bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characteristics of fault zones in sandstones from NW England: application to fault transmissibility
Authors: Beach Alastair , Lawson Brown J. , Welbon Alastair I. , McCallum Jean E. , Brockbank Paul , Knott Steven 
Published: April 2008

Abstract
Faults within outcrops of Permo-Triassic sandstones from NW England have been analysed, and their throws and fault zone thicknesses measured. These data were collected in order to provide a basis for estimating fault zone transmissibility. Logarithmic plots of fault throw versus fault zone thickness from the same localities show a positive correlation, and this relationship can be used to estimate fault zone thicknesses from fault throws derived from seismic data within similar successions. By combining fault zone thickness with laboratory-derived measurements of fault zone permeability, we show that fault transmissibilities can be estimated for input into reservoir simulation. These results can be applied to the assessment of seal potential and transmissibility in offshore oil and gas fields reservoired in Permo-Triassic sandstones. Layer thickness has a control on the fault populations, giving rise to separate population slopes for faults contained within a distinctive layer compared with those that extend outwith the layer. If layer thickness effects are not taken into account, extrapolation of a single power law trend may lead to an overestimation of the number of small faults in a population.
Controls on the evolution of the Namurian paralic basin, Bohemian Massif, Czech Republic
Authors: Kumpera O. 
Published: April 2008

Abstract
The Namurian A paralic molasse deposits of the Upper Silesian Coal Basin form erosion remnants of an extensive foreland basin located in the eastern part of the Bohemian Massif. This basin represents the latest stage of development of the Moravian-Silesian Paleozoic Basin (Devonian-Westphalian). The paralic molasse stage of the foreland basin evolved from foreland basins with flysch and with marine molasse. The deposition of the thick paralic molasse (Ostrava Formation) started in the Namurian A. In comparison with other coal-bearing foreland basins situated along the Variscan margin in Europe, this is characterized not only by earlier deposition, but also by a different tectonic setting. It is located in the Moravian-Silesian branch of the Variscan orocline striking NNE-SSW, i.e. perpendicularly to the strikes of more western European foreland basins. In the Viséan and Namurian, the foreland basin developed rapidly under the influence of the western thrustfold belt in the collision zone. The deposition was influenced by contrasting subsidence activities of the youngest and most external trough — Variscan foredeep — and the platform. The Upper Silesian Basin shows therefore a distinct W-E lithological and structural polarity and zonation.
A depositional and diagenetic model for the Eocene Sulcis coal basin of SW Sardinia
Authors: Dreesen Roland , Bossiroy Dominique , Swennen Rudy , Thorez Jacques , Fadda Aurelio , Ottelli Luciano , Keppens Eddy 
Published: April 2008

Abstract
Detailed sedimentological, mineralogical and petrographical analysis of closely spaced cored boreholes has enabled the development of a revised depositional model for the early Eocene coal-bearing Produttivo Formation of the Sulcis Basin. The deposition of autochthonous-hypautochthonous palustrine-lacustrine coals and associated carbonates was interrupted episodically by sedimentation of allochthonous lithocalcirudites and lithocalcarenites. The latter clastics display characteristic upward shoaling tidal flat sequences related to marine incursions. This interpretation is in contrast to the previously accepted fluvial origin of the detrital episodes. The coarse basal transgressive lag deposits consist of various carbonate intraclasts, dolosparite, grains consisting of calcite cement and euhedral-subhedral evaporite-bearing quartz grains. Combined stable isotope and cathodoluminiscence analysis has revealed a complex diagenetic history for the clastic deposits. The potential extrabasinal or intrabasinal provenance of the clasts, in particular the origin of the evaporite relicts, is discussed. The subtropical-tropical coastal marshes of the Florida Everglades (USA) are proposed as a possible modern analogue for the subbituminous Sulcis coals.
Chemical characteristics, mineralogical composition and rank of high sulphur coking coals of Middle Miocene age in the Gökler coal field, Gediz, Turkey
Authors: Karayigit A. I. , Whateley M. K. G. 
Published: April 2008

Abstract
Most Miocene coals in Turkey are of subbituminous to lignite rank. The Gökler coal field in the western part of Turkey contains mainly high sulphur coals of bituminous rank. The chemical characteristics, mineralogical composition and rank of high sulphur coking coals of Middle Miocene age in the coal field are investigated for the first time. A total of 46 channel and core samples were collected from underground mine workings and from boreholes drilled in the coal field.

