Experimental and Simulation Study of Matrix Fracture Interaction in Sandstone Core Samples by CO2, CH4 And N2 Injection

Abstract

In this study, it is aimed at investigating matrixfracture interaction mechanisms with gas injection in a fractured sandstone core system. Influence of a fracture on matrix-fracture interaction processes and effects of type of the gas injected (namely, carbon dioxide, methane and nitrogen), initial gas saturation and diffusion coefficient in terms of oil recovery are studied by an experimental and simulation work. Gas oil gravity drainage and diffusion mechanisms are studied by introducing CO2, N2 and CH4 gases to the system and obtaining corresponding oil recoveries with time. An artificial fracture is created around Berea sandstone cores and system is kept at a pressure of 250 psi and at a reservoir temperature of 70 °C. n-decane is used as the oil phase. Experiments carried out with CO2 injection has resulted in higher oil recoveries than experiments carried out with CH4 and N2 respectively. It is obtained that availability of initial gas saturation in matrix increased recovery in CO2 experiments. A simulation study is also carried out to compare experimental results using CMG (Computer Modeling Group Ltd.) WinProp (Microsoft Windows™ based Phase-Behavior and Fluid Property Program) and GEM (Generalized Equation-of-State Model Compositional Reservoir Simulator) on a core scale basis. Keyword: Matrix-Fracture Interaction, Gas-Oil Gravity Drainage, Diffusion, CO2, N2 and Methane Injection, Oil Recovery