注CO2条件下花岗岩破裂特征的试验研究

CO2增强型采热系统（CO2-EGS）工程中CO2作用下岩石的水压破裂行为是目前亟需解决的一个关键科学问题。从福建漳州采取花岗岩露头，利用自主研制的厚壁圆筒式致裂仪进行了不同流体（CO2、水）的水压致裂试验，研究了CO2、水入渗致裂后花岗岩的破裂特征及破裂机制。研究表明：随着致裂液黏度的减小，试样破裂过程会形成更多且更曲折的微裂纹分支，这意味着，采用CO2压裂可能更有利于形成缝网，从而有助于提高增强型采热（EGS）工程中换热效率；试样的破裂压力随着致裂液黏度的减小而降低，而较低的破裂压有助于注入井的安全运行；试验结果可用从对流换热角度分析的流体岩石相互作用机制解释，进而验证了其准确性。

Experimental study of the fracture characteristics of granite under CO_2 injection condition

The hydraulic fracturing (HF) behavior under CO2 condition is a key scientific issue in CO2-enhanced geothermal system project. The granite specimen was taken from the quarry in Zhangzhou, Fujian province. HF experiments were conducted to investigate the effects of CO2 and H2O on the HF process and crack propagation by using a new independently developed hollow cylinder. This study reveals that with the decrease of the viscosity of the fracturing fluid, a greater number and more sinuous microcrack branches form in the fracture process. This indicates that CO2 fracturing may be more conducive to the formation of the crack network, which helps to increase the heat exchange efficiency in the CO2-EGS projects. The fracture pressure of the specimen decreases with decreasing the viscosity of the fracturing fluid, which leads to the safe operation of the injection well with a lower value. The experimental results consist with the interaction mechanism of fluid rock from the convective heat transfer perspective, and its accuracy is verified.