bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neogene palaeosurfaces in the volcanic area of Central Slovakia
Authors: Lacika Ján 
Published: April 2008

Abstract
Two types of Neogene palaeosurfaces occur in the Central Slovakia Volcanic Area, these being volcanic and planational in origin. The volcanic palaeosurfaces are currently represented as topographic remnants which were originally created as a result of Neogene-Pleistocene andesite-rhyolite (Badenian-Panonian) and basaltic (Pontian-Upper Pleistocene) volcanic activity in the region. During the intervening and subsequent periods of relative volcanic and tectonic quiescence, geomorphological processes of landform evolution became dominant and, consequently, a total of four generations of Neogene planation surfaces may be identified in the study area. From the topmost, or oldest surface, these are: a high-level Middle Miocene surface; an Upper Miocene middle or intramontane level; an intermediate level of Pontian age; and lowermost, a sub-montane level dated as Upper Pliocene-Lower Pleistocene, found at the present river level. All of the Neogene palaeosurfaces in the Central Slovakia Volcania Area, of both volcanic and erosional origins, currently display an advanced state of erosion and dissection as a result of Alpine uplift effects: a total of six main types of relief may be recognized.
High-altitude palaeosurfaces in the Bolivian Andes: evidence for late Cenozoic surface uplift
Authors: Kennan L. , Lamb S. H. , Hoke L. 
Published: April 2008

Abstract

Low relief palaeosurfaces are widely preserved in the Cordillera Oríental of the Bolivian Andes at altitudes between 2000 m and 4000 m in a region up to 100 km wide and 600 km long. Remnants of these nearly horizontal or gently undulating erosion surfaces, from 5 to 2000 km
2
in area, cut across folded Palaeozoic to Cenozoic bedrock. They appear to be erosional pediments formed between 12 and 3 Ma along broad, low gradient, valleys, which are generally undeformed. In detail, the morphology of surface remnants can be used to construct two distinct palaeodrainage basins. Very little of the material eroded during surface cutting appears to have remained within the Cordillera Oriental and must have been carried into a foreland basin, now preserved in the Subandean fold and thrust belt. The palaeovalleys are generally parallel to the dominant north-south structural grain, forming a tortuous low gradient drainage system which flowed into the foreland basin in an east-west distance of < 150 km. Reconstructions of the drainage systems suggest that they have been uplifted
c.
2 km since their formation. These estimates are consistent with plausible models of uplift of the Cordillera Oriental as a consequence of intense deformation in the Subandean fold and thrust belt since
c.
10 Ma. However, only since 3 Ma have the surfaces been deeply dissected by drainage cutting more directly across the structural grain. The timing of deep dissection may be partly related to a climate change to wetter and colder conditions.
Variation in thermal history styles around the Irish Sea and adjacent areas: implications for hydrocarbon occurrence and tectonic evolution
Authors: Green Paul F. , Duddy Ian R. , Bray Richard J. 
Published: April 2008

Abstract
Thermal history is a major factor in determining hydrocarbon prospectivity in the Irish Sea region. Early application of Apatite Fission Track Analysis (AFTA®) to exploration wells revealed early Tertiary palaeotemperatures around 110°C or more. More recent studies in the Irish Sea and adjacent areas, using a combination of AFTA and vitrinite reflectance (VR), have revealed at least three additional palaeo-thermal episodes: pre-Permian (>290 Ma), late Permian to mid-Triassic (260 to 220 Ma) and Early Cretaceous (140 to 110 Ma). Other evidence of early paleo-thermal effects, for which timing is only constrained to the interval 300 to 150 Ma, may reflect these or additional episodes.

In some areas, early effects involved extremely high palaeogeothermal gradients. Early Cretaceous gradients are unconstrained due to a lack of wells in which palaeotemperatures reflect this episode. Early Tertiary palaeotemperatures derived from AFTA and VR in wells from the southern part of the East Irish Sea Basin define a consistent linear depth profile with a gradient of only 10°C km
−1
. Wells from the north of the region also define a broadly consistent profile but with a much higher gradient. The low gradients are thought to reflect flow of hot fluids while the high gradients to the north may be associated with igneous activity in that region.

