bluuebunny/crossref_metadata_2025_split huggingface dataset:
The evaluation of coal borehole data for reserve estimation and mine design
Authors: Whateley M. K. G. 
Published: April 2008

Abstract
Information derived from the evaluation of the borehole data from a potential coalfield is used in five stages of the project programme. These are geological interpretation, reserve estimation, mine design and coal preparation studies and financial evaluation. This paper will elaborate on part of the first three of these stages. The range of methods available to calculate the resource potential and the confidence of these estimates will be discussed, as well as the geological information needed to form the basis for accurate reserve estimation and mine design. The importance of extracting the maximum amount of information from each borehole is stressed. Careful logging of boreholes will, for example, provide geotechnical information which will be invaluable in the design of both surface and underground mines, as well as assist with groundwater modelling.
Evaluation of the Barapukuria coal deposit NW Bangladesh
Authors: Norman P. S. 
Published: April 2008

Abstract
Bangladesh is a flat, mainly agricultural country with a population exceeding 110 million (770 people per square kilometre). The country occupies a delta plain at the confluence of the two great river systems: the Ganges (Padma) and the Brahmaputra (Jamuna). The country’s complex geological history is largely obscured by a ubiquitous cover of late Tertiary to Quaternary sediments, up to several kilometres thick. This has hampered industrial development as the bulk of the country’s minerals are concealed by this thick cover, making them difficult to identify, evaluate and exploit. Recently, Bangladesh has begun to exploit natural gas from the tectonic belt in the east of the country for electricity generation. Much of the electricity in the west of the country is transmitted large distances from the power stations in the east resulting in intermittent supply and high transmission losses. Permian (Gondwana) coal was discovered in NW Bangladesh in the 1960s, and soon a substantial deposit had been evaluated in Jamalganj, near Bogra. Although these relatively deep reserves were not developed, the Geological Survey of Bangladesh continued with a programme of regional exploration, recognizing that other, shallower, deposits might exist to the north of Bogra and Jamalganj. In 1985, a ‘wildcat’ exploration borehole drilled on a gravity anomaly at Barapukuria discovered substantial thicknesses of coal. After further drilling, the Government of Bangladesh requested international technical assistance for the full evaluation of the deposit and a feasibility study to evaluate its potential. In 1987, the British Government’s Overseas Development Administration (ODA) engaged Wardell Armstrong, International Mining Consultants, to carry out the study in two phases. This paper is a brief case history of the Barapukuria Coal project, from discovery to evaluation. If developed, the coal mine and dedicated coal-fired power-station have the potential to transform NW Bangladesh economically and industrially.
The use of integrated software techniques to evaluate a bedded clay deposit
Authors: Henley S. , Palmer Q. G. , Tucker D. K. 
Published: April 2008

Abstract
This paper describes the use of an integrated software system in the evaluation of a layered Ball Clay deposit in the western part of the Hampshire Basin. The site has been investigated by core drilling over the past 15 years and very detailed lithological logs have been prepared together with a comprehensive set of physical and chemical test results.
A three-dimensional cellular block model was created using DATAMINE software to produce a seven layer model for the deposit. The main clay seam was divided into four horizons based on quality criteria and 14 different physical and chemical properties were interpolated into each of these layers. From this model, the reserves were then calculated on the basis of the proposed pit design. In addition, a series of grade plans were produced for seven of the more critical properties, together with contour and isopach maps of each clay horizon plus the sandy overburden. These plans may be used for the control of clay quality during production and for the prediction of changes in those clay properties which may affect product blending.
The structure and thickness of the basal non-productive clay sequence was also modelled in order to assess areas where this sequence is thin and susceptible to rupturing by high piezometric pressure in the underlying sand sequence. Isopachyte plans and cross sections were generated to demonstrate the variations in thickness of this sequence across the site.
This case history demonstrates the way in which a computer modelled database can be used to provide comprehensive structural interpretation, quality control and volumetric assessment of a bedded deposit with complex variation in both physical and chemical properties.
The use of low cost geostatistical software in reserve estimation
Authors: Nathanail C. P. , Rosenbaum M. S. 
Published: April 2008

