Reservoir characterization and identification of new prospect in Srikail gas field using wireline and seismic data

Although reservoir characterization has been carried out by many researchers on the sedimentary package of the Bengal basin hydrocarbon province, integration of petrophysical and seismic sequence-based reservoir evaluation is rarely taken into account. This paper focuses on the identification of gas zones, reserve estimation and identification of new prospects in Srikail gas field within the eastern fold belt of Bengal basin integrating four wireline logs and 2D seismic data. Our study finds seven hydrocarbon-bearing zones (A, B, C, D, E, F and G) within the measured depth between 2429.5 and 3501 m. Petrophysical properties of seven hydrocarbon-bearing zones indicate that they are good quality reservoir sands. The gas horizons were mapped on seismic sections which reveal that the NW–SE anticlinal structure is largely affected by channels in the crest and western flank. The channels are infilled by fine-grained sediments which act as cap rock on northern and western parts of the structure. Thus, the anticlinal structure and fine-grained sediments make a potential trap for hydrocarbon accumulation and laterally and vertically well-distributed sequence remnants are the main reservoir rocks in this area. Volumetric reserve estimation of these sands provided a total gas initially in place as 552 billion cubic feet. Moreover, all the four wells are drilled in the southern block of the structure, and since there is a structural continuity from south to the north, it is highly recommended to drill a well up to 3000 m depth in the northern block to test its hydrocarbon potentiality. Overall, the outcomes of this study contribute new insights for reservoir characterization and identification of new prospects in an efficient way.

Geology of the Patharkhola Area, Almora District, Uttarakhand (India): With Special Reference to the Lithology and Field Relation

The Patharkhola area (longitude 79°09'E to 79°17'56''E and latitude 29°47'42''N to 29°56'69''N) covering an area of about 125 square Kms situated in Almora District, Uttarakhand forming a part of the Almora Nappe has been selected for the detailed geological mapping at an scale of 2 cm equal to 1 Km. The rocks mainly include phyllites, schists and gneisses forming an anticlinal structure showing phyllites in the NW, S to SW and in the western part of the area, while the schists occur in the folded outcrop pattern in between both the limbs of the fold and the gneisses occur in the core of the fold. Although thin quartzitic bands has also been noticed interbedded with phyllites and schists. Several transverse faults have been noticed in the area under investigation which has been demarcated in the map. Bulletin of Department of Geology, vol. 20-21, 2018, pp: 1-6

Sedimentological and Palynological Approach for Determining the Depositional Environment of the Outcropping Surma Group Mudrocks in the Sitakund Anticline, Chittagong-Tripura Fold Belt, Bangladesh

Sitakund anticlinal structure exposes about 1.5 km of Surma group sediments and has been chosen for a comprehensive study of the mudrocks depositional environment based on sedimentological and palynological evidences. Five mudrock facies have been identified in this region. They are Mudstone Dominated, Sand/Silt Streaked Shale, Fissile Shale, Laminated Shale and Lenticular Bedded Shale. The palynological assemblages from these samples have been analyzed qualitatively, and a variety of pollen, spores, algae and fungi identified. The pollen and spores have been attributed to parent plants located at the immediate and more regional surrounding areas during the deposition of these sediments. Palynological assemblages incorporates ample of Palmae grains such as spores in the Palmipollenites and Proxaperites and predominance of pteridophytic spores. The occurrences and abundances of these pollens indicate that the deposition of the Surma mudrocks took place at the proximity of the shore level. Coastal fluvial environment is also triumphed after the previous depositional event which is apparent by the occurrence of palynomorphs of pteridophytes, angiosperms and algal origin. Dhaka Univ. J. Sci. 66(1): 37-42, 2018 (January)

Le Trias a caractere extrusif de la zone des domes; example de la structure de Debadib-Ben Gasseur (Tunisie septentrionale)

