CO2细管驱油实验混相动态特征表征方法

摘要

CO2在多孔介质驱油过程中,当CO2-原油体系具备一定条件时,就会发生油气混相的动态相平衡.通过室内细管物理模拟实验,研究CO2-原油体系的混相动态特征.实验表明:当CO2体积分数大于85％时,CO2-原油体系可以达到混相状态;产出气中甲烷和氮气的相对体积分数超过70％,CO2混相驱为蒸发气驱;CO2混相驱效率为CO2驱替效率和CO2混相效率之和,其中CO2混相效率还可细分为CO2抽提效率和传质/扩散效率.量化CO2与原油过渡区间的混相特征,提出“混相长度L细管”和“相对混相长度Lr细管”2个参数,L细管、LI细管和实验压力主要分布在2个区间:(1)横向上,L细管为0.20～0.45 m,Lr细管为0.10～0.3 m,压力为20～ 40 MPa;(2)纵向上,Lr细管为0.20～0.80 m,Lr细管为0.10～0.50 m,压力为24～32 MPa;(3)重合范围,L细管管为0.20～0.45 m,Lr细管细管为0.10～0.30 m,压力为24～32 MPa.该CO2驱油实验结果对其他CO2驱混相动态特征表征具有一定的指导作用.%In the process of CO2 (carbon dioxide) oil flooding/displacement in the porous media,the dynamic or kinetic phase equilibrium of the oil and gas mixture phase will take place when the CO2-crude oil system has a certain conditions.By means of the indoor slim-tube physical simulation experiment or test,the miscible dynamic characteristics or features of the CO2-crude oil system were figured out.The experimental study results show that the CO2-crude oil system can reach the miscible conditions when the CO2 volume fraction is more than 85％;at the time of the relative volume fraction of the methane and nitrogen in the produced gas is more than 70％,the CO2 miscible flooding is turned into the evaporation gas flooding;the efficiency of the CO2 miscible flooding is the general sum of the CO2 displacement efficiency and CO2 miscibility efficiency,and moreover the CO2 miscibility efficiency can be divided into CO2 extraction efficiency and mass transfer/diffusion efficiency.The miscible characteristics or features in the transitional zone between the CO2 and crude oil were quantified and detailed,two parameters that are namad as “miscible length Lslim-tube” and “relative miscible length Lr slim-tube” were proposed.Two lengths stated above and the experimental pressures are mainly distributed and spread in two intervals in detail:(1) In the lateral direction,the Lslim-tube is 0.20-0.45 m,the Lslim-tube is 0.10-0.30 m,and the pressure is 20-40 MPa;(2) In the vertical direction,the Lslim-tube is 0.20-0.80 m,the Lr slim-tubeiS 0.10--0.50 m and the pressure is 24-32 MPa;(3 ）For the range of the coincidence,the Lslim-tube is 0.20-0.45 m,the Lslim-tube is 0.10-0.30 m,and the pressure is 24-32 MPa.The experimental research results of the CO2 oil flooding possess a certain guides for the characterization of the dynamic characteristics of the other CO2 miscible floodings.