Abstract
Geostatistical techniques are now well over a quarter of a century old. Despite initial scepticism caused by misuse due to poor understanding of geostatistics, the spatial correlation between sample points is now commonly incorporated in the assessment of ore reserves.
The recent appearance of several low-cost software packages, written for the ubiquitous IBM compatible personal computer, now permits geostatistics, once the exclusive domain of university researchers and large mining companies, to be more widely available. Such packages offer a choice of variogram models, incorporate anisotropy, support a number of kriging methods, enable limited three-dimensional interpolation and produce high-quality graphical output. Their relative ease of use can do nothing, however, to overcome either the inherent limitations of the PC operating system (MS-DOS) or ignorance on the part of the user of geostatistical techniques.
An understanding of the theory of geostatistics, together with a clear definition of the problem to be solved and a knowledge of the capabilities of the software to be used, are essential if the mistakes made with ore reserve assessment in the early days are not to be repeated by today’s geostatistical apprentices.
Low-cost software has been used as an aid to planning an investigation of the resource around a sand pit and for the assessment of reserves at an opencast coal site.
ONE-D: a program for one-dimensional composite optimization
Authors: Diering J. A. C. 
Published: April 2008

Abstract
The process of compositing sample data from drillholes or traverses for orebodies bounded by a grade cut off rather than a geological boundary can be time consuming. A method for the optimal computation of such composites is described in this paper. A computer program ONE-D has been written which maximizes the dollar value of a composite subject to constraints on minimum and maximum length and a user definable seed value. The seed value is used to force composites to be ‘close’ to a desirable mining line. For complex layered structures, interactive intervention from the user is allowed when structures bifurcate or are folded.
A personal overview of geostatistics
Authors: Royle A. G. 
Published: April 2008

Abstract
The need for accurate data is emphasized and a ‘safe’ in situ sampling formula is developed. Observations on sampling and sample preparation follow. Suggestions are made to ease the problems of variogram modelling.
The more recent forms of kriging are described, with emphasis being laid on their practical utilities. Other directions of development are indicated and it is suggested that professionals who do not claim to have a wide knowledge of geostatistics should nevertheless make known their views on what they require from geostatisticans. What were once regarded as peripheral, rather than core, systems are finding wider usages. Examples are database management, graphics that introduce carry-over from CAD-CAM systems, and, of course that much abused title ‘Information Technology’ and its synonyms. With regret it must be noted that many recent symposia have been mostly concerned with theoretical notions whose practical applications remain obscure.
Recoverable reserve estimation by conditional simulation
Authors: Ravenscroft Peter J. 
Published: April 2008

Abstract
Recoverable reserves are defined as the tonnage and grade that can be recovered above a given cut-off grade in a selective mining operation. Their estimation depends on three factors: the support, information and constraint effects. These factors are discussed, and some traditional methods for estimation of global and local recoverable reserves are reviewed. The technique of conditional simulation is proposed as a practical alternative to some of the more complex methods currently used. The broad concepts of conditional simulation are discussed, and some alternative simulation methods presented. A case study on a set of real mining data illustrates the use of the conditional simulation approach to recoverable reserve estimation, with the support and information effects being modelled very simply. Results are compared with the discrete gaussian model, and with ordinary kriging, which is shown to be unsuitable for recoverable reserve estimation.
Qualitative modelling: fractal geometry in mineral deposit evaluation
Authors: Walduck G. P. 
Published: April 2008

