页岩气藏流动机理与产能影响因素分析

为研究气体在页岩储层中的流动机理并分析影响页岩气藏产能的控制因素，基于广泛的文献调研，描述了页岩气在页岩储层中流动主要经历的3个过程：解吸附、扩散和渗流，分析了其影响因素和适用条件。在此基础上，利用数值模拟方法分析了吸附气含量、Langmuir体积、Langmuir压力、扩散系数、基质渗透率、微裂缝渗透率和压裂诱导裂缝导流能力等因素对页岩气水平井产能的影响情况。结果表明：①天然气地质储量保持不变时，随吸附气含量增高，水平井日产气量和相同开发时间累积产气量逐渐降低，地层平均压力下降速度加快；②相同吸附气浓度条件下，随Langmuir体积和Langmuir压力的增加，水平井日产气量和相同开发时间累积产气量逐渐降低，初期产量递减速度加快；③气体扩散系数对产能影响较小；④基质渗透率介于1.0×10^-9～1.0×10^-6 mD时，基质渗透率是控制水平井产能的主要因素，随基质渗透率增加，日产气量和累积产气量迅速增加；⑤基质渗透率大于1.0×10^-6 mD 时，基质渗透率和微裂缝渗透率均是控制水平井产能的主要因素，日产气量和累积产气量随基质渗透率和微裂缝渗透率的增加而增加；⑥随压裂诱导裂缝导流能力增加，水平井累积产气量逐渐增加，累积产气量增幅逐渐减小，压裂诱导裂缝存在着最优导流能力。

Flow mechanism of shale gas reservoirs and influential factors of their productivity

In order to understand the flow mechanism of shale reservoirs and analyze the controlling factors of their productivity,we performed extensive literature review,summarized the three stages of gas flow in the shale formations,namely desorption,diffusion and seepage flow,and analyzed their influential factors and application conditions.Numerical simulation methods were applied to study the influential factors of productivity of horizontal shale gas wells,such as adsorbed gas content,Langmuir volume,Langmuir pressure,diffusion coefficient,matrix permeability,micro-fracture permeability,hydraulic fracture conductivity,etc.The findings are as follows:(1) Assume that gas-in-place is constant,the higher the adsorbed gas content is,the lower the daily output and accumulative shale gas production at the same development stage are and the more rapidly the average reservoir pressure drops.(2) Assume that adsorbed gas contents are the same,the daily output and accumulative shale gas production at the same development stage are getting lower and the initial flow rate decline speeds up along with the increasing of Langmuir volume and Langmuir pressure.(3) The gas diffusion coefficient has a minor influence on productivity.(4) When being between 1.0×10-9 and 1.0×10-6 mD,matrix permeability will become the major factor controlling the productivity of horizontal shale gas wells.Daily output and accumulative production will increase rapidly along with the increasing matrix permeability.(5) When matrix permeability is larger than 1.0×10-6 mD,both matrix permeability and microfracture permeability are the major factors controlling the productivity of horizontal shale gas wells.Daily output and accumulative production will increase along with the increasing of matrix permeability and microfracture permeability.(6) The accumulative gas production of horizontal wells increases progressively but the amplitude of production growth decreases along with the increasing of conductivity of hydraulic fractures with optimum conductivity.