基于霍克-布朗强度准则的水力压裂离散元数值模拟研究

Discrete element numerical simulation of hydraulic fracturing based on Hoek-Brown strength criterion

基于霍克-布朗强度准则提出了一种修正的破裂压力公式,并用颗粒流离散元(particle flow code,PFC)软件建立水力压裂模型进行了验证。对不同地应力状态下的岩石水力压裂过程进行了数值模拟,通过将模拟计算得到的破裂压力结果与所提出的修正破裂压力公式的解进行对比,发现2者在不同地应力状态下都比较吻合,验证了修正的破裂压力公式的可靠性。同时,研究了不同地应力状态对水力裂纹的扩展、数目、宽度、直径等的影响。研究结果对水力压裂增产技术在非常规油气的开采应用中有积极的指导作用。

A modified breakdown pressure formula is proposed based on Hoek-Brown strength criterion,and the formula is verified by a hydraulic fracturing model established by particle discrete element software PFC(particle-flow code).The hydraulic fracturing process of rocks under different in-situ stress states is numerically simulated.By comparing the breakdown pressure results obtained from the simulation calculation and the modified breakdown pressure formula proposed in this paper,it is found that the solutions are consistent under different in-situ stress states,and the reliability of the modified breakdown pressure formula is verified.In addition,the effects of different in-situ stress states on the propagation,number,width,and diameter of hydraulic cracks are studied.The research results have a positive guiding role for the application of hydraulic fracturing stimulation technology in the exploitation and application of unconventional oil and gas.