bluuebunny/crossref_metadata_2025_split huggingface dataset:
A logging correlation scheme for the Main coal seam of the North Bohemian brown coal basin, and the implications for the palaeogeographical development of the basin
Authors: Mach Karel 
Published: April 2008

Abstract
A method for correlating the Main coal seam in the North Bohemian brown coal basin by interpreting borehole logs is described. The most important well log was the gamma-gamma density log, but in some boreholes it was also necessary to use the natural radioactivity and electric resistance logs or technological sampling of the core. All these methods, at various levels of sensitivity, reflect changes in the amount of organic matter in the borehole profile. Vertical changes of coal matter content characterize variations of sedimentation conditions. In close boreholes gamma-gamma density logs are easily correlatable so that changes of sedimentation can be correlated over great distances. The method has been used to correlate the main seam along the axis of the basin. The main result of this correlation is that coal-bearing sedimentation occurred uninterruptedly along the main axis of the basin, with the development of swamp and lake conditions. During the swamp conditions peat accumulated over the majority of the present basin area, whilst during the shallow lake conditions the region of clastic sedimentation was controlled by the distance from the inflowing sediment source. The coal-bearing sedimentation cycle started by a levelling of the palaeorelief by infilling the depressions, and was followed an extension of the sedimentation area. Compaction of the previously deposited layers affected the ensuing strata. No significant variations in stratal thickness were found along the length of the main borehole line nor in any of the auxiliary lines whole, indicating that tectonic controls in basin subsidence were unimportant. Thus changes of sedimentation conditions dominantly of climatic conditions caused water levels in the basin area to fluctuate. For many reasons it is concluded that the correlatable boundaries are isochronal. The correlation scheme represents the first really objective correlation of the main coal seam over the area of the whole North Bohemian basin.
Seismic monitoring for rockburst prevention in the Ostrava-Karviná Coalfield, Czech Republic
Authors: Holub Karel 
Published: April 2008

Abstract
Seismic activity in the Ostrava-Karviná Coalfield is continuously monitored by networks of seismographic stations located both underground and on the surface. Software has been implemented for statistical analysis and various types of data display to aid interpretation. Practical experience obtained in long-term seismic monitoring has proved that it is an indispensable part of the rockburst prevention scheme applied in underground mines in this region. Continuous seismic monitoring enables us to delimit seismically active areas, observe the trends of seismic activity in time and space so that we can make more accurate estimates of local rockburst hazard, and check the effectiveness of the rockburst prevention methods used.
An analysis of mining induced seismicity and its relationship to fault zones
Authors: Kaláb Zdeněk 
Published: April 2008

Abstract
Intense induced seismicity has resulted from long-standing mining activity in the Karviná part of the Ostrava-Karviná Coal District, Upper Silesian coal basin. Interpretation of mining induced seismic events in combination with other knowledge (geological, tectonic, geomechanical, technological) aids the understanding of failure processes in the rock mass. Seismological observations over a three-year period were analysed. Four sets of mining-induced seismic events have been tested to evaluate the seismicity of important fault zones. It follows from the analysis that the seismic activity on important fault zones occurs only as a consequence of mining activities. Accumulations of mining induced seismic events occur on stress concentrators, which may be geological and/or anthropogenic structures.
Desulphurization of low-rank coals by low-temperature carbonization
Authors: Asmatulu R. , Acarkan N. , Onal G. , Celik M. S. 
Published: April 2008

Abstract

A lignite sample from the Istanbul region with 14.18% inherent moisture, 11.01% ash, 1.86% total sulphur, 47.24% volatile matter, 41.75% fixed carbon and 5590 kcal kg
−1
calorific value as dried basis has been subjected to a set of systematic low-temperature carbonization tests. The tests have been carried out as a function of particle size, temperature and heating time. A semicoke product containing 15.22% volatile matter, 16.67% ash, 68.04% fixed carbon contents with 63% desulphurization on the basis of total sulphur has been obtained under the optimum conditions of 650°C temperature and 50 minutes of heating time. The product has a calorific value of 6403 kcal kg
−1
but does not have enough strength for use as a fuel and thus needs to be improved by briquetting.
Amelioration of high organic sulphur coal for combustion in domestic stoves
Authors: Whateley Michael K. G. , Gencer Zafer , Tuncali Ertem 
Published: April 2008

