Cryogenic liquid nitrogen fracturing is expected to provide an effective stimulation method for hot dry rock reservoirs to increase heat production. This paper establishes a three-dimensional model to calculate the distributions of temperature and stress of the reservoir rock when liquid nitrogen is injected into the wellbore. The sensitivity of different parameters and water fracturing to the stress state is studied. The results indicate that when liquid nitrogen is injected into the bottom of well, a huge heat exchange occurs on the rock surface, which generates great thermal stress on the fluid-solid interface, and the value of thermal stress exceeds the tensile strength of rock. For the effect of parameters, the primitive temperature of the rock has a significant impact on the value of maximum principal stress. The pressure drop and ambient pressure affect the thermal stress slightly. At the same time, a series of experiments are conducted to validate the effect of thermal stress induced by liquid nitrogen injection on the rock fracture. As the temperature rises, the shale samples are broken more severely at the action of thermal stress. Thus, the study of liquid nitrogen fracturing provides a scientific and effective method for geothermal exploitation.

中文翻译：

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干热岩油藏低温液氮注入过程中井筒周围温度和应力分布的数值研究

低温液氮压裂有望为干热岩储层增加产热提供有效的增产方法。本文建立了一个三维模型来计算液氮注入井筒时储层岩石的温度和应力分布。研究了不同参数和水压裂对应力状态的敏感性。结果表明，液氮注入井底时，岩石表面发生了巨大的热交换，在流固界面产生了很大的热应力，热应力值超过了岩石的抗拉强度。对于参数的影响，岩石的原始温度对最大主应力值有显着影响。压降和环境压力对热应力的影响很小。同时，开展了一系列实验，验证了液氮注入引起的热应力对岩石裂缝的影响。随着温度的升高，页岩样品在热应力的作用下破碎更严重。因此，液氮压裂的研究为地热开发提供了一种科学有效的方法。