Experimental Investigation on the Characteristics of Complex Fractures Created by Supercritical Carbon Dioxide in a Layered Tight Sandstone Formation Available to Purchase

Carbon dioxide (CO₂) fracturing has the advantage of creating complex hydraulic fractures (HFs). However, the characteristics of HFs induced by supercritical CO₂ (Sc-CO₂) in tight sandstones remain unclear. In this study, laboratory true triaxial fracturing experiments were conducted on the layered Chang-7 tight sandstones and the influences of multiple factors were studied. Experimental results showed that the complexity of HFs created by Sc-CO₂ fracturing could be significantly enhanced compared with that of slickwater fracturing, but only improved to a limited extent compared with that of liquid CO₂ fracturing. Sc-CO₂ fracturing tends to induce complex HF network in the case of small horizontal differential stress (less than 5 MPa). However, it is still possible for Sc-CO₂ fracturing to generate complex HF network even under a high horizontal stress difference (over 8 MPa). A large pumping rate is conducive to generating HF branches because of the high diffusivity of Sc-CO₂. Compared with open-hole completion, perforation completion can induce more HFs in the vicinity of the wellbore and also reduce the breakdown pressure. The obtained results may provide laboratory evidence for CO₂ fracturing treatment design in tight sandstone formations.