含微裂缝页岩储层渗流模型及压裂井产能
Seepage model and productivity prediction of fractured wells in shale gas reservoirs with discontinuous micro-fractures
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摘要: 根据页岩气储层纳微米孔隙和微裂缝结构特征,建立含微裂缝表面层基质-裂缝双重介质球形模型.综合考虑扩散和滑移对页岩气产能的影响,利用Langmuir等温吸附方程描述页岩气的解吸吸附,通过Laplace变换和Stehfest数值反演,得到页岩气藏压裂井定产和定压条件下的井底流压和产量的解析解,并进行页岩气藏压裂井产能预测及影响因素分析.结果表明:微裂缝是页岩气基质微观孔隙和宏观裂缝运移的主要渗流通道;微裂缝的渗透率越大和长度越长,页岩气井产量越大.Abstract: A dual-porosity medium with micro-fractured spherical matrix blocks was achieved on the basis of the structure characteristics of nano-micro pores and micro-fractures in shale gas reservoirs. The Laplace space solution of the dimensionless bottom hole pressure of fractured well production was obtained in consideration of the seepage,diffusion and desorption mechanism of shale gas and applying the Laplace transform and the Stehfest numerical inversion. Type curves of dimensionless production were plotted and the influencing factors of the type curves were identified. The results show that the matrix surface improves gas transfer from the matrix medium to the fracture network due to matrix micro fractures. Increasing the permeability and length of micro fractures accelerate the productivity significantly.