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The early Cretaceous sand intervals of Lower Goru Formation (LGF) are significant reservoir for hydrocarbons and are situated in study area of Sawan gas field, Middle Indus Basin, Pakistan. This integrated study focuses on the development of stratigraphic traps and reservoir geometries in paleo-depositional environment through sequence stratigraphic and diagenetic analysis of productive Lower Goru sandstone. The datasets of well-logs from five wells (Sawan-1, Sawan-2, Sawan-3, Judge-1, and Nara-1), core samples from two wells (Sawan-1 and Sawan-2) and 2D seismic section (line: PSM96-133) are used in this study. The key system tracts including lowstand, transgressive, and highstand system tracts are identified with several progradational and retrogradational parasequences. The bounding stratigraphic surfaces are identified as sets of onlaps and downlaps unveiling different episodes of rise and fall in sea level with different sedimentation conditions. A depositional model is generated to map the paleo-environment of the reservoir by integrating the results of stratigraphic analysis. The log trends and seismic stratigraphic analysis showed the thickening trend of productive C-sand interval towards the eastern direction followed by gradual thinning in the middle part and shale-out trend towards the south and west part of the area. This indicates that the paleo-depositional direction was from east to west in shallow marine settings. The petrography and diagenesis results reveal that reservoir sands are iron chlorite-cemented sublitharenites to lithic arenites. The porosity and permeability of the reservoir is preserved due to a high amount of early diagenetic pore-lining iron chlorite, which commonly coats the surface of the quartz grains. The facies depositional environment is a wave dominated lowstand shelf edge delta system in which proximal delta front sands constitute the best reservoir. The outcomes of this research hold significant promise for advancing the comprehension of diagenetic processes and their influence on reservoir properties within the Lower Goru sandstone and its surrounding regions. [ABSTRACT FROM AUTHOR]

The present study is focused on the subsurface mapping for groundwater accumulation in an area located southwest of Rawlakot city, Azad Kashmir to model groundwater condition using geo-electrical measurements. Vertical Electrical Soundings are conducted using a Schlumberger electrode configuration with AB/2 ranging from 1.5 to 250 m. The results of Vertical Electrical Sounding data are interpreted qualitatively using iteration software IPI2win which indicates four distinct lithological units, i.e., shale, clayey shale, clay and weathered clayey sandstone. Based on the Vertical Electrical Sounding data it is inferred that the top soil is mostly composed of 15 m thick shale to clay beds of Quaternary alluvium having apparent resistivity between 18-70 Om. With an increase in the depth, the shale and clay beds are gradually replaced by sandstone beds (100-300 Om) from a depth of 40-100 m. The generated apparent resistivity section, pseudo section and spatial distribution of apparent resistivity map at 30 m, 40 m, 60 m and 80 m are in agreement with the geology and hydrological conditions of the study area. The results inferred that the favourable aquifer conditions are present in the 20-50 m thick weathered sandstone beds having intercalation of clays. The apparent resistivity sections show that the North-East and North-West regions have comparatively good reservoir potential for groundwater. [ABSTRACT FROM AUTHOR]

Seismic reflection method along with well log serves as an important tool for characterization of reservoir. The present study focuses on blend of parameters derived from seismic data such as acoustic impedance, reflection coefficient, interval velocities, and then usage of density-velocity relation to graphically interpret the lithology by means of Gardener et al. (1974) density-velocity graphical relation. The above results were also justified by incorporating well log data of Indus Marine 1A well. The interval velocity in the Middle Miocene Gaj Formation ranges from 9944 ft/sec to 12532 ft/sec and represents soft lithologies towards south western and south eastern part of the study area. The Acoustic impedance and reflection coefficient values also exhibited a decreasing trend towards the southeastern and southwestern part of study area and indicate presence of soft lithology. However, central part of the study area added by high values of acoustic impedance, reflection coefficient, density and interval velocity are indicative of sand. The Gardner graph (generated on the basis of density-velocity relation) confirmed the lithology of the Middle Miocene Gaj Formation as shale (dip lines) and sandstone (strike lines). This lithological interpretation was later on confirmed by lithology interpretation of well log data of Indus marine 1A (Ali, 2013). Based on the analysis the area is structurally less complex and comprises mostly of gentle sloping depositional layers of thick interbedded shale and sandstone (Ali, 2013). The sandstone dominates in the central part of study area while shale is mostly incorporated towards the south east and south west part of the area. The Offshore Indus Basin remains a frontier area as few wells drilled till now could not hit the commercial hydrocarbons. Considering the thick sedimentary fill and its deformational history, Offshore Indus Basin has a variety of potential plays which requires more studies. [ABSTRACT FROM AUTHOR]

The research mainly involves the petrophysical analysis of Chanda deep-01 and to mark the best reservoir zone while second part of the research work was to correlate the Lockhart Limestone of Chanda deep-01 with exposed Lockhart Limestone at Nathia Gali in Hazara region on the basis of porosity and thickness. To interpret petrophysical properties, different logs were used which include gamma ray log, neutron log, density log, long latero log, spontaneous potential and sonic log. Exposed Lockhart Limestone unit was studied in the field and petrographically analyzed. The thickness acquired from field was 242m while porosity estimated by thin section study was about 11% .The petrophysical properties calculated at Chanda deep-01 well estimated the thickness to be 170m and porosity to be 9.5% along with volume of shale 5.5% and water saturation 29.3%. In the same zone, hydrocarbon saturation turned out to be 70.6%. These values confirmed Lockhart limestone to be the best reservoir in Chanda deep-01 well. The exposed unit in Hazara was then correlated and the porosity difference with subsurface unit in Chanda deep-01 was estimated to be 1.86%. The changes in porosity at different locations of same formation were interpreted to be due to overburden pressure, facies changes, diagenesis and pressure dissolution. [ABSTRACT FROM AUTHOR]