Optimization of CO2 EOR and geological sequestration in high-water cut oil reservoirs

Abstract In terms of the collaborative optimization of CO 2 flooding for Enhanced Oil Recovery (EOR) and CO 2 sequestration, previous studies have co-optimized both cumulative oil production and CO 2 sequestration by various algorithms. However, these solutions fail to optimize the CO 2 injection schemes for high-water cut oil reservoirs. This paper presents an optimization methodology for CO 2 flooding and sequestration in high-water cut oil reservoirs. The production optimization was carried out by adjusting the injection and production rate. To solve the proposed objective functions, the simultaneous perturbation stochastic approximation (SPSA) algorithm is applied in this paper, and the CMG-GEM module is utilized to simulate the reservoir production performance. A typical high-water cut reservoir in the Shengli oilfield was used to verify the feasibility of the presented methodology. In this paper, the production performance and net present value (NPV) for continuous gas injection under different water cuts were analyzed. The optimal timing of transforming from water flooding to gas displacement for the high-water cut reservoir was optimized. In addition, the optimal water–gas ratios for Water-Alternating-Gas (WAG) flooding were determined. The sensitivity of NPV to gas injection price and carbon subsidy was analyzed. The results show that when the gas price is 0. 178 /m 3 and the carbon subsidy is 0. 0169 /m 3, the optimal timing of transforming from water flooding to gas injection should be earlier than the time when the water cut is 0. 82. Through the combination of NPV, cumulative oil production rate, and CO 2 sequestration volume for WAG flooding, the optimal WAG ratio should be 1: 2. The presented method in this paper considers various economic indicators and can optimize CO 2 flooding and sequestration in high-water cut oil reservoirs efficiently, which can provide some guidance for the design of CO 2 flooding schemes in high-water cut oil reservoirs.