bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE EVOLUTION OF THE DEAD SEA FLOATING ASPHALT BLOCKS: SIMULATIONS BY PYROLYSIS
Authors: Bein A. , Amit O. 
Published: December 2007

The asphalts found as floating blocks on the Dead Sea and deep‐seated in wells differ from all other asphalts of the area, mostly by their more abundand and much better preserved n‐alkance. Since biodegradation was found to be the main alteration process through which crude oil was alterd into aphalts, such well‐preserved n‐alkanes are unexpected. A hypothesis of secondary generation of theise alkanes was tested bny pyrolysis simulations of asphalt at 300d̀C during periods ranging up to 60 days. The abundance and distrubution pattern of the n‐alkanes in the simulated asphalts after 14 days of heating resembles that of the floating asphalt blocks and that found at a depth of 3,500 m. In addiation to saturated hydrocarbons, aromatics and gases were also formed at the expense of resins and asphaltenes. The H/C ratio was balanced by the formation of pyrobitumen and by a gradual decrease of the H/C ratio in the residual resins and asphaltenes. The gas formed contained about 60 to 80% methane with an isotopic composition of‐41 to 42%%. The hydrocarbon content of the simulated asphalt (gas and liquids) increased from about 15% at the stariting material to about 60% after 60 days of heating.The recognition that asphalts in the Dead Sea basin are secondarily subjected to alteration upon burial might be of economic importance. Asphalts buried to a depth at which maturation conditions are close to that reached in the pyrolysis simulation at 300d̀C after about 60 days may be counted on as source material for hydrocarbons.
QUATERNARY TURBIDITES IN A NERITIC ENVIRONMENT: WELL CNR VE 1, VENICE, ITALY
Authors: Favero V. , Passega R. 
Published: December 2007

Turbidites are generally deep‐sea deposits. By contrast, the turbitdites which form a large part of the nearly 1000m Quaternary section, cored in well CNR Venice 1, do not seem to have been deposited at sea depths much greater than 200m. Sea depth, determined mostly by ecological analyses of faraminifera, gradually decreases as the basin was filled with sediments. In the upper part of the well, above 302 m, turbidite sedimentation was replaced by alternating fluvitile and very shallow marine deposition.In well CNR Venice 1, turbite characteristics vary with the sea depth and the gradient of sea slopes. If near riveer mouths, the slope gradient is sufficient, sediments debouching from rivers readily form turbity currents. The displaced fauna in sand and in shale turbidites is fresh‐water. When gradients decrease, sediments are distributed along the coast and form submarine deltas or coastal shelves. If these shelves are limited by a sandy slope, turbidity currents may originated on this slope. Displaced fauna in the sand turbidites is marine littoral. If sediments of the slope limiting the coastal shelf are silt and clay, muddy turbidity currents can originate provided the gradient is 1% or more.A critical factor of sedimentation of Venice neritic turbidites is the very fine grain‐size of the sands. Turbidity current suspensions probably were stable as they could be supported by a moderate bottom turbulence. Suspensions therefore were not likely to settle rapidly when the gradient decreased to form fan‐like deposits. They flowed to the bottom of the basin where they spread and made their thickest deposits.Turbidites similar to Venice Quaternary turbidites may be common in ancient neitic basins, where gradients were sufficiently steep. These turbidites can form good petroleum reservoirs as well as impervious shale beds and permeability barriers.
HYDRODYNAMICS—DOES IT TRAP OIL?*
Authors: Magara Kinji 
Published: December 2007

In order for the hydrodynamics of meteoric water to be an important trapping mechanism for hydrocarbon accumulations, it must have existed for a long geologic period extending from the time of secondary hydrocarbon migration and its accumulation to the present time. However, in most interior sedimentary basins, the present hydrodynamic patterns are considered to have been developed only a short while ago (geologically speaking), after the significant uplift and the associated erosional events which caused the present topographical relief. Most petroleum accumulations were probably formed a long time before the development of the present hydrodynamic flow patterns, and hence must be explained by different mechanisms that have been effective for a much longer geologic period.This paper also discusses other possible problems in applying the hydrodynamics concept to understanding the formation of petroleum accumulations, such as the lack of proper water passways and outlets in several basins, the difficulty of moving water through hydrocarbon‐saturated sections of a reservoir, and the difficulty of keeping significant salinity gradients in a reservoir where active water flow has taken place.
PROBABLE GAS HYDRATE IN CONTINENTAL SLOPE EAST OF THE NORTH ISLAND, NEW ZEALAND
Authors: Katz Hans‐Rudolf 
Published: December 2007

