Reducing breakdown pressure of tight reservoirs via in-situ pulses: Impact of mineralogy

Industrial growth increases the demand for natural gas worldwide, which is considered as one of the cleanest types of fossil fuels and most reliable energy source (BP, 2013). Unconventional gas represent a giant resource of natural gas, however, requires massive fracturing. One of the challenging problem that operators face is the high breakdown pressure for deep and tight reservoirs. Several lost potentials are recorded worldwide due to high breakdown pressure that exceeds pumping limitations or completion rating. Several attempts were tried to reduce the breakdown pressure by cyclic fracturing, low viscosity fracturing fluid, perforations and high pressurization rate. However, even with the existing techniques, still high breakdown pressure present a persistent challenge. Increasing the injection rate of the fluid into the rock corresponded to a lowering of the breakdown pressure. The higher injection rate allows more fluid to enter the shale porosity thus transmitting the injection pressure to more points within the shale formation, which reduces the breakdown pressure. The developed methodology reduces breakdown pressure and enables fracking high stress rocks by increasing the injectivity prior to fracturing. Thermochemical will be injected to create microfractures, improve permeability, and reduce young's modulus of tight reservoirs prior to fracking. By creating microfractures and improving injectivity, the required breakdown pressure will be reduced, and fracturing will be enabled. Moreover, experimental results showed that thermochemical treatment reduces young's modulus of the rock, thus reducing rock stiffness.