Our preferred interpretation of the early Tertiary palaeo-thermal effects involves a combination of burial by around 1.5 to 2 km of post-Triassic sediment and the thermal effects of hot fluid flow, probably from north to south and associated with igneous activity. This interpretation is consistent with geological evidence and is supported by structural data, sonic velocity data and geochemical observations.
Different combinations of these episodes lead to a wide variety of thermal history styles across the region. The southern part of the East Irish Sea Basin, containing major accumulations of oil and gas, is characterized by the most suitable thermal history conditions for generation and preservation of hydrocarbons to the present day. In adjacent regions, thermal histories are more complex, and those identified to date are generally less suitable particularly for preservation of hydrocarbons to the present day. Future exploration in these areas will require a thorough understanding of the thermal history of Carboniferous source rocks in order to define the most prospective regions.
Real and relict direct hydrocarbon indicators in the East Irish Sea Basin
Authors: Francis A. , Millwood Hargrave M. , Mulholland P. , Williams D. 
Published: April 2008

Abstract
Seismic amplitude anomalies associated with the presence of hydrocarbon gas now play an important role in the exploration of the East Irish Sea Basin. Tilted flat spots were first observed on data acquired by JEBCO Seismic Ltd. in 1986 within the productive Triassic reservoir of the Sherwood Sandstone Group located in Quadrant 110 (offshore North Wales). With hindsight Direct Hydrocarbon Indicators (DHIs) can now be identified on seismic data acquired in earlier phases of the exploration of the East Irish Sea Basin, although many anomalies were not always identified as such at that time.
This study determines the geophysical parameters by which amplitude anomalies associated with diagenetic variations could be separated from anomalies associated with the presence of gas in the reservoir. The predicted model results are compared with the seismic response of proven fields, discoveries and relict or palaeo-DHIs around the basin. Practical implications for effective exploration, development and production methods in the Sherwood Sandstone are suggested.
Bulgarian low rank coals: geology and petrology
Authors: Šiškov George D. 
Published: April 2008

Abstract
The largest coal-forming maximum in Bulgaria took place during the Neogene. Fifteen coal deposits are located in four coal-bearing provinces. The coal deposits south of the Balkan Mountains were formed in small grabens and depressions filled with molasse. Only the coals in Northern Bulgaria were formed in a small palaeodelta. The coal measures are of varying thickness and contain a few coal seams, with compact to complex structure and a range of thickness. Three groups are defined on the basis of maceral composition, allowing a reconstruction of the coal-forming ecosystems and the genesis of the genotypes during biochemical coalification. According to Alpern’s classification the coals have middle to high ash content (ashy to coaly facies). They are of huminite type with low liptinite and inertinite content, and of low rank — lignite and mat brown coals.
The distribution of sulphur in the Palaeocene coals of the Sindh Province of Pakistan
Authors: Baqri S. R. H. 
Published: April 2008

Abstract
46 samples of coals were collected, representing eastern and western coalfields of the Sindh Province of Pakistan to investigate any systematic quantitative changes in total sulphur. The coal is Palaeocene in age and the number and thickness of coal seams decreases from east to west. The sulphur content was determined as total sulphur on an elemental analyser Carlo Erba model EA 1108 on a dry basis. The sulphur content displays systematic variations and increases gradually from east to west. It is about 1.44% in the eastern coalfields at Tharparkar, 2.55% in the central coalfields at Badin and 4.95% in the western coalfields at Lakhra. The Palaeocene coalfields of the Sindh Province were deposited in shallow continental lagoonal areas towards Tharparkar in the east and comparatively down dip deeper areas with brackish waters (deltas, estuaries) towards the Lakhra in the west. The distribution of sulphur displays a good theoretical example in the change of depositional environment from fresh water to brackish waters environments. It is concluded that the coalfields with low sulphur occur in the east as compared to the coalfields with high sulphur in the west.
Geological research into gas sorbed in the coal seams of the Carboniferous in the Mšeno-Roudnice Basin, Czech Republic
Authors: Holub V. , Eliáš M. , Hrazdíra P. , Franců J. 
Published: April 2008

