Abstract: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. Stratigraphical… Show more
“…2 ) have been selected to study spatial variation of petrophysical properties of Bokabil Formation in the Surma Basin. The petrophysical analysis of the well logs from these gas fields had been carried out by many authors 52 , 56 – 59 , However those studies were general, brief, and not focused on the Bokabil Formation. Therefore, the qualitative and quantitative analysis have been carried out by the available well logs data in a consistent manner.…”
Section: Methodsmentioning
confidence: 99%
“… Figure 2 Map of Bangladesh in the inset showing the extent of study area. Location of the gas fields within Surma basin and the outcrop location 52 . The map was created using Adobe Illustrator CC 2021 ( https://www.adobe.com/uk/products/illustrator.html ).…”
Section: Methodsmentioning
confidence: 99%
“…The Sylhet Limestone, Kopili shale and Jenum formations are the potential major source rocks of the Surma Basin 47 – 49 . The studied Upper Bokabil Sandstone unit of Bokabil Formation in Surma Basin is the most significant hydrocarbon bearing unit in the Surma Basin as well as Bengal Basin 23 , 50 – 52 , which comprises medium to fine grained, moderately sorted, trough cross bedded sandstone with a few isolated mud drapes and defined the depositional environment as a braided fluvial system 53 . The regionally extensive Upper Marine Shale unit of Bokabil Formation is the main top seal unit which comprises predominantly dark gray to black shale with a little amount silt and indicating marine transgression over Sylhet as well as other parts of the Bengal Basin 54 , 55 .…”
Section: Regional Geology and Stratigraphymentioning
Large-scale geological sequestration of CO2 is one of the most effective strategies to limit global warming to below 2 °C, as recommended by the Intergovernmental Panel on Climate Change (IPCC). Therefore, identifying and characterizing high-quality storage units is crucial. The Surma Basin, with its four-way dip closed structures, high-quality reservoirs, and thick regional cap rocks, is an ideal location for CO2 storage. This study focuses on the Bokabil Formation, the most prominent reservoir unit in the Surma Basin. Detailed petrographic, petrophysical, XRD, and SEM analyses, along with mapping, have been conducted to evaluate the properties of the reservoir and cap rock within this formation. The Upper Bokabil Sandstone in the Surma Basin ranges from 270 to 350 m in thickness and consists of fine- to medium-grained subarkosic sandstones composed of 70–85% quartz and 5–12% feldspar, with good pore connectivity. Petrophysical analysis of data from four gas fields indicates that this unit has a total porosity of 21–27.4% and a low shale volume of 15–27%. Cross plots and outcrop observations suggest that most of the shales are laminated within the reservoir. The regional cap rock, known as the Upper Marine Shale (UMS), ranges in thickness from 40 to 190 m and contains 10–40 nm nano-type pores. A higher proportion of ductile materials with a significant percentage of quartz in the UMS indicates higher capillary entry pressures, enhancing its capacity to hold CO2. Using the CSLF method with a 6% cut-off of the available pore volume, it is estimated that 103 Mt, 110 Mt, 205 Mt, and 164 Mt of CO2 can be effectively stored in the Sylhet, Kailashtila, Habiganj, and Fenchuganj structures, respectively. Due to the shallow depth of the storage unit and the thick cap rock, the southern Surma Basin is the optimal location for CO2 injection.
