Experimental Investigation on Failure Mechanism of Hot Dry Rock under Microwave Irradiation

Hot dry rock (HDR) geothermal energy is clean energy that can meet people's demand for low carbon. The traditional hydraulic fracturing method is challenging to break HDR dominated by granite, mainly because of HDR's high temperature and hard characteristics. Microwave irradiation is considered a proven approach to breaking granite. This study investigates the failure mechanism of HDR at 500 degrees C-800 degrees C under microwave irradiation. The experiments cover preheating, uniaxial compression, granulometric analysis, binocular vision monitoring (BVM) technique, and X-ray powder diffraction. The result shows that the uniaxial compression strength of granite decreases the most at 500 degrees C-600 degrees C, which is 62.77% on average. The failure form is from the brittle failure (untreated) to ductile failure (800 degrees C) with the rise of the microwave irradiation temperature. The microwave makes a particle size in the range of 0.6-2.36 mm the most apparent particle size of granite after uniaxial compression. The BVM technique reconstructs the surface deformation with a 0.7% error. Microwaves cause heat accumulation near the rock near the magnetron, resulting in the formation of crack networks and a molten cavity. The possibility of microwave-assisted fracturing of HDR is discussed at the end of the article.

Automated summary

This study investigates the failure mechanism of high temperature hot dry rock (HDR) under microwave irradiation. The experiments show that the uniaxial compression strength of granite decreases the most at 500℃-600℃, with an average reduction of 62.77%. The failure form changes from brittle failure (untreated) to ductile failure (800℃) with the increase of microwave irradiation temperature. Microwaves cause heat accumulation near the magnetron, resulting in the formation of crack networks and a molten cavity.