Abstract
The spacial distribution of the physical characteristics of a mineral deposit (its elevation, thickness, grade, etc.) can be estimated with measurable limits of accuracy by geostatistical techniques, but the estimates are smoothed. Local fluctuations of such variables as hanging-wall position or orebody thickness may be of great importance to the planning function, since they can influence choice of equipment or have an important and unavoidable effect on grade dilution or ore recovery. Fractal geometry can be used to generate qualitatively detailed views of these variables, with their complexity explicit. This paper describes several constructs using fractal concepts for two-dimensional image generation. The images can be derived from data sets and used for purposes such as the planning of mineral extraction systems; they are faithful to the original seed data. The constructs are analysed and compared, through their semi-variograms, with conventional models.
Can sediment geochemistry record changes in coastal upwelling palaeoproductivity? Evidence from northwest Africa and the Arabian Sea
Authors: Shimmield Graham B. 
Published: April 2008

Abstract

The causes and consequences of organic carbon (C
org
) burial in sediments underlying regions of coastal upwelling are of profound importance to studies of palaeoceanography and palaeoclimatology alike. The primary control on coastal upwelling, wind stress and resulting Ekman transport, is linked intimately to variation in the Earth’s insolation record via a variety of feedback mechanisms. In comparison, the nutrients required to sustain productivity, and the factors affecting the C
org
content of the sediment, are related to variation in global glacial boundary conditions. Using a variety of geochemical indicators, it is apparent that the record of upwelling off northwest Africa, driven by the northeast trade winds, is characterized by arid glacial conditions and high wind stress sustaining elevated euphotic zone productivity. The resulting C
org
accumulation record reflects higher palaeoproductivity during glacial episodes. In contrast, the Arabian Sea upwelling is seasonal. Faunal and geochemical (Ba/Al, U/Th ratios) indicators suggest strong interglacial (23 ka) cyclicity in the Southwest Monsoon. The C
org
record is spatially and temporally consistent, but in disagreement with other palaeoproductivity indicators. These results point to the decoupling of surface ocean productivity in areas of coastal upwelling from deep-ocean circulation and nutrient supply. This result has important consequences for driving atmospheric
p
CO
2
changes on timescales less than that of oceanic mixing. Further applications of geochemical tracers to areas of coastal upwelling, such as northwest Africa and Peru, are needed urgently.
Foraminiferal production and monsoonal upwelling in the Arabian Sea: evidence from sediment traps
Authors: Curry W. B. , Ostermann D. R. , Guptha M. V. S. , Ittekkot V. 
Published: April 2008

Abstract

Planktonic foraminifera collected in sediment traps in the Arabian Sea during 1986 and 1987 responded to the southern Asian monsoon with changes in productivity, relative abundance of species and isotopic shell chemistry. Most species of foraminifera increased in flux shortly after the advent of the southwest monsoon.
G. bulloides
increased its production rate by three orders of magnitude. The isotopic chemistry of
G. ruber
recorded the increase in monsoon upwelling by increasing its δ
18
O values by about 1‰, accurately reflecting the average 4°C sea surface temperature decrease associated with the upwelling. The mean value of δ
18
O for
G. ruber
was greater in the western Arabian Sea than in the central or eastern basins because upwelling in that region cools surface water. The carbon isotopic composition of
G. ruber
does not have a clear temporal or geographical relationship to upwelling. While its δ
13
C values decreased in the western Arabian Sea during the upwelling event, the mean δ
13
C values remained higher in the western than in the eastern and central Arabian Sea. This longitudinal gradient is opposite to that expected from the geographical gradient of upwelling: the region with the most intense upwelling should have lower δ
13
C values in surface waters because of the upwelling of low-δ
13
C water to the surface.
Organic matter variations in sediments from DSDP sites 362 and 532: evidence of changes in the Benguela Current upwelling system
Authors: Meyers Philip A. 
Published: April 2008

