Hydraulic fracturing is widely used to stimulate unconventional
reservoirs, but a systematic and comprehensive investigation into the
hydraulic fracturing process is rare. In this work, a discrete
element-lattice Boltzmann method is implemented to simulate the
hydro-mechanical behavior in a hydraulic fracturing process. Different
influential factors, including injection rates, fluid viscosity, in-situ
stress states, heterogeneity of rock strengths, and formation
permeability, are considered and their impacts on the initiation and
propagation of hydraulic fractures are evaluated. All factors have a
significant impact on fracture initiation pressure. A higher injection
rate, higher viscosity, and larger in-situ stress increase the
initiation pressure, while a higher formation permeability and higher
heterogeneity decrease the initiation pressure. Injection rates and
heterogeneity degrees have significant impacts on the complexity of
generated fractures. Fluid viscosity, in-situ stress states, and
formation permeability do not change the geometrical complexity
significantly. Hydraulic fractures are usually tensile fractures, but
many tensile fractures also have shear displacement. Shear fractures are
possible and the shear displacement can be significant under certain
conditions, such as a high injection rate, and a high heterogeneity
degree.