Gamma and resistivity logs for characterization of Gondwana coal seams at the Northwestern part of Bangladesh

Different parameters obtained through geophysical borehole logging using self potential, resistivity, gamma–gamma, neutron, natural gamma, and acoustic tools, help in the identification of strata and estimation of the physical, electrical, and acoustical properties of the subsurface lithology. In the coal mining industry, currently, the main application for the logs is to determine coal seam depth, thickness together with coal seam quality, qualitatively. Gamma and resistivity logging in seven boreholes at the Phulbari Coal Basin show high resistivity value and low gamma count rate data in coal seams than the interbeds. An attempt has been made to identify and characterize Gondwana coal seams to a limited extent of seam depth, thickness, and quality in seven boreholes together with draw relationship between resistivity, gamma count rate, and ash content of coal at the Phulbari Coal Basin of Bangladesh.     

Suspended sediment in the Ganges and Brahmaputra Rivers in Bangladesh: observation from TM and AVHRR data

Remote sensing was used to understand the seasonal and spatial variation of suspended sediment in the Ganges and Brahmaputra Rivers in Bangladesh for two different discharge periods. Suspended sediment concentration (SSC) in these rivers was estimated from the reflectance of Landsat TM band 3. During the high discharge period, SSC in the Ganges is higher than that in the Brahmaputra. But in the low discharge period, this is reversed. Both erosional and depositional processes are active on their flood plains. Significant fluctuations in SSC and in suspended sediment load were observed along their courses because of river bank erosion and deposition and/or scouring and aggradation of river beds. Owing to scouring and turbulence, SSC increases markedly at the confluence of these rivers. Reflectance of AVHRR band 1 data was also analysed to study the distribution of suspended sediment along other reaches of these rivers. Like SSC, reflectance at the confluence zone increases compared with that in the Brahmaputra. However, this increase is not marked compared with the Ganges. The influence of their tributaries on the suspended sediment load could be inferred from the pattern of reflectance. Remote sensing data used in this study was corrected for atmospheric effects. Copyright © 2001 John Wiley & Sons, Ltd.     

An “Olympic” framework for a green decommissioning of an offshore oil platform

Oil and gas offshore platform and installations have a limited life of operations. When oil runs out, many terms are used to describe the situation: abandonment, removal, disposal, decommissioning, etc. Even the issue of decommissioning is now at the forefront of deep water oil drilling for many reason (the enormous costs required for disposal, the increasing number of rigs which required removal, the need to protect the marine environment, legal frameworks), there are very few published researchers studying the problem according to its different facets (legal, environmental, economical etc.). In this paper, we apply the concept of “Olympic” supply chain developed by Lakhal et al. Lakhal, SY, H'Mida S, Islam R. Green Supply Chain parameters for a Canadian Petroleum Refinery Company. International Journal of Environmental Technology and Management, IJETM 2007:7;56–67. to provide feedback for life-cycle offshore platforms. Our approach starts from platform development projects environmentally, exploit it in the respect of the environment and have an efficient decommissioning project.     

Characteristics of meteorological drought in Bangladesh

Meteorological drought events occur in Bangladesh are diagnosed using monthly rainfall and mean air temperature from the surface observations and Regional Climate Model (RegCM) by calculating Standardized Precipitation Index (SPI) and Palmer Drought Severity Index (PDSI) for the period 1961?C1990. The historical records of drought event obtained from the Bangladesh Bureau of Statistics and International Disaster Database are used to verify the SPI and PDSI detected events. The SPI and monthly PDSI are obtained for 27 station data across Bangladesh as well as for two subregions over the country. Result based on the observed data shows that regional information is better in drought diagnosis compared to the point information. The regional analysis is able to detect about 80?% of the drought events occurred during the study period. Frequency of moderate drought is higher for all over the country. The SPI calculated from RegCM rainfall shows that the detection of moderate drought events is 10, 7, and 21?% overestimated for 1-, 3-, and 6-month length, respectively, compared to using of observed data. For extreme drought cases, detection is overestimated (underestimated) by 25?% (79?%) for 1-month (6-month) length. The PDSI results for model and observed data are nearly same to SPI calculations. Model monthly PDSI result is overestimated (underestimated) by 29?% (50?%) for moderate (severe) drought events with reference to the observed PDSI. Hence, RegCM output may be useful to detect 3?C6-month (monthly to seasonal) length moderate drought events over a heavy rainfall region likely Bangladesh.     

