Laboratory and field-scale parameter optimization of CO2 huff–n–puff with the staged-fracturing horizontal well in tight oil reservoirs

Abstract

With the help of large-scale physical simulation experiment technology, the physical simulation experiments of the CO2 huff–n-puff with the staged-fracturing horizontal well could be acheived. We studied the production process of CO2 huff–n–puff and influence of different parameters affect oil recovery during the CO2 huff-n-puff procedure, ultimately, the operation parameters were optimized by numerical simulation. The results show that CO2 can quickly enter the deep formation through the horizontal well and the fracture during the huff period and staged-fracturing horizontal well can greatly increase the contact area between CO2 and crude oil, which improves the efficiency of extraction, dissolution, reduction of viscosity between CO2 and crude oil. During the puff period, the horizontal well and fractures can reduce the flow resistance effectively, so as to improve the flow capacity of crude oil. After 3 cycles of CO2 huff and puff, the oil recovery can be enhanced by 11.13%~21.39% compared with that obtained by elastic flooding, which indicates that the exploitation method of CO2 huff–n–puff can improve the development effects of tight oil reservoirs. CO2 huff-n-puff injection parameters are optimized, the results show that the optimum time of injection is 1 year, the optimum soaking time is 30d, and the optimal injection pore volume is 0.18HCPV. This research can provide a certain technical support for effective development of tight oil reservoirs.