A quantitative evaluation for excess pore pressure and wellbore stress around a cased well under steam injection

Key words:  steam injection  coupled thermal-hydraulic-mechanical model  Galerkin finite element method  excess pore pressure  wellbore stress

Abstract:

Based on the continuum mechanics theory,a coupled thermal-hydraulic-mechanical model corresponding to excess pore pressure and effective stress of thermal well under steam injection, was presented. In order to derive an effective numerical solution, a Galerkin finite element method with fully implicit and sequential iterative algorithm was adopted to design related computer codes. The numerical results show that excess pore pressure around cased well reaches 13. 8 MPa when the heating rate reaches 46.82 C /d. Thereby the effective stress near the well approaches the maximum value of radial stress with 14 MPa，tangential stress With 9 MPa, respectively. Therefore, an optimum programming for warming time or heating rate in steartvinjection should include various factors such as thermal-hydraulic response, in-situ stress and the strength of casing structure.