气井压裂后稳态产能模型

针对均质等厚气藏中的一口压裂气井，文章从广义达西定律出发，并考虑近井地带的非达西渗流、压裂裂缝壁面污染以及支撑裂缝限制性入口对渗流的影响。依据气井压裂后的渗流规律，假定气井压裂后，气体渗流流量可以近似看作是两部分的叠加：一是远裂缝区域气体的流动为径向流，裂缝左右两端的径向流合为一个完整的径向流，气体径向流入缝端；二是支撑裂缝壁面区域气体的流动为线性流，气体沿垂直裂缝壁面方向线性流入裂缝。两部分气体最终汇流在裂缝内，而裂缝内气体的流动为线性流，流量逐渐增加。根据此原理，文章推导出稳态情况下和拟稳态情况下的压裂气井产能模型，由此求得无阻流量。为了现场应用的方便，考虑压裂后气井渗流能力的变化，一点法α值与裂缝的无因次导流能力有关，故利用榆林气田多口压裂气井测试资料，拟合了变系数的压裂气井一点法无阻流量公式，可用于预测该气田的各气井压裂后的无阻流量，其它气藏也可以借鉴推广。

STEADY-STATE MODEL OF GAS WELLS AFTER FRACTURING

Aiming at a fractured gas well in homogenous gas reservoir with constant thickness, according to the generalized Darcy law, the influence of the non Darcy percolation in the zones near the borehole, the wall pollution of the fractured fractures and the limited entries of the propped fractures on the percolation are considered. Based on the percolation law of gas wells after fracturing, it is assumed the gas flowing rate can be approximately regarded as the stack of 2 parts: One is the radial flow that happens in the zones far away from the fractured fractures, i.e. the radial flow from the left and right edges of the fractures forms an integrate radial flow and enters the ends of the fractures; The other is linear flow that happens within the propped fractures, i.e. the gas flows into the fractures along the direction vertical to the fracture walls. The gas from the 2 parts confluxes in the fractures finally. The gas flowing within the fractures is linear and the flowing rate increases gradually. Based on the principle, the productivity model of fractured gas wells is developed under the conditions of steady state and pseudo steady state, and the open flow capacity can be derived. For easily applying in the fields, considering the variation of percolation capacity of gas wells after fracturing and the coefficient “α” of the single point method are relative with the non dimensional conductivity of the fractures, with the testing data of several fractured gas wells in Yulin area, the formula of open flow capacity with the single point method is obtained for the fractured gas wells with various coefficient, which can predict the open flow capacity of each gas well after fracturing in the gas field. The method provides the reference for the other gas reservoirs.