bluuebunny/crossref_metadata_2025 huggingface dataset:
Desulphurization of low-rank coals by low-temperature carbonization
Authors: Asmatulu R. , Acarkan N. , Onal G. , Celik M. S.
Published: April 2008

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

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

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

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

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

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

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

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

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

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

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

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

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.
Reservoir characterization: how can anisotropy help?
Authors: Owen Roderick J. , Li Xiang-Yang , Macbeth Colin D. , Booth David C.
Published: April 2008

We present a brief review on the use of seismic anisotropy for reservoir characterization. Seismic anisotropy utilizes the concept of scattering interference from subwavelength heterogeneities and may provide a powerful tool for characterizing these heterogeneities. An ordered system of reservoir heterogeneity may display seismic anisotropy diagnosed by shear-wave splitting, and the polarization of the fast split shear-wave (
qS1
), the time delay between the two split shear-waves (
qS1, qS2
), and the differential reflectivity at normal incidence may be used to quantify the heterogeneities. An example of field data obtained from a multicomponent seismic survey is presented to demonstrate how hydrocarbon production can be correlated with seismic anisotropy, and its potential application to reservoir characterization.
Numerical simulation of fluid flow in complex faulted regions
Authors: Foley L. , Daltaban T. S. , Wang J. T.
Published: April 2008

Faults exist in most hydrocarbon reservoirs. In general, they interfere with the transport of the fluids within the porous medium, and in other cases they may compartmentalize the reservoir and alter its connectivity. When performing any simulation procedure on a faulted reservoir it is important to take account of the sealing characteristics of the faults, especially (1) the effects of the pressure distribution across a fault and (2) the relationship between the porosity and permeability of the fault zone material and that of the bulk reservoir rock.

Current numerical fluid flow modelling techniques of faults are generally limited to the use of special connections, which involve modifying the transmissibilities between cells of the finite difference simulation grid. In many cases, the simulated flow is allowed to occur only between cells which are physically in contact. This may not be appropriate in the event of flow occurring along the fault plane and thus between a number of blocks which are not adjacent to each other. Modelling of fluid flow in complex faulted regions may be enhanced by implementing a boundary-fitted co-ordinate technique. This allows the geometry of the fault to be represented more accurately by constructing the simulation grid around the fault zone such that the inner boundary of the grid is coincident with the boundary of the fault. The permeability of the reservoir in the vicinity of the fault needs to be described using available information on fault zone characteristics (e.g. cataclastic slip band densities, clay smear potential, cementation etc.) to enable the construction of permeability distributions in the faulted region.
Curvature analysis of gridded geological surfaces
Authors: Stewart S. A. , Podolski R.
Published: April 2008

Surface curvature is related to strain and hence fracture density in most lithologies relevant to hydrocarbon exploration, and can be calculated at negligible expense as a surface attribute of horizons mapped on three-dimensional (3D) seismic data. Surfaces mapped using 3D seismic exist as data grids. Direct application of strict mathematical approaches to curvature measurement of gridded data is hindered by several problems inherent to discretized data. The grid node spacing in a horizontal plane is initially equal to the 3D seismic bin spacing and is some arbitrary value greater than the infinitely small mathematical limit, so the measured curvature is also arbitrary. Poor resolution of reflectors gives noise which can be removed by smoothing, but this subjective step impacts subsequent curvature extraction.

Fracture distributions also reflect the effect of large- and small-scale fold structures so there is merit in measuring curvature at a range of scales in addition to that defined by the grid node spacing. As curvature varies with direction of measurement, observations in the grid
x
and
y
directions alone are unlikely to coincide with the key maximum and minimum curvature values. Resampling a data grid using a large sliding window permits curvature measurement at a range of different wavelengths, and several orientations can be searched in addition to those parallel to the grid axes. Problems which are present regardless of the sample interval include inherent curvature of geological structures, signal aliasing and regional surface tilt relative to the horizontal grid reference plane.

