Experimental Study of Pumping Rate Effect on Hydraulic Fracturing of Cement Paste and Mortar

Excerpt

Hydraulic fracturing has been widely used not only in hydrocarbon extraction but also to enhance the utilization of geothermal energy by creating or extending fracture networks in reservoirs. Fracture generation and propagation are mainly controlled through the pumping rate and viscosity of the injection fluid; fracture behavior also depends on lithology and in situ pressure. To investigate the evolution of the breakdown pressure and the fracture initiation pressure in the toughness-dominated regime, a comprehensive range of pumping rates is applied here to artificially made cement paste and mortar specimens whose microstructures differ by the presence or absence of aggregate. Optical inspection of fractured specimens by endoscopic and three-dimensional X-ray computed tomographic imaging reveals the morphological features of the fractures. …