Investigating Wellbore Stability through Coupled Hydro-mechanical Finite Element Analysis

Wellbore stability has been a key issue in oil industry considering increased need for lower-paid energy and operation. Stresses around a wellbore are redistributed while drilling, and high stress concentration is induced in this area which should be treated using appropriate mud pressure in order to prevent instability problems. In conventional drilling, safe mud pressure is usually determined using analytical solutions. For wellbores drilled in shale, however, the mud pressure measured through conventional method would be unsafe because of complexities imposed by various shale issues, such as anisotropy. For this reason, applying other methods like numerical modelling is essential in this field. In this paper, coupled hydro-mechanical analysis has been utilized in order to estimate safe mud pressure for a wellbore drilled in a poro-elastic shale. Results obtained using elastic models have been compared with those of poro-elastic models to evaluate effect of the constitutive model on them. The evaluation demonstrates that taking the effect of pores into consideration has a significant effect on the numerical modelling results, so that it is indispensable to use coupled hydro-mechanical analysis in wellbore stability problems.

کلیدواژه ها:

Wellbore stability ، Shale ، Poro-elasticity ، hydro-mechanical coupling