RESERVOIR CHARACTERIZATION OF MEHAR BLOCKS USING SEISMIC AND WELL DATTA

Abstract

Mehar Block, Middle Indus Basin, Pakistan, conducts seismic 3D reflection and well data interpretation. The principal gas-producing reservoirs in the area include the Sui Main Limestone, Dunghan Formation Limestone Beds, Ranikot Formation Lower Sandy Part, and Pab Sandstone. The Mughalkot and Sembar Formation shale is the most likely source rock in the area. The study in this dissertation includes seismic data interpretation of subsurface geological formations, petrophysical assessment of the reservoir rock units, and reservoir characterization modeling. Gridding (time and depth) and contouring are used to assess the structural traps prospects (time and depth). The top of the Sui Main Limestone and Ranikot Formation have all their time and depth contour maps. Sui Main Limestone depths range from 2445 to 3062 meters, whereas Ranikot Sandstone depths range from 3228 to 3559 meters. Thrust bound anticline with one limb confined by thrust fault, according to subsurface interpretation. On the west, both of the Sui Main Limestone and the Pab sandstone have higher values up to 4756 m. Using well data from Mehar-01, a petrophysical examination of the Sui Main Limestone, Dunghan Formation, Ranikot Formation, and Pab Sandstone was performed. For all of the reservoirs specified in well Mehar-01, the results reveal satisfactory reservoir Figures. Ranikot sandstone has a Vsh of around 35%, an effective porosity of 16 %, and a water saturation of 45%, indicating a gas-rich reservoir with a hydrocarbon saturation of 60%. Ranikot exhibits better reservoir behavior at Zone-1(3239.6 - 3244.9) intervals than Zone-2 (3519.56 - 3530.2). Rock physics analysis is performed to confirm the results of petrophysics and compute reservoir rock parameters to obtain better knowledge of reservoir properties. The decrease in acoustic impedance and vp/vs ratio indicates existence of gas sands. Shaly sands appear in cross plots where there are high values of vp/vs ratio and impedance A model based inversion of 3D seismic was done to calculate the acoustic impedance of Mehar area. The impedance is further used for the quantitative interpretation. A statistical wavelet at zero phase is extracted from original data which is a matching filter between seismic trace and synthetic trace at well location. A low frequency DRSML QAU vi model is then build from the interpreted horizons and well log information. Model based inversion is then performed which was plotted with corresponding acoustic impedance. So our zone of interest is Ranikot, in this portion having low impedance value. Porosity values are high at or zone of interest.