Reservoir Characterization of Cambay Shale, Cambay Basin, India

Abstract

To define a subsurface reservoir model, two necessary parameters are permeability and capillary pressure. The prediction of these parameters is complicated as there cannot be determined directly from the well logs. And the use of sophisticated equations and data from different depths and areas are required for the evaluatation of these parameters. This work aims to study the pore throat and pore volume of Cambay shale in Sanand East, Cambay, Gujarat, India. The nanometre scaled pore systems of gas shales are an important control on hydrocarbon storage. Petrophysical data were utilized to work out resource number for Cambay shale. Capillary Pressure is related to the interfacial tension, the wettability and pore throat radius. Using various data of pore throat radius, the Capillary Pressure has been calculated. The data have been systematically plotted and it can be inferred from graph that the Capillary Pressure and pore throat radius are inversely related. Thus with increase in pore throat radius the Capillary Pressure reduces. One of the most important parameters that decide the flow of hydrocarbon in the reservoir is permeability. It is simply the ability to transmit fluid. In this project the permeability has been calculated using pore throat radius and core porosity. Accordingly, graphs has been plotted which shows that the permeability increases with pore throat radius logarithmically. Dynamic and elastic parameter determination for the rock strength using the P-wave velocity, S-wave velocity, Poisson’s ratio, Rigidity Modulus and Bulk Modulus are carried out. Primary wave results and secondary wave results are carried out at varying Confining pressures. Poisson’s ratio and Young’s modulus decides the fracturing job and completion intervals. Ductile shale behaves as a very good seal whereas brittle shale is likely to get fractured Seismic anisotropy is the variation of wave velocity along different directions in a material. Preferential mineral alignment, layering, microcracks, kerogen inclusions and fracturing all cause seismic anisotropy observed in many crustal rocks. Shales are the most abundant lithology in a sedimentary basin and exhibit a relatively large degree of anisotropy. Ultrasonic measurements are carried out on develop of Cambay shale to study its anisotropy. The elastic constants and Thomsen parameters are calculated and plotted against the Confining pressure on a suite of two plugs of the Cambay shale. The variation of velocities on different plugs of the same suite indicates that the Cambay shale is anisotropic