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页岩富含纳米孔,纳米孔气体传输不同于宏观流体流动.基于滑脱流动和克努森扩散两种传输机理,分别以分子之间碰撞频率和分子与壁面碰撞频率占总碰撞频率的比值作为滑脱流动和克努森扩散的权重系数,耦合这两种机理,建立了理想气体传输模型.同时考虑高压条件下真实气体分子间相互作用力和气体分子自身体积对气体传输的影响,建立了页岩纳米孔真实气体传输模型.模型可靠性通过分子模拟结果验证.结果表明:纳米孔真实气体传输模型能够更合理地描述所有的气体传输机理,包括连续流动、滑脱流动和过渡流动;真实气体效应对气体传输的影响可高达23%,其受压力、温度、纳米孔尺度和气体类型的控制;在室内实验条件下模拟页岩纳米孔气体传输时,用氦气代替甲烷,低估了甲烷的传输能力65.09%;用氮气代替甲烷,高估了甲烷的传输能力106.27%.
The shale is rich in nanopores, and the nanoporous gas transport is different from the macroscopic fluid flow. Based on the two transport mechanisms of slip flow and Knudsen diffusion, the collision frequency between molecules and the ratio of molecular to wall collision frequency to total collision frequency are taken as Slip flow and Knudsen diffusion weight coefficient coupling the two mechanisms to establish an ideal gas transmission model.At the same time, under the high pressure conditions, the interaction between the real gas molecules and gas molecules own volume on gas transmission, the establishment of the page Rock nanopore real gas transport model.The model reliability is verified by the molecular simulation results.The results show that the nanopore real gas transport model can describe all the gas transport mechanisms more reasonably, including continuous flow, slippage flow and transitional flow. The real gas effect The effect on gas transport can be as high as 23%, which is governed by pressure, temperature, nanopore size and gas type; replacing methane with helium instead of methane when simulating gas transport in shale nanopores under laboratory conditions underestimates the methane transport Capacity of 65.09%; Replacement of methane with nitrogen, overestimated the methane transmission capacity of 106.27%.