Application of CO2 fracturing technology for terrestrial shale gas reservoirs

Abstract

China boasts of abundant terrestrial shale gas resources. Compared with marine shale, terrestrial shale has smaller thickness, lower content of brittle minerals, higher content of clay minerals, and lower pressure. Hence, the development technology for marine shale gas, especially the fracturing technology, is not entirely applicable to terrestrial shale. To this end, aimed at the reservoir characteristics and fracturing difficulties, the features of liquid CO2 foam and CO2 energized fracturing technology were analyzed, and their application tests were carried out in the gas shale in the Chang-7 Member of Mesozoic Yangchang Fm in the Ordos Basin. The application results showed that pure liquid CO2 at a discharge rate of 2.0 m3/min was capable of fracturing shale gas reservoirs in Chang-7 Member with a rapid liquid unloading, and ignition could be conducted after 24 h. Meanwhile, CO2 energized fracturing greatly improved the fracturing fluid flowback speed and rate to shorten the liquid unloading period, which all benefited the terrestrial shale gas exploration and development. Moreover, based on the analysis of the state-of-the-art of fracturing technologies and facilities in China, the application prospect and development idea were presented of the CO2 fracturing technology applied in terrestrial shale gas development.