Assessing the applicability of unsaturated effective stress models to tensile fracturing of sandstone in CO2‐water two‐phase fluids

The description of rock effective stress in CO 2 ‐water two‐phase fluid (CWTPF) is a key issue in the mechanical stability analysis of CO 2 geological sequestration. Related simulation studies often directly used the unsaturated effective stress models without verifying their applicability. In this study, we present a self‐developed hollow‐cylinder tensile tester and a corresponding experimental method to measure the fracturing pressure of sandstone in CWTPF. Based on the apparatus, we conducted tensile fracturing experiments of sandstone in CWTPF. We also carried out fracturing tests of sandstone saturated with water under different effective confining pressure to fit the function of the sandstone's fracturing pressure and effective confining pressure. Then, we selected seven typical unsaturated effective stress models and Finally, we compared the results from the prediction models and experiments to indirectly verify the applicability of these unsaturated effective stress models under CWTPF conditions. The results indicated that the model proposed by Bishop and Donald in 1961 could best describe the effective stress of the tested sandstone in tension fracturing behavior under CWTPF condition. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd