Cement failure probability analysis in water injection well

• Brittle cement and elastic cement show the same failure characteristic.
• The compressive strength of the cement has little influence on the cement capacity.
• The elastic cement shows better behavior than the brittle cement.
• Cement fatigue failure and tensile failure are the two highest failure probability modes in water injection wells.

In the petroleum industry, the salt water was produced along with oil and gas. Due to the environment issue, the oil companies choose, the cheap and convenient way, to inject salt water into the reservoir. Because of the cycle load that injects water periodically, the cement fatigue failure should be considered in cement design. In this paper, the cement compressive failure, shear failure, tensile failure and fatigue failure modes were considered with different bottomhole pressures. The uncertainties of casing mechanical properties, cement mechanical properties, formation mechanical properties and wellbore geometry were also considered in the study. Based on the analysis, it is shown that within the cement compressive strength requirement, the wellbore service life can be increased by enhancing cement plastic behavior. The elastic cement with higher plasticity showed better behavior than brittle cement though the brittle cement has higher compressive strength.