Impact of Relative Permeability Hysteresis on Water-Alternating-Gas WAG Injectivity: Modeling and Experimental Study

Abstract Gas injection is a proven enhanced oil recovery (EOR) process, representing the leading EOR-technique in the United States. In recent years, gas EOR technologies are expanding to more challenging (deeper and tighter) reservoirs. In gas injection, there are two basic techniques – continuous gas flooding and water-alternating-gas (WAG) injection. The WAG injection promises improved sweep efficiency, with water being used for mobility control and stabilizing displacement fronts, but suffers from injectivity loss due in part to gas trapping. This injectivity loss can have a major impact on project economics. In this work, we study the modeling of relative permeability hysteresis and its impact on WAG injectivity under both immiscible and miscible conditions.Core flooding experiments are also performed and simulated to understand and quantify the WAG injectivity. Our study showed that the most significant impact of gas relative permeability hysteresis on WAG injectivity lies in the water injectivity reduction following gas flooding. Experimental results confirmed the reduced water injectivity, and this effect can be modeled and sufficiently captured by the gas relative permeability hysteresis.