Abstract

Despite the proximity to Ankara, raw coal mined in the Beypazari basin cannot be used as a domestic fuel in Ankara because the high combustible sulphur content would add to the already severe pollution problems in that city. This study investigated a method of reducing the SO
2
emissions by adding lime (CaO) to the coal prior to combustion. Sorbent, as lime, was added to the combustion chamber (a domestic stove), by pretreating the coal by mixing crushed coal with lime and molasses and turning the coal into briquettes. Lime was added to lump coal for comparative purposes. The ratio of Ca
free
: S was varied for a series of combustion tests, and the heating efficiency and the amount of sulphur fixed in the ash were determined. The results of the tests show that optimum sulphur retention and heating efficiency were obtained when the Ca
free
: S molar ratio was between 0.95 and 1.15 for the briquettes and between 1.00 and 1.25 for the lump coal. For lump coal, 50% of the total sulphur could be fixed in the ash and at least 75% of the heating efficiency retained. During combustion of the briquettes, at least 57.5% of the sulphur could be fixed in the ash and at least 85% of the heating efficiency could be achieved. This suggests that the addition of lime to briquettes may be a feasible way of reducing the SO
2
emissions for domestic stoves.
The possibility of underground gasification of Bulgarian Dobrudja’s coal
Authors: Douchanov Douchko , Minkova Venecia 
Published: April 2008

Abstract

The gasification of coal within underground coal seams and using the combustible gas as a fuel is an idea that has attracted scientists for many years. Some success in gasifying thick coal seams near the surface has been demonstrated in recent experiments in the USA. Tests on underground coal gasification in Belgium and France have been carried out supported by the Energy Commission of the European Communities since 1978. The latest tests at Thullin, Belgium carried out by a joint Belgium and German team are thought to be promising. The depth of the seams has been selected as representative of Southern European and some Mid-European coals as an essential first attempt before moving to a further stage, at around 900–1000 metres depth. Work on this programme is at an early stage and its progress will be watched with much interest. For Bulgaria it is of vital importance to develop underground coal gasification on Dobrudja’s coal (1.5 10
9
t) — as an important energetic strategy and the possibility of environmental utilization of this resource.
Method for estimating methane emissions from Polish coal mining
Authors: Grzybek Ireneusz , Gawlik Lidia , Suwała Wojciech , Kuzak Ryszard 
Published: April 2008

Abstract
To improve the accuracy of estimations of methane emissions from coal mining, a study of the Polish mine-specific method of methane measurement has been undertaken. To carry out the study, the following assumptions have been made: (1) Methane emissions are proportional to the gas content of coals; (2) The single mine average gas content is a function of both exploitation depth and gas distribution; (3) The total volume of methane released during mining is in proportion to the total gas content, while the volume emitted from post-mining processes and from waste rock storage to the residual gas content. The study has shown that: (1) There are four sources of methane emission from coal mining: mining and post-mining processes, degassing systems and barren rocks storage; (2) Emission from degassing systems should be measured directly, while the emissions from the other sources could be estimated and characterized by release factors; (3) The release factors for mining processes are described by parabolic equations, which have been defined by comparing total measured emissions from venting and degasing systems with in-situ methane content. For the remaining emission sources the factors are equal either to the average residual gas content or to the total gas content, depending on the proportion of residual to the total gas content; (4) Release factors and emissions, calculated for Polish coal mining were found to be four times less than had been previously suggested.
Energy trends in SE Asia
Authors: Sladen Chris 
Published: April 2008

