基于REV尺度格子Boltzmann方法的页岩气流动数值模拟

结合页岩扫描电镜图像,提出页岩气藏物理模型,采用表征单元体积(representative elementary volume,REV)尺度格子Boltzmann方法,考虑滑脱效应,模拟页岩气在页岩气藏中的流动.模拟结果表明,页岩气主要沿着天然裂缝窜进,但在有机质和无机质中也存在缓慢的流动,且有机质中的流速要略大于无机质中的流速.通过改变地层压力,研究地层压力对页岩气渗流特性的影响.研究结果表明,整个流场的速度和渗透率均随着地层压力的下降而增加.

NUMERICAL SIMULATION OF SHALE GAS FLOW BASED ON THE LATTICE BOLTZMANN METHOD AT REV SCALE

During the seepage of the shale gas,its effect is due to the large Knudson number,which makes the gas molecules slip from the solid surface.Based on the REV (representative elementary volume) scale lattice Boltzmann method,the flow of the shale gas is simulated with consideration of the slippage effect.With the scanning electron microscope image,a physical model with organic rock,nonorganic rock and natural fractures is taken,and then the shale gas flow in the model is simulated.The simulated results indicate that the shale gas mainly flows in the natural fractures.However,the shale gas also flows slowly in the organic and nonorganic rocks,and the velocity in the organic rocks is larger than that in the nonorganic rocks.The influence of the reservoir pressure on the shale gas seepage is also studied by varying the reservoir pressure.It is indicated that with the decrease of the reservoir pressure,the Knudson number increases and the slippage effect intensifies,thus the velocity and the permeability of the whole fluid field increase.