CO2混相驱极限井距解析方法与驱油特征研究  

Study on analysis method of critical well spacing and displacement characteristics in CO2 miscible flooding

作　　者：迟杰 CHI Jie(School of Basic Sciences, Shengli College, China University of Petroleum, Dongying 257061, China)

机构地区：[1]中国石油大学胜利学院基础科学学院,山东东营257061

出　　处：《西北大学学报（自然科学版）》2020年第6期996-1004,共9页Journal of Northwest University（Natural Science Edition）

基　　金：山东省高校科研计划A类基金资助项目(J18KA201);中国石油大学胜利学院“春晖计划”基金资助项目(KY2017004);中国石油大学胜利学院引进高层次人才科研启动基金资助项目(KQ2019-008)。

摘　　要：为准确计算特低渗透油藏CO2混相驱极限井距,基于非达西混相渗流理论,考虑CO2与原油混相过程降低了原油黏度及油相启动压力梯度,建立一维混相渗流数学模型,使用解析函数精确求解CO2浓度衰减区内浓度的变化,推导出特低渗透油藏CO2混相驱极限井距的计算新方法,开发极限井距计算软件进行井距算例的计算,绘制理论图版,并分析纯CO2渗流区、CO2浓度衰减区及纯油区分别对极限井距的贡献。结果表明,极限井距随注气井底压力的增大而增大,随注气速度的增大而减小;纯CO2渗流区对极限井距的贡献最大,CO2浓度衰减区的贡献居中,纯油区的贡献最小;在同一时刻,注气速度越大,CO2浓度衰减区的长度越长,对同一注气速度,CO2浓度衰减区长度会随时间的增大而增大,但在某一个时刻之后,CO2浓度衰减区的长度会保持一个常数不变。To calculate the critical spacing of CO2 miscible flooding in ultra-low permeability reservoirs accurately,based on non-Darcy miscible seepage theory,considering the reduction of viscosity of crude oil and threshold pressure gradient of oil phase caused by the miscible process of CO2 and crude oil,one dimensional percolation mathematical model is established.In this paper,the analytic function is used to solve the concentration variation in the CO2 concentration decline area and the new computational method of critical well spacing of CO2 miscible flooding in ultra-low permeability reservoirs is deduced.The critical well spacing calculation software is developed and the theoryplate is established,and the contributions of pure CO2 seepage area and CO2 concentration decline area and pure oil region on critical well spacing is analyzed,respectively.The new method only need input the basic physical parameters of reservoir rock and fluid to calculate critical well spacing.The results show that the critical well spacing increases with the gas injection bottom pressure and decreases with the gas injection rate;the pure CO2 seepage area contributes the most to the critical well spacing,the contribution of the CO2 concentration attenuation area is middle,and the pure oil areathe minimum;at the same time,the higher the gas injection rate,the longer the length of the CO2 concentration attenuation area.For the same gas injection rate,the length of the CO2 concentration attenuation area will increase with time.The length will remain constant after certain time point.

关 键 词：特低渗透油藏 混相驱 极限井距 启动压力梯度 传质-扩散-吸附方程 

分 类 号：TE34[石油与天然气工程—油气田开发工程]