The results of the proximate analyses as well as total sulphur analyses and calorific values on an air-dried basis show on average 1.2% moisture, 22.9% ash, 34.6% volatile matter, 6.9% total sulphur contents and 5850 kcal kg
−1
calorific value. X-ray powder diffraction studies of the coal samples on an air-dried basis show quartz, pyrite and calcite to be the dominant minerals; kaolinite, hydromuscovite, dolomite, gypsum, iron sulphate hydrate and rarely illite/smectite and feldspar constitute the remainder. Secondary calcite in random fractures surfaces of the coals is especially abundant in samples obtained from an area adjacent to the fault zones. The mean random reflectance values (%Rr) of telocollinite vary between 0.50 and 0.95%. These values show that the rank can be determined as a high volatile bituminous stage. In addition, these coals can form isotropic coke. Fluorescence intensities of sporinite are weak to very weak. The mean random vitrinite reflectance values within the coal field generally increase towards southern parts of the coal field. It is thought that this increase can be related to the recent hydrothermal antimony mineralization in the southeastern parts of the coal field.
Comparison of structures derived from mine workings and those interpreted in seismic profiles: an example from the Kačice deposit, Kladno Mine, Bohemia
Authors: Opluštil Stanislav , Pešek Jiří , Skopec Jiří 
Published: April 2008

Abstract
Five seismic profiles across the Kačice coal deposit were reinterpreted and compared with observations in mine galleries. The comparison shows that approximately 80% of normal faults with displacement exceeding 5 m detected on the seismic profiles really exist. In contrast, in only two cases have mine workings shown faults (vertical displacement 10–15 m) that have not been identified by seismic measurements. Discrepancies may be mostly explained by: (i) misinterpretation of the fault with slope of the presedimentary palaeorelief accompanied by differential compaction; (ii) virgation of faults and misinterpretation of a fault zone composed of several small faults individually below the detection limit but whose aggregate displacement is detected, giving the appearance of a single fault; (iii) faults which die away toward the overburden indicating synsedimentary movements in the deposit.
Improvements in direct coal liquefaction using beneficiated coal fractions
Authors: Barraza J. , Cloke M. , Belghazi A. 
Published: April 2008

Abstract

Beneficiated coal fractions from Point of Ayr coal (North Wales) were liquefied in order to determine their effect on conversion, product and metal distribution in coal extract solutions. The coal fractions were obtained in a dense medium cyclone separation unit, using aqueous solutions of Ca(NO
3
)
2
, as medium, of relative density 1.26. The original coal and the coal fractions were liquefied in an autoclave with hydrogenated anthracene oil (HAO) as solvent. Liquefaction results show an improvement in conversion for the overflow fractions over the feed coal, together with a shift in the net product distribution toward higher oils content and lower asphaltenes and preasphaltenes material in the liquid products. A marked decrease in the proportion of Al, Mg, Mn and Si was found in the extracts using overflow coal. However, Ti and Ca, which are deactivating elements of the hydrocracking catalyst used to upgrade the coal liquids, increased their proportion.
Coalbed methane migration in and around fault zones
Authors: Boardman E. L. , Rippon J. H. 
Published: April 2008

Abstract
One of the characteristics of all operating coalbed methane fields is the considerable variation in producibility success within these fields and even between adjacent wells, suggesting that very site-specific controls are operating. The most likely control in many coalfields is geological structure, particularly faults, which can divide the ground into fluid migration pathways and zones with bypassed, retained gas. Apart from the faulted zone itself adjacent ground will have been subject to dilational or contractional strain, and the strain profiles on either side of the fault will have their own individual permeability characteristics which may be further modified by subsequent burial history. Although any one well will be site-specific, this introductory paper seeks to describe the general ways in which modern understanding of faults and their associated strained ground can contribute to better well spacing and detailed siting and therefore a greater proportion of successful completions.
Exploration history of the offshore Southeast Sumatra PSC, Java Sea, Indonesia
Authors: Wight A. , Friestad H. , Anderson I. , Wicaksono P. , Reminton C. H. 
Published: April 2008

