Geological Input Research Articles

A probabilistic approach to improved geological knowledge and reduced exploration risks using hydrocarbon migration modelling

This paper elaborates a methodology for assessing the consequences of uncertainties in the source and reservoir models on hydrocarbon phase distributions in prospects by improving the a-priori probability distributions. The uncertainties of geological systems can be described by probabilistic distributions of quantified geological variables, such as source rock and reservoir thicknesses. A Monte Carlo simulation of hydrocarbon generation, expulsion, migration and entrapment is carried out with probabilistic distributions defining important input variables. A weight for each simulation run is computed from a misfit function that describes how well the modelled oil and gas columns fit the observed columns in a set of calibration wells. These weights are used to compile a-posteriori probability distributions of the input variables. The resulting probability distributions, therefore, describe the uncertainties of the geological system after the calibration of the migration model. In a demonstration example from the Tampen Spur area of the North Sea, the most sensitive geological input distributions become significantly narrower, thus limiting the range of possible outcomes. Other distributions become more uneven, with peaks and lows. The changes in the variable distributions have been quantified and variables can, therefore, be ranked with respect to their impact on changes in probabilities for key outcomes. A large number of simulation runs is required for the proposed method to be effective because many simulation runs result in too large a misfit. A statistical fit of a second-order function to the misfit values allows for the effective screening of input variables, thus reducing the computing time, in the demonstration example, to 15% of the unscreened times. The result of the analysis is that the effect of geological uncertainties on output values is effectively reduced and that a quantitative learning has been obtained. This knowledge can be applied in other hydrocarbon generation and migration studies within the study area, allowing for more rapid and more accurate estimates of oil and gas resources before drilling.

Environmental magnetic approach towards the quantification of pollution in Kathmandu urban area, Nepal

The Kathmandu Valley is a bowl-shaped intermontane basin, which occupies an area of 583 km 2 in the heart of the Himalayas, with its floor at ≈1400 m and the surrounding mountains attaining a height of 2000–2800 m. It is inhabited by ≈1.5 million people, concentrated mostly in three cities, Kathmandu, Patan and Bhaktapur. Due to rapid but uncontrolled urbanisation and factors such as traffic movement, emissions from brick-kilns, cement factories, waste disposal and biomass burning, environmental pollution has been constantly increasing; adversely affecting land, water, air and biological systems. In order to quantify the degree of environmental pollution using magnetic methods, magnetic susceptibility of soils, sediments and roadside materials, in and outside the Kathmandu urban area has been measured. In areas far from roads or industry, median magnetic susceptibility is between 3 and 35 × 10 −5 SI, similar to that observed in the valley-filling clastic sediments and hence consistent with geologic or pedogenic origin. In traverses of in situ susceptibility across roads, a 5-m wide zone situated on either side of the asphalt-paved road exhibits an enhancement zone with maximum susceptibility of 240–850 × 10 −5 SI occurring 0.5–2.5 m from the road edge. In urban recreational areas, magnetic susceptibility varies within a broad range (3 to >100 × 10 −5 SI) with lowest values occurring ≈50 m from surrounding roads, in areas least disturbed by human activity. A systematic increase in susceptibility towards the roads or industrial sites is observed. Within urban areas, in the vicinity of heavy traffic or industrial sites, the upper 30–50 cm of soil profiles exhibit frequent enhancement in susceptibility, of one or two orders of magnitude, higher than those expected from geologic input. Such enhancement is attributed to input from anthropogenic or industrial sources. Magneto-mineralogical analyses and scanning electron microscopy on magnetic extracts, grain size fractions or bulk samples of road dust and soils, suggest lithogenic magnetite-like minerals and anthropogenic magnetic spherules to be the dominant contributors to the magnetic susceptibility signal. As the soils, sediments and roadside material exhibit significant susceptibility contrasts, which are most effective in identifying traffic-related pollution “hotspots”, it is highly desirable that the potential of susceptibility maps of the entire area affected by urbanisation, be fully explored to assess the status of environmental degradation.

