CO驱气体赋存特征微观可视化实验

Microscopic visualization experiment on gas occurrence characteristics in CO flooding

赵乐坤 刘同敬 张营华 陈辉 韩富强 周建 江绍静 姚约东

ZHAO Lekun LIU Tongjing ZHANG Yinghua CHEN Hui HAN Fuqiang ZHOU Jian JIANG Shaojing YAO Yuedong

中国石油大学(北京)石油工程学院 中国石油大学(北京)非常规油气科学技术研究院 中石化胜利油田分公司勘探开发研究院 北京金士力源科技有限公司 陕西延长石油(集团)有限责任公司

College of Petroleum Engineering, China University of Petroleum (Beijing), Beijing 102249, China Unconventional Petroleum Research Institute, China University of Petroleum (Beijing), Beijing 102249, China Exploration and Development Research Institute, SINOPEC Shengli Oilfield Company, Dongying 257000, Shandong, China Beijing Jinshiliyuan Technology Co., Ltd., Beijing 102200, China Shaanxi Yanchang Petroleum (Group) Co., Ltd., Xi’an 710075, Shaanxi, China

CO₂微观赋存特征对现场利用CO₂驱油提高采收率具有重要意义，然而目前的实验手段无法直观揭示CO₂驱油过程中的赋存状态，相关研究成果较少。采用微观渗流模拟技术，通过刻蚀不同孔喉特征二维微观可视模型，开展了CO₂混相与非混相驱及气驱后水驱微观可视化驱替实验，明确了不同驱替方式、不同驱替阶段和不同孔喉特征下CO₂的赋存特征。结果表明，CO₂赋存特征受驱替方式、驱替阶段和孔喉特征的共同影响，CO₂驱阶段，CO₂赋存特征主要受驱替方式影响，其次是孔喉特征影响；气驱过程中CO₂主要以连续相形式存在，但混相驱时局部CO₂富集且处于超临界状态，部分溶解在残余油中，而非混相驱富集现象不明显；气驱后转水驱过程中，CO₂赋存特征受驱替方式和孔喉特征的共同影响，混相驱替时，低渗透模型中气体赋存形式呈分散的泡状，细小喉道中存在段塞，高渗透模型中以密集的段塞为主、分散的泡状为辅；非混相驱替时，低渗透模型细小喉道中存在段塞，高渗透模型以小段塞为主，集中分布于喉道中间。研究成果有助于研究CO₂微观驱油机理和CO₂赋存特征，对提高CO₂驱油效率和辅助CO₂埋存研究具有理论指导意义。

The CO microscopic occurrence characteristics are significant for the study of CO flooding to enhance the oil recovery. However, the form variation and occurrence characteristics of gas in CO flooding have been rarely discussed so far. By using the microscopic flow simulation technology, a two-dimensional microscopic visualization model considering different pore throat characteristics was built. With the model, microscopic visualization displacement experiments were performed on CO miscible flooding, CO immiscible flooding, and water flooding after gas flooding, to clarify the occurrence characteristics of CO under different displacement processes, displacement stages and pore throat characteristics. The results show that the occurrence characteristics of CO are jointly controlled by displacement process, displacement stage and pore throat characteristics. During CO flooding, the occurrence characteristics of CO are mainly affected by displacement process, followed by pore throat characteristics. During gas flooding, CO occurs mainly as a continuous phase. During miscible flooding, CO is enriched and in a supercritical state locally, and partially dissolved in the residual oil. The phenomenon is unobvious during immiscible flooding. During water flooding after gas flooding, the occurrence characteristics of CO are jointly affected by displacement process and pore throat characteristics. During miscible flooding, the low-permeability model exhibits the gas occurrence in dispersive bubble form, and as slugs in fine throats, while the high-permeability model demonstrates the gas occurrence dominantly as dense slugs, supplemented by dispersive bubble form. During immiscible flooding, the low-permeability model shows slugs in fine throats, while the high-permeability model reveals the dominance of small slugs, which are concentrated between throats. The research findings are conducive to the study of CO microscopic displacement mechanism and occurrence characteristics, and of theoretical guiding significance for research on improvement of CO flooding efficiency and contribution to CO storage.

10.13639/j.odpt.202208025