Abstract

The Offshore Southeast Sumatra Production Sharing Contract (PSC) is situated in the Java Sea, just north of Indonesia’s capital, Jakarta. It was the first to produce offshore oil in Indonesia and has so far produced over 0.8 × 10
9
BOE. The crude is low sulphur, waxy and sourced by Oligocene lacustrine shales. Over 200 exploration wells have been drilled from 1970 to the present, with 21 commercial accumulations discovered. Reservoirs are Oligocene to early Miocene in age with around 25% of the reserves in carbonates and 75% in fluvial-alluvial clastics. The main basins, Sunda and Asri, are retro-arc, N-S-oriented, asymmetric half-grabens situated between the stable Sunda Shield and the active volcanic arc on Java island.

This paper describes the acquisition of the area and traces its history from the initial discovery at Cinta-1 in 1970, through the oil price rise and fall of the 1980s, to the discovery of a new productive basin in 1987. Exploration is not only reliant on technological advances and available budgets, so other factors relevant to the history of exploration are also included.
Gravity anomalies and deep structural controls at the Sabah-Palawan margin, South China Sea
Authors: Milsom John , Holt Robert , Ayub Dzazali Bin , Smail Ross 
Published: April 2008

Abstract
The hydrocarbon-rich southeastern margin of the South China Sea is divided by NW-SE lineaments into a series of sharply contrasting segments distinguished by, among other things, abrupt changes in gravity patterns. The Sabah segment is bounded to the SW by the Tinjar or West Baram line and to the NE by the Balabac line at the southwest margin of the Sulu Sea. The most prominent gravitational feature of this segment is the strong freeair gravity low associated with the Sabah Trough which lies about 150 km offshore. Seismic reflection data suggest that loading by prograding sediments and gravity driven thrust sheets has depressed the extended continental crust of the South China Sea below its level of local isostatic compensation, producing the trough as a foreland basin in which sedimentation has failed to keep pace with subsidence. The load masses themselves, supported in part by the rigidity of the underlying crust and lithosphere, are above their levels of local compensation and deep Neogene sedimentary basins lie on the flanks of Bouguer and free-air gravity highs. Gravity values decrease across the Sabah coast so that the Crocker Ranges, including Mt Kinabalu, rest in rough isostatic equilibrium on presumably weaker lithosphere. The free-air gravity anomaly associated with the Sabah Trough is smaller than would have been predicted from the thickness of the water column, suggesting crustal thinning beneath the trough axis. This is not a characteristic of normal foreland basins and can therefore be assumed to predate basin formation. It can be concluded that the NE-SW trending belts of parallel gravity anomaly and geomorphology, of which the Sabah Trough is the most obvious, have been controlled by the pre-existing fabric of the crust and lithosphere of the South China Sea since they are discordant to the Palaeogene geological trends in Sabah. Reconstructions of the Tertiary history of the Sabah segment can be based on this assumption, which also suggests that sediments deposited in rift basins formed during the Palaeogene break-up of the South China margin were the source for much, if not all, of the hydrocarbon reserves of the area.
Reservoir characterization and modelling: a framework for field development
Authors: Archer John 
Published: April 2008

Abstract
This introductory paper seeks to highlight some of the challenges for reservoir simulation modelling that are presented by proper reservoir characterization and by appropriate cross-scaling of petrophysical parameters. The significance of tensorial representation of effective fluid-phase permeabilities is indicted by a number of examples.
In the UKCS (United Kingdom Continental Shelf) an important contribution to increased recoverable reserves is being made by the application of technology and by the reduction of reservoir description uncertainty. Some developments in reservoir simulation are indicated by examples from innovative well technologies: infill drilling locations indicated from enhanced understanding of flow directions; gas injection and gas condensate behaviour; and fractured reservoir performance.
The paper aims to provide a framework for the design and modelling of improved hydrocarbon recovery processes.
Polygonal faulting in the Tertiary of the central North Sea: implications for reservoir geology
Authors: Lonergan Lidia , Cartwright Joe , Laver Rod , Staffurth Joe 
Published: April 2008