The Debadib-Ben Gasseur anticlinal structure, situated between El Kef and the Algero-Tunisian border, belongs to one of the main diapiric, alignments of the oriental Maghreb. It constitutes an elliptic form oriented NE-SW. The heart is occupied by Triassic residual evaporites containing basaltic volcanites which seem to indicate an extensional setting during the Triassic period. The contact between the saliferous bodies and surrounding Cretaceous-Tertiary age rocks is locally underlined by conglomerates including reworked Triassic blocks and glauconite, suggesting a sedimentary contact. Biostratigraphic and sub-surface data could indicate, in terms of model reconstitution, an extrusive system with numerous phases starting in the Aptian and acting until the Tertiary period. However, tectonic events are clearly expressed during the Miocene.

The use of graptolites in the stratigraphy of the Southern Uplands: Peach's legacy

ABSTRACTLapworth, at the time of his 1878 paper on the Moffat Series, was the world's foremost expert on graptolites, and in that paper he gave the first great demonstration of the biostratigraphical value of graptolites. Peach & Home's resurvey of the Southern Uplands of Scotland extended Lapworth's ideas and his use of graptolites across the entire region. Peach's graptolitic work for the Survey is discussed: even though he identified a smaller repertoire of graptolites than Lapworth had, and often identified their general horizons rather than exact zone, his results are considered broadly correct. His faunal lists often emphasise the oldest faunas from the Moffat Shale inliers, presumably in order to stress their supposedly anticlinal structure. Subsequent work has seen a great extension of graptolite taxonomy and provided more detailed biostratigraphical subdivision, especially in the Silurian. The model of the Southern Uplands as an imbricate thrust stack is constrained by identifying the youngest (rather than oldest) fauna from the Moffat Shale inliers or, where possible, graptolites from the overlying greywacke formations. Such work has enabled the identification of about 25 thrust tracts in SW Scotland and of out-of-sequence thrusting in the Moniaive and Peebles areas to the NE.

Late Quaternary Morphotectonics of the Hetauda Dun, Nepal Sub Himalaya

The Hetauda Dun, a tectonic valley in the Sub-Himalaya, is separated from the Gangetic plain by the Outer Churia Range. This range was upheaved in the late Pleistocene giving rise to the Dun valley. The tectonics of the area are characterised by fault propagation tectonics caused by the migration of the active front from the Central ChuriaThrust (CCT) to the Himalayan Front Thrust (HFT). After the closure of the Dun, another active anticlinal structure related to thrust imbrication has developed in the central part of the valley on the hanging wall of the CCT. The crustal movement continues under the same stress field of the prior tectonic phase, characterised by the shortening of the Sub-Himalaya along the NNW-SSE direction.

Electromagnetic sounding in the Columbia Basin, Yakima, Washington

A controlled‐source electromagnetic (CSEM) survey was conducted near Yakima, Washington, to map the thickness and resistivity of a thick volcanic sequence overlying a sedimentary section and to infer structure in the sediments. The survey was conducted with a frequency‐domain system employing loop transmitters 400–500 m on a side and three‐component SQUID magnetometer receivers separated from the loop by 1 to 5 km. Data collected along a 30 km profile orthogonal to regional strike were interpreted initially with 1-D layered models, which were then pieced together to make a geoelectric section. Induction logs in a 5000 m exploration hole at one end of the profile agree very well with the CSEM soundings made around the hole. The geoelectric section reveals a smoothly varying thickness of volcanics with a pronounced anticlinal structure approximately concordant with a surface topographic ridge. To assess the validity of inferring lateral structure from 1-D interpretations, we made scale models of an anticlinal structure and of a surface inhomogeneity and conducted CSEM measurements over the scale models. Layered‐model inversions of these data show that the anticlinal structure and its location are very well determined by 1-D inversion, but its height and width are not accurately determined. CSEM sounding over the surface inhomogeneity model shows that this feature does not significantly degrade the interpretation of a deep target layer. In this setting, a geoelectric section made up from 1-D interpretations provides good qualitative measures of subsurface structure and also provides excellent starting models for detailed 2-D or 3-D modeling.