Ma Nianhao, Li Chaofan, Wang Fei, Liu Zhiwei, Zhang Yu, Jiang Luming, Shu Yong, Du Dongxing
Geo-Energy Research Institute, College of Electromechanical Engineering, Qingdao University of Science and Technology, Qingdao 266061, Shandong, China.
Petro China Research Institute of Petroleum Exploration & Development, Beijing 100083, China.
ACS Omega. 2022 Feb 22;7(9):8013-8022. doi: 10.1021/acsomega.1c07165. eCollection 2022 Mar 8.
Although flooding technology has found wide application in low-permeability reservoir development practices, the oil recovery enhancement mechanisms for different injection fluids still lack specific focus based on comprehensive investigations. Therefore, in this paper, supercritical CO (ScCO), N, and water injection processes in oil-saturated low-permeability tight cores were comparatively studied. To reveal the effect of physicochemical properties of the injection fluid on the oil recovery efficiency, the Berea sandstones with three permeability levels and kerosene were employed in this study to exclude other parameter influences. The flooding processes employing various injection media were investigated based on quantitative comparisons of the oil recovery factor and the displacement pressure difference at two system pressures. The experimental results show recovery efficiencies of 59-91 and 84-92% with the increasing permeability for the ScCO injection process at system pressures of 15 and 25 MPa, respectively, which are much higher than 26-40 and 21-52% in the N case and 43-46 and 45-49% in the water cases. Interfacial tension (IFT) measurement results indicate that miscibility conditions have been achieved for the ScCO/oil system, thus leading to much higher oil recovery. On the other hand, the pressure difference results show a similar magnitude of 10 MPa/m for both ScCO and N processes, which is much lower than the 100 MPa/m for the water flooding cases. Comprehensive comparison shows that ScCO shows great advantages in the application of unconventional reservoirs. It is expected that our research work could enrich the investigations of CO flooding and the in-depth understanding of the mechanisms and better guide the utilization of CO.
虽然驱替技术在低渗透油藏开发实践中已得到广泛应用，但基于全面研究，不同注入流体提高采收率的机理仍缺乏具体聚焦。因此，本文对油饱和低渗透致密岩心中的超临界CO₂（ScCO₂）、N₂和水驱替过程进行了对比研究。为揭示注入流体物理化学性质对采收率的影响，本研究采用了三种渗透率水平的 Berea 砂岩和煤油，以排除其他参数的影响。基于在两种系统压力下采收率因子和驱替压差的定量比较，研究了采用各种注入介质的驱替过程。实验结果表明，在系统压力为 15 和 25 MPa 时，ScCO₂注入过程的采收率分别为 59 - 91%和 84 - 92%，且随着渗透率增加而提高，远高于 N₂驱替情况下的 26 - 40%和 21 - 52%以及水驱情况下的 43 - 46%和 45 - 49%。界面张力（IFT）测量结果表明，ScCO₂/油体系已达到混相条件，从而导致更高的采收率。另一方面，压差结果表明 ScCO₂和 N₂驱替过程的压差幅度相似，均为 10 MPa/m，远低于水驱情况的 100 MPa/m。综合比较表明，ScCO₂在非常规油藏应用中具有很大优势。预计我们的研究工作能够丰富 CO₂驱替研究，深入理解其机理，并更好地指导 CO₂的利用。