Abstract
Diatom-rich nannofossil oozes from DSDP Sites 362 and 532 on the Walvis Ridge continental terrace contain light-dark cycles which are related to fluctuations in upwelling intensity over these sites from Middle Miocene to Holocene times. The dark intervals in the alternations result from dissolution of carbonates and addition of clastic components. Oxidation of marine-derived organic matter is important to dissolution of carbonates in these sediments. Concentrations of organic matter in the dark sections are enhanced by larger contributions of both marine and land-derived material than in light sections. The dark sections appear to correlate with periods of greater Antarctic ice volumes, suggesting that regional upwelling was intensified and that transport of organic matter from Africa by winds and possibly rivers was increased during these times.
Sedimentological borehole image analysis in clastic rocks: a systematic approach to interpretation
Authors: Bourke Lawrence T. 
Published: April 2008

Abstract
Detailed study over the four years since the introduction of the Formation MicroScanner Tool* (FMS) has resulted in the evolution of a systematic interpretation approach to the extraction of a formal sedimentological description of extensive reservoir intervals using borehole images in clastic sediments. This approach takes account of thorough log quality control and the recognition of non-geological artifacts and involves the integration of the available open hole logs to establish lithology, along with the incorporation of core or sidewall cores as ‘hard’ lithological and textural data to ensure interpretation confidence.
The approach is practical and straightforward. However, a workstation provides significant advantages to the skilled interpreter compared with a paper-based analysis. After quality control and recognition of artifact images, five interpretation steps are suggested. (i) Fine-calibrate open hole logs (conventional lithology indicators) from sidewall and conventional core samples. Enhance lithology recognition using dipmeter resistivity curves. (ii) Annotate the above lithological information onto FMS images. (iii) Constrain feature recognition from images using local geological knowledge. (iv) Pick and classify feature dips, then check dip category validity by generating dip and azimuth histograms. Reclassify as necessary. (v) Extract relevant sedimentary and lithological data from images to construct a conventional sedimentological facies description.
One of the key aspects of borehole image analysis is the development of an interpreter’s skill in recognizing geological features from microresistivity images. Finally, aspects of core reconciliation such as depth matching are considered.
Application of FMS images in poorly recovered coring intervals: examples from ODP Leg 129
Authors: Salimullah A. R. M. , Stow D. A. V. 
Published: April 2008

Abstract

A thick sedimentary section was penetrated at three sites in the West Central Pacific during the Ocean Driling Program (ODP) Leg 129. Although average core recovery ranged from 17.3 to 29.5%, recovery in some intervals falls as low as 0–5%. Furthermore, the recovered portion of the core is conventionally assigned to the topmost part of the cored interval, although this is now known to be incorrect in most instances in consolidated parts of the section. These drawbacks have led to incomplete and even erroneous sedimentological interpretations. High-resolution electrical (Formation MicroScanner) images of the borehole obtained by scanning the borehole wall with arrays of small electrodes pressed against the borehole surface can provide:

(1)
detailed sedimentary structure and texture of missing sections of each core, through calibration with visual data obtained from recovered cores;

(2)
the original sedimentary features, where these have been disturbed or brecciated during drilling, as well as drilling artifacts on the borehole wall;

(3)
recognition of sedimentary facies (e.g. slump units in hole 801B) in non-recovered intervals;

(4)
correct location of recovered portions within the cored interval, through matching of specific sedimentary features.

Examples of these applications of the FMS images to the poorly recovered ODP Leg 129 cores are presented. The use of FMS logging has widespread application in any borehole where conventional cores have not been taken or where core recovery is limited. However, log calibration with core samples is essential.
Wireline log signatures of resedimented volcaniclastic facies, ODP Leg 129, West Central Pacific
Authors: Salimullah A. R. M. , Stow D. A. V. 
Published: April 2008

