Laboratory Demonstration of Geothermal Rock Cooling to Reduce Breakdown Pressure in Hydraulic Fracturing

Abstract Hot dry rocks of Geothermal reservoirs are characterized by very low permeability and high temperature. These rocks are required to be fractured in order to circulate the fluids to extract the heat energy. The fracturing process in such formation faces many challenges due to extreme heat and very high breakdown pressure. This study explores an innovative approach of using endothermic fluids to reduce breakdown pressure by providing a thermal shock to the heated geothermal rock. The thermal shock develops microcracks in the rock formation which leads to the reduction in strength and breakdown pressure. The methodology involves treating the granite rock samples with endothermic chemical reactions between ammonium chloride (NH4Cl) and sodium hydroxide (NaOH) to generate a thermal shock. The results shows that the endothermic chemicals significantly reduces both strength and breakdown pressure of the granite rocks. The strength of the core sample was found to be reduced from 43465 psi to 37190 psi which is almost 14.4% reduction. The breakdown pressure of the granite rock reduces from 3179 psi to 2740 psi which is nearly 13.8% reduction. The novel method not only reduces the breakdown pressure but also improves the overall efficiency of the fracturing operation by reducing the horsepower requirement and fluid pumping cost.