Comparison of the optimal water-alternating-gas injection strategies using 1-D and 2-D reservoir simulations

Abstract

Emissions of greenhouse gases into the atmosphere, in particular, carbon dioxide (CO2), are an urgent environmental problem. Today, the technology of carbon capture and storage (CCS) in oil reservoirs is proposed as a solution to this problem. This can not only assist with decarbonization of the near-Earth space, but also contributes to an increase in oil recovery. Since CO2 is part of the gases that accompany oil production, the release of the associated petroleum gases is unacceptable and their burning is harmful to the environment. Thus, gas injection is more environmentally and economically beneficial. In this work, we compare the optimal strategies of CO2 flooding into oil reservoirs within the framework of 1-D and 2-D compositional modeling. The optimization criterion is the maximization of economic profit, i.e. the Net Present Value (NPV). For different injection strategies we determine the injected volume of gas and water, at which NPV is maximum. We also consider an alternative optimization criterion, which is based on retaining the maximum volume of CO2 in the oil reservoir. The grid convergence of the 2-D numerical solution is studied. The results of the simulation demonstrate that the optimal strategies obtained by 1-D simulations qualitatively agree with those obtained by the 2-D simulations, which makes it possible to consider a 1-D modeling appropriate in determining optimal strategies for dispersed injection of water and gas.