低渗透砂岩油藏注CO_2混相条件研究

A study on the miscible conditions of CO_2 injection in low-permeability sandstone reservoirs

着重介绍了细管实验条件对最小混相压力实验确定方法测试结果的影响。通过数值模拟方法发现,当细管长度越长、细管直径越小、驱替速度越大、孔隙度越小,则得到的最小混相压力值也越小。另外,还讨论了油藏温度、注入气组成及原油的组成与性质对混相压力的影响情况。通过对比国内外注CO2混相驱油藏与流体的条件,说明了中国原油很难实现CO2混相的原因即地层温度高、地面油粘度大。建议开展降低最小混相压力技术及加强防止气体突破技术的研究,以解决注气过程中气体波及效率低的问题,实现较高的采收率。

This article illustrates the impacts of slim-tube experimental conditions on test results of minimum miscibility pressure（MMP）. The numerical simulation results show that the MMP is smaller when the slim-tube＇ s length is longer, diameter is smaller, displacement speed is greater, and the porosity is smaller. In addition, it discusses the influences of reservoir temperature, injected gas compositions and crude oil compositions and properties on the miscible pressure. Through comparing the condition of CO2 miscible flooding reservoirs and fluid flow in foreign and domestic fields,it explains the reasons behind the difficult application of CO2 miscible flooding in China＇ s fields are high formation temperature and high oil viscosity. It is suggested that a research on technologies of reducing minimum miscibility pressure and preventing gas breakthrough be carried out to address the issue of low sweep efficiency of injected gas and to enhance oil recovery.