A numerical method for potential implementation of underbalanced drilling in high pore pressure reservoirs

Rising demand to increase productivity as well as reducing drilling damages has encouraged companies to use underbalanced drilling (UBD) technology. In this study, a numerical simulation is applied to evaluate the feasibility of UBD in high pore pressure reservoirs. To achieve this objective, the minimum possible mud weight that ensures wellbore stability is estimated by considering an elastoplastic model. Furthermore, the growth of the plastic area around the wellbore is studied and utilised as an indicator of wellbore instability. When the growing plastic volume around the wellbore equals the drilled wellbore's volume, the finite-difference model results in the optimum mad weight for the formation. Moreover, a detailed study is conducted in the zones with no safe mud windows to determine the optimum applications. The work of the paper is applied to real field data for justification, where the feasibility of UBD implementation in high pore pressure reservoirs is acknowledged.