Quantifying the Reduction in Breakdown Pressure based on Fluid Saturation

Hydraulic fracturing is an integral part of geomechanics and is employed to improve the productivity from unconventional reservoirs. It is performed by injecting fracturing fluid at high pressures to induce fractures in the formation. Reservoir conditions and petrophysical properties differ from formation to formation further requiring to optimize the design of the fracturing process. This paper aims to address one such issue by quantifying the reduction in breakdown pressure because of saturation condition of the reservoir. An experimental study is performed on tight sandstone rocks by using a robust setup. Fracturing fluid is injected into tight sandstone samples by means of a central hole until fracture is induced. Samples were saturated by brine and reservoir oil. Based on the experimental results, Significant reduction in the breakdown pressure of brine saturated samples was seen and moderate reduction in the oil saturated samples as compared with dry cores. This was confirmed by comparing with UCS and Brazilian tensile tests.