油气层爆燃压裂裂缝动态延伸模型

Fracture dynamic extending model for oil formation exploding fracturing

基于油气层爆燃压裂造缝加载模型,建立地层破裂和止裂压力、爆燃气体渗滤、裂缝延伸长度和宽度以及爆燃气体的质量守恒与能量守恒计算模型,并耦合求解,分析爆燃压裂过程中井筒压力、裂缝几何形态变化。结果表明:火药爆燃后,井筒中的压力、温度迅速上升,达到地层破裂压力时起裂,裂缝开始延伸;在火药爆燃、气体渗滤作用下,爆燃气体的压力先增加后减小,最后降至地层初始压力;在爆燃加载条件相同的情况下,随裂缝条数的增加峰值压力和裂缝长度均减小;裂缝延伸过程中裂缝宽度先增大后减小,裂缝条数越少,裂缝宽度最大值和最终值越大。

Based on fracture initial loading model of reservoir exploding fracturing,the models including calculation model of starting-crack pressure and stopping-crack pressure,model of exploding gas infiltration,model of fractures extending length and width,and model of exploding gas mass and energy conservation were established.And the models were coupled and solved.The variation of wellbore pressure and fracture geometry were analyzed.The results show that the wellbore pressure and temperature rapidly increase after explosive exploding,and the wellbore pressure causes fracture initiation as well as fracture extension when the pressure reaches formation breakdown pressure.The pressure of exploding gas firstly increases and then decreases to formation pressure under the effect of explosive exploding and gas infiltration.Both of the peak pressure and fracture length decrease with the fracture number increasing,and the fracture width firstly increases and then decreases during the fracture extending.The fewer the fracture number,the bigger the fracture maximum width as well as final width under the same explode loading condition.