Experimental and Modeling Investigation on Artificial Fracture Conductivity for Hybrid Fracturing in a Deep Carbonate Reservoir Using an Acid and a Proppant

Acid-fracture conductivity generated by acid-fracturing often decreases rapidly with increasing closure pressure in a deep carbonate reservoir, resulting in a significant decline in productivity. Hybrid acid-proppant fracturing that combines acid-fracturing and proppant-fracturing effectively mitigates this issue. However, there have been limited comprehensive and systematic experimental and modeling investigations on the hybrid fracture conductivity. To bridge this knowledge gap, the acid-fractures were classified by the quantitative characterization of morphology, then hybrid-fracture conductivity was tested, and the prediction model was also developed by advanced curved surface fitting methods. The results show that four categories of acid-etched fracture morphology are identified: uniform, longitudinal groove, transverse groove, and random groove. Higher degrees of nonuniform acid-etching and larger proppant sizes result in greater hybrid-fracture conductivity. The prediction model of hybrid-fracture conductivity, incorporating fracture morphology, rock mechanics, and proppant parameters, shows that closure pressure is the primary factor to reduce the conductivity, and the technology measures to enhance the conductivity of the four types of acid-etched fracture are different. The research provides certain guidance for the design of hybrid fracturing in a deep carbonate reservoir.