页岩基质中甲烷传质输运产能计算模型

页岩气藏基质中存在吸附气和游离气,通过扩散和渗流两种传输机制进行流动。为了研究页岩气藏基质产气规律,推导了一维页岩基质产气量计算公式,扩散体积流量与入口压力成线性正比关系,渗流体积流量与入口压力成二次函数关系,渗透率越高、扩散系数越大,则体积流量越大。在此基础上,设计了全直径页岩岩心甲烷解吸、扩散、渗流耦合实验,研究了产气量与压力的变化关系;并通过拟稳态阶段的实验数据验证了一维页岩基质产气量计算公式的正确性。利用模型计算结果预测了页岩气传质输运实验未来体积流量的变化趋势:当入口压力达到15 MPa时,渗流体积流量在耦合流量中所占比例接近50%;当入口压力低于15 MPa时,扩散体积流量在耦合流量中所占比例较高。

Methane production and mass transport calculation model in shale matrix

Matrix of shale gas contains adsorbed gas and free gas. They flow in shale gas matrix by diffusion and transport two kinds of mechanisms. In order to research gas production law in shale gas matrix, on the one hand, one-dimensional gas production calculation model of shale matrix was derived. Diffusion volume flow with inlet pressure is linearly proportional relationship. Seepage volume flow with inlet pressure is quadratic function. Higher permeability and lager diffusion coefficient make the volume flow greater. Methane desorption, diffusion, flow coupling experiments of whole diameter shale core was designed. The relation between gas production and pressure was studied. The correctness of gas production formula in shale matrix was verified by the quasi-steady experimental data of shale gas. The model results predict the experimental volume flow of future trends of shale gas mass transfer and transport. When the inlet pressure reaches 15MPa, seepage volume flow is close to 50% in the proportion of the coupling flow. When the inlet pressure is lower than 15MPa, diffusion flow is high proportion in coupling volume flow.