有限厚度地层中水平缝滤失计算模型研究

压裂液向地层的滤失速度是压裂设计和压后评估分析时确定裂缝几何尺寸最关键的因素之一.现有的水平缝滤失计算模型是针对均质储层而建立的,不能用于裂缝性储层压裂液的滤失计算.基于裂缝性储层的流体渗滤理论,建立了有限厚度裂缝性地层中通过水平缝的压裂液滤失模型,采用付氏正交变换原理对模型进行求解,获得了便于实际应用的解析解.应用表明,裂缝性油藏水平缝滤失速度随滤失时间而降低,但等效的综合滤失系数却随滤失时间的增加而增加.采用滤失速度与滤失时间的平方根成反比的经典滤失理论计算水平缝中受净压力影响的压裂液滤失速度会带来较大误差.论文模型和计算结果对于水平缝的压裂设计具有一定指导意义.

A new model for calculation fracturing fluid leakoff through horizontal fracture in height-limited formations

Filtration rate of fracturing fluid into formation is one of key factors to determine fracture geometry in the design of fracturing and the evaluation after fracturing.Present computation model of filtration for horizontal fracture,established for homogeneous reservoir,could not be used for filtration calculation of fracturing fluid in naturally-fractured reservoir.Based on fluid percolation theory of fractured reservoir,a new model is set up to modeling fluid filtration through horizontal fractures in naturally-fractured reservoir with limited height.Analytic solution feasible for practical application is acquired by using Fu' orthogonal exchange principle.The result shows fluid filtration rate of horizontal fractures in natural fractured reservoir decreases with filtration time,but equivalent comprehensive filtration coefficient increases with time.Classic filtration theory will cause bigger errors to calculate filtration rate of fracturing fluid influenced by net pressure of horizontal fractures.The model and calculation result both provide certain guidance for the fracturing design of horizontal fractures.