Mechanism and prediction analysis of sustained casing pressure in “A” annulus of CO2 injection well

High value of sustained casing pressure (SCP) threatens the wellbore essential safety and environmental protection seriously. Considering the special and complex characteristic of SCP in “A” annulus of CO2 injection well, a prediction model of buildup of casing pressure has been proposed in this paper. Then finite difference method was used to solve the discrete equations in order to predict the SCP variation with time. The value is closely related to size and position of leak point, leakage rate, height of annular protective liquid, length of gas column at wellhead and the state of CO2. The buildup of SCP in one well in Jilin Oilfield is obtained by this model, which is in good agreement with the actual result, verifying the reliability of coupled model and calculation method.

► Special and complex characteristic of SCP in “A” annulus of CO2 injection well has been proposed.
► Present paper described the reason and process of gas channeling leading to SCP in “A” annulus.
► Prediction model and calculation method of casing pressure in “A” annulus have been developed.
► The prediction accuracy is verified by illustration.