Anomolous seismic horizons which (1) are strongly reflective, i.e. have a high impedence contrast; (2)cut across bedding planes of sediments;(3)are subparallel with the sea floor; and (4)increase their sub‐bottom depth with increasing depth of sea floor (and thus with decreasing temperature of bottom water) are tentavely identifed as the base of a gas hydrate layer. The anamalous reflections occur below waters 1000‐2500m deep, and along 500km of the continental slope. Some 10–20,000 sq km appear to be underlain by gas hydrates.The hydrate layer is often associated with structural anomalies(anticlines, tilted faultblocks). These would allow gas to migrate up‐dip into pressure and temperature conditions suitable for hydrate formation. Since the hydrate‐cemented layer itself acts as a barrier to gas migration, free gas will be trapped and accumulated in the sediments beneath it.It is concluded that huge amounts of hydrocarbon gas, both free gas and solid hydrate, have accumulated in this continental margin. On land, gas and oil generation is widespread, mainly originating from overpressured, Lower Teritiary to Upper Cretaceous shales. From seismic evidence the same formations appear to extend under the shelf and continental slope. The extensive occurence of gas hydrates would confirm that organicrich, terrigenous sediments have extensively been deposited in these areas.
EXPLORATION PROSPECTS AND FUTURE PETROLEUM POTENTIAL OF THE CANADIAN ARCTIC ISLANDS
Authors: Rayer F. G. 
Published: December 2007

The offshore and onshore area of the Canadian Arctic Archipelago, 1.7 million sq km, is one of the most prospective frontier regions in Canada. The first onshore well was drilled at Winter Harbour in 1961, and the first offshore well was drilled from an ice‐strengthened island at Hecla in 1974. To date, more than 140 wells have been drilled, and 12.0 Tcf of recoverable gas have been discovered as well as a small amount of oil. The gas is largely Lower Jurassic, with smaller amounts in Triassic and Lower Cretaceous strata.The Canadian Arctic Archipelago is actually underlain by two prospective basins: the older Franklinian geosyncline, or basin, Cambrian through Devonian; and the younger Sverdrup successor basin, Late Mississippian through Middle Eocene. The principal orogenic events to affect the area were the Caledonian uplift (Devonian), the Ellesmerian orogeny, a compressive fold system was produced with décollement of the southern part of the Franklinian on the Ordovician Bay Fiord salt. Vertical uplift, with compression in the east, dominated the Eurekan orogeny.Objectives in the Franklinian basin include sub‐Bay Fiord (sub‐Ordovician) structures—mainly Lower Paleozoic carbonates and some terrigenous clastics; supra‐salt folds of the Parry Islands fold belt—Ordovician‐Devonian reefs and porous shelf carbonates; other Lower Paleozoic reef bodies; and porous Devonian clastics in the Parry Islands fold belt. Sverdrup basin objectives include mainly terrigenous clastic reservoirs in Pennsylvanian‐Cretaceous rocks, with structural (salt anticlines and diapirs; some folds in the east) and stratigraphic (pinchouts on the flanks of structures, and along the folds) possibilities. The greatest potential in the Sverdrup basin is in the central and western parts. Ultimate recovery of gas is estimated to be at least 125 Tcf.
SEDIMENTOLOGY OF THE BRAE OILFIELD, NORTH SEA: FAN MODELS AND CONTROLS
Authors: Stow Dorrick A. V. , Bishop Clive D. , Mills Stephen J. 
Published: December 2007

