Experimental study on hydraulic fracture propagation in tight volcanic reservoirs

ABSTRACT: The volcanic basalt and breccia reservoirs in Sichuan, China are dense and highly heterogeneous. Lithology and in-situ stress characteristics have important effects on hydraulic fracture propagation. In this study, basalt and breccia outcrops were made into 300mm × 300mm × 300mm samples to conduct true triaxial hydraulic fracturing physical experiments. The law of hydraulic fracture propagation in tight volcanic reservoirs under different lithologies and stress conditions was studied. The results show: 1. the volcanic rock is high in strength, and brittle fractures mainly happen during fracturing. The pressure drop curve is mostly a unimodal curve; 2. Fracture morphology is related to lithology and in-situ stress distribution. Natural fractures and veins have a certain induction effect on the direction of fracture propagation. The smaller the in-situ stress difference, the more natural fractures develop, the fracture turning phenomenon is the more obvious; 3. the rupture pressure of basalt increases with the increase of the horizontal ground stress difference, and the rupture pressure of the breccia decreases with the increase of the horizontal ground stress difference. Through this study, the morphological characteristics of hydraulic fracturing fractures in different strata were obtained, the characteristics of hydraulic fracturing in volcanic rock formations in Sichuan were mastered, and the fracture propagation law of igneous rock formations was revealed. The results provide a reference for volcanic rock fracturing parameters optimization.