Experimental investigation of frost heave force on tubing and casing

Currently, CO2 injection is mainly used to rejuvenate oil reservoirs as a tertiary oil recovery technology. During the cryogenic CO2 injection process, when the temperature drops below the freezing point of water, the volume expansion caused by the freezing of the water in the tubing and casing annulus generates a frost heave force. This additional force increases the risk of tubing fracture and shortens the life of the well. Therefore, in this paper, a laboratory experiment is carried out to analyse the characteristics of tubing and casing stress under the effect of a frost heave force. The results show that the frost heave force in the annulus squeezes the tubing and casing into an ellipse during the freezing process and that the strength of the frost heave force is approximately equivalent to the internal pressure of 104 MPa in a thin-walled cylinder pressure vessel of the same size. The experimental results explain the tubing and casing failure mechanism with the effect of frost heave force and provide a theoretical basis for providing a solution to improve the service life of tubing and casing in a cryogenic CO2 injection well.