Total, or Gaussian, curvature which is the product of the maximum and minimum curvatures may not be the best format for presenting curvature data, as strata characterized by zero total curvature may be significantly strained within cylindrical fold structures. Instead, the sum of the absolute values of the principal curvatures gives a representation of spatial variance in strain due to maximum and double curvature.
Strain partitioning during flexural-slip folding
Authors: Couples Gary D. , Lewis Helen , Geoff Tanner P. W.
Published: April 2008

In upper-crustal structures, folding by flexural slip leads to the partitioning and ordering of strains, which are commonly expressed by means of faults, fractures and joints. Flexural slip occurs along only some of the numerous layer-to-layer contacts within a sedimentary rock sequence, and these active bedding-plane slip surfaces partition the succession into mechanical units, each of which, although composed of many rock layers, deforms as though it were a single beam. Thus, in upper-crustal flexural-slip folds, the strain domains associated with bending are sharply deliminted by the active slip horizons and also are related to structural position within the beam. Progressive folding leads to the development of additional active slip surfaces and, therefore, to an increased number of mechanical units which each develop bending strains. As a result of this sequence of events, there is a hierarchical overprinting of strains, which leads to considerable complexity in fracture fabrics; nevertheless, order in the fracture patterns is retained. Most petroleum reservoirs appear to be affected by fracture networks created during flexure, and their fluid flow characteristics are probably related to a fracture-dominated, flexural deformation state which is disposed relative to the layering, is inhomogeneous, and is not distributed stochastically throughout the whole rock volume.
Structural geology of the Gullfaks Field, northern North Sea
Authors: Fossen Haakon , Hesthammer Jonny
Published: April 2008

The large amount of structural data available from the Gullfaks Field have been used to unravel the structural characteristics of the area. Two structurally distinct subareas have been revealed (a major domino system and an eastern horst complex) that show significant differences with respect to fault geometry, rotation and internal block deformation. The main faults have very low dips in the domino system (25–30°) as compared to the horst complex (65°), whereas most minor faults are steep in all parts of the field. Forward modelling indicates that the horst complex balances with rigid block operations. However, the domino area underwent significant internal deformation, reflected by the low acute angle between bedding and faults, and by non-planar bedding geometries. The internal deformation is modelled as a shear synthetic to, but steeper than, the main domino faults. This deformation explains a large-scale (kilometre sized) drag zone that has a triangular geometry in cross-section. Much of this shear deformation occurred by strain-dependent grain reorganization in the poorly consolidated Jurassic sediments, which led to a decrease in porosity. A strain map is presented for the domino area, indicating where the porosity is likely to have been decreased due to internal shear. Hangingwalls are generally more deformed (sheared) than footwalls. This is seen on both the kilometre scale (large-scale drag) and the metre scale (local drag).
Recent UK legal developments relating to pollution of water resources
Authors: Mylrea Kathy
Published: April 2008

The new UK statutory contaminated land provisions are expected to come into effect in 1997. Land will be contaminated for the purposes of the legislation if the presence of substances in, on or under it mean that significant harm is being caused or there is a possibility of such harm being caused or pollution of controlled waters is being caused or is likely to be caused. In a separate legal development, powers contained in the Water Resources Act 1991 for dealing with water pollution are also being strengthened. There is some concern that there is potential for overlap or conflict between these two regimes.

Developments at EU level include a communication of European Community water policy. It is expected to lead to a framework directive on water resources. The European Commission is shortly expected to take some action on the issue of liability for Environmental Damage.
Methyl tertiary butyl ether (MTBE): a groundwater contaminant of growing concern
Authors: Burgess W. G. , Dottridge J. , Symington R. M.
Published: April 2008

