双重介质页岩气藏水平井压力动态特征

Study on the pressure dynamic feature of horizontal wells in dual-porosity shale gas reservoir

研究页岩气水平井开发渗流规律。依据页岩气藏储层地质及开发特征,建立页岩气渗流模型,充分考虑页岩气在基质中的吸附-解吸、Knudsen扩散及渗流作用,采用表观渗透率函数、岩石压缩性吸附影响系数,对常规油气藏渗流方程进行修正,并考虑球型基质向裂缝不稳态扩散窜流,建立无穷大外边界双重介质页岩气藏水平井渗流模型,绘制页岩气藏水平井渗流压力曲线图版,分析储层、渗流及水平井等敏感参数对水平井压力变化特征影响。结果表明在页岩气藏渗流中后期阶段,表观渗透率函数、岩石压缩性吸附影响系数对水平井压力特征影响较大。扩散-渗流、吸附-解吸特征是准确描述页岩气渗流规律的重要因素。

Based on the reservoir geology and development characteristics of shale gas reservoir, a shale gas seepage model was established to study the shale gas seepage law in horizontal well development. On the basis of desorption, diffusion and flow of shale gas in the matrix, the apparent permeability function and adsorption coefficient are used to correct the flow equation of conventional oil and gas reservoir. In consideration of the unsteady flow from spherical matrix to cracks, the unsteady seepage model of horizontal well in shale gas reservoir with dual medium under the condition of infinite boundary is established, and the pressure graph plate of horizontal well for the shale gas reservoir is presented and used to analyze the influence of sensitive parameters, such as reservoir, seepage and horizontal well, on the characteristics of pressure change of horizontal well.It shows that the apparent permeability function and adsorption coefficient have a great influence on pressure characteristics of horizontal well in the middle and late seepage stages of shale gas reservoirs. Therefore, gas diffusion-seepage and adsorption-desorption are important factors in accurately describing the seepage laws of shale gas. Through the systematic study, the seepage model of shale gas reservoir is improved, which provides a reliable basis for the efficient development of horizontal wells in shale gas reservoir.