Applied structural geology and basin analysis, geodynamics and deformation within the lithosphere, petroleum geology and exploration geophysics.
Abdullah, R. and Rosenbaum, G. 2017, Orogen-perpendicular structures in the central Tasmanides and implications for the Paleozoic tectonic evolution of eastern Australia, Tectonophysics, 694, 444-463.
The curvilinear ~E-Wstructures of the southern Thomson Orogen are approximately orthogonal to the general ~N-S structural trend of the Tasmanides of eastern Australia. The origin of these orogen-perpendicular structures and their implications to tectonic reconstructions of eastern Gondwana are not fully understood. Here we use geophysical data to unravel the geometry, kinematics and possible timing of major structures along the boundary between the Thomson Orogen and the southern Tasmanides (Delamerian and Lachlan orogens). Aeromagnetic data from the southern Thomson Orogen showWNW, E-Wand/or ENE trending structural grains, corresponding to relatively long wavelength linear geophysical anomalies. Kinematic analyses indicate strike-slip and transpressional deformation along these geophysically defined faults. Structural relationships indicate that faulting took place during the Benambran (Late Ordovician to Middle Silurian) and Tabberabberan (late Early to Middle Devonian) orogenies. However, some of the described crustal-scale structures may have developed in the Cambrian during the Delamerian Orogeny. Interpretation of deep seismic data shows that the crust of the southern Thomson Orogen is substantially thicker than the Lachlan Orogen crust, which is separated from the Thomson Orogen by the north-dipping Olepoloko Fault. A major lithospheric-scale change across this boundary is also indicated by a contrast in seismic velocities. Together with evidence for the occurrence of Delamerian deformation in both the Koonenberry Belt and northeastern Thomson Orogen, and a significant contrast in the width of the northern Tasmanides versus the southern Tasmanides, it appears that the southern Thomson Orogen may represent the locus of orogen-perpendicular segmentation, which may have occurred in response to along-strike plate boundary variations.
Khanam, F. Rahman, M.J.J. Alam, M.M. and Abdullah, R. 2017; Facies characterization of the Surma Group (Miocene) sediments from Jalalabad Gas Field, Sylhet Trough, Bangladesh: study from cores and wireline logs; Jour. of the Geol. Society of India, 89 (2)
The Sylhet trough located on the north-eastern margin of present Bengal basin, contains ~22 km of Tertiary sediments and well known as a hydrocarbon producing province. A detailed facies characterization of the subsurface Miocene Surma Group sediments (especial emphasis on reservoirs sandstones) from Jalalabad gas field within the Sylhet trough has been done using core log analysis and wireline log (gamma ray) interpretation. Texture and sedimentary structures of the cores suggests that the nine individual lithofacies types which can be grouped together into three facies associations, namely, fine-grained facies associations (FFA), medium-grained facies association (MFA) and coarse-grained facies associations (CFA). Major changes in gamma ray log motifs and various bounding discontinuities indicate six para-sequence sets (basin wide) and twenty eight para-sequences (local environmental changes) within the depth range from 2200-2800 m. Detailed facies analysis of the cores and wireline log reveals that the interbedding facies within the associations in the Surma Group commonly develop small-scale fining-upward (FU) cycles, coarsening-upward (CU) and random intercalations (RD). The sediments of the Surma Group of the Jalalabad field have been interpreted as deposits of the shallow marine to tide-dominated deltaic depositional setting. The cyclic nature of sedimentation pattern of the Surma Group probably records an almost continuous existence of this prograding deltaic regime and a tectonic setting characterized by a mixture of prolonged basin subsidence and regional transgression coupled with sporadic regressive phases.
Hossain, A., Hossain, D. and Abdullah, R., 2015, Structural and stratigraphic interpretation of geophysical data of Fenchuganj Gas Field in the Surma Basin, Bangladesh; Journal of the Geological Society of India, 86 (2), 148-154.
The Fenchuganj structure trending in NNE-SSW direction is a surface anticline (reverse faulted) in the eastern part of the Surma basin, Bangladesh. The eastern flank of the structure has steeper dip than the western one. The present study includes seismic and geological data interpretation which gives details about structure and stratigraphy of the area. Well log interpretation was done to infer lithological pattern and the hydrocarbon potential zones. Correlating the seismic interpretation and well log analysis, four gas sands have been identified at depths 2000m to 3100m. Depending on the present findings, it is concluded that further investigation can give valuable information about real sub-surface structure and hydrocarbon occurrence in this area.
