Collaborative optimization of CO2 flooding and storage in high water cut reservoirs

Abstract

In order to achieve the multiple purposes of the highest CO2 flooding recovery and the largest CO2 storage in high water cut reservoirs， an objective function of collaborative CO2 flooding and storage optimization for high water cut reservoirs based on economic net present value （NPV） was established by considering CO2 injection cost， CO2 flooding and storage benefits. Combined with the reservoir numerical simulation method， we used simultaneous perturbation stochastic approximation （SPSA） to solve the objective function iteratively. Taking a high water cut reservoir in Shengli Oilfield as an example， the different injection timings of water transferring to CO2 were set according to the different characteristics of water cut in the reservoir at different times. The optimization of water injection and CO2 injection schemes was carried out， respectively， and the differences in production behavoir and NPV under the two injection methods were compared. The influence of gas injection timing on cumulative oil production and CO2 storage was analyzed， and the optimal gas injection timing was determined. In addition， the effects of different gas injection prices and CO2 storage subsidy schemes on their economic benefits were analyzed. The results show that the water cut should be lower than 0.97 during waterf transferring CO2 injection to make the CO2 flooding project profitable in high water cut reservoirs. The high project profit can be guaranteed as CO2 is injected earlier when the CO2 injection price is 1.2 yuan/m3， and the carbon subsidy is 0.114 yuan/m3.

Keywords

• co2 flooding
• collaborative optimization
• co2 storage
• real-time optimization
• high water cut reservoir