页岩气无限导流压裂井压力动态分析

我国页岩气可采资源量巨大,但页岩气藏大多数井的自然产能很低或无自然产能,开发过程中要实施储层压裂改造才具备生产能力。为此,在常规气藏压裂研究的基础上,针对页岩气产出过程中的降压、解析、扩散、渗流等特点,从页岩气渗流机理入手,以点源函数方法为基础,应用菲克拟稳态扩散模型,研究了页岩气在基质和裂缝中的单相流动,建立了页岩气藏无限导流压裂井评价模型,讨论了吸附系数、裂缝储容系数和窜流系数等参数对压力动态的影响,分析了页岩气藏压裂井动态特征及部分参数估计方法,解决了无法确定页岩气藏动态参数的难题,首次绘制了页岩气藏压裂井典型曲线。研究成果可为页岩气藏的合理高效开发提供技术支持。

Transient pressure analysis of infinite conductivity fractured wells for shale gas

Although recoverable resources of shale gas are very abundant in China, very low or even no natural productivity can be obtained for most of the wells in shale gas reservoirs, and productivity will be available only when some stimulation measures are taken during the shale gas development. Therefore, based on a study on the fracturing of conventional gas reservoirs, in view of the characteristics of pressure drawdown, desorption, diffusion, and fluid flow during the output of shale gases, we start from the filtration theory and adopt the Quasi steady state Fick diffusion according to the point source function method, to study the single phase flow of shale gases in the matrix and fractures. Based on the above, we set up an evaluation model on the infinite conductivity fractured well of shale gas reservoirs, to discuss the influences of parameters, such as adsorption coefficient, fracture storage coefficient, and cross flow coefficient on the pressure performance and analyze the dynamic characteristics of the fractured wells in shale gas reservoirs together with some estimation methods of parameters. As a result, the problem of indeterminable dynamic parameters of shale gas reservoirs is thus resolved and typical curves of fractured wells in shale gas reservoirs are drawn for the first time. This study will provide technical support for the high efficiency development of shale gas reservoirs.