Modeling of Non-Darcian Flow of Fractured Sandstone Reservoirs: Experimental Approach

An experimental technique for modeling both matrix and fracture flow behavior in a fractured porous media is presented in this paper. A high-pressure cell with a virtual infinite stiffness system (HPTT 250KN/14Mpa) has been used for sample testing.Cylindrical homogeneous sandstone sample of 6 cm diameter and 12 cm length has been prepared from slurry of sandstone, water and sodium silicate solution. This sample was exposed to 49 MPa confining pressure, 48 MPa pore pressure and 50 MPa axial pressure to simulate in situ reservoir conditions. CO2 gas was passed through the slurry to react with the sodium silicate and form cement bonds between the sandstone grains under the set reservoir conditions. Absolute permeability of the ‘homogeneous’ sandstone sample was determined for various pressure drops. The sample was exposed to in situ effective stresses by controlling confining, pore and axial pressures to shear the sample and create a fracture in a desired direction. Absolute permeability once again has been determined for a range of pressure drop values. Plots of pressure drop versus flow rate show a linear trend indicating Darcian flow behavior in the homogeneous case while exhibiting non-linear trends in the fractured case suggesting a non-Darcian flow behavior. This supported a previous hypothesis that necessitated the use of the Forchheimer equation for modeling fluid flow through fractures. This approach can be considered to be far superior to conventional dual-porosity, dual-permeability modeling

Keywords:

Modeling , Fracture , Non-Darcy , Porous media