Objective The application prospects of supercritical CO2 fracturing technology are broad,currently.It is necessary to ascertain crack initiation pressure and the law of fracture extension in supercrtical CO2 fracturing in order to guide on-site application better.Methods Based on this,considering the influence of temperature changes during the fracturing process on the physical properties of CO2 and the thermal stress effect in rocks,a thermal fluid solid coupling supercritical CO2 fracturing model is established.The effects of horizontal stress differences,natural crack approach angle and CO2 injection temperature on fracture initiation are explored.Results The on-site test was carried out in Well Y of Yangchungou.The results show that supercritical CO2 fracturing can significantly reduce the fracture initiation pressure compared with hydraulic fracturing;Even under high levels of stress difference,complex crack morphology can still be obtained.The approach angle of natural fractures increases,the initiation pressure increases,and the complexity of fractures increases accordingly.The larger the difference between the CO2 injection temperature and the formation temperature,the more obvious the thermal stress induction effect and the more complex the fracture morphology.Conclusions On-site applications have shown that injecting pad injection supercritical CO2 can effectively reduce the fracturing pressure,which is beneficial for improving the net pressure inside the fracture in subsequent hydraulic fracturing and improve the effect of reservoir transformation.
关键词
超临界CO2压裂/热流固多场耦合/热应力/相场模型/阳春沟区块
Key words
supercritical CO2 fracturing/thermal fluid solid multi-field coupling/thermal stress/phase field model/Yangchungou block
万方数据