MODFLOW 2000 head uncertainty, a first-order second moment method.

A computationally efficient method to estimate the variance and covariance in piezometric head results computed through MODFLOW 2000 using a first-order second moment (FOSM) approach is presented. This methodology employs a first-order Taylor series expansion to combine model sensitivity with uncertainty in geologic data. MODFLOW 2000 is used to calculate both the ground water head and the sensitivity of head to changes in input data. From a limited number of samples, geologic data are extrapolated and their associated uncertainties are computed through a conditional probability calculation. Combining the spatially related sensitivity and input uncertainty produces the variance-covariance matrix, the diagonal of which is used to yield the standard deviation in MODFLOW 2000 head. The variance in piezometric head can be used for calibrating the model, estimating confidence intervals, directing exploration, and evaluating the reliability of a design. A case study illustrates the approach, where aquifer transmissivity is the spatially related uncertain geologic input data. The FOSM methodology is shown to be applicable for calculating output uncertainty for (1) spatially related input and output data, and (2) multiple input parameters (transmissivity and recharge).

Using calibrated shale gouge ratio to estimate hydrocarbon column heights

Fault-zone composition, estimated using the shale gouge ratio (SGR) algorithm, can be empirically calibrated with pressure data to define depth-dependent seal-failure envelopes relating SGR to fault-zone capillary entry pressure (FZP) by the equation: FZP (bar) = 10 (SGR/27 − C). C is 0.5 for burial depths less then 3.0 km (9850 ft), C is 0.25 for burial depths between 3.0 and 3.5 km (9850–11,500 ft), and C is 0 where the burial depth exceeds 3.5 km (11,500 ft).The seal-failure envelope provides a method to estimate the maximum height of a hydrocarbon column that can be supported by the fault. Leakage of hydrocarbons across a fault occurs when the buoyancy pressure exceeds the capillary entry pressure of the fault and is not confined to the crest of the structure or even to where the SGR value is lowest.Established calibration diagrams based on across-fault pressure differences have overgeneralized the relationship between increasing SGR and increasing pressure support. Calibration diagrams based on buoyancy pressure show that gas and oil data exhibit a correlation between increasing SGR and increasing buoyancy pressure but only between SGR values of 20 and 40%. No increase in the strength of a seal is present, as reflected by an increase in maximum supportable buoyancy pressure, at SGR values greater than about 40% for both gas and oil data. Column heights do not continue to increase in the SGR range 50–100%.Estimating hydrocarbon column heights using seal attributes depends upon the geologic input to the model, in particular, pressure data, volumetric shale fraction, and the precision of the three-dimensional mapping of reservoir geometry in the vicinity of the fault.

Review of Geological Aspects of Slope Engineering

The dominant slope-forming materials in Hong Kong, namely colluvium, saprolitic soils and weathered granitic and volcanic rocks, are inherently variable. The importance of appropriate geological input in local slope engineering has been recognised for over 40 years. Recent improvements in geological knowledge and developments in geological aspects of site Investigation, slope design and construction practice are reviewed, with emphasis on understanding of landslide mechanisms and detection of potentially adverse ground conditions. Most of these improvements have arisen from systematic landslide Investigations, or as a result of follow-up research and development studies. There is scope for further enhancement of practice in several areas, including appraisal of the Influence of discontinuities and transient adverse groundwater conditions on slope stability, characterisation of saprolites and colluvial soils in terms of engineering properties, site inspection/mapping during ground Investigation andfor Engineer Inspections in slope maintenance programmes, verification of ground conditions assumed in prescriptive design work, and risk assessment Of londsliding on natural terrain.

