Pumping Rate-Dependent Temperature Difference Effect on Hydraulic Fracturing of the Breakdown Pressure in Hot Dry Rock Geothermal Formations

Abstract

Abstract The development of hot dry rock geothermal formations requires hydraulic fracturing to create a thermal extraction area between injection and production wells. A high breakdown pressure increases the operation cost during hydraulic fracturing and possibly causes a large risk of induced seismic activity under certain conditions. This paper conducted laboratory hydraulic fracturing experiments under true triaxial stress and reservoir temperature conditions to investigate the temperature difference effect on the breakdown pressure. An analytical model that considered the temperature difference effect was developed to estimate the breakdown pressure. In hot dry rock geothermal formations, the temperature difference between the injection fluid and the reservoir rock can induce thermal shock which can break rocks; thus, the breakdown pressure can be decreased. In addition, thermal shock is influenced by the pumping rate. This influence is also considered in the analytical model.