Investigations of Miscible Water Alternating Gas Injection Efficiency in Layered Sandstone Porous Media

Abstract

Carbon dioxide (CO 2 ) flooding deliberated as one of the most common and feasible used gas to improve oil recovery. CO 2 utilization has grown significantly due to availability, greenhouse effect and easy achievement of miscibility relative to other gases. There have been limited experimental efforts conducted at core-scale focused on evaluating the influence of permeability heterogeneity on oil recovery. Thus, the results from this manuscript are essential to highlight the importance of geological uncertainties in the current and future enhanced oil recovery projects. This manuscript presents a coupled experimental and simulation study to assess the effect of cross bedded reservoir heterogeneity on WAG flooding performance. We performed core flooding experiments with a fluid system consisting of n-C 10 , synthetic brine, and CO 2 at a temperature of 343 K and 17.2 MPa pore pressure. In addition to the experimental work, a 2D core scale CMG-GEM simulation associated with PVT module CMG WinProp has been built based on our experimental results. We found that oil recovery decreases dramatically with increasing permeability ratio of cross bedded core samples. Besides, our results revealed channeling of injected CO 2 in high permeability beds leaving a considerable amount of oil untouched in low permeability bed. Furthermore, we pronounced a water shielding effect which reduces further contact of the injected CO 2 with oil. We thus conclude that reservoir heterogeneity significantly impact WAG flooding performance and evaluation of these influences on oil recovery before any field application are essential.