基于多场耦合效应的水平井压裂应力场分析

Analysis of Stress Field of Horizontal Well Fracturing Based on Multi-Field Coupling Effect

为了有效分析水平井压裂过程中的应力场分布情况,考虑应力-渗流-温度多物理场因素的耦合作用,利用有限元数值模拟手段,开展了对水平井压裂裂缝近井应力场的模拟分析。首先通过岩石物理力学参数测定试验,得到了有限元分析的基本数据;之后引入应力-渗流-温度耦合理论,建立了水平井扰动应力场的有限元分析模型,模拟计算得到研究区的压力、温度和应力分布情况;最后,综合多场耦合效应得到近水平井筒裂缝周围的应力场变化规律,确定裂缝在平行井筒方向对其周围应力场的扰动范围主要集中在1倍的裂缝长度以内,裂缝产生的诱导应力降低了原井筒附近的压应力大小。将数值解结果与已有扰动应力数学模型计算的相应解析解进行对比,验证了有限元模型求解的合理性,为水平井压裂应力场的分析研究提供了一定的基础和参考。

In order to analyze the distribution of stress field in the process of horizontal wells fracturing effectively, the multi-field coupling effect was considered and the finite element numerical simulation analysis was applied. Firstly, through the determination test of rock physical and mechanical parameters, the basic data were obtained. Then introducing the theory of stress - seepage - temperature coupling, the finite element analysis model of the disturbance stress field in horizontal well fracturing was established. The results of pressure, temperature and stress distribution in the study area were simulated and calculated. Finally, combined with the multi-field coupling effect, the change law of the stress field around the fractures was achieved. It was found that in the parallel wellbore direction the stress disturbance range of one fracture was mainly concentrated within 1 time of its length and its induced stress made the original compressive stress around the wellbore reduced. Comparing the numerical solution results with the corresponding analytic solutions of the existing disturbed stress mathematic model, the rationality of the finite element model was verified. It can provide a certain basis and reference to study the stress field in horizontal wells frac- turing.