热力射流温度场及温度应力数值模拟研究

Numerical Simulation of Temperature Field and Temperature Stress of Hydrothermal Spallation

热力射流破岩技术是指利用高温介质诸如超临界水对岩石进行快速局部加热达到破碎岩石的目的。由于岩石基质热导率很低,因此会在岩石表面形成温度应力。当温度应力超过岩石的强度,会在岩石内部形成微裂缝,且裂缝不断扩展最终使得岩石表面发生热裂解,热裂解作用导致岩石表面从本体脱落从而使得岩石破碎。基于热-固耦合理论建立了热裂解钻井模型,利用Crank-Nicolson差分方法求解得到了热裂解过程中井底岩石温度场和温度应力的分布规律。结果表明,在热裂解钻井过程中,岩石受热部分温度迅速升高,在径向和轴向方向上产生温度梯度;受热部分体积膨胀在径向方向上受到压应力作用,在轴向方向上发生屈曲,受到剪应力作用。研究成果对热裂解钻井的现场应用具有十分重要的指导意义。

Hydrothermal spallation drilling technology uses a high-temperature medium such as supercritical water for rapid heating of the rock locally to break the rock. The rock matrix has a very low thermal conductivity. Consequently, temperature stresses are formed on the rock surface. When the temperature stresses exceed the rock’s strength, micro-cracks are formed inside the rock, and the crack will continue to expand and eventually cause thermal cracking on the rock surface, which causes the rock surface to fall off from the body, leading to breaking of the rock. Based on the thermo-solid coupling theory, a thermal cracking drilling model was established, and the distribution laws of temperature field and temperature stresses of the rock at the well bottom were obtained using the Crank–Nicolson differential method. The results show that, during the thermal cracking drilling process, the temperature of the heated part of the rock increases rapidly, and temperature gradients are generated in the radial and axial directions. The volume expansion of the heated part is subjected to compressive stress in the radial direction,and shear stress in the axial direction under buckling.