Laboratory test study on supercritical carbon dioxide fracturing granite: a quantitative review

Supercritical carbon dioxide (ScCO2) fracturing to transform geothermal reservoirs is a new technology in geothermal development, with great prospects. In this paper, the current laboratory test methods and test results of ScCO2 fracturing granite are reviewed, and the breakdown pressure and fracture parameters are discussed, and the existing problems and suggestions are given. The results show that the breakdown pressure of ScCO2 is 19.26-26.99% lower than that of water. The breakdown pressure is positively correlated with confining pressure and injection flow rate, and negatively correlated with temperature. ScCO2 tends to form shear fractures, induce more fracture branches and more complex fracture morphology than other fracturing fluids. Compared with water, the density of fracture branches increased by 17.82-60.54%, and the complexity of fracture morphology increased by about 4%. Existing studies have shown that ScCO2 has the advantages of low breakdown pressure, good fracture formation effect, no pollution and water resource saving. It is suggested that further research should be carried out regarding fracturing fluid properties, laboratory tests, theoretical derivation and engineering application in the future, to accelerate the application process of ScCO2 in deep geothermal development.

Automated summary

Supercritical carbon dioxide (ScCO2) fracturing is a promising technology for transforming geothermal reservoirs. This paper reviews the current laboratory test methods and results of ScCO2 fracturing granite, discusses the breakdown pressure and fracture parameters, and provides suggestions for improvement. The results show that the breakdown pressure of ScCO2 is lower than water and is influenced by confining pressure, flow rate, and temperature. ScCO2 tends to form shear fractures and has a higher density of fracture branches and more complex fracture morphology compared to other fracturing fluids. Further research on fluid properties, laboratory testing, theoretical derivation, and engineering application is recommended to accelerate the use of ScCO2 in deep geothermal development.