Methyl tertiary butyl ether (MTBE) is a fuel oxygenate rapidly becoming the preferred alternative to leaded and other, unleaded, additives in petrol. MTBE was introduced in the US as a fuel oxygenate in 1979, and has been used in the UK since the mid 1980s. Environmental legislation is expected to lead to increased use of MTBE in the future. Current UK legislation allows MTBE to constitute up to 10% by volume of unleaded petrol. MTBE has a low toxicity, yet its low odour and taste threshold makes it a problem at concentration levels above 2–3 μgl
−1
in water. It is more than ten times more soluble than the BTEX components of fuel, is apparently not retarded by sorption, and is reported to be non-biodegradable. Suggestions that MTBE exhibits co-solubility with BTEX components, thereby increasing their mobility, add to concerns about its behaviour in aquifers. This paper reviews the properties of MTBE and the limited published work on its behaviour as a groundwater contaminant.
Minewater remediation at a French zinc mine: sources of acid mine drainage and contaminant flushing characteristics
Authors: Sadler Piers J. K.
Published: April 2008

Recent closure of a zinc mine in southwestern France has resulted in flooding of workings and discharge of contaminated minewater from the workings, polluting a small stream. The minewater discharge is of near neutral pH and is contaminated with high levels of zinc, cadmium, manganese, iron and sulphate. With the exception of iron, concentrations of these contaminants have fallen dramatically since the discharge arose.

The main source of recharge to the mine is likely to be overlying aquifers associated with near-surface weathering. A classification is proposed to explain the hydrogeochemical sources of contaminants and the changes in discharge water quality with time. Primary sources related to active sulphide oxidation dominate the minewater chemistry in the unflooded workings, whilst secondary sources related to remobilization of secondary minerals dominate in the flooded workings. Prediction of contaminant flushing rates has been carried out on the basis of this classification. Zinc and cadmium levels are expected to reach stable medium-term levels within 2–5 years of the discharge first occurring.

Potential remediation strategies include plugging of the discharging mine portal and flooding of upper workings, coupled with conventional chemical and wetland treatment.
Investigation and clean-up of jet-fuel contaminated groundwater at Heathrow International Airport, UK
Authors: Clark L. , Sims P. A.
Published: April 2008

British Airways in 1987 discovered a leak of jet fuel (kerosene) at Heathrow Airport, west of London. The leak had led to free-phase kerosene floating on top of the shallow water-table beneath the site, with thicknesses of product of almost 1 m in places. WRc alert was employed to undertake a programme of investigations to delimit the free product. Work was then initiated to remove the free product from the water-table and restore the aquifer. This has been successful, with a total of 39 4001 of kerosene being recovered from the site. The recovery of kerosene took about four years of continuous work, illustrating the difficulty of aquifer remediation and the long time involved in remediation programmes.
Remediation of a petroleum spill to groundwater at a fuel distribution terminal (Long Island, USA) using pump-and-treat and complementary technologies
Authors: Holden John M. W. , Tunstall-Pedoe Nadine
Published: April 2008

A petroleum leakage to groundwater of up to 4000 m
3
was discovered in November 1987 at a fuel terminal site on Long Island, USA. A pure petroleum product pool of up to 1 m in thickness was floating on the water-table, and associated dissolved hydrocarbon and halogenated hydrocarbon plumes appeared to extend in three directions from source areas within the site. Risk assessments indicated that some local private wells were threatened by the migration of a dissolved petroleum plume. The petroleum spill is being treated using pump-and-treat technology with associated free product recovery, soil vapour extraction, air sparging wells and intrinsic bioremediation techniques. The treatment is proving to be successful, with half the petroleum free product being recovered and protection of the local residents and groundwater achieved.
Contaminant migration from disposal of acid tar wastes in fractured Coal Measures strata, southern Derbyshire
Authors: Banks D. , Nesbit N. L. , Firth T. , Power S.
Published: April 2008

