Abstract: In response to the problem of high longitudinal non-homogeneity and unclear mechanism of hydraulic fracture initiation and propagation in grain-type shale oil reservoirs, the combination of discrete element fracture simulation and hydraulic fracturing physical modeling experiments was used to study the influence of factors such as vertical geostress difference, viscosity of fracturing fluid, pumping process, and perforation cluster spacing on the fracture propagation pattern of grain-type terrestrial shale oil reservoirs. The results show that: The de-viscosity and slip of weak structural surfaces between layers is an important reason for the stagnation of longitudinal propagation of fracture height in grain-type shale oil reservoirs, and the smaller the vertical principal stress difference is, the easier the laminar surfaces are activated, and the growth of fracture height is suppressed; the use of alternating pumping of high-viscosity and low-viscosity fracturing fluids is conducive to the realization of balanced longitudinal and transversal propagation of hydraulic fractures, and the realization of 3D development of reservoirs; the reduction of the perforation cluster spacing and the increase in the number of perforation clusters can significantly increase the area of hydraulic fractures and the reservoir drainage area. The study results are of great significance for realizing the deep penetration stimulation of grain-type shale oil reservoirs in the longitudinal direction and increasing the production of a single well.

Key words: grain-type shale oil reservoir, hydraulic fracture, fracture propagation, intensive cutting, pumping pressure curve, discrete lattice algorithm