Abstract
Interpretation of regional two-dimensional seismic surveys and three-dimensional seismic surveys in the central North Sea has demonstrated the existence of a pervasive polygonal network of normal faults affecting Tertiary shale-dominated slope and basin-floor depositional systems. The area affected by the faulting encompasses most areas of hydrocarbon production from Tertiary sandstone reservoirs. The polygonal fault networks were active during sedimentation and early burial. Throws measured on individual faults range from 8 to 100m, with average fault plane dips of 45°. Lengths of individual fault segments range from 80 to 1400m, and average fault spacings range from 100 to 500m. The high density and the polygonal geometry of the faults make seismic interpretation of the Lower Tertiary interval problematic, and can lead to misinterpretation of faults as apparent seismic-stratigraphic features.
The recognition of this fault system has consequences for the development of of fields in Tertiary reservoirs. The remaining hydrocarbon potential in the Lower Tertiary could be considered predominantly to be stratigraphic plays, but the presence of faults active during sedimentation and early burial implies that this play concept is too simplistic, particularly for Eocene reservoirs. The role of both syn-depositional and early-burial normal faulting on original reservoir distribution and post-depositional modification should be considered further. The presence of this fault system may also be important for secondary migration into Lower Tertiary reservoirs from Kimmeridge Clay Formation source rocks. The existence of an interconnected fault and fracture network in the low-permeability mudrocks may have provided an efficient vertical migration pathway for charging isolated lower Tertiary sandstone reservoirs. Finally, the maximum fault throws of between 50 and 100m are large enough to represent potential barriers for lateral communication in sandstone reservoirs where individual sand bodies are commonly 25–100m thick.
Mechanisms for
85
Sr migration through glacial sand determined by laboratory and
in situ
tracer tests
Authors: Williams G. M. , Hooker P. J. , Noy D. J. , Ross C. A. M. 
Published: April 2008

Abstract

Prediction of solute transport based on the laboratory measurement of radionuclide/sediment sorption parameters has been compared with field tracer tests involving the release of
85
Sr and a conservative tracer
131
I into a radially divergent flow field around a recharge well in a confined glacial sand aquifer. Tracer breakthrough was monitored in multi-level sampling installations. Two tests at different imposed rates of groundwater flow were conducted. At average flows up to 5 m day
−1
, the retardation of
85
Sr at a given sampling point was lower than that observed with an average flow rate of 0.5 m day
−1
, suggesting a kinetic control on sorption. Sequential selective leaching was also undertaken to study the geochemical phases responsible for sorption. In a core consisting predominantly of medium sand, approximately 80% of the
85
Sr was present in ion exchange sites, with 12% in the carbonate phase. The remaining 8% was recovered easily by extraction with distilled water. Kinetic data for Sr sorption on sand and silt core material suggested a two-stage process which could be fitted by two empirical sorption/desorption rate constants. These were used to simulate the effect of kinetics of sorption on the breakthrough curves for strontium. The retardation of
85
Sr at the lower flow rate was in relatively good agreement with laboratory values derived from batch sorption experiments lasting several days. At the high flow rate, longitudinal dispersivity α
L
for
85
Sr was larger than that for
131
I, but this discrepancy reduced at the lower flow rate where some convergence to the
85
Sr values was observed. A possible explanation is that at the high flow the opportunity for
131
I diffusion into relatively static porewater was limited; whereas with solutes moving at a lower rate there was a greater opportunity for diffusion into ‘dead end’ pores.
Detection of point sources of contamination by chlorinated solvents: a case study from the Chalk aquifer of eastern England
Authors: Misstear B. D. R. , Rippon P. W. , Ashley R. P. 
Published: April 2008