Regional variations in atmospheric deposition and sources of anthropogenic lead in lake sediments across the Canadian Arctic

Stable Pb isotope profiles in dated lake sediment cores were used to gauge the relative amounts and possible sources of anthropogenic Pb deposited from the atmosphere in different regions of the Canadian Arctic. A distinct north-south difference was found. In four High Arctic lakes (i.e., north of 66°N) in this study, recent Pb isotopic shifts or concentration increases attributable to anthropogenic Pb were negligible. The maximum possible contribution from anthropogenic Pb was 0 to 19% of acid-leachable Pb in the 1980s or 1990s. In contrast, two lakes in the Hudson Bay region displayed significantly lower Pb isotope ratios and threefold to fivefold increases of Pb concentrations in modern sediments, corresponding to anthropogenic Pb inputs of at least 72 to 91% of leachable Pb. Eurasian urban and industrial Pb is known to dominate the High Arctic atmosphere. A possible explanation for its negligible influence on northern lake sediments is that atmospheric Pb deposition at northern latitudes is reduced compared with southern regions and is small compared to local geological inputs. 210Pb deposition declines with increasing latitude, apparently because of declining precipitation rates; stable Pb deposition may be similarly affected. Meteorological considerations and variations in the post-1900 Pb isotopic trajectories indicated that the predominant anthropogenic Pb source region in NW Hudson Bay was Eurasia, while in SE Hudson Bay, it was Canada and the United States, with a minor Eurasian component.

Mid‐Palaeocene palaeogeography of the eastern North Sea basin: integrating geological evidence and 3D geodynamic modelling

ABSTRACTThe Mid‐Palaeocene palaeogeography of Denmark and the surrounding areas have been reconstructed on the basis of published geological data integrated with 3D geodynamic modelling. The use of numerical modelling enables quantitative testing of scenarios based on geological input alone and thus helps constrain likely palaeo‐water depths in areas where the geological data are inconclusive or incomplete.The interpretation of large‐scale erosional valleys and small‐scale circular depressions at the Mid‐Palaeocene Top Chalk surface in the Norwegian–Danish basin as either submarine or subaerial features is enigmatic and has strong implications for palaeogeographical reconstructions of the eastern North Sea basin.A 3D thermo‐mechanical model is employed in order to constrain the likely palaeo‐water depths of the eastern North Sea basin during the Palaeocene. The model treats the lithosphere as an elasto‐visco‐plastic continuum and models the lithospheric response to the regional stress field and thermal structure. The model includes the effects of sea‐level change, sedimentation and erosion, from the Mid Cretaceous to the present. Modelling results reproduce to first order geological data such as present sediment isopachs and palaeo‐water depths.It is concluded that the Mid Palaeocene water depths in the Norwegian–Danish basin were about 250 m. The erosional valleys and circular depressions at the top of the Upper Cretaceous‐Danian Chalk Group are thus interpreted to have formed in relatively deep water rather than due to subaerial exposure. Likely interpretations of the structures are therefore submarine valleys and pockmarks.

Comparison of popular AVO attributes, AVO inversion, and calibrated AVO predictions

Amplitude variation with offset techniques are used by exploration, development, and production teams to assist hydrocarbon identification in clastic depositional settings. While exploration groups tend to use AVO attributes for detection and risk quantification, exploitation and production groups use AVO attributes for reservoir characterization and even fluid-front monitoring. Accurate geoscience and engineering reservoir charcterization (parametrization) improve prediction of hydrocarbon reserves and reservoir production. It is therefore essential to understand which seismic attributes will best contribute to the characterization of the reservoir. This paper focuses on the accuracy of AVO attributes commonly used in reservoir characterization. In particular, the effectiveness of intercept-gradient, lambda-mu-rho λ-μ-ρ), and elastic impedance AVO attributes, and their ability to accurately predict reservoir extent are presented. Derivative AVO attribute volumes that are caliabrated to well data are also compared. It can be argued that these techniques are essentially the same, because each attribute set comes from the measurement of AVO across a velocity-corrected CMP gather. But some geoscientists prefer one attribute type to another or only have access to a certain attribute. This paper examines methodology differences between the various AVO attributes and, more importantly, compares the final reservoir description predicted by these attributes. Please note that looking for the best AVO attribute for reservoir characterization does not mean that this attribute will be the sole seismological contribution to the reservoir parameterization for reservoir simulations. Rather it is a method to determine the best AVO input (if any) to accompany other geophysical and geologic inputs to the modeling. A data model with variable reservoir thicknesses was constructed using well log data from the middle Miocene section on the northern continental shelf of the Gulf of Mexico. A thin blocky sand encased by shales was selected as the reservoir. This sand, when gas-saturated, can be categorized as a class …