Abstract

In 1994 research in the Czech Republic began into coalbed methane (CBM). The target of this research is the coal seams of the Mšeno-Roudnice Basin, in the region between Mělník and Benátky nad Jizerou. This region was chosen as a model area for evaluating the CBM potential in the Permo-Carboniferous continental basins in the Bohemian Massif. The first stage of the work was directed towards obtaining data for basin analysis, the completion of lithological, stratigraphic and structural surveys particularly concentrated on fault deformation of the basin filling. A general study was conducted into the problem of the sorbed gases with respect to the occurrence of CBM. The latest interpretation of laboratory analysis of the Mělník Main coal seam shows a methane content of 4–10 m
3
/t in the coal at a depth of 250 to 800 m.
Structure, stratigraphy and petroleum geology of the SE Nam Con Son Basin, offshore Vietnam
Authors: Matthews S. J. , Fraser A. J. , Lowe S. , Todd S. P. , Peel F. J. 
Published: April 2008

Abstract
New well and seismic data acquired during recent exploration of the SE Nam Con Son Basin, offshore Vietnam, have been evaluated to assess the tectonostratigraphic evolution.
The offshore Vietnamese region has evolved in response to the complex relative motions of Indochina, Peninsular Malaysia, Borneo and the East Vietnam/South China Sea during the Cenozoic. On a regional scale these motions have been accommodated by strike-slip fault development, crustal extension and contraction. Rift pulses occurred in the SE Nam Con Son Basin from the Palaeogene to the earliest Late Miocene in response to the interaction of East Vietnam/South China Sea rift propagation and regional transtensional shear to the west of the evolving ocean basin. The structural evolution was complicated by mild contractional deformation during the Middle Miocene which was broadly synchronous with development of the largest inversion structures in the nearby West Natuna Basin.
The oldest dated Tertiary rocks in the SE Nam Con Son Basin are fluvio-deltaic sediments of Late Oligocene age which have been penetrated by several wells. Early to Mid-Miocene depositional environments ranged from non-marine to outer shelf, with a predominantly clastic basin-fill. The thickest Lower to Middle Miocene occurs in N-S- to NE-SW-trending half grabens.
A regionally recognized truncational unconformity of late Mid-Miocene age has resulted partly from the combined effects of the mild inversion and by the erosion of uplifted footwalls. During the Late Miocene there was rapid and widespread deepening of depositional environments, synchronous with net-extensional fault reactivation on many previously developed rift structures. The stratigraphic response to this increased bathymetry was the growth of isolated carbonate build-ups on pre-existing structural highs, progradation of the palaeo-Mekong delta system and associated deep-marine submarine channel development and erosion.
This pulsed structural and stratigraphic evolution has resulted in deposition of source, reservoir and seals, and produced a variety of potential trapping styles.
Predicting reservoir quality during exploration: lithic grains, porosity and permeability in Tertiary clastic rocks of the South China Sea basin
Authors: Worden R. H. , Mayall M. J. , Evans I. J. 
Published: April 2008

