水平井体积压裂簇间距优化方法

Optimization of cluster spacing in horizontal well volume fracturing

簇间距是水平井分段多簇压裂设计过程中的一个重要参数。为了进一步提高致密储层水力压裂增产效果,沟通水力裂缝和天然裂缝形成复杂缝网,采用有限元数值模拟方法研究水平井缝网压裂的簇间距优化问题。通过建立均质各向同性储层内三维水力裂缝的诱导应力差模型,从降低应力影效应的不利影响和利用应力影效应的有利影响两个方面分别建立了最小簇间距优化模型和最大改造体积簇间距优化模型,结合裂缝转向机理确定最优簇间距优化原则。研究结果表明:(1)裂缝偏转角度越小,最小簇间距增大;(2)储层改造体积随着簇间距的增加先增大后减小,改造体积最大值所对应的簇间距即为最优簇间距;(3)同一裂缝流体压力条件下,主应力转向角度变化对最大改造体积簇间距的影响小。综合最小簇间距模型和最大改造体积簇间距模型,可以得出最优簇间距,该方法为低渗透储层缝网压裂时的裂缝优化设计提供了参考。

Cluster spacing is an important parameter in the design of horizontal well staged multi-cluster fracturing. In order to further improve the performance of hydraulic fracturing in highly tight reservoirs by communicating the hydraulically-induced fractures and natural fractures, the finite element numerical simulation was used to determine the optimization of cluster spacing in horizontal well frac network fracturing. Based on the induced stress difference model of three-dimensional hydraulically-induced fractures in homogeneous isotropic reservoirs, the minimum cluster spacing optimization model and the maximum SRV cluster optimization model were established respectively with consideration to reducing the adverse effect of the stress shadow and using the beneficial effect of the stress shadow. Then, combined with fracture diverting mechanism, the cluster spacing optimization principles were determined. The results show that the smaller the fracture deflection angle is, the higher the minimum cluster spacing is. The stimulated reservoir volume （SRV） increases and then decreases as the cluster spacing increases, and the cluster spacing to which the maximum SRV corresponds is the optimal cluster spacing. Moreover, the principal stress diverting angle has small impact on the maximum SRV cluster spacing under the same fracture fluid pressure. By combining the minimum cluster spacing model and the maximum SRV cluster spacing model, the optimal cluster spacing can be obtained. This method provides a reference for the fracture optimization design of the frac network fracturing in low permeability reservoirs.