ROSE, E. P. F. & NATHANAIL, C. P. (eds) 2000. Geology and Warfare. Examples of the Influence of Terrain and Geologists on Military Operations. xiv+498 pp. London, Bath: Geological Society of London. Price £85.00, US $142.00; members' price £39.00, US $65.00; AAPG/SEPM/GSA price £51.00, US $85.00 (hard covers). ISBN 1 86239 065 7.

ROSE, E. P. F. & NATHANAIL, C. P. (eds) 2000. Geology and Warfare. Examples of the Influence of Terrain and Geologists on Military Operations. xiv+498 pp. London, Bath: Geological Society of London. Price £85.00, US 65.00; AAPG/SEPM/GSA price £51.00, US $85.00 (hard covers). ISBN 1 86239 065 7. - Volume 138 Issue 3

Geological characterization of weak cataclastic fault rocks with regards to the assessment of their geomechanical properties

A new quantitative method for the characterization of weak cataclastic fault rocks (e.g. fault breccia, gouges) is presented. Applied to find correlations with geomechanical laboratory tests, the thin section and X-ray diffraction analyses used for the method are on a similar scale. The method is shown to be appropriate for the characterization of a large range of different types of weak cataclastic fault rocks (kakirites) and involves appraising their mineralogical composition and microstructural characteristics. The correlation of the geological and geomechanical properties of kakirites based on this approach has shown promising results. The method could provide, in the future, the required geological input data for a mathematical modelling of the geomechanical behaviour of cataclastic fault zones.

Iron Deposits of the Labrador Trough

The Labrador Trough contains world-class iron deposits which have been mined since 1954. The direct shipping of Knob Lake ores were mined at Schefferville from 1954 to 1982. Concentrate production began in 1961 in the southwest end of the Trough, with three mines currently producing concentrate and pellets at a rate of 35 Mt per year. West and north of Schefferville, several billion tonnes of taconite have been outlined in fine-grained, cherty magnetite iron formation. Several deposits of highly metamorphosed magnetite-specularite iron formation are located west of Ungava Bay. Numerous studies have shown that this medium- to fine-grained iron formation can be beneficated to 66% to 68% iron. In the area from Wabush Lake to Mont-Wright, a medium- to coarse-grained friable specularite-quartz iron formation is repeated by folding to form several large deposits. In this area, three mining operations are located with reserves and resources in the order of 5 billion tonnes. The iron deposits occur within iron formation in sediments in the extensive Proterozoic geosyn-cline called the Labrador Trough. Several facies of iron formation within the Sokoman Formation reflect variations in chemical composition and depositional conditions. The correlation between the mineralogy and textures is discussed to illustrate the development of different types of iron ores. This band extends for about 1100 km southeast of Ungava Bay through both Quebec and Labrador. Further south, it turns southwest past the Wabush and Mont-Wright areas to within 300 km of the St. Lawrence River. The iron formation is essentially folded and faulted along most of its length. The degree of metamorphism is variable, ranging from intense in the northern and southern portions to greenschist facies in the central portion. The stratigraphy, structure and mineralogy of the producing mines are described along with the history of discoveries. Geological input is required to achieve the strict specifications of the international iron ore market.