“…2 ) have been selected to study spatial variation of petrophysical properties of Bokabil Formation in the Surma Basin. The petrophysical analysis of the well logs from these gas fields had been carried out by many authors 52 , 56 – 59 , However those studies were general, brief, and not focused on the Bokabil Formation. Therefore, the qualitative and quantitative analysis have been carried out by the available well logs data in a consistent manner.…”
Section: Methodsmentioning
confidence: 99%
“… Figure 2 Map of Bangladesh in the inset showing the extent of study area. Location of the gas fields within Surma basin and the outcrop location 52 . The map was created using Adobe Illustrator CC 2021 ( https://www.adobe.com/uk/products/illustrator.html ).…”
Section: Methodsmentioning
confidence: 99%
“…The Sylhet Limestone, Kopili shale and Jenum formations are the potential major source rocks of the Surma Basin 47 – 49 . The studied Upper Bokabil Sandstone unit of Bokabil Formation in Surma Basin is the most significant hydrocarbon bearing unit in the Surma Basin as well as Bengal Basin 23 , 50 – 52 , which comprises medium to fine grained, moderately sorted, trough cross bedded sandstone with a few isolated mud drapes and defined the depositional environment as a braided fluvial system 53 . The regionally extensive Upper Marine Shale unit of Bokabil Formation is the main top seal unit which comprises predominantly dark gray to black shale with a little amount silt and indicating marine transgression over Sylhet as well as other parts of the Bengal Basin 54 , 55 .…”
Section: Regional Geology and Stratigraphymentioning
Large-scale geological sequestration of CO2 is one of the most effective strategies to limit global warming to below 2 °C, as recommended by the Intergovernmental Panel on Climate Change (IPCC). Therefore, identifying and characterizing high-quality storage units is crucial. The Surma Basin, with its four-way dip closed structures, high-quality reservoirs, and thick regional cap rocks, is an ideal location for CO2 storage. This study focuses on the Bokabil Formation, the most prominent reservoir unit in the Surma Basin. Detailed petrographic, petrophysical, XRD, and SEM analyses, along with mapping, have been conducted to evaluate the properties of the reservoir and cap rock within this formation. The Upper Bokabil Sandstone in the Surma Basin ranges from 270 to 350 m in thickness and consists of fine- to medium-grained subarkosic sandstones composed of 70–85% quartz and 5–12% feldspar, with good pore connectivity. Petrophysical analysis of data from four gas fields indicates that this unit has a total porosity of 21–27.4% and a low shale volume of 15–27%. Cross plots and outcrop observations suggest that most of the shales are laminated within the reservoir. The regional cap rock, known as the Upper Marine Shale (UMS), ranges in thickness from 40 to 190 m and contains 10–40 nm nano-type pores. A higher proportion of ductile materials with a significant percentage of quartz in the UMS indicates higher capillary entry pressures, enhancing its capacity to hold CO2. Using the CSLF method with a 6% cut-off of the available pore volume, it is estimated that 103 Mt, 110 Mt, 205 Mt, and 164 Mt of CO2 can be effectively stored in the Sylhet, Kailashtila, Habiganj, and Fenchuganj structures, respectively. Due to the shallow depth of the storage unit and the thick cap rock, the southern Surma Basin is the optimal location for CO2 injection.
“…With time, the depositional environment started to be shallower as the Bengal Delta is a southward prograding delta system [15,69]. Further, in the southward direction from the lower delta front setting in the upper part of the Lower Surma, the depositional environment was more terrestrial according to different studies completed based on seismic and wireline log data and the global Miocene sea-level curve [33,[73][74][75][76]. The entire lower part and a portion of the middle part of the Upper Surma are not well exposed over a thickness of about 1100 meters in the study area.…”
Section: Depositional Environment and Sandbody Architecturementioning
confidence: 99%
“…Different distributary channels were active during that time that deposited huge amounts of coarser sediments in their mouth bars by rapid deceleration of unidirectional flow generated in the upstream rivers [51,55]. A thick succession of fluvial sediments have been interpreted by numerous researchers in different studies, most of those works are based on seismic or outcrop studies conducted further downstream in other parts of the Bengal Basin [33,[73][74][75][76]. Previous studies based on outcrops and indications from wireline logs suggest that the unexposed Surma Group deposits in the study area are deltaic and braided fluvial deposits [74].…”
Section: Depositional Environment and Sandbody Architecturementioning
Well-exposed fluvio-deltaic Surma Group successions of the northeastern Surma Basin provide a direct analogue to its equivalent subsurface successions—the main hydrocarbon reservoirs in Bangladesh. The various levels of lateral and vertical heterogeneities lead to changes in the subsurface sandbody distributions and their reservoir qualities across fields. The present study aims to identify the heterogeneities in the fluvio-deltaic Surma Group successions by detailed sedimentological analysis of the Mio-Pliocene-aged Surma Group successions. Eleven lithofacies have been identified and based on the recurring pattern of these facies within the Surma Group, five facies associations have been identified. The facies associations indicate that these deposits originated from diverse depositional settings, ranging from the prodelta to the alluvial to delta plain. As a whole, they represent a progressive shallowing upward succession with two transgressive events in the upper and lower parts of the Surma Group. Five levels of heterogeneities such as prodelta mud (HL-I), tidal heterolithic deposits (HL-II & III), interbedded mud units in delta front (HL-IV), and intercalated mud laminae, drapes (HL-V) have been identified in the fluvio-deltaic Surma Group. The study suggests that the various levels of reservoir heterogeneities are controlled by the occurrence and distribution of various facies associations.
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