In excess of 60 000 m
3
of acidic tar wastes from a lubricating oil factory have been disposed in old clay pits at a site on Coal Measures strata near Belper, southern Derbyshire, UK. A site investigation was carried out to assess the nature and volume of the waste, the extent of contaminant migration and possible remediation options. The wastes have migrated as free phase, gravity-driven flows of semi-fluid tar. These tar flows have led to contamination of on-site ponds by hydrocarbon emulsions and dissolved phase contaminants. Limited groundwater contamination by dissolved phase contaminants has also occurred. At present, no impact on off-site surface water receptors has been detected and no risk to any water abstraction has been identified. The site investigation has confirmed the exceedingly complex nature of the Coal Measures sequence. The Coal Measures exhibit some aspects of a multilayer aquifer system, dominant fracture flow mechanisms, strong anisotropy governed by fracture orientation and a heterogeneous and discontinuous distribution of groundwater heads. Indications of strong vertical head gradients, possibly related to under-drainage by mine workings, were detected.
Great Bridge Marl Pit: a case study in the prevention of contaminant migration
Authors: Gore Barry C. , Campbell Ian M.
Published: April 2008

Great Bridge Marl Pit is a former brick pit located in the West Midlands. The pit is infilled by an assortment of materials including a wide range of toxic and aggressive substances (most significantly phenolic liquids). Phase 2 of the Black Country Spine Road (opened 1995) crosses the pit on a raised embankment.

Prior to the construction of the road, the site was derelict and contaminated groundwater within the pit was thought to present only a minor risk to the adjacent River Tame and virtually no risk to local groundwater abstractions. Mobile contaminants within the pit were contained by a combination of the geometry of the pit, the location of the bulk of the contaminative materials within the base of the excavation and the low permeability of the base of the excavation.

However, impact of road construction over the site, in particular the preconsolidation of the pit infill by surcharging, was considered to have the potential to mobilize significant volumes of contaminated groundwater from within the pit and therefore to present a considerable risk of pollution of the River Tame.

To minimize the potential for contaminant migration, groundwater flow within the Marl Pit and in its immediate vicinity was controlled during the surcharging period by the installation of a groundwater abstraction system. Contaminated water abstracted during the surcharging was disposed of to trunk sewer and treated at the local water treatment works. The efficiency of the groundwater abstraction system was assessed by monitoring groundwater pressures and concentrations of contaminants in a number of strategically located boreholes around the margins of the site.

During the surcharging period the groundwater control system successfully controlled excess groundwater pressures generated beneath the surcharge and there was no evidence of an increase in contaminant migration from the pit; in fact a considerable reduction in the volume of contaminated groundwater present within the pit is likely to have occurred.
Large submarine slides on the NE Faeroe continental margin
Authors: Van Weering Tjeerd C. E. , Nielsen Tøve , Kenyon Neil H. , Akentieva Katja , Kuijpers Antoon. H.
Published: April 2008

High-resolution seismic profiles of the NE Faeroe margin show large-scale slumping and sliding of the middle and lower continental slope, affecting sediments of presumed Miocene, Pliocene and Quaternary age. Mass-flow deposits on the upper slope are partially covered by more recent deposits, presumed to be contourites. A TOBI deep-tow side-scan sonar mosaic, in combination with deep-towed penetrating echosounder results, shows that the slump complex on the upper slope consists of a buried slide scar, bottleneck slides, debris-flow lobes and a number of shallow slides. Sliding at the middle and lower continental slope seems more recent and shows a steep, irregular main slump scar and very large, intact, angular blocks. The base of the slide at the lower continental slope shows numerous narrow and diverging tracks, 10–15 km length, that end at individual blocks. Several types of debris flows have been mapped, some with longitudinal flow fabrics.
Debris flows on the Sula Sgeir Fan, NW of Scotland
Authors: Baltzer A. , Holmes R. , Evans D.
Published: April 2008

This paper describes the various debris-flow processes which have occurred on the Sula Sgeir Fan, a well-documented feature situated on the Hebrides Slope, NW of Scotland. The Sula Sgeir Fan covers an area 65 km in length and 28 km in width, between the 400 m and 1200 m bathymetric contours. The fan appears as a build-up of stacked debrisflow packages with transparent acoustic facies. These are termed glacigenic debris flows, as they are derived from sediment deposited by ice at the shelfbreak. However, on the southwestern edge of the Sula Sgeir Fan, and on its northeastern flank, there are different acoustic features which are described here as ‘classic’ debris flows. They are larger than the glacigenic type, and a scarp or a sliding scour characterizes their heads; they are thought to have been triggered by seismic events. Associated with these ‘classic’ debris flows are features on the seismic profiles interpreted as gas- or liquid-escape structures.
The Var submarine sedimentary system: understanding Holocene sediment delivery processes and their importance to the geological record
Authors: Mulder Thierry , Savoye Bruno , Piper David J. W. , Syvitski James P. M.
Published: April 2008