Abstract
Groundwater contamination by chlorinated solvents such as trichloroethene is of increasing concern in the UK. This paper describes a case study of chlorinated solvent contamination of the Chalk aquifer at a groundwater supply source in eastern England. The investigations comprised two phases: the first phase focused on the extent and nature of the contamination within the main Chalk aquifer (both in the fissures and in the Chalk matrix); and the second phase targeted the sources of contamination through detailed sampling of the unsaturated drift at suspect sites. The volatile nature of the organic contaminants required special hygiene procedures during drilling and sampling to avoid cross-contamination between boreholes, or loss of contaminants in the samples collected. Four potential sources of contamination were identified within an industrialized area about 1 km up hydraulic gradient from the contaminated well. However, the contamination was found to be extremely localized, with closely spaced investigation boreholes at individual sites giving highly varied results. To be successful, investigation boreholes had to target precise locations where these chemicals were known or suspected to have been used or stored. Therefore, a key aspect of the investigation was a solvent usage survey prior to each phase of drilling.
Morphology and sedimentation on the Hebrides Slope and Barra Fan, NW UK continental margin
Authors: Armishaw Julie E. , Holmes Richard W. , Stow Dorrik A. V. 
Published: April 2008

Abstract
Rapidly deposited Neogene sands and Pleistocene glacigenic sediments originating from NW Britain were transported across the shelf and downslope to the Barra Fan depocentre. In contrast, the Holocene interglacial shelf environment is typified by sediment winnowing, sea-floor polishing and transport of relatively small volumes of sediment along the shelf to the northwest. Interpretation of swath bathymetry, 32 kHz side-scan sonar, 3.5 kHz pinger, sea-bed photography and near-bottom current survey data on the shelf edge and slope provides good morphological evidence for both downslope and alongslope sedimentary processes on this composite slope-front fan. On the northern fan a corrugated shelf edge gives rise to a network of channels on the upper slope, which incise into Pleistocene and older sediments and funnel sediment to middle and lower fan. An underpinning variable topography on the fan bulge originates from major and minor slide masses, sediment creep and debris flows. These are reworked by spatially and secularly variable strong-to-weak bottom currents and redistribute material across and down fan forming transverse and linear bedforms, draped sandy contourite sheets and moulded drifts.
Mechanical properties of terrigenous muds from levee systems on the Amazon Fan
Authors: Marc Audet D. 
Published: April 2008

Abstract
The mechanical stability of channel levees may be an important control on channel avulsion and sediment distribution patterns in submarine fans. Levee stability depends on the shear strength of the levee sediments, which in turn depends on how the sediments are deposited and compacted. Long, continuous sections of levee sediments on the Amazon Fan were recently cored during Leg 155 of the Ocean Drilling Program. The porosity-depth profiles from Sites 939 and 944, situated on the levee of the Amazon Channel, were analysed using a theoretical compaction curve derived from soil mechanics theory. By fitting the theoretical compaction curve to porosity-depth data, estimates of the compression index and the void ratio at 100 kPa effective stress were determined. The compression index of the levee sediments was estimated to be 0.58–0.68. The mechanical parameters of the levee sediments are consistent with published geotechnical data for remoulded clays. Undrained shear strengh data from Leg 155 were analysed using an infinite slope analysis to determine the slope angle for failure as a function of burial depth. The variations in the shear strength measurements were bounded by critical slope angles of 1–3°. The higher bound of 3° tends to be consistent with maximum slopes measured near the levee crest near Site 938 on the Blue channel. The lower bound of 1° appears to be consistent with the slope of the sediment deposit blanketing the slope away from the levee crest. The top 55 m of Site 941, sited in the Western Debris Flow, show a relatively undisturbed, normally compacted porosity profile, even though the sediments show soft-deformation features. In contrast, the core samples between 55 and 68 m show lower porosity values compared with the porosity profile from Site 939. This low-porosity zone was interpreted as a zone of reworked or sheared sediment that could be the failure surface of a translational slide.