Abstract
Tertiary sandstones in the Gulf of Thailand, Malay and South China Sea basins have been supplied with sediment rich in pelitic metamorphic rock fragments, weathered basic igneous rock fragments and micaceous rock fragments by similar drainage systems. We have analysed data from the Gulf of Thailand and Malay basins to predict reservoir quality in the South China Sea basin. These Tertiary sandstones contain 20–40% lithic rock fragments that are rich in clay minerals. There are good correlations between both porosity and permeability and the total clay mineral content. They undergo rapid loss of porosity with depth at a rate commensurate with sandstones bearing 20–40% ductile grains. The relationship between porosity and permeability is also strongly influenced by the presence of ductile grains. The rapid loss of permeability with porosity is a result of ductile grains being squeezed between the rigid grains, blocking pore-throats and leaving isolated, ineffective porosity. Mineral cements seem to be unimportant modifiers of porosity or permeability. The rapid loss of porosity with depth and the decrease in permeability with porosity leads to low permeabilities at shallow depths relative to many other hydrocarbon provinces (e.g. North Sea, Gulf of Mexico, etc.) which have lower ductile grain contents. We have used modelled compaction curves for sandstones with 20 and 40% ductile grains to predict a porosity value for any given depth. We have also used sandstones of 100 and 300 μm grain size to predict permeability for a given porosity. The combination of these predictions can be used to predict permeability as a function of depth of burial. The choice of ductile content and grain size will depend upon the conditions of deposition. The main positive reservoir quality anomaly may result from overpressure generation before or during the final phase of burial.
Fault seal analysis of SE Asian basins with examples from West Java
Authors: Beach Alastair , Lawson Brown J. , Brockbank Paul J. , Knott Steven D. , McCallum Jean E. , Welbon Alastair I. 
Published: April 2008

Abstract
A regional fault seal analysis study of SE Asian basins was carried out in order to define trends for predicting sealing faults. Map and well data were analysed and relationships were obtained between fault and reservoir parameters and fault seal. The parameters found to be most useful for discriminating between sealing and non-sealing faults in the region were fault strike, fault mode (oblique slip faults are most likely to be sealing), fault throw (faults with high throws are most likely to be sealing), depth (shallow faults are most likely to be sealing) and thickness-throw. Other parameters measured, some of which are useful for fault seal prediction in some basins, are: fault type (bounding faults, within-field faults, across-field faults), net-to-gross ratio, average reservoir porosity, average reservoir permeability, differences in hydrocarbon contact elevation across faults, hydrocarbon column height held back by sealing faults, and reservoir pressure and temperature. Data from over 150 faults from fields within West Java are presented to illustrate the main results of the analysis.
Constraints on strike-slip motion from seismic and gravity data along the Vietnam margin offshore Da Nang: implications for hydrocarbon prospectivity and opening of the East Vietnam Sea
Authors: Roques D. , Matthews S. J. , Rangin C. 
Published: April 2008

Abstract
The Vietnamese continental margin records the tectonic processes which have controlled opening of the East Vietnam Sea basin. The geometry and chronology of Cenozoic structures linked to the opening of this marginal basin have been studied offshore Da Nang (central Vietnam), based on unpublished data acquired by BP Exploration from 1989 to 1991. These data demonstrate that a N160° E fault trend is the main structural orientation recognised on both gravity and seismic data. Important crustal extension on shallow-dipping fault planes striking N060° E and connected to the N160° E faults is observed also. This horse-tail map-pattern is compatible with transtensional dextral motion along the N160° E faults. The discrepancy between the amount of motion observed onshore and offshore suggests the presence of a major shear zone which trends subparallel to the east Vietnam margin. This shear zone is located in the region of the offshore Qui Nhon ridge, which is blanketed by carbonate sediments. These carbonates have been drilled and dated as Middle Miocene. Dextral motion along this shear zone diminished during the late Early Miocene (around 20 Ma.), as evidenced by the onset of carbonate deposition on top of the ridge. This is broadly synchronous with propagation of the East Vietnam Sea basin towards the southwest. This major shear zone has been a fundamental part of the fault network which developed during opening of the East Vietnam Sea.
The structural development of the offshore Da Nang region has resulted in the development of contrasting sub-basin geometries; those within the major shear zone appear to be relatively restricted laterally whereas those to the east display geometries more typical of extensional sub-basins. Both sub-basins show a variety of potential hydrocarbon trapping styles and by analogy with comparable areas in SE Asia have the potential to contain important oil reserves, in addition to the considerable volume of gas already proven by recent drilling.
Tertiary response to oblique subduction and indentation in Sumatra, Indonesia: new ideas for hydrocarbon exploration
Authors: Howells Chris 
Published: April 2008