Submarine fans are important to the petroleum industry for their reservoir and source‐rock potential. There are a variety of fan types that can be characterized by different fan models. In assessing which model, if any, is appropriate for a particular area or field it is important to evaluate the controls that operate to determine the type of fan developed. Most present‐day fans that have been studied are deep‐water oceanic; more work is required on modern examples of shallow‐water, small‐basin fans which are particularly relevant to hydrocarbon exploration.Jurassic and Tertiary objectives are important in the North Sea and include both nearshore‐sandstone and submarine fan reservoirs. The Brae oilfield is an Upper Jurassic reservoir on the western faulted margin of the North Sea Central rift system. Detailed core, electric log, dipmeter and seismic data have been examined. The Brae field comprises at least three small overlapping submarine fans that form a sediment apron along the scarp margin and that were deposited by a variety of gravity‐flow processes in a shallow basin below wave base. Tectonic control on fan development has resulted in up to six fining upwards megasequences (50‐150m) within the overall fining upwards basin fill (300–600 m). There has been a large intermittent supply of coarse detritus across a narrow littoral zone and down a steep slope. Short, sedimentladen rivers supplied mud and plant débris, and a complex interdigitation of coarse‐and fine‐grained facies has resulted.The Brae fans are an important example of the fault‐controlled, shallow, small‐basin type and are most closely analogous to the Jurassic fans of East Greenland. Reservoir characteristics are dependent on diagenesis, facies and fault distribution, and vary markedly along the fault margin. A clear understanding of the controls and models is essential for continued exploration and development in this part of the North Sea.
SOME ASPECTS OF THE OCCURRENCE OF PROTO‐KEROGEN IN RECENT OOIDS
Authors: Ferguson J. , Ibe A. C. 
Published: December 2007

Recent oolites from the Bahama Banks are shown to contain 1.23–4.13 wt% organic carbon of algal origin, chiefly in the form of proto‐kerogen. Characterization of the ogranic matter by routine optical and chemical means revealed that, although it is immature, it has a very high potential for generating petroleum hydrocarbons.It is suggested that with rise in temperature due to burial, and perhaps to catalytic influence of the host sediments, this proto‐kerogen of algal‐amorphous facies would, through time, generate significant amounts of hydrocarbons. In those oolite deposits with adequate porosity, the hydrocarbons could accumulate as petroleum.
RELATIONSHIP BETWEEN DIAGENESIS AND PORE FLUID CHEMISTRY IN NIGER DELTA OIL‐BEARING SANDS
Authors: Lambert‐Aikhionbare D. O. 
Published: December 2007

The sandstones of the Niger delta oil reservoirs are predominantly quartz arenites, yet silica cementation in the form of quartz overgrowth is at a minimum. This apparent lack of cementation is attributed among other things to the low concentration of silica in formation water, which results in low bulk‐volume reduction, little pressure‐solution and consequently, under‐compaction.Under‐compaction is aided by early calcite cementation which probably occurs at the boundary between the fresh waters of the Benin formation and the brackish to saline pore‐waters of the paralic sequence. Early cementation may have aided the discriminate entry of hydrocarbons into the reservoirs of the area.Entry of hydrocarbon into reservoirs appears to inhibit diagenetic processes as significant differences in mineral assemblages exist between hydrocarbon and non‐hydrocarbon reservoirs. Kaolinite is the dominant authigenic mineral in most hydrocarbon reservoirs whereas kaolinite, siderite, pyrite, calcite as well as minor amounts of smectite and illite occur in many non‐hydrocarbon reservoirs. The presence of mainly kaolinite in most reservoir rocks is suggestive of early entry of hydrocarbons into them. This deduction is at variance with the presently‐accepted theory of hydrocarbon generation within the deeply buried section of the paralic Agbada formation and the overpressured marine Akara shales. Instead, it suggests generation and migration of hydrocarbons from the paralic shales adjacent to the reservoirs.Lack of cemetation in most hydrocarbon reservoirs results in the production of very fine materials (“fines”) with the oil. It is proposed that most of the kaolinite present in many petroleum reservoirs is produced with such fines. The removal of kaolinite, in this way, reduces the hazard of permeability loss which would have occurred due to blocking of throat‐passages by floating kaolinite platelets.
ESTIMATION OF IRREDUCIBLE WATER SATURATION AND EFFECTIVE PORE SIZE OF MUDSTONES
Authors: Honda Hiromi , Magara Kinji 
Published: December 2007