Time–temperature relations for the remagnetization of pyrrhotite (Fe 7S 8) and their use in estimating paleotemperatures

Paleotemperature controls the maturation of coal and hydrocarbons in sedimentary basins and is also important in determining paleogeothermal gradient and hence tectonic style in exhumed metamorphic terrains. One method of estimating paleotemperature analyses the partial remagnetization of a rock due to heating in thick volcanic or sedimentary sequences, over subcrustal heat sources such as plumes, or at convergent plate margins. The overprinted natural remanent magnetization (NRM) of a rock records both the age and the paleotemperature of remagnetization, but a temperature correction from laboratory to geological time scales is required, using theoretical time–temperature relations. Time–temperature relations are well known for magnetite (Fe 3O 4) but are reported here for the first time for pyrrhotite (Fe 7S 8), another common NRM carrier. Data for each mineral separately yield independent estimates of paleotemperature if geologically reasonable estimates of heating time can be made. Paleotemperature can be estimated without geological input if data for both minerals are combined. Together with the age of remagnetization, determined from the paleomagnetic pole of the NRM overprint, these paleotemperature estimates can be used to infer the history of heating and uplift following burial. As a test case, we examine thermally acquired NRM overprints carried by pyrrhotite (Fe 7S 8) and magnetite (Fe 3O 4) in the Milton Monzonite of southeastern Australia. These overprints record a heating event about 100 Ma ago, probably thermal doming prior to rifting of the Tasman Sea, that upgraded coal rank in the Sydney Basin. Extrapolating from laboratory to geological times, using the new time–temperature contours for pyrrhotite, we estimate that the presently exposed Sydney Basin in the vicinity of the Milton Monzonite was remagnetized by heating to 165±30°C for ≈100 ka. Assuming a paleogeothermal gradient of 70°C/km appropriate for young or incipient rifts, the depth of burial at the time of remagnetization is estimated to have been 2.3±0.4 km. This figure is in excellent agreement with independent estimates based on reflectance data for the coal accessory mineral vitrinite.

Ad Hoc Committee on Global Climate Issues: Annual Report

The AAPG Ad Hoc Committee on Global Climate Issues has studied the supposition of human-induced climate change since the committee's inception in January 1998. This paper details the progress and findings of the committee through June 1999. At that time there had been essentially no geologic input into the global climate change debate. The following statements reflect the current state of climate knowledge from the geologic perspective as interpreted by the majority of the committee membership. The committee recognizes that new data could change its conclusions. The earth's climate is constantly changing owing to natural variability in earth processes. Natural climate variability over recent geological time is greater than reasonable estimates of potential human-induced greenhouse gas changes. Because no tool is available to test the supposition of human-induced climate change and the range of natural variability is so great, there is no discernible human influence on global climate at this time.

ABSTRACT: Geologic Information and Seismic Data-How Much Do We Need?

Abstract Much effort has gone into jointly using geologic information and seismic data. At the same time the variety of tasks addressed using such data has expanded quite significantly. We have moved from simple correlations for mapping structures to detailed analysis of reservoirs including defining flow units and parameter distributions. We are also building intricate velocity models for sophisticated methods of depth imagery. It seems quite reasonable to seek great detail where there is an available database of geologic information to accompany seismic values. Such goals like optimizing reservoir performance or fully understanding stratigraphic systems make detail analysis clearly worthwhile. In fact, several geostatistical tools exist for addressing such projects and these are often coupled with advanced neural network approaches to enhance decision making. For the case of velocity models to guide depth imaging, the quest for detailed geologic information is often unrealistic in view of the stage when such tools are sometimes applied. Depth imaging is frequently used in preliminary studies to assist in basic understanding and mapping. At such times geologic information is sparse or even non-existent. Hence approaches requiring significant a priori geologic inputs are not likely to perform well. We advocate balancing what we are attempting to accomplish with the degree of geologic information available. Methods that recognize such balance are illustrated. Recommendations are also given for attaining both reasonable and reliable results. End_of_Record - Last_Page 247-------