The Var system extends off Nice in the Western Mediterranean. It comprises a river, a delta and a submarine valley leading to a deep-sea fan that together have been in operation since the Early Pliocene. The Var system is an area experiencing active sediment transport, where at least three major types of sediment transfer process are identified: hyperpycnal turbid plumes, surge-like turbidity currents generated by shallow failures induced by excess pore pressure during river flood periods, and by large earthquake-triggered slides. The last two processes might generate higher-density turbidity currents, but at different return intervals. Hydrological data, direct observations of the sea floor, geotechnical testing and numerical modelling confirm the very high frequency of these sediment transfer events. Some of the processes have catastrophic surge behaviour, others are continuous during periods of river flooding. In the latter case, all the sediment supplied to the vicinity of the river mouth is transferred seaward without or with only brief periods of deposition. The geological record of such continuous activity remains difficult to identify. The palaeo-events identified in sedimentary series are often widespread, high-magnitude events with return periods close to a millennium, i.e. usually beyond historical records. Normal ‘background’ processes provide only thin deposits that are not interpretable in the geological record.
Upper slope sand deposits: the example of Campos Basin, a latest Pleistocene-Holocene record of the interaction between alongslope and downslope currents
Authors: Viana A. R. , Faugères J.-C.
Published: April 2008

Upper slope sand deposits constitute large accumulations of well-sorted very fine to coarse sand that are of great economic interest. A depositional model is here proposed based on hydrographic, physiographic and sedimentological characteristics of the modern Campos Basin margin, SE Brazil. Data comprise long-term bottom-current measurements, long and short cores, high-resolution seismic lines and side-scan sonar records. Results indicate that offshelf bed-load transfer of sand is driven by shelf bottom currents forced by combined oceanographic and meteorological factors, among them the ‘sea-floor polishing effect’, the rotatory sweeping of the sea bed by mesoscale eddies. The main conditions for development of upper slope sand accumulations are: (1) convex outer shelf-slope morphology; (2) sandy sediment available at the shelf edge; (3) net offshelf transport of shelf sands induced by shelf-edge bottom currents; (4) the presence of a relatively strong slope boundary current. Transfer to the slope occurs as successive, short-distance-flowing sand fluxes. The latter occur mainly through shelf-edge incisions and lead to elongated and narrow sand lobes on the upper slope. The convex morphology of the upper margin controls the Brazil Current (BC) flow and two main zones can be identified: a BC ‘funnelling zone’ where the current is accelerated, and a BC ‘expansion zone’ where the current has its speed decelerated. Reworking by the southward-flowing Brazil Current develops gravel lag deposits, erosional scours, and interchannel sand waves on the upper slope (between 200 and 350 m water depth). Downslope, the reduction of slope current intensity enhances the development of flat sand sheets, controlled by the northward flow of the Brazil Counter-Current. The upper Quaternary vertical facies succession is there characterized by a coarsening-to fining-up asymmetric sequence. Upper Pleistocene sand-mud intercalations are overlain gradually or with a sharp or erosive contact by lower Holocene coarse to finegrained clean sands that grade to upper Holocene fine-grained muddy sands toward the top.
Hemipelagites: processes, facies and model
Authors: Stow Dorrik A. V. , Tabrez Ali R.
Published: April 2008