A theoretical consideration of immobile water saturation in mudstone is made by means of a capillary model of a porous medium using the air and water absolute permeabilities of a sample. The calculated values of immobile water saturation of the Tertiary mudstones from Japan tend to support a generally‐accepted concept; virtually all the water in mudstones is irreducible. Immobile or irreducible water saturation increases gradually with decrease of porosity of mudstones; 15% porosity is a critical value beyond which mudstones contain 100% immobile water in the pores.Pore sizes of the mudstones estimated by the same model are considerably greater than those estimated by Welte (1972), and are more comparable with Momper's (1978) atypical pore size range of mudstone. The result of analysis indicates that radius of principal pores of the mudstones, which are effective on fluid flow, ranges from about 0.1–0.5 μm. The result thus suggests that even relatively large hydrocarbon molecules can effectively pass through the rock.
THE RECENT (MIOCENE‐QUATERNARY) REGMATIC SYSTEM OF THE WESTERN MEDITERRANEAN REGION: A New Model of Ensialic Geodynamic Evolution, in a Context of Plastic/Rigid Deformation
Authors: Boccaletti M. , Conedera C. , Dainelli P. , Gočev P. 
Published: December 2007

By comparing the features observed on Landsat images with the known geological data, a regmatic system that controlled the entire Neogene to Recent structural evolution of the Western Mediterranean area has been recognized.The system consists of two principal conjugated shear trends, reactivating old fractures, the NE‐SW, or Moulouya, and the NW‐SE, or Gafsa. With these, an E‐W trend of prevailing shear character (Gibraltar) and a N‐S trend with mostly tensional movements (Tyrrhenian), are associated. The trends that characterize the system are always present in all the segments of the circum‐Mediterranean chains and continue in the forelands and in the marine areas, although some may prevail.The orientation and the relative movements of the fractures of the system are consistent with the slip‐line field that develops in a plastic‐rigid mobile area, when this is placed between two non parallel converging rigid blocks. The system evolves according to a monoclinic scheme, which is in turn complicated by the variations of the crustal thickness in the deformed zone and by some pre‐existing discontinuities. A progressive migration in time of the major deformations towards the SE is also observed. Mechanisms of intracontinental subduction induced by the shear system are then postulated. The new proposed model may open up new leads for the identification of prospects in the exploration for hydrocarbons, particularly along the orogenic belts.
FACIES DISTRIBUTION AND PETROLEUM GEOLOGY OF THE BOMBAY OFFSHORE BASIN, INDIA
Authors: Basu D. N. , Banerjee A. , Tamhane D. M. 
Published: December 2007

In view of the recent oil and gas dicoveries in the Bombay Offshore basin, its detailed geology has been worked out in terms of its source rock and reservoir potential. An agewise, layer‐cake lithofacies analysis and five depositional model maps from Paleocene to Middle Miocene age, together with a number of paleotectonic sections has led to the reconstruction of a xeneralized depositional model of the basin as a whole. This proposed depositional model envisages the Bombay Offshore basin as a shelf‐to‐basin carbonate model. During Paleogene and Early Neogene time the clastic supply by the proto‐Narmada river from the NE resulted in delta progradation up to the Dahanu depression, which was a region of pro‐deltas and lagoons with a considerable thickness of finer clastics. Beyond the Dahanu depression, the Bombay High and Bassein‐Alibag‐Ratnagiri shelf remained open carbonate platforms, while the DCS area was the locale of shelf‐edge carbonate build‐up.The potential targets for exploration are the deltaic sandstone to the north in the Tapti area—particularly where the sandy facies interfingers with the shales and the porous limestone horizons in the Bombay Platform, Bassein‐Alibag‐Ratnagiri shelf and the DCS trend. The Dahanu depression is thought to be the main source rock area.
SPECIFIC GRAVITY AS A KEROGEN TYPE AND MATURATION INDICATOR WITH SPECIAL REFERENCE TO AMORPHOUS KEROGENS
Authors: Kinghorn R. R. F. , Rahman M. 
Published: December 2007