Abstract

SE Asia is undergoing rapid economic growth, achieving annual increases in gross domestic product of 6–15% in a number of countries. In many instances, the growth has been underpinned by rapid establishment and development of indigenous petroleum resources. Accompanying this growth, is a steady and significant increase in energy consumption. To meet the increasing energy requirement, oil, gas and coal production are steadily increasing. Oil consumption considerably exceeds regional production; the supply gap is widening and the shortfall is principally made up by oil imports from Middle East countries. Replacement of produced oil reserves is increasingly difficult in SE Asia. In the future, gas is expected to become a much more significant energy source. In addition to large gas reserves already found, but currently undeveloped, there are a wide variety of exploration opportunities for further gas. Technological breakthroughs expected in the next 5–30 years will also increase the attractiveness of gas as the preferred energy source in SE Asia during the next 50 years. These include advances in the use of gas which is heavily contaminated with CO
2
, improvements which enable more commercial developments of deepwater gas, and a continued improvement in coal-bed methane technology.
Miocene carbonate buildups offshore Socialist Republic of Vietnam
Authors: Mayall M. J. , Bent A. , Roberts D. M. 
Published: April 2008

Abstract
A variety of carbonate accumulations can be identified offshore Vietnam. The best reservoirs are developed in large, fault-controlled, buildups which have undergone extensive leaching during emergence. More moderate reservoir quality is present in platform facies which extend over large areas and in small buildups usually developed on footwall crests. This paper describes the setting, facies, diagenesis and reservoir quality of the various carbonate types.
Early Tertiary basin formation and the development of Lacustrine and quasi-lacustrine/marine source rocks on the Sunda Shelf of SE Asia
Authors: Cole J. M. , Crittenden S. 
Published: April 2008

Abstract
The Tertiary basins of the Sunda Shelf of SE Asia were formed in the ?Mid- to Late Eocene and accumulated thick intervals of syn-rift lacustrine and low salinity organic rich shales throughout the Late Palaeogene. Towards the end of the Oligocene and into the Early Miocene marine transgression occurred throughout the region. A change to deep open marine sedimentation followed by a general shallowing and deposition throughout the Neogene, of great thicknesses of marginal marine and paralic sediments. The syn-rift sediments are the most important hydrocarbon source rocks in this region, although precise dating of them is difficult due to the long-ranging nature of the palynomorphs and the paucity of the microfauna. However characteristics of the depositional environments and nature of the source rocks deposited within separate provincial basins that were wholly or partially landlocked can be assessed from a detailed examination of the isolated palynomorph and kerogen assemblages. A classification of lacustrine depositional environments within the region on this basis is presented.
Permeability heterogeneity within the Jerudong Formation: an outcrop analogue for subsurface Miocene reservoirs in Brunei
Authors: Prosser D. J. , Carter R. R. 
Published: April 2008

