Modeling of a well-bore composite cylinder system for cement sheath stress analysis in geological sequestration of CO2

For the geological sequestration of atmospheric CO2 to be viable, it is important that cement sheath integrity of the well-bore is preserved for a long period. Apart from other modes of failure, the early age damage to the annular cement seal can initiate leakage of CO2 caused by excessive well-bore pressure and temperature increase/decrease. A composite axi-symmetric multi-cylinder well-bore model has been studied using both analytical and numerical techniques. Static structural and thermal analysis has been performed to investigate the variation of stresses along cement radius for different combinations of well-bore internal and external pressures and temperatures. In addition to that, linear mechanical properties of different cement systems have been investigated to compare the suitability of different cementing materials in well-bore situation. It has been demonstrated from the analysis results that cement with low Young s modulus experiences lower tensile stresses than cement with high Young s modulus for some cases of wellbore internal and external pressures. From the analysis, it also turns out that temperature increase or decrease can develop tensile radial stresses in the cement sheath. In the end, a failure analysis has been presented for different cement systems using Mohr-coulomb failure theory. Copyright 2012 ARMA, American Rock Mechanics Association.