Mineral‐free kerogen concentrates have been fractionated into their components by the use of differential and sequential gravity separation methods. The density of each component within a kerogen depends upon its chemical composition which is a function of the original organic matter and its level of organic maturation.The mineral‐free kerogen concentrates were analysed for the elements carbon, hydrogen and oxygen and these results, combined with visual kerogen examination, allowed estimations of kerogen type and degree of maturation to be made.The separation procedure also allows the composition of the sedimentary organic matter to be assessed and thus, with the knowledge of the level of maturity and the possible convertibility of each component into fluid hydrocarbons, a more accurate assessment of the hydrocarbon potential of the kerogen can be obtained.The quantity of unproductive carbon can be identified by density separation, and the different types of amorphous kerogen can also be identified and separated by means of this method. The oil‐prone amorphous kerogens have lower specific gravities than the amorphous gas‐prone material.
PETROLEUM GEOCHEMISTRY OF LATE CRETACEOUS AND EARLY TERTIARY SHALES PENETRATED BY THE AKUKWA‐2 WELL IN THE ANAMBRA BASIN, SOUTHERN NIGERIA†
Authors: Ekweozor Chukwuemeka M. , Gormly James R. 
Published: December 2007

The concentration, type and thermal maturity of organic matter from the Imo Shale, Nkporo Shale and the upper parts of the Nkalagu Formation which were penetrated by the Akukwa‐2 well are presented. The organic carbon content ranged from 0.4–3.5%. The kerogens from the various formations were of the humic and mixed varieties. Evidence from independent thermal maturity parameters (namely, average vitrinite reflectance (R0%), Tmax and transformation ratio from Rock‐Eval, n‐alkanes distribution pattern, and hopane “fingerprint”) combined to locate the top of the ‘oil window’ within the Nkporo Shale at a depth of approximately 2,000 m from the surface. This corresponds to a threshold temperature of circa 65°C.Sedimentary organic matter which is favourable for both gas and oil generation is therefore probably abundant in the Anambra basin. Hydrocarbon reservoirs are possibly located at relatively shallow depths where accumulations of heavy oils may also be expected.
THE APPLICATION OF FACIES PARAMETERS ADN MAPPKING TECHNIQUES TO EXPLORATION OF THE SUBSURFACE LOWER CRETACEOUS OF THE QUATTARA DEPRESSION, WESTERN DESERT EGYPT
Authors: Elzarka Mohamed Hossny 
Published: December 2007

The occurrence of oil in some fields of the Qattara Deprrssion is largely controlled by the lithological composition of the Lower Cretaceous succession. The lithologic percentage adn ratio; classifying, entropy and distance functions; entropy ratio, relative centre of gravity, variance, covariance adn relative standard deviation; adn tripartite and entropy facies parameters have been calculated for sections studied. They have then been correlated with optimum parameters, i. e. teh average composition fo four oil‐bearing sections. Similarity or departure of the calculated parameters from those of of the optimum composition facilttates delineation of areas favourable for finding oil.Thus, this tool provides a valuable means for the prospecting for and explorastion of new oil and gas deposits, as indicated in teh case study presented.
THE SE AFRICA TRIPLE JUNCTION AND THE DRIFT OF MADAGASCAR
Authors: Flores Giovanni 
Published: December 2007

In a paper published in 1970, the Author expressed the view that the Mozambique Channel originated as Madagascar drifted to the NE from the Mozambique‐Natal coast. A further analysis of that view in the light of recently acquired data now enables him to formulate the hypothesis set out in this paper, namely that:(a). The geometry and tectonics of the Lebombo‐Zoutspansberg‐Buzi elongated fractures accompanied by Jurassic and Cretaceous effusives define a triple junction similar to the present‐day Red Sea‐Afar‐Gulf of Aden triple junction;(b). An initial rifting of the Channel occurred as the swell originating the triple junction produced a stretching of the continental crust and the initial separation of the Indo‐Malgache Landmass from Africa along the two eastern branches of the triple junction, while the middle one (Zoutspansberg) was being reduced to an abortive rift; and(c). Only when the thinned continental crust was stretched to the point of rupture did the oceanization process set in, with the production of “classical” spreading centres and magnetic anomalies.The latter process probably began in the Cretaceous, and was accompanied by impressive flows of alkaline lavas on the continental side and basalts in the oceanic area.Considering that, if this hypothesis is correct, the proto‐channel in Early Jurassic time was a narrow seaway, as suggested also by the juxtaposition of the major Mozambique and Madagascar fault lineaments; and considering that Madagascar has numerous shows and seepages of petroleum, probably of Jurassic age, the hypothesis discussed may have considerable bearing on the petroleum possibilities of the deeper Mozambican, Jurassic section, whose existence is indicated by several of the offshore seismic profiles recently run. Any oil generated in that section is likely to have migrated up‐dip on both sides of the proto‐channel.