Abstract
The Jerudong Formation (early Tortonian) cropping out at Punyit Beach (Negara Brunei Darussalam) comprises a heterolithic succession of deltaic strata. Probepermeameter data have been used to evaluate the spatial nature of permeability heterogeneity within shoreface, lagoon and distributary channel environments. Strata at outcrop comprise the same lithologies as those at depth in the abandoned Jerudong Field, and provide an analogue for parts of the Jerudong Formation and equivalents in other Bruneian oilfields.
Identified permeability heterogeneities are associated with contrasts of up to three orders of magnitude, occurring at facies, genetic facies unit, bed-set, bed and laminar scales. Distributary-channel facies display the best outcrop permeability (>7000 mD). They include trough cross-stratified fills of relatively straight (often tidal) distributaries, and laterally accreted point bar sandstones deposited within meandering channels. These facies display upward decreasing permeability trends. Shoreface facies may also display high (>6000 mD) permeability, but are characterized by upward increasing permeability and are significantly more heterogeneous than channel facies. Lagoon fill successions are highly heterolithic, comprising sandstones, siltstones and mudstones with a wide range of permeabilities.
5 cm spaced outcrop permeability data are more variable, and display ‘average’ permeabilities several orders of magnitude larger than occur within similar facies encountered in the subsurface.
The spatial scale, frequency and magnitude of permeability variation within the Jerudong Formation indicate that facies packages observed at outcrop are of sufficient scale (4–10 m thickness) to provide potentially useful scaled elements for flow simulation.
A model using 0.25 m scale grid blocks has allowed assessment of intra-facies permeability variation (associated with bedding/cross-bed sets) upon recovery within different channel fills. The model predicts both trough cross-stratified and laterally accreted channel fills are heterogeneous with respect to waterflood, and preferential imbibition into their lower parts. Trough cross-stratified channels flood more rapidly than laterally accreted channel fills, where more fingering of the flood front occurs. Lagoon fill deposits display variable waterflood characteristics dependent upon sand content. Within both simulations, heterolithic lagoon fill facies appear to effectively compartmentalise modelled reservoir successions with respect to vertical cross flow.
Platform-top and ramp deposits of the Tonasa Carbonate Platform, Sulawesi, Indonesia
Authors: Wilson M. E. J. , Bosence D. W. J. 
Published: April 2008

Abstract
This study presents a detailed facies analysis of shallow-water platform and ramp deposits of an extensive Tertiary carbonate platform. Temporal and spatial variations have been used to construct a palaeogeographic reconstruction of the platform and to evaluate controls on carbonate sedimentation The late Eocene to mid-Miocene shallow-water and outer ramp/basinal deposits of the Tonasa Carbonate Platform, from the Pangkajene and Jeneponto areas of South Sulawesi respectively, formed initially as a transgressive sequence in a probable backarc setting. The platform was dominated by foraminifera and had a ramp-type southern margin. Facies belts on the platform trend east-west and their position remained remarkably stable through time indicating aggradation of the platform-top. In comparison outer ramp deposits prograded southwards at intervals into basinal marls.
Tectonics, in the form of subsidence, was the dominant control on accommodation space on the Tonasa Carbonate Platform. The location of ‘barriers’ and the resultant deflection of cross-platform currents, together with the nature of carbonate producing organisms also affected sedimentation, whilst eustatic or autocyclic effects are difficult to differentiate from the affects of tectonic tilting.
Moderate- to high-energy platform top or redeposited carbonate facies may form effective hydrocarbon reservoirs in otherwise tight foraminifera dominated carbonates, which occur widely in SE Asia, and have not been affected by extensive porosity occlusion.
A tectonic model for the onshore Kutai Basin, East Kalimantan
Authors: Chambers John L. C. , Daley Timothy E. 
Published: April 2008

Abstract
Past structural geological models for the Samarinda Anticlinorium have included gravity-driven slumping, shale diapirism and thrusting related to regional tectonic events. New geological cross-sections utilizing LASMO-acquired data over structures in the Runtu Block have been constructed from both surface geological measurements and 1993–1994 vintage seismic data. Relatively rigid deltaic and shelf sediments have been deformed into box-folds, above disharmonically folded shale-rich pro-delta and bathyal sediments. Detachment of these structures appears to be at the top of, or within, over-pressured shales at the base of Lower Miocene deltaic packages.
Gravity data, acquired along with seismic data, suggests semi-regional uplifts of the underlying over-pressured strata which would have been initially deposited as a flat or gently inclined unit. Basement configuration is not visible on seismic but gravity and aeromagnetic data show that it is deep throughout the study area, ranging between 7 and 14km. The implication of the structural models is that relatively small amounts of shortening are interpreted to have occurred across these near-surface structures and that the amount of relative uplift is large. This model suggests that basin inversion may be the cause of the structural styles illustrated in this paper.
Data presented supports a tectonic model for the central Kutai Basin involving inversion of a deep Palaeogene rift basin which gives rise to apparent broad regional folding of the shale rich over-pressured section. Closer spaced folding in the near surface, normally pressured and thus less ductile deltaic and shelf section of the Samarinda Anticlinorium, is a result of the same inversion.
Fault seal prediction: the gouge ratio method
Authors: Freeman B. , Yielding G. , Needham D. T. , Badley M. E. 
Published: April 2008

