Abstract: The degassing of crude oil in the formation will increase the seepage resistance,which seriously affects the development effect of low permeability reservoirs.This paper takes a low permeability reservoir in Weicheng as an example,using steady state water flooding test method to explore the effect of oil viscosity change on the oil water two⁃phase threshold pressure gradient,and study the effect of threshold pressure gradient on the effective displacement pressure difference in low permeability reservoirs.The results show that the threshold pressure gradient increases with the increase of oil viscosity after oil degassing,which results in the decrease of effective displacement pressure difference between wells.When the injection and production pressure difference is small,it is difficult to establish effective displacement.At the same time, some countermeasures are put forward to deal with this problem.The research results are of guiding significance for the design of injection⁃production well pattern and the later adjustment in low permeability reservoirs.

Key words: Low permeability reservoir, Formation oil degassing, Threshold pressure gradient, Effective displacement pressure difference

摘要： 地层原油脱气导致渗流阻力增大，严重影响低渗透油藏的开发效果。以卫城某油藏为例，通过稳态法水驱油实验，研究了原油黏度变化对油水两相启动压力梯度的影响，进而研究了启动压力梯度变化对低渗透油藏有效驱替压差的影响。研究表明，地层原油脱气后，随着原油黏度的增大，启动压力梯度增大，导致井间有效驱替压差减小，当注采压差较小时，将难以建立有效驱替；提出了针对这一问题的应对措施。研究成果对于低渗透油藏注采井网设计及后期的治理调整具有指导意义。

关键词: 低渗透油藏, 地层原油脱气, 启动压力梯度, 有效驱替压差