beersheba nose), separating the North Sinai Maghara Basin from the Central Israel‐Hermon trough, the latter being disturbed by Lartet's (1869) Neogene‐Quaternary wrench movement of over 100 km sinistral displacement. A rather shallow platform in the north includes Galilee, Lebanon and North Anti‐Lebanon.The clastics of the Liassic‐Bathonian part of the sequence are connected with the wearing‐down of the Arabian Massif in the south and SE. Yet the thickening of the early Oxfordian shales in the offshore wells points to derivation from some landmass in the west, now hidden beneath the Mediterranean.
THE PLESHET BASIN: A NEWLY‐DISCOVERED LINK IN THE PERIPHERAL CHAIN OF BASINS OF THE ARABIAN CRATON
Authors: Cohen Z. , Flexer A. , Kaptsan V. 
Published: December 2007

Evaluation of existing magnetometric, gravimetric, seismic and well data indicates that a large basin, some 300 km long, 100 km wide and up to 13.5 km deep, occupies the greater part of the Sinai‐Israel offshore area. The basin, referred to here as the Pleshet Basin, is flanked by a series of magnetic and gravimetric anomalies, interpreted as being caused by basement highs.None of the wells drilled in the basin penetrated the Jurassic section. It is suggested, however, that the thick sedimentary sequence filling the basin includes strata of Paleozoic to Quaternary age.Wells drilled in the SE part of the basin showed an increase in clastic content in a NW direction. The source of these clastics is therefore to be sought in the west. It is perhaps the basement ridge that presumably forms the western flank of the basin, or even a large land‐mass further away.The Pleshet Basin occupies a position similar to that of the prolific basins of the Middle East within the unstable shelf belt that surrounds the Arabo‐Nubian Massif. It here postulated that the Pleshet Basin is a potentially hydrocarbon‐generative depression.
ISOSTATIC BALANCE DURING SEDIMENT LOADING AND UNLOADING IN CONTINENTAL MARGINS
Authors: Magara K. 
Published: December 2007

The initiation of a sedimentary basin may be explained by a mechanism which is related to global tectonics and sea‐floor spreading. Once the initial shape of a basin is formed, the sediments which were removed and transported from the nearby inland area will be deposited in the basin, where active burial and compaction take place under conditions of isostatic balance.Cambining concepts of isostasy and sediment compaction, both the subsidence of the crust and the rise or fall of the sedimentary surface in a continental margin basin can be estimated. The first model proposed is here applied to four major basins–the Mississippi, Mackenzie, Niger and Amazon. The sedimentary surface, in general, tends to rise as the radio of depositional area to erosional area decreases and/or porosity at the base of the sedimentary basin increases (undercompaction).The second model proposed may be applicable for areas of carbonate sedimentation; deposition takes place primarily by chemical and biological processes, regardless of inland erosion.
THE FORMATION AND DISTRIBUTION OF MESOZOIC‐CENOZOIC SEDIMENTARY BASINS IN CHINA
Authors: Zaiyi Tian 
Published: December 2007

Numerous intraplate, fault‐bounded basins have been developed on the Chinese landmass as a result of interactions between the Pacific, Asian and Indian Plates since Mesozoic‐Cenozoic times. In Eastern China, continental‐rift basins were formed in a geodynamic regime during which the continental crust was stretched and thinned, and moved slowly towards the Pacific Ocean. These rift basins may be distinguished from those in NE, Northern and Southern China, due to differences in basement configuration and evolution.In Central China, cratonic subsidence depressions exist, with thin‐skinned décollement tectonics, fold belts and minor fore‐deeps. These include the Ordos, Sichuan and Chuxiong Basins, which can be differentiated according to their stage of development.In Western China, crustal compression resulted in horizontal shortening and vertical thickening; thus, fore‐deep and intermontane basins were developed, usually associated with basement thrust‐faulting.
THE CASE FOR EARLY GENERATION AND ACCUMULATION OF OIL
Authors: Wilson H. H. 
Published: December 2007

Uncertainties remain concerning the common assumption that economic oil pools result only from deep, catagenic oil generation. These uncertainties stem from the many geological criteria that point to early oil entrapment and, furthermore, from the failure to resolve problems of oil migration out of, and through, consolidated sediments.Early oil emplacement is indicated by the preferential charging of paleostructures, inhibition of diagenesis and compaction by reservoired oil, folded oil‐water contacts, and by evidence supporting the immaturity of huge heavy‐oil deposits.The uncemented and uncompacted nature of the Athabasca “tar sands”, the perfect preservation of fossil wood within them, and the tilted oil‐water contacts at the Athabasca, Peace River and Cold Lake accumulations, support geological deductions of very‐early oil emplacement, and geochemical criteria for its immaturity.If such huge volumes of oil are immature, this would be in harmony with geological observations which conclude that pools of mature oil most probably result from in‐reservoir maturation of early‐expelled, biogenically‐generated heavy oil and methane.Hydrocarbons that remain in source rocks are maturated during burial, but are immobilised by progressive loss of effective permeability.