Abstract

The reduction in pore throat size attributable to the enhanced clay content in the fault rock between two juxtaposed reservoir bodies is able to produce an effective seal to hydrocarbon migration. The gouge ratio, when applied to sand-shale sequences, indicates the proportion of phyllosilicate material that is expected to be incorporated into the fault rock, hence it provides a measure of the seal capacity. Gouge ratios for faulted reservoir sequences are computed from data that are routinely available from fields at the appraisal or production stage. We present a repeatable methodology that maximizes the use of seismically based geometric data and well-based stratigraphic and compositional data. The resulting gouge ratio calculations can be used comparatively at the scale of individual faults, fields or basins. We examine an example fault from the Oseberg Syd Field that is known to seal and we show that a threshold shale gouge ratio of 18% will support a cross-fault pressure difference of
c.
8 bar.
Flow through fault systems in high-porosity sandstones
Authors: Manzocchi T. , Ringrose P. S. , Underhill J. R. 
Published: April 2008

Abstract
Small-scale faults in high-porosity sandstones form highly connected systems over a range of length scales. The effective permeability and oil recovery in such systems are strongly controlled by their geometrical architecture. This paper describes partially sealing faults in terms of: (a) characterization of their spatial distribution; (b) their effects on reservoir compartmentalization; and (c) their significance for fluid flow. Four suites of numerical flow simulations in highly compartmentalized fault systems are used to assess the influence of geometrical variability on single- and two-phase flow. The single-phase suites demonstrate that effective permeability is approximately linearly related to the number of fault-enclosed compartments present in a fault system. Use of a fault heterogeneity measure allows effective permeability for a geometrical case to be estimated from fault density and fault and matrix permeability. The two-phase simulations model water-floods, and show the relationships between length scale, fault system geometry and oil recovery. In a self-similar fault system, oil recovery is preferentially inhibited at the smaller length scales. Oil recovery is influenced by compartment volume distribution and is therefore sensitive to fault clustering. The fault density necessary to severely affect either single- or two-phase flow is likely to occur only close to structures which are large relative to the scale under consideration. This improved understanding of the relative influences of fault system geometry, density and petrophysics should lead to significantly improved hydrocarbon recovery from faulted high-porosity sandstones.
Assessment of the effects of sub-seismic faults on bulk permeabilities of reservoir sequences
Authors: Walsh J. J. , Watterson J. , Heath A. , Gillespie P. A. , Childs C. 
Published: April 2008

Abstract

Single-phase horizontal bulk permeabilities for 3 km × 3 km volumes of varying thickness of a typical Brent permeability sequence have been calculated, both before and after faulting by a range of sub-seismic fault arrays, with maximum fault displacements of 20m – 2m. The models incorporate realistic juxtaposition geometries across fault surfaces. Results are expressed in terms of fractional bulk permeabilities (
Kf
), i.e. ratio of bulk permeability of faulted model and of pre-faulting model. Fault and fault array variables modelled and tested were fault density, spatial distribution, orientation distribution and fault zone permeability relative to the host rocks, expressed as transmissibility factor (
Tf
). Realistic fault zone thicknesses were incorporated by use of a scaling factor. Low, moderate and high fault densities have significant and markedly different effects on
Kf
whereas the effects of spatial and orientation distribution variations are slight except at very low
Tf
values (
Tf
< 0.001). The relative insignificance of fault spatial distributions is due to closer fault spacing resulting in locally high hydraulic gradients which increase flow through fault surfaces unless these surfaces have very low
Tf
values. Prediction of fault zone hydraulic properties remains the most important factor contributing to modelling uncertainties.