致密气藏分段多簇压裂水平井产能计算新方法

水平井分段压裂技术可有效改造致密油气藏,压后产能计算方法是一大研究难点。为更加快速有效地计算水平井压后产能,根据等效渗流理论,采用高渗透带表征复杂多簇缝网,利用平板流公式推导等效渗透率及高渗透带宽度的关系式;基于点汇离散法,应用位势理论和势的叠加原理,考虑裂缝间的相互干扰,建立致密气藏分段压裂水平井非稳态产能计算模型;以川西须5段页岩砂岩交互水平井分段多簇压裂为实例进行压后产能预测,半年后期稳产在2. 5×104m3/d左右。日产量模拟结果表明:高渗透带长度对低渗透致密气藏分段多簇压裂水平井产能影响最大,高渗透带条数次之,而高渗透带渗透率和间距对日产量影响相对较小;以累计产量为目标优选出高渗透带渗透率为40μm2,高渗透带半长为80～100 m,高渗透带条数为4条,间距为50 m。

A new method for calculating the productivity of the staged multi-bunch fractured horizontal well in tight gas reservoirs

Multi-stage fracturing technology in the horizontal well can effectively stimulate tight oil and gas reservoirs, the calculating method of the post-frac productivity is a big study difficulty. For the faster and more efficient calculation of the horizontal-well post-frac productivity, according to the theory of equivalent percolation, with the help of the characterized complex multi-bunch fracture new in the high-permeability band, the relational expression between the equivalent permeability and width of the high-permeability band was derived by using the plate flow formula. Based on point-convergence discrete method, and moreover by means of the geopotential theory and its superposition principle, with the consideration of the interferences among the fractures, an unsteady capacity calculating model was established for the staged-fractured horizontal wells in the tight gas reservoirs. Taking the staged multiple-bunch fracturing of the shale and sandstone horizontal wells in Member Xu-5 in West Sichuan as an example, the post-frac productivity was predicted, the output was stable at about 2.5×10^4m^3/d in the late half year. The simulated results show that the high-permeability belt length has the greatest effect on the productivity of of the staged multi-bunch fractured horizontal well in the low-permeability tight gas reservoir, followed by the number of the high-permeability belt;while the permeability and spacing of the high-permeability belt have relatively little effects on the daily yield. Taking the cumulative production as the target to optimize, the permeability of the high-permeability belt should be 40 μm^2, the half length of the belt should be 80-100 m, the number of the high-permeability belt should be 4 and the their spacing should be 50 m.