基于格子玻尔兹曼的润湿性对降压效果的研究

改变油藏润湿性和降低油水界面张力是解决低渗/特低渗油田注水压力高问题的有效方法。而室内驱替实验时，表面活性剂浓度不仅影响油水界面张力，还会影响岩石表面润湿性能，无法准确评价表面活性剂的润湿性能对降压效果的影响。格子Boltzmann方法通过控制流体和固体间作用参数能够独立控制界面张力大小，并能够模拟任意接触角变化。因此，基于格子Boltzmann方法，应用二维平板模型，考虑粗糙表面，设置微观梯形结构，研究了毛管数、邦德数及黏度比等不同无量纲数条件下润湿性改变对降压率的影响。结果表明，毛管数越小，邦德数越大、黏度比越大、接触角越小，降压率越高、降压效果越明显；接触角存在一个最佳范围，超过此范围继续降低接触角，降压效果不明显；对于多孔介质，改变润湿性对降压率影响比单通道更加明显。

Simulation Study on the Effects of Wettability on Depressurization Based on Lattice Boltzmann Model

Changing the wettability of a reservoir and decreasing the oil-water interfacial tension is an effective method for solving the high pressure water injection problem in low and ultra-low permeability oil fields. However, during in-lab displacement experiments, the surfactant concentration not only affects the interfacial tension between oil and water, but also the wettability of the rock surface. As such, the effect of the surfactant wetting ability on depressurization cannot be accurately evaluated. Lattice Boltzmann models can control the interfacial tension independently through the interaction parameters between fluid and solid, and simulate any change in contact angle. Based on a lattice Boltzmann two-dimensional plane model, considering surface roughness and creating a micro-ladder structure, this study investigated the effects of changing wettability on depressurization rate under the dimensionless parameters of capillary number, Bond number, and viscosity ratio. The results show that with decreasing capillary number, the Bond number and viscosity ratio increase, and with decreasing contact angle, the depressurization rate and depressurization effect improve. There is an optimum range for the contact angle. Continued decrease in the contact angle outside this range produces no obvious depressurization. The changing wettability has a more pronounced effect on the depressurization rate for a porous medium than for a single channel.