Object and Pixel-Based Reservoir Modeling of a Braided Fluvial Reservoir

To assess differences between object and pixel-based reservoir modeling techniques, ten realizations of a UK Continental Shelf braided fluvial reservoir were produced using Boolean Simulation (BS) and Sequential Indicator Simulation (SIS). Various sensitivities associated with geological input data as well as with technique-specific modeling parameters were analyzed for both techniques. The resulting realizations from the object-based and pixel-based modeling efforts were assessed by visual inspection and by evaluation of the values and ranges of the single-phase effective permeability tensors, obtained through upscaling. The BS method performed well for the modeling of two types of fluvial channels, yielding well-confined channels, but failed to represent the complex interaction of these with sheetflood and other deposits present in the reservoir. SIS gave less confined channels and had great difficulty in representing the large-scale geometries of one type of channel while maintaining its appropriate proportions. Adding an SIS background to the Boolean channels, as opposed to a Boolean background, resulted in an improved distribution of sheetflood bodies. The permeability results indicated that the SIS method yielded models with much higher horizontal permeability values (20–100%) and lower horizontal anisotropy than the BS versions. By widening the channel distribution and increasing the range of azimuths, however, the BS-produced models gave results approaching the SIS behavior. For this reservoir, we chose to combine the two methods by using object-based channels and a pixel-based heterogeneous background, resulting in moderate permeability and anisotropy levels.

Environmental geology in urban development

Environmenta l geology, although well est ablished in the geological fra ternity, is still little understood by the rest of the community. This lack of appreciation on its u sefulness in urban planning and land development has resulted, to some extent, in the sterilisation or non-optimal use of mineral resources in Malaysia, particularly with respect to non-metallic minerals. In a ddition, development over geologically hazardous areas, without proper mitigating measures, has contributed towards man-ma de disasters, thus addili.g to the cost of remedial and maintenance work. Another outcome, especially during periods of rapid development and without appropriate environmental geological inputs, has been increased erosion, landslides, flash floods , pollution of waters, rapid run-off and even lowering of the groundwater table. The long-term effect ofthis is a n increase of water-stressed areas, especially during the dry season. Environmental geology can also be applied in many other areas of urba n planning s uch as for the disposal of solid and toxic waste, determination of sources for water supply, infrastructure development (roads, dams, airports, seaports etc.), recreation and tourism, land reclamation, identification and clean-up of contaminated sites, as well as conservation, among others. Inspite of its wide variet y of applications insufficient use of geology is m ade in urban planning. Environmental geology maps and reports (also known as engineering geology maps in Europe) can significantly assist the planner in planning of townships, preparation of structure and local plans or in drawing up oflayout plans for specific projects. Even during the development stage advantage should be taken to update the geological database and consultants and developers should, with the help of geologists, translate it into potential en vironmental impa cts and thus put in place appropriate mitigating measures. Although the applications of environmental geology are numerous yet it is insufficiently used. The reasons include insuffi cient or lack of cross professional interaction and lack of training in maximising the use of geology for urban planning and land development. This is compounded by the fact that reports written by geologists are too technical in nature and understood ma inly by geological specialists. Furthermore the scale of maps is critical as, more often than not, they tend to be on a reconnaissance scale that are more appropriate for macro landuse planning. For site specific projects, maps on a detailed scale (1:1,500-1:5,000) will be more useful to enable the incorporation of elements of environmental geology in planning. There is certainly an urgent need to close this communication gap in Malaysia, in particular, and Southeast Asia, in general. In North America, Europe and Australia, progress h as been made but more can be done. There is also an urgent need to produce simple thematic maps and reports, understandable to planners, architects, engineers, developers and even politicians, to ensure that maximum advantage is taken of geological inputs for urban planning and development. The thematic maps should cover geology, geochemistry of rocks, soils and water s, geotechnical properties of soils and rocks, mineral resources, especially construction materials, geotechnical classification of slopes, landslides, flood-prone areas, thickness of overburden (rock line), distribution and thickness of peat, groundwater flow pattern etc. However maps such as gen eral foundation suitability, potential waste disposal sites, relative compressibility, sinkhole susceptibility, ripperbility potential, landslide s usceptibility etc., derived from the raw data collected, will be easier to use and more useful to t h e planner or developer. The additional cost is very small when compared to t h e cost of the proj ect or the potential benefits expected. Since the early nineties and subs.equently after the 1995 amendments to the Town and Country Planning Act (1976), geological inputs are now a requirement. For bigger projects such as the Kuala Lumpur International Airport at Sepang, the new a dministrative centre for Kuala Lumpur (Putrajaya), the information technology city named Cyberj aya and t h e International Commonwealth University of Malaysia, appropriate geological inputs were provided for l ayout plans. However this practice is not the norm and for the State level it is recommended that the Geological Survey Department be co-opted into

