CO2混相驱储层吸气能力预测

Gas absorption prediction for reservoirs with CO2 miscible flooding

吴晓东 尚庆华 安永生 王玉霞

WU Xiaodong SHANG Qinghua AN Yongsheng WANG Yuxia

中国石油大学石油工程教育部重点实验室，北京　102249 延长石油 集团 有限责任公司研究院，陕西西安　710075 河南油田勘探开发研究院，河南南阳　473132

MOE Key Laboratory of Petroleum Engineering, China University of Petroleum, Beijing 102249, China Research Institute of Yanchang Petroleum, Xi’an 710075, China Research Instit ute of Petroleum Exploration &

为了预测注 CO2时储层吸气能力，为 CO2驱配注及注气参数的优化设计提供理论基础，在前人研究的基础上，建立了二维 CO2混相段塞驱物理模型和数学模型，考虑混相段塞对注气过程的影响，经理论推导建立了 CO2混相驱吸气能力计算模型。模拟计算结果显示： CO2混相驱注入压力与注气速度近似成线性关系，且注入压力越大，注气速度也越大；地层压力呈阶梯状分布，表现为 3个不同的压力梯度，且超临界 CO2区和混相区的压降较小，压力主要消耗在地层原油渗流区；吸气能力随累积注气量和段塞长度的增加而不断增强，吸气指数随累积注气量的增加呈对数型增长，随段塞长度的增大呈线性增长。

In order to forecast gas absorption of reservoir with CO2 flooding, and provide theory basis for CO2 injection alloca-tion rate and relevant parameters optimization design, on the basis of previous studies, the physical model and mathematical model were established for two-dimensional CO2 miscible slug flooding. Taking the effect of miscible slug on injection process into account, theoretical derivation was conducted to obtain the calculation model of gas absorption capacity for CO2 miscible flooding. Simulation calculated results show that the relationship between CO2 injection pressure and injection velocity are approximate linear, and the bigger the injection pressure, the higher the injection velocity. Formation pressure is in stair distribution, and presents three different pressure gradients. The pressure drops in supercritical CO2 region and miscible phase region is relatively low, which means that the pressure mainly was consumed in crude seepage area. Gas absorption ability enhances as the cumulative injection quantity and the miscible slug length increase. Gas absorption index presents a logarithmic type growth with rise of the cumulative gas injection volume and will grow linearly with the slug length increase.