地应力对爆炸压裂影响规律的数值模拟研究

Numerical Simulation for the Effect of Ground Stress on Explosive Fracturing

  • 摘要: 为了揭示地应力场对井内爆炸压裂作用下裂缝形成及分布的影响规律,进行了井内爆炸压裂室内模拟试验。基于弹塑性损伤理论建立了井内爆炸压裂数值计算模型,在借助试验结果验证模型准确性的基础上,研究探讨了地应力场对爆炸压裂作用下裂缝扩展规律的影响。研究结果表明:试验条件下,炮眼内炸药爆炸后并未对炮眼造成粉碎性破坏,且裂缝沿曲线扩展;爆炸压裂作用下井壁围岩中将产生长而宽的主裂缝和短而细的次裂缝;主裂缝扩展方向受地应力场控制,垂直于最小水平地应力方向;不同地应力场条件下,裂缝扩展范围及密度亦随之发生改变。 研究表明,准确掌握地应力大小及方位,有利于控制主裂缝的扩展及分布形态。

     

    Abstract: In order to reveal the influence of ground stress on the fracture and propagation during explosive fracturing,the lab experiment of explosive fracturing was carried out,and the fracturing numerical model established based on elastic-plastic-damage theory.By means of the testing result and its accuracy verification of the numerical model,the influence of ground stress on fracture and distribution in explosive fracturing was studied.The study results show that the explosive did not crush the surrounding rock of the borehole,and cracks created and extended in curved forms;the primary long and wide cracks and secondary short and narrow cracks are formed by explosive fracturing in surrounding rocks of borehole,the propagation of primary cracks,which are perpendicular to the minimum horizontal in-situ stress direction,is controlled by ground stress;the length and quantity of cracks also vary with different ground stress.Consequently,learning about the magnitude and direction of the ground stress is helpful for the control of propagation and distribution of the primary cracks in explosive fracturing.

     

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