考虑应力阻隔和干扰效应的分段多簇压裂诱导应力计算模型

Calculation Model for Induced Stress Considering the Effect of Stress Resistance and Stress Interference in Staged Multi-cluster Fracturing

针对水平井分段多簇压裂过程中段内多条裂缝同步扩展的形成特点,考虑裂缝间存在的应力阻隔效应和应力干扰效应,分析了段内各条裂缝诱导应力的影响范围以及其相对于不同位置处的有效净压力,建立了水平井分段多簇压裂段内不同位置处诱导应力计算模型.通过研究得出如下认识:第N段压裂之前段内各点受到的诱导应力为之前各段最后一条裂缝产生的诱导应力的叠加,第N段压裂过程中段内各点受到的诱导应力是与其相邻的裂缝产生的;最小水平地应力方向的诱导应力抵消了一部分缝内净压力,应根据应力阻隔和应力干扰效应以及之前各段压裂诱导应力的分布计算每条裂缝相对于左右两侧地层的有效净压力以及诱导应力.考虑多条裂缝同步扩展时的应力阻隔和应力干扰效应以及有效净压力变化的分段多簇压裂诱导应力计算模型更为符合实际的工况情况,具有较高的精度,能够为水平井分段多簇压裂优化设计提供更为准确的理论指导.

A induced stress calculation model of different positions in staged multi-cluster fractures in horizontal wells was established by analyzed the size of induced stress of fractures and the corresponding effective net pressure in different positions, in view of the formation characteristics of multi-fracture extend synchronously in the process of staged multi-cluster fracturing in horizontal wells and the stress resistance and stress interference between fractures. The results show that： the induced stress of the last fracture in every fracturing stage which is fractured before, will add up to the next fracturing stage. The induced stress in every fracturing stage is generated with its adjacent fracture. The induced stress in the direction of minimum horizontal stress can offset a small part of fracture net pressure, the effective net pressure and induced stress created by previous fracturing in the position of every fracture which is relative to each sides of the formation should be calculated according to the stress resistance and stress interference in staged multi-cluster fracturing, and the distribution of every induced stress in fracturing stages. This induced stress calculation model with high precision can conform to the actual situation more closely, and provide more theoretical guidance during the optimization means and methods of staged multi-cluster fracturing in horizontal wells.