Recherche pétrolière et gazière

Abstrait

Study of the cyclic injection of CO2 in unconventional tight oil reservoirs

Shicheng Zhang

An experimental-work was conducted for Cyclic CO2 Injection Process (CCIP) in low-permeable tight coresamples. CCIP is an EOR method involving of huff, shut-in and puff periods. The work of CCIP and oilproduction in unconventional-formations is generally a task of fluid, rock and operating constraints. Laboratory-work was performed to evaluate numerous designing parameters of CCIP to differentiate the parameters with highly influence on the hydrocarbon-production and to understand the influence of CCIP in tight-reservoirs. The consequences of the above unreliable parameters as well as the water-saturation with different salinityconcentrations on the procedure of CO2 EOR have not been fully comprehended. Therefore, it’s definitely indispensable to evaluate the more important parameters which influence the operation. The principal aim of this work is to ameliorate procedures for designing CCIP in order to optimize CO2-injection and maximize wellproduction. The outcome shows that the presence of brine will have an adverse impact on oil-production, demonstrating that increasing fracturing-fluid flow back will increase production. This can be used for a better understanding of optimization design of fracturing-fluids. Furthermore, the results show that water-saturation has an effect on the oil-production during CCIP for production period of 15 minutes at the end of the fourth cycle, the oilrecovery for the core that is only saturated with oil (C-1) was 77.74%, compared with 30.40% for core that initially was saturated with water and then with oil (C-2). Finally, it is concluded that in both cases C-1 and C-2, CCIP has potential to produce an incremental oil-recovery from unconventional-reservoirs.