Abstract
During Ocean Drilling Program Leg 129, two sites (800, 801) were drilled in Pigafetta Basin and one site (802) in East Mariana Basin, West Central Pacific. At all three sites, a thick (192–211 m) Cretaceous succession of dominantly volcaniclastic sediments was encountered, and at site 802 a further 222 m of Miocene-Pliocene volcaniclastics were drilled. These sediments are composed mainly of volcaniclastic material that has been resedimented downslope by various mass-flow processes including slumps, debris flows and turbidity currents. Sedimentary structures and textural variations observed in the recovered section can be used to calibrate the corresponding high-resolution Formation Micro-Scanner (FMS*) images and Dipmeter Micro-resistivity readings. Gamma ray log shapes show grain size evolution within a facies. Fining-upwards and coarsening-upwards grain size trends are observed for some sequences of turbidites and debrites. No obvious change in grain size is observed through massive structureless sandstones. CCA (calcium yield in decimal fraction) and CSI (silicon yield in decimal fraction) readings from the geochemical combination logs, correlated with visual compositional data, are useful to define calcareous and siliceous turbidite facies. This combination of wireline logs has been used in the poorly recovered intervals of volcaniclastic section in the ODP Leg 129 sites to improve significantly our understanding of basinal sedimentation and tectonics in the area.
High-frequency pseudo-Rayleigh waves as a new indicator of shear velocity
Authors: Raaen Arne Marius 
Published: April 2008

Abstract
In slow formations, where the shear velocity is lower than the mud compressional velocity, several indirect methods have been used to estimate shear velocity from full waveform acoustic logs. These methods include Stoneley wave velocity and inversion of refracted P-wave amplitude. In this paper we show that in addition to the methods previously reported, the amplitude of the leaky pseudo-Rayleigh waves may in some cases be strongly dependent on the shear wave velocity of the formation. Numerical analysis has shown that there is also some dependence on the velocity and attenuation of the mud, and the borehole radius, whereas the amplitude of the leaky pseudo-Rayleigh waves is quite insensitive to the compressional velocity of the formation and the intrinsic anelasticity of the formation. The predictions have been confirmed by model experiments in a slow formation. It is felt that the effect may be a useful tool, for example, in the study of stress dependent velocities around a borehole.
Downhole mineralogy logs: mineral inversion methods and the problem of compositional colinearity
Authors: Harvey P. K. , Lovell M. A. 
Published: April 2008

Abstract
The inversion of chemical data derived from geochemical and related nuclear spectroscopy tools to provide mineralogy logs is now a widespread approach to the interpretation of these data. The most valuable of such transforms attempt to provide the percentages of actual phases present (minerals and fluids) at each depth interval rather than the ideal minerals occurring in simple theoretical models. Of the numerous problems involved in the inversion for a particular phase assemblage, the most serious is probably that of compositional colinearity in which three or more of the phases sought lie on, or close to, the same compositional plane. Depending upon the algorithm used for the inversion the effects of such compositional constraints may vary between a failure to find any (numerical) solution, failure to find a unique solution, or a solution which may be significantly in error for only a very small deviation in the chemical log or phase compositions. These effects are illustrated using geochemical logs from sedimentary environments together with examples from laboratory derived and numerically simulated geochemical data.
The third age of wireline log analysis: application to reservoir diagenesis
Authors: Selley R. C. 
Published: April 2008

Abstract
Geophysical well logs were first developed to identify the porosity and fluid composition of potential petroleum reservoirs. Subsequently their use was extended to include diagnosing the depositional environment of reservoirs, as an aid to predicting their geometry. Both these techniques are now routine.
A new age of the application of geophysical logs now dawns due to the enhanced understanding of the diagenetic processes that affect petroleum reservoirs, including cementation which destroys porosity and solution which enhances it. These ideas can be used to interpret both conventional porosity logs and the new types of log that, when carefully interpreted, allow vertical variations in mineralogy to be measured.
Three main diagenetic effects can be recognized in geophysical well logs: facies-related diagenetic phenomena; cemented and leached zones related to migrating diagenetic fronts of acid meteoric or deep connate fluids; and diagenetic effects related to petroleum migration and entrapment.