Mitigating Wellbore Stability Risks through Geomechanical Solutions

Abstract

Abstract Geomechanical modeling is a key driver in attaining optimum wellbore stability while drilling horizontal wells in the orientation of the minimum horizontal stress (Shmin). Although geomechanical modeling remarkably helped to obtain best estimates on minimum required mud weights for ensuring stable wellbore, these models still have uncertainties along the horizontal wellbores. Multiple factors contribute to wellbore instability such as lateral changes in rock mechanical and strength properties, formation pressure, and localized digenetic effects. An improved geomechanical workflow has been developed to manage uncertainties and enhance operational efficiency. The proposed methodology is composed of calibrated geomechanical models for wellbore stability assessment that to be applied for upcoming planned wells during drilling operations. A number of key parameters were identified to build customizable geomechanical solutions and deliver stable wells. These key parameters include occurrence and sequence of strong/weak formation intervals and risk of differential sticking across depleted intervals. Each plan well requires a solution that includes computation of minimum required mud weight, formulation of mud system to handle multiple failure mechanisms, design of Logging-While-Drilling (LWD) Bottom Hole Assembly (BHA), and real-time geomechanical monitoring. Upon implementation of this methodology, the horizontal