Improved Prediction of Reservoir Behavior Through Integration of Quantitative Geological and Petrophysical Data

Summary This paper presents a cost effective, quantitative methodology for reservoir characterization that results in improved prediction of permeability, production and injection behavior during primary and enhanced recovery operations. The method is based fundamentally on the identification of rock types (intervals of rock with unique pore geometry). This approach uses image analysis of core material to quantitatively identify various pore geometries. When combined with more traditional petrophysical measurements, such as porosity, permeability and capillary pressure, intervals of rock with various pore geometries (rock types) can be recognized from conventional wireline logs in noncored wells or intervals. This allows for calculation of rock type and improved estimation of permeability and saturation. Based on geological input, the reservoirs can then be divided into flow units (hydrodynamically continuous layers) and grid blocks for simulation. Results are presented of detailed studies in two, distinctly different, complex reservoirs: a low porosity carbonate reservoir and a high porosity sandstone reservoir. When combined with production data, the improved characterization and predictability of performance obtained using this unique technique have provided a means of targeting the highest quality development drilling locations, improving pattern design, rapidly recognizing conformance and formation damage problems, identifying bypassed pay intervals, and improving assessments of present and future value.

Abstract: Evaluation of Geological Input Parameters in an Exploration Project; How to Organize the Data and Use them in a Model.

Abstract: Evaluation of Geological Input Parameters in an Exploration Project; How to Organize the Data and Use them in a Model.

Prediction of volumes and risk in hydrocarbon exploration: a quantification of geology

The prediction of the hydrocarbon potential of a specific trap or of a number of specific traps (venture), referred to herein as prospect appraisal, concerns a probabilistic exercise based on the quantification of geology in terms of structural closure, reservoir quality, hydrocarbon charge, and the retention potential of the seal. Its objectives include: (a) prediction of the hydrocarbon volumes that could be present in the trap from an analysis of its geologic attributes; (b) the amount of uncertainty introduced in the volumetric prediction by the uncertainties in the subsurface geology; (c) the risk that one or more of the essential attributes of the prospect are underdeveloped and recoverable reserves are absent. The uncertainty of the geologic input requires a probabilistic approach, for which the Monte Carlo procedure is well suited.

Thermal springs of Malaysia and their potentialdevelopment

The study on the potential development of hot springs for the tourism industry in Malaysiawas conducted. Out of the 40 hot springs covered, the study identified 9 hot springs having a high potential for development, 14 having medium potential and the remaining 17 having low or least potential for development. This conclusion was arrived at after considering the technical and economic feasibility of the various hot springs. Technical feasibility criteria includes geological factors, water quality, temperature and flow rate. The economic feasibility criteria considers measures such as accessibility, current and market potentials in terms of visitors, surrounding attractions and existing inventory and facilities available. A geological input indicates that high potential hot springs are located close to or within the granite body and associated with major permeable fault zones. They normally occur at low elevation adjacent to topographic highs. High potential hot springs are also characterised by high water temperature, substantial flowrate and very good water quality which is important for water-body contact activities such as soaking. Economic criteria for high potential hot springs are associated with good accessibility, good market, good surrounding attractions like rural and village setting and well developed facilities and infrastructures.