Bangladesh is a country with limited sources of energy and since 1990 natural gas has been its main source of energy. Most of the exploration approaches had been conducted onshore especially in the central and eastern part of Bangladesh, particularly in northeastern Sylhet basin. Among the hydrocarbon provinces, the East Delta Hill Tract province is an under explored petroleum province in Bangladesh. An exploratory well drilled in Sitakund anticline was found dry but no reasonable cause was perceived why that well went dry. Although many works had been carried out in Chittagong Hill Tracts but none of them was cumulative and descriptive. In this study, the overall hydrocarbon prospect of the Chittagong Hill Tracts was analyzed by mapping of potential zones on the basis of the evaluation of regional structure and construction of lithocolumn of the prospective zones. The five elements of the petroleum system discussed thoroughly to find overall petroleum prospect of the study area. Source rocks of Chittagong Hill Tracts are mainly Bhuban shale, reservoir rock is sandstone from Bhuban-Bokabil formation, the way of migration path is both through longitudinal and cross fault. The data of source rock and seal is collected from previous researches. Multiple types of traps have been found there. Conventional anticlinal traps which are highly disturbed due to tectonic instability & the core part are shale diapirism. Most of the anticlines are plunging and the nose or plunge area might be prospective to HC for being comparatively less faulted. Broad synclinal areas between tight narrow anticlines are another prospective area for HC. These similar types of synclines are also found in Tripura, India which is a highly prospective area for petroleum and their small anticlinal hums within syncline are also prospective. Some stratigraphic traps have also been found in Tripura from where production has been started already. Both Chittagong Hill Tracts and Tripura Fold Belts are parts of great Arakan Fold Belts, so similar type of structures might be prospective here. Apart from these, Bangladesh is a deltaic country. So stratigraphic trapment like channel sand, pinch-outs is possible. Considering all the elements of petroleum prospectivity of the area and

Sediment-routing controls on sandstone texture and bulk petrography have been evaluated in linked alluvial–coastal–shelfal deposits of the Upper Cretaceous Castlegate Sandstone, Blackhawk Formation, Star Point Sandstone, and Mancos Shale (Western Interior Basin, Utah and Colorado, USA) using thin-section analysis of representative outcrop samples in the context of a high-resolution sequence stratigraphic and paleogeographic framework. The studied strata record deposition from two styles of sediment-routing system within an overfilled foredeep and contiguous intra-continental seaway. First, multiple transverse drainages supplied sand to fluvial, shoreline, and shelf segments of sediment-routing systems characterized by down-dip transport distances of 150–450 km and significant strike-oriented sediment transport along the shoreline. Second, the distal shoreline–shelf segment of an axially supplied sediment-routing system was characterized by sand transport for a distance of c. 300 km. Bulk petrographic composition indicates that transverse sediment-routing systems were sourced from catchments that supplied quartz-rich sand with a subordinate lithic component, while the large axial sediment-routing system was sourced from a catchment(s) supplying slightly more feldspathic sand. Thin-section measurements of mean grain size, sorting, skewness, and ratio of minimum-to-maximum diameter (a proxy for sphericity) are similar for sandstones deposited in fluvial, shoreline, and shelf segments of the transverse sediment-routing systems and in the shoreline–shelf segment of the axial sediment-routing systems, although hydrodynamic sorting is important in locally segregating grain-size populations within each segment. Further, textural analysis of detrital quartz, feldspar, and lithic sand-grain populations shows little evidence of relative change in mean grain size or apparent grain sphericity with downsystem distance, implying that sand-grain populations of different petrographic composition did not undergo significant differential mechanical breakdown during transport. Instead, the textural characteristics of these sand-grain populations are inferred to have been controlled mainly by bedrock lithology and recycling in source catchments. The textural signal of sediment-source areas then propagated downsystem in the sand fraction of detrital sediment supply. This inference is supported by the fine- to medium-grained, well- to very well-sorted character of all sandstone samples, consistent with recycling of sandstones and quartzites from the Sevier fold-and-thrust belt.

The Fenchuganj gas field is located in Surma basin and is uniform throughout the whole southern area. This study deals with the development of secondary porosity of the gas bearing reservoir sandstone rocks with the microscopic analysis of the core sample rock slides from well 2 of Fenchuganj gas field. The study shows the secondary porosity was generated at the particular depths of 1479-1497 m, 2768-2783 m and 3615-3624 m of Fenchuganj well no.2. The study demonstrates that diagenetic parameters, such as compaction, pressure solution, and cementation, are not the only ones that affect reservoir quality. Other elements include the reservoir rock's chemical environment, acidic water infiltration or dissolution, the presence of any other secondary processes, etc. Acidic water intrusion may have acted as an agent in generation of these secondary porosities. On contrast, the rocks in 2190 m, 3424-3432 m and rest of 3615-3624 m depth, had lost its porosity by the adverse effects of compaction, cementation as well as pore pressure solution. The overall porosity of the rock samples F-2 (1479–1497 m), F-6 (2768–2783 m), and F-10b (3615–3624 m) is around (35–40%), (30–35%), and (20–25%), respectively, indicating excellent, very good, and good reservoir quality for rock slide F-2, F-6, and F-10b, respectively. Changing of chemical environment and consequent dissolution process may contribute to enhance the potentiality of reservoir rock. The Dhaka University Journal of Earth and Environmental Sciences, Vol. 11(1), 2022, P 43-52

Shahbazpur structure is located in the southern Part of the central deep basin in the Hatia trough, where lie all the largest Gas fields of Bangladesh. A method is established to delineate the structural mapping precisely by interpreting four 2D seismic lines that are acquired over Shahbazpur structure. Moreover direct hydrocarbon indicators (DHI) related attributes are analyzed for further confirmation for presence of hydrocarbon. To do this synthetic seismogram generation, seismic to well tie, velocity modelling and depth conversion are performed. A limited number of seismic attributes functions that are available in an academic version of Petrel software are applied to analyze attributes. Seismic attribute analyses that are used in this interpretation mainly are associated to bright spot detection. Presence of bright spots or high amplitude anomaly over the present Shahbazpur structure, reservoir zone are observed. This signature will play a very important role in next well planning on the same structure to test the shallow accumulation of hydrocarbon. For better understanding of this shallow reserve, it is suggested to acquire 3D seismic data over Shahbazpur structure which will help to evaluate the hydrocarbon accumulation and to identify gas migration pathways. Dhaka Univ. J. Sci. 64(2): 135-140, 2016 (July)

The Bay of Biscay is considered France’s most prospective offshore region, but a complex geodynamic history has so far hindered its development. The landward side of the Parentis Basin has significant oil shows in late Barremian Limestones and early middle Jurassic dolomites. The offshore extension however has a thicker depocentre with a contrasting burial history resulting in plays more difficult to define – dampening drilling enthusiasm to date. Although the basin remains poorly understood this study has found the evidence of petroleum potential. Due to somewhat limited well control the risk remains a significant factor in further exploration. A maturity window in the Early Cretaceous has suggested targeting of more subtle structural and robust stratigraphic intervals on the footwall block could potentially be prospective. This study would recommend a rigorous 3D basin modeling project (outside the scope of this study) and acquisition of minimum 2D seismic between the existing block and onshore Parentis fields – this would allow better understanding of the transitional structure and subsequently the disparity in burial history/charge timing. The Dhaka University Journal of Earth and Environmental Sciences, Centennial Special Volume June 2022: 89-102