Detailed sedimentological studies have been carried out on Pleistocene to Recent sediments from the Makran margin and on Miocene to Recent sediments from the Oman margin of the NW Indian Ocean. In both area, hemipelagites make up
c.
50% of the succession, being closely interbedded with turbidites (Makran) and pelagites (Oman). Their sedimentary features (structure, texture, fabric and composition), bedding style and rates of sedimentation are reported and compared with previous detailed studies of both modern and ancient hemipelagites. A composite facies model is presented. Hemipelagites are finegrained sediments typically occurring in deep-water settings. They generally comprise an admixture of >10% biogenic pelagic material and >10% terrigenous or volcanigenic material, in which >40% of the terrigenous (volcanigenic) fraction is silt size or greater (i.e. >4 µm). They are deposited by a combination of vertical settling and slow lateral advection. Hemipelagites are mostly thoroughly bioturbated with ichnofossils including
Zoophycos, Planolites, Chondrites, Phycosiphon
and others. They are generally devoid of primary sedimentary structures, except for an organic-rich facies deposited in anoxic conditions which has a distinctive fissile lamination. The submicroscopic fabric is closely packed with subparallel alignment of clays. The grain size is strongly influenced by the composition, although in general the deposits are fine grained (mean size 5–35 µm), and poorly sorted, in some cases with bimodal, trimodal or polymodal grain-size distributions. The composition includes a biogenic fraction that is calcareous and/or siliceous, and a terrigenous fraction dependent on the nature of the supply pathway, i.e. river plumes, aeolian dust, glacigenic input or volcaniclastic fallout. Chemogenic components (phosphorites, glauconite, ferromanganese nodules) are common in some settings, whereas high organic carbon contents characterize others. Cyclic bedding, typical of climatic forcing, is common although bed boundaries are generally very gradational. Sedimentation rates typically vary from <5 cm/ka to >20 cm/ka and greatly influence development of the different characteristics outlined above. Extremely high rates (>100 cm/ka) occur in zones of hemipelagic sediment focusing, such as slope canyon systems and sediment pathways.
Changes in groundwater chemistry due to rising groundwater levels in the London Basin between 1963 and 1994
Authors: Mühlherr I. H. , Hiscock K. M. , Dennis P. F. , Feast N. A.
Published: April 2008

Commencing in the last century, groundwater abstraction has modified groundwater flow and lowered groundwater levels in the Chalk aquifer of the London Basin. Since the 1960s, a decline in pumping has caused a constant rise in groundwater levels and groundwater is now re-entering strata which had formerly been dewatered. In order to assess the effects of the changed hydraulic conditions on the chemical composition of groundwater, Chalk groundwater samples along a transect from Watford to Croydon across the London Basin were analysed for several chemical parameters in 1994, and compared with results from a similar hydrochemical study reported in 1963.

A general deterioration in groundwater quality was identified. Much higher sulphate and alkali and alkaline earth metal concentrations were found in almost the entire study area and are associated with the reflushing of formerly dewatered strata. In the Chalk outcrop areas, high nitrate, sulphate, chloride and sodium concentrations indicate anthropogenic aquifer pollution. Several chemical and physical processes that control the groundwater chemistry down-gradient towards the centre of the Basin were identified. Finally, five groundwater zones established in 1963 on the basis of hydrochemistry were revised to produce three groundwater zones.
Aquifer susceptibility to side-effects of groundwater exploitation
Authors: Adams B. , Macdonald A. M.
Published: April 2008

Aquifer vulnerability has become a ‘cornerstone’ of groundwater protection policies, taking into account, as it does, aspects of pollution resulting from applied contaminant load. However, this is not the whole story and groundwater resource degradation can also result from other impacts of development such as piezometric level decline, saline intrusion and subsidence. It is generally the case that such impacts are normally diagnosed after they have occurred. Nevertheless, it is evident that certain aquifers are more susceptible to these impacts (often referred to as ‘over-exploitation’) than others.

As a first step towards a method to determine aquifer susceptibility to such impacts, a diagnostic method is introduced as a means to provide managers and planners with an additional method of evaluating potential aquifer degradation as a result of development.

The method, as presented, is at an early stage of development and cannot yet be used for inter- regional comparisons. Used critically, however, the authors believe it provides a useful tool for giving a first estimate of aquifer susceptibility. Planned future developments of the methodology are also presented.