Experimental Study of Fracture Propagation in Deep Tight Sandstone Reservoirs Under Different Stress States and Formation Characteristics

Studying the propagation behavior of hydraulic fracturing fractures is of great significance for understanding the mechanism of fracture propagation in deep unconventional reservoirs. The goal of unconventional oil and gas reservoir fracturing transformation is to form a complex fracture network system and increase the effective transformation volume of the reservoir. This article conducts physical model experiments on fracturing under different reservoir stress conditions to determine whether complex pressure fractures can be formed. The main controlling factors for the formation of complex pressure fractures are analyzed, and the influence of each factor is quantitatively studied through numerical simulation. The results indicate that the difference in geostress has a significant impact on the formation of pressure cracks. As the difference in geostress increases, the lateral extension range of pressure cracks significantly decreases, resulting in a phenomenon parallel to the direction of maximum horizontal geostress. As the injection volume decreases, the phenomenon of early fracturing bifurcation propagation gradually decreases, with a small number of bifurcations appearing. In the subsequent fracturing process, the main trend of fracture extension is more pronounced in reservoirs with lower fluid injection rates. In addition, low-viscosity fracturing fluids seem to be more prone to forming fracture zones with more developed branching fractures. This study can provide technical support and reference for fracturing construction in deep tight oil reservoirs.