Analysis and test on stress-strain of cement sheath in shale gas wells with hydraulic fracturing

The sealing failure of cement sheath which caused annulus pressure in shale gas wells have significantly affected the safe and efficient development of shale gas. In view of the integrity of cement sheath which is affected by the high fluid pressure in casing during the hydraulic fracturing treatment, an experimental device for testing the integrity of cement sheath is established. In addition, the analytical model for calculating the stress and strain of the well system is established based on parameters of the experimental device. The analytical model for calculating the circumferential strain at outer wall of the steel cylinder is achieved. The error of stress-strain between analytical calculated results and the experimental results is very small. In sensitivity analysis, the parameters which affect the stress on cement sheath interface is discussed. This study has a certain reference value for the design of experiment device and the analysis of sealing ability of cement sheath in shale gas wells.