Effect of cement sheath induced stress on well integrity assessment in carbon sequestration fields

Carbon sequestration describes long term storage of carbon dioxide into geological formations. Depleted oil and gas reservoirs can be considered as a desirable storage vessel for carbon sequestration. Well cement is one of the vulnerable leakage pathways in high pressure and corrosive environments. The integrity of the cement sheath in high pressure environment must be maintained to avoid the contamination of atmosphere and underground drinking water. This paper presented an analytical solution to evaluate the cement sheath integrity of wells exposed to CO2 considering the effect of cement sheath induced stress (CSIS) and formation pressure variation due to CO2 injection. The proposed model was validated through the comparison of the proposed model with Atkinson's analytical model and Carter's finite element model. The well logging records further verified the analytical model. A field case analysis indicated that the maximum injection pressure (MAIP) would be underestimated if CSIS is not considered. The proposed model can be used to evaluate the cement sheath integrity in carbon sequestration fields and other gas/water injection wells in oil production fields. It can also help to design and optimize the operation parameters of the hydraulic fracturing operations. (C) 2017 Elsevier B.V. All rights reserved.