Zhang Yulong, Shi Leiting, Ye Zhongbin, Chen Liang, Yuan Na, Chen Ying, Yang Hao
State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, Sichuan 610500, China.
Chengdu Technological University, Chengdu 611730, China.
ACS Omega. 2022 Jul 29;7(31):27291-27299. doi: 10.1021/acsomega.2c02246. eCollection 2022 Aug 9.
In recent years, gas injection, especially CO injection, has been acknowledged as a promising approach for enhanced oil recovery (EOR) and CO capture and storage (CCS), especially for tight reservoirs. However, when CO is injected into the oil reservoirs, it can disturb the equilibrium of the system and lead to chemical reactions between CO, formation water, and reservoir rocks. The reactions will alter some geochemical and physicochemical characteristics of the target reservoirs. However, the reactions still lack quantitative characterization at the pore scale, especially under reservoir conditions. Herein, we conducted an experimental study of the interactions between CO, brine, and rocks in the Mahu oilfield at 20 MPa and 70 °C. The low-field nuclear magnetic resonance (LF-NMR) measurements showed that the incremental amplitude for tight cores of CO-rock-water tests was larger than that for CO-rock tests, and the amplitude alteration presented significant differences corresponding to different types of minerals and pores. Furthermore, the interplanar spacing of the core samples was increased with the increase of reaction time in the CO-rock experiments but still lower than that in CO-rock-water tests. This research demonstrated evident changes in the geochemistry in tight reservoirs caused by CO, brine, and rock reactions. The results of this study may provide a significant reference for the exploration of similar reservoirs in the field of CO-EOR and CO sequestration.
近年来，注气，尤其是注二氧化碳，已被公认为是提高采收率（EOR）和二氧化碳捕集与封存（CCS）的一种有前景的方法，特别是对于致密油藏。然而，当向油藏中注入二氧化碳时，它会扰乱系统的平衡，并导致二氧化碳、地层水和储层岩石之间发生化学反应。这些反应将改变目标油藏的一些地球化学和物理化学特征。然而，这些反应在孔隙尺度上仍缺乏定量表征，尤其是在油藏条件下。在此，我们在20MPa和70℃条件下对玛湖油田中二氧化碳、盐水和岩石之间的相互作用进行了实验研究。低场核磁共振（LF-NMR）测量结果表明，二氧化碳-岩石-水实验中致密岩心的增量幅度大于二氧化碳-岩石实验，且幅度变化因矿物和孔隙类型不同而存在显著差异。此外，在二氧化碳-岩石实验中，岩心样品的晶面间距随反应时间的增加而增大，但仍低于二氧化碳-岩石-水实验中的晶面间距。这项研究证明了由二氧化碳、盐水和岩石反应导致的致密油藏地球化学的明显变化。本研究结果可为二氧化碳提高采收率和二氧化碳封存领域类似油藏的勘探提供重要参考。