Abstract
The Tertiary basins of Sumatra, which lie along the leading edge of the Eurasian Plate, comprise a mature hydrocarbon province whose origin and subsequent evolution are closely related to the processes of oblique subduction and indentation that have resulted from the collision of the Indo-Australian and Eurasian plates. The Sumatran basins exhibit a general rift-sag geometry with broad plate-margin parallel sag basins overlying a series of N-S-oriented grabens. It is these N-S-oriented grabens, whose origin and subsequent development are still debated despite extensive oil industry data, that control the distribution of the lacustrine sediments which are the primary source-rock for hydrocarbons in Sumatra. The Ombilin Basin provides high quality outcrops of sediments of equivalent age and depositional setting that may be studied, providing new insights into petroleum exploration of the basin itself that may be applied to the more mature areas of Sumatra.
The Ombilin Basin shows a three-fold evolution. Initial sedimentation in the Eocene appears to have been controlled by normal fault displacements and not strike-slip motions. This suggests a close genetic relationship with the N-S-oriented early Tertiary grabens currently located within the back-arc region (North, Central and South Sumatra Basins), and that the Ombilin Basin did not originate as a local pull-apart related to the Sumatra Fault Zone. Subsequent sedimentation in the basin (Oligocene) was dominated by fluvial deposition which is shown to have had a tectonic control at a time of active volcanism and strike-slip faulting. This is taken to indicate modification of the initial basin style by strike-slip activity along the Sumatra Fault Zone. The final phase of sedimentation in the basin (Early Miocene) is dominated by marine deposits which form the lower part of a transgressive-regressive wedge of regional extent. This wedge of sediments buries the earlier graben systems and is related to thermal subsidence. Uplift of the basin to its present intramontane setting and differentiation from the Central and South Sumatra Basins took place in the Mid-Miocene or later.
The model for the Ombilin Basin proposed here is that of a wrench-modified rift basin and is quite different from previous models giving the possibility for development of new play concepts. A similar genetic origin to the Central and South Sumatra Basins is clearly suggested, highlighting the applicability of the Ombilin Basin as an exploration model for the Sumatra graben and other analogous basins in SE Asia.
Identification and spatial distribution of fractures in porous, siliciclastic sediments
Authors: Gabrielsen Roy H. , Aarland Randi-Kristin , Alsaker Einar 
Published: April 2008

Abstract
Spatial and size distribution data of fractures provide essential information in statistical bulk strain estimates and in predictive fracture scaling models for sediments which have undergone brittle deformation. Most fracture populations in naturally deformed sediments include structures which originated at different stages, and in response to different conditions during the deformation history of the rock. Hence, the final fracture population may contain fractures which genetically are related to gravitational (near-surface) instabilities, burial, uplift and unroofing, thermal expansion and contraction, and regional tectonism. Furthermore, grain size, bed thickness and different rheological properties may strongly influence the fracture style and frequency.
Particularly when only well cores are available, identification of fractures of different genetic origin is difficult, and fracture classification and predictive modelling can only be accomplished with data acquired from careful fracture logging. In such logging, information on position of the well relative to major structures, the geometry of nearby faults, and the general geological (sedimentary and tectonic) environment need to be included. Also, fracture frequencies should be compared to, and normalized according to, lithology and bed thickness, and the fracture frequency diagrams should be corrected for eventual well deviation before predictive fracture frequency modelling is performed.
Potential contamination of groundwater by pulverized fuel ash
Authors: Lee S. , Spears D. A. 
Published: April 2008

Abstract
Disposal sites containing pulverized fuel ash (PFA) generate leaches which could contaminate surface and groundwaters. PFA has elevated concentrations of soluble salts and trace elements, including As, B, Cd, Cr, Mo, Ni, Pb, Se, V and Zn, which are associated with the surfaces of PFA particles. Batch and column leaching tests in the laboratory have been used to predict the environmental impact of PFA. However, laboratory testing may not reproduce natural conditions in the field. The majority of the field-based studies have been concerned with the relatively rapid release of trace elements from the surfaces of the PFA particles. Less information is available on the longer-term leaching behaviour of field-disposed PFA, where elements may be originating from the silicate glass and minerals. Two recently completed field-based studies suggest that leachate from older PFA could potentially contaminate groundwater over a period of many years.