中文摘要：

低渗透油藏开发过程中存在启动压力梯度，CO2混相驱过程复杂，需要进行深入研究。将CO2混相驱过程分为原始油相带、注气前缘带、混相油带和注气后缘带，主要采取短岩心驱替实验测定启动压力梯度。研究表明，低渗透岩心的压力梯度与流量关系图都呈凹型分布，存在非线性流动和线性流动。启动压力梯度的主要影响因素有流体粘度、有效渗透率、流体密度和气油比等。启动压力梯度与岩心渗透率成幂函数变化，指数为-0．482。

英文摘要：

Threshold pressure gradient exists in the development of low permeability reservoir. The process of CO2 miscible flooding is very complicated, demanding further research. It can be divided into 4 zones including original oil phase zone, frontal phase zone of gas injection, miscible oil phase zone and injection. Indoor short core experiments are Studies show that the pressure gradient-flow is divided to nonlinear flow and linear flow. effective permeability, fluid density, gas oil ability are based on power function, and the trailing phase zone of gas used to study the threshold pressure gradient of different flooding diagrams of low permeability core are in concave distribution which The main factors of threshold pressure gradient are fluid viscosity, ratio, and so on. The threshold pressure gradient and core perme- index is about -0. 482.