考虑壁面分维数的压裂液返排速度计算模型

基于分形理论，考虑裂缝壁面粗糙度对裂缝缝宽的影响，对原有压裂液返排过程裂缝中速度分布数学模型进行了修正。根据支撑剂的受力模型，建立了支撑剂发生回流的临界流速计算模型。根据使支撑剂发生回流的临界流速以及裂缝中速度分布数学模型，求解出支撑剂发生回流的具体位置。以吉林油田嫩平1井压裂数据为例，计算得出使支撑剂发生回流的压裂液临界返排流速应大于在距井口5 m处截面处的最大速度，由此各该井在压裂液返排过程中，支撑剂不发生回流。

Calculation Model of Backflow Velocity of Fracturing Fluid Considering Fractal Dimension of Fracture Surface

The previous mathematical model of velocity distribution of fracturing fluid in the fracture during backflow has been modified considering the influence of fracture roughness on the effective width of the fracture based on fractal theory. The model of the backflow of prop-pants to calculate the critical velocity was established based on the mechanical model of prop-pants. Based on the critical velocity of the backflow of prop-pants and the mathematical model of the velocity distribution within the fracture，the position where backflow occurs can be determined. According to the data from Nenping No.1 in Jilin Oilfield，we have obtained the critical velocity of the fracturing fluid to precipitate the backflow of prop-ants:greater than that of the fracturing fluid at 5 meters away from the entrance of mine shaft，so the prop-pants do not flow back during the backflow of fracturing fluid.