低渗油藏非线性渗流特征及其影响

Nonlinear percolation feature of low permeability reservoirs and its effect

针对低渗透油藏渗流阻力大,注水效果差等问题,根据物理模型实验资料,推导了低渗透油层的渗流数学方程,并研究了低渗油层中油、水渗流特征及其规律。研究表明:低渗储层中的渗流具有启动压力梯度,启动压力梯度与储层的渗透率成反比,与原油极限剪切应力成正比。低渗储层的渗透率越小,单井产量减小幅度越大;同时,单井产量减小幅度随原油的极限剪切应力和井距的增大而增大。因此,可采用压裂或打水平井等技术手段对油层实施有效改造,通过降低原油剪切应力、使用小井距和较大的生产压差来改善开发效果。

In view of the high filtration resistance and poor water injection results of low-permeability oil reservoirs, this paper derives a mathematical equation of percolation for low-permeability reservoirs according to the experimental data of physical models, and studies the percolation features and regularity of oil and water. Results show that the starting pressure gradient of the percolation exists in low-permeability reservoirs. It is inversely proportional to permeability, but is directly proportional to ultimate shear stress of oil. The lower the permeability is, the greater the extent of single-well output decrease is. What's more, the extent of single-well output decrease increases as the ultimate shear stress becomes bigger and the distance between wells gets larger. So reservoirs can be reconstructed effectively by fracturing and drilling horizontal wells. And the results of developing low-permeability reservoirs can be improved by lowering shear stress of oil and applying small well spacing and greater production pressure difference.