Petrophysical Reservoir Characterization of Habiganj Gas Field, Surma Basin, Bangladesh

The previous studies on the petrophysical and volumetric analysis of Habiganj gas field were based on limited well data. As the accuracy of volumetric analysis relies greatly on petrophysical parameters, it is important to estimate them accurately. In this study we analyzed all eleven wells drilled in the Habiganj field to determine the petrophysical parameters. Analysis of the well logs revealed two distinct reservoir zones in this field termed as upper reservoir zone and lower reservoir zone. Stratigraphically, these two reservoir zones are in the Bokabil and Bhuban Formation of Surma Group. Petrophysical analysis shows significant differences between the two zones in terms of petrophysical parameters. Porosity in the upper reservoir zone ranges from 12% to 36%, with an average of 28%. This zone is highly permeable, as indicated by the average permeability of 500 mili Darcy (mD). The average water saturation in this zone is around 18% suggesting high gas saturation. The lower reservoir zone has an average porosity, permeability, and water saturation of 12%, 60mD, and 43%, respectively, indicating poor reservoir quality. An analysis of log motifs indicates that the upper reservoir zone is composed of stacked sands of blocky pattern. The sands in this interval are clean, as indicated by the lower shale volume of 12-15%. The average thickness of this zone is 230m, and the presence of this zone in all the drilled wells suggests high lateral continuity. The lower reservoir zone consists of sand bodies of serrated pattern. The sands have high shale volume and are laterally discontinuous. Overall, the upper reservoir zone has superior petrophysical properties to the lower reservoir zone. Although the reservoir quality of the lower reservoir zone is poorer than that of the upper zone, this zone can be considered as the secondary target for hydrocarbon production. Petrophysical parameters of this study were estimated from all the eleven wells drilled in this field; hence the values are more accurate. The reported values of the petrophysical parameters in this study are recommended to use to re-estimate the reserves in Habiganj field. The Dhaka University Journal of Earth and Environmental Sciences, Vol. 10(1), 2021, P 1-10

Petrophysical and petrographic characteristics of Barail Sandstone of the Surma Basin, Bangladesh

The Barail sandstone in the Surma Basin is a medium- to coarse-grained pinkish-colored rock exposed near the northeastern margin of Bangladesh. In this study, we evaluated the reservoir quality of the Barail sandstone based on its petrophysical and petrographic characteristics. Petrophysical analyses of outcropped samples showed that sandstones are made up of 16.48% porosity and 132.48 mD permeability. Sandstone density ranges from 1.94 g/cm3 to 2.37 g/cm3, with a mean value of 2.12 g/cm3, shown as moderately compacted sandstone. Integrated data such as bulk density, porosity, permeability, Rock Quality Index (RQI), Normalized Porosity Index (NPI), Flow Zone Indicator (FZI), compressive strength, etc. with their relationships indicate that Barail sandstone owing characters to become a good petroleum reservoir. The rock samples consisted mainly of quartz with an insignificant amount of rock fragments and plagioclase feldspar and are categorized as sub-arkose to sub-litharenite. The rock samples also contains lithic (andesine, microcline, muscovite, biotite, etc.) of granitic and gneissic fabric and some volcanic product like aguite, albite, andesine, garnet, spinel and ulvo-spinel indicating the source of nearby orogeny. The euhedral to subhedral shape of the quartz grain in a porphyritic texture, moderately sorted with a smaller amount of clay minerals indicating the moderately mature rock type. The iron oxide border around the quartz grain also indicates that the Barail sandstone was deposited under dry climatic condition.

Geomorphological Study of Jaflong Area near Dauki Fault Using Remote Sensing and Geographic Information System

Geomorphology is closely related to geology, soil science, hydrology and environmental science and is being increasingly applied in planning, mining and hydrological sectors, and within environmental consultancy and tourism. The study area lies in the north-eastern part of the country and tectonically this area belongs to Surma Basin situated into Bengal Fore deep zone of Bengal Basin also known as Sylhet Trough. Under this study an attempt was made to establish the relationship between geomorphic unit and existing landuse based on remote sensing data. In the study area nine landuse categories were identified through remote sensing and GIS techniques. Two different physiographic units which are North-Eastern Terrace Land and Surma-Kushiyara Flood Plain are belongs to the study are. Moreover two surface geological units include Young Gravelly Sand and Marsh Clay and Peat are also there. From analysis no relationship has been found between landuse classes with its physiography and surface geology. Environ. Sci. & Natural Resources, 12(1&2): 151-155, 2019

Geochemical Appraisal on History and Evolution of Barail Sandstones of Zote-Ngur, Champhai District, Mizoram, India

Mizoram is part of Surma basin which later evolved into the present state of geological terrain due to Indo- Myanmar tectonic collision during the Oligocene period. The present work deals with geochemical characteristics of Barail sandstones exposed in Champhai area of eastern region in Mizoram. The major/minor oxides, trace elements and rare earth elements data are used to infer the geological history and evolution of the sandstone in the study area of Champhai. The petrographic study shows the presence of various detrital grains like quartz, lithic fragments, feldspar, chertz, mica, etc., which are cemented by siliceous and ferruginous materials. Geochemically, the sandstones indicate high wt% of SiO2, Al2O3 and MgO compared to Upper Continental Crust (UCC) while rest of the major oxides indicate low concentrations. The geochemical classification indicated the sandstones as litharenite and wacke. The chondrite normalised REE pattern shows the enrichment of HREE and depletion of LREE with negative Eu anomaly. The value of Eu/Eu*, La/Lu, La/Co, Th/Sc, Th/Co, Cr/Th and high ratio of LREE/HREE of Barail sandstone suggest felsic source rock. The analysis of paleoweathering history indicated moderate to intensive weathering in the provenance. Various tectonic discriminant function diagrams suggested Active Continental Margin settings.