Simulation Study on Water-Alternating-Gas (WAG) Injection with Different Schemes and Types of Gas in a Sandstone Reservoir

Water-Alternating-Gas (WAG) injection is one of the Enhanced Oil Recovery (EOR) techniques applied in oil and gas industry. In a WAG application, there are a lot of combinations of WAG schemes to be selected from. The common stated problem is to determine the optimum WAG schemes for a certain field. Different WAG schemes can be formed by adjusting the WAG parameters, i.e. WAG ratio, WAG injection rate, WAG cycle sizes and etc. Another problem is the ambiguous feasibility of other type of gas in WAG application. The objective of this Final Year Project (FYP) was to simulate and determine the impacts of WAG parameters on the recovery for a sandstone reservoir, and also to evaluate the feasibility of different types of gas in WAG injections. This project was carried out by using a compositional simulator developed by Computer Modeling Group Ltd (CMG). The inputs needed for the simulations were collected from the literatures available. This study focuses on WAG application in a sandstone reservoir. The performance of each scheme was evaluated based primarily on the ultimate recovery. From these outcomes, various WAG schemes and the impacts of each WAG parameter can be compared, and thus deciding the optimum one. It was concluded that WAG ratio, WAG injection rate and types of WAG gas have profound effects on WAG performance, while WAG cycle sizes has insignificant impact on the recovery.