Micro-CT and FIB–SEM imaging and pore structure characterization of dolomite rock at multiple scales

With improvements of imaging techniques and computational power, Digital Rock Physics (DRP) has been increasingly used to determine transport and elastic properties of reservoir core plugs. Since numerical computations highly rely on accurate 3D representations of the porous microstructure of the rocks, the imaging technique and the scale at which the imaging is performed is a critical parameter. In this paper, we introduce a multiscale imaging workflow that uses both micro-X-ray tomography (micro-XCT) and focused ion beam combined with scanning electron microscope (FIB–SEM) to characterize a dolomite rock from the microscale to the nanoscale. This allows for the accurate capture of the different heterogeneities that exist in the carbonate (texture, mineralogy, pore size). The reconstructed microporous structures were then used to successfully predict elastic and permeability properties of selected carbonate.     

Petrophysical evaluation of subsurface reservoir sandstones of Bengal Basin,Bangladesh

The present study has been carried out for core and log based petrophysical evaluation of subsurface reservoir sandstones considering at least one well from each of the Kailas Tila, Titas, Bakhrabad and Shahbazpur gas fields of Bangladesh. Core analysis results show that average core porosity, permeability and pore throat values are 20%, 209 mD and 44020 Å, respectively. These measured values support that the sandstone reservoirs are categorized as good quality reservoirs. Core porosity values usually exceed thin section porosity. Different cross-plots indicate that permeability is largely dependent on porosity. Permeability and porosity are also dependent on textural parameters that include size, shape, sorting and matrix of the reservoir sandstones. It reveals from both thin section study and different cross plots that diagenetic cements are the main controlling factors of the reservoirs. Quantitative determination of the volume of cements shows that cements have inverse correlation with porosity and permeability. Log based petrophysical parameters include shale volume, porosity, water and hydrocarbon saturation, permeability, moveability index and bulk volume of water. The average values of the mentioned parameters are 20%, 22%, 26%, 74%, 110 mD, 0.28 and 0.05, respectively. The most important parameters are porosity and permeability, which indicate that log porosity exceeds core porosity and log permeability significantly lags behind core permeability. The study also reveals that 23 gas zones covering total thickness of 385 m sandstones mostly posses good quality reservoirs except few moderate quality reservoirs.     

Waste loading in shrimp and fish processing effluents: potential source of hazards to the coastal and nearshore environments

On average, only 30-40% of the global fishery production is consumed fresh and the rest 60-70% is processed for human consumption and other purposes. Although the proportion of the total fishery production that are processed remained relatively stable over the last decade, the total bulk of processed fishery commodity increased due to the steady increase in the total fishery production. Processing of large bulk of fish, shrimp and other aquatic organisms produces a corresponding large bulk of by-products and wastes. Although recent trend shows that much of these wastes are made into various value added products, considerable quantities are discharged as the processing effluents with large volume of waters used in processing. Reports suggest that fish and shrimp processing effluents are very high in biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), fat-oil-grease (FOG), pathogenic and other microflora, organic matters and nutrients, etc. Fish and shrimp processing effluents are, therefore, highly likely to produce adverse effects on the receiving coastal and marine environments. Although substantial reduction of the waste loads is possible by applying available simple techniques, this is not in practice in most part of the world due to lack of proper managerial and regulatory approach. The present paper reviews the characteristics of fish and shrimp processing effluents as a potential source of coastal and marine pollution and, using the existing data, analyzes the global production and discharge of waste loads from the processing plants and discusses available options for waste treatment and management.