Abstract: Using the method of “pessure⁃consumption” and Micro⁃flow measurement instrument the start⁃up pressure gradient of water flooding and microemulsion flooding in low permeability reservoir is actually measured.Analyzed the characteristics of nonlinear seepage and the effect with mechanization of start⁃up pressure gradient of microemulsion in low permeability reservoir.The result show that the pessure⁃consumption curve of low permeability reservoir is a concave⁃up curve which has non⁃Darcy seepage flow characteristic. The start⁃up pressure gradient and permeability in a power,and start⁃up pressure gradient are increasing with the reduction of permeability.The average start⁃up pressure gradient of flooding water is 0.050 MPa/m,and the average start⁃up pressure gradient of micro emulsion flooding is 0.039 MPa/m.The reason why microemulsion can reduce start⁃up pressure gradient is that it can decrease interfacial tension and resistance coefficient.The lower the interfacial tension of micro emulsion,the small start⁃up pressure gradient.

Key words: Low permeability reservoir, Microemulsion, Start?up pressure gradient, Non?linear seepage, Interfacial tension

摘要： 利用微流量计量仪，通过“压差⁃流量”法，精确测定了低渗透油藏水驱和微乳液驱的启动压力梯度，深入分析了低渗透油藏非线性渗流特征，重点研究了微乳液对低渗透油藏启动压力梯度的影响和作用机理。结果表明，低渗透油藏的“压差⁃流量”曲线是一条上凹型曲线，具有非达西渗流特征。启动压力梯度与渗透率呈乘幂关系，启动压力梯度随渗透率的减小而增大，水驱平均启动压力梯度为0.050 MPa/m，微乳液驱平均启动压力梯度为0.039 MPa/m。微乳液之所以会有效降低启动压力梯度，是因为它能够显著降低界面张力，减小了边界层的渗流阻力。微乳液界面张力越低，启动压力梯度也就越小。

关键词: 低渗透, 微乳液, 启动压力梯度, 非线性渗流, 界面张力