Abdullah, R., Yeasmin, R., Ameen, S.M.M., Khanam, F., and Bari, Z. 2015; 2D Structural modelling and hydrocarbon potentiality of the Sitakund structure, Chittagong Tripura Fold Belt (CTFB), Bengal Basin, Bangladesh; Journal of the Geological Society of In
The Sitakund anticline is located within the Chittagong Tripura Fold Belt of the Bengal basin is considered to be the youngest structural feature of the western flank of the Indo-Burman ranges. An attempt has been made to delineate hydrocarbon trap configuration by integrating both surface and sub-surface observations, determining the nature of deformation, predicting the sealing probabilities and relationship between different petroleum elements. 2D structural modelling along the Sitakund anticline suggests that the structure may have a suitable fault-trap setting for hydrocarbon accumulation. Along the footwall block the Bokabil sandstones (with porosity up to 14%) covered by cap rock of Upper Marine Shale (UMS) juxtaposes against the shale-rich Bhuban Formation of the hanging-wall block provides such fault-trap geometry. While relatively high Shale Smear Factor (>75%) and low Shale Gouge Ratio (~ 1.33) indicates that the east dipping major thrust fault may provide sufficient sealing properties. In addition, shale diapirism at the core of the anticline may result intrusion of clay into faults considerably raising the sealing ability along the main thrust.
Abdullah, R., Hossain, D., Alam, M. R., 2013; Delineation using geophysical data of the hydrocarbon bearing zone in the Begumganj Structure, Hatia Trough, Southern Bengal Basin, Bangladesh; Journal of the Geological Society of India, 82 (9), 271-276.
The Begumganj structure of the Hatia Trough in Bengal Basin has proved it’s hydrocarbon potentiality. Several seismic sections have been analyzed to construct different maps and to interpret subsurface geology, structure and stratigraphy. These maps reveal that the Begumganj structure is an elongated to oval shaped asymmetrical anticline having the general trend NNW-SSE. No major faults affecting the structure could have been identified. Most of the reflectors are strongly affected by channels, especially at the western flank. Based on the analysis of seismic and available well data, the only gas bearing strata at depth of 2995 m (or TWT 2.02 seconds) has been identified. The structure is interpreted as a strati-structure entrapment because shale fill channel truncated this layer on western flank and at the crestal part of the anticline. The structure probably formed after the deposition of sediments. The channel has formed after the corresponding unit cut has been deposited. The channels eroding the reservoir unit range from Late Miocene to Early Pliocene age where the anticline probably begun to form during the Pliocene. Strong increase in amplitude (bright spot), possibly associated with hydrocarbon, has been apparent on seismic lines BG 9 and BG 10. The stratigraphic succession based on the information of the wells drilled on this structure and it’s surrounding fields reveals that the lithological sequences range from Miocene to Recent age where the only proven gas producing sand zone is located in the Bhuban Formation.
Rahman, M.J.J., McCann, T., Abdullah, R. and Yeasmin, R., 2011, Sandstone diagenesis of the Neogene Surma Group from the Shahbazpur Gas Field, Southern Bengal Basin, Bangladesh, Austrian Journal of Earth Sciences; 104 (1), 114-126.
This study examines the various diagenetic controls of the Neogene Surma Group reservoir sandstones encountered in the Shahbazpur-1 petroleum exploration well from the southern part of the Bengal Basin, Bangladesh. The principal diagenetic minerals in the Surma Group sandstones are quartz overgrowths, Fe-carbonates (mainly Fe-calcite) and authigenic clay minerals dominantly chlorite, illite-smectite and mnor kaolinite. Compaction played a more extensive role than cementation in destroying primary porosity. Cementation was important in drastically reducing porosity and permeability in sandstones at depths of 1796.5, 2015.5 and 3019 m and is typically poikilotopic, pore-filling blocky Fe-calcite cement. Illite-smectite and chlorite occur as pore-filling and porelining authigenic phases. Sandstones having good porosities (20% to 30%) and high permeabilities (20 mD to 415 mD) are well sorted, and tend to be relatively coarse grained and more loosely packed with better rounded grains. They are typically found at depths ranging from ~2290 m to 3411 m. These high quality reservoir rocks are, however, not uniformly distributed resulting in compartmentalization of the reservoir-quality units, which are interbedded with sandstone layers showing low to moderate porosity (1 to <20%) and low permeability (0.6 to 4.5 mD). These sandstones are typically poorly sorted, strongly compacted and contain significant higher proportions of cements.
Kabir, A.S.M.S., Hossain, D. and Abdullah, R., 2011; 2-D Electrical imaging in some geotechnical investigation of Madhupur Clays, Bangladesh; Journal of the Geological Society of India, 77 (1), 73-81.
Electrical imaging or electrical tomography is a survey technique suitable for the investigation of areas of shallow complex geology, where the use of other electrical and electromagnetic techniques is less effective. An electrical image has been delineated at a site located in front of the Department of Geological Sciences, Jahangirnagar University, Dhaka, Bangladesh. 16 soil samples were collected from two boreholes located on the image line and geotechnical parameters such as unit weight, water content, grain size, plastic limit, liquid limit and plasticity index were measured in the laboratory. These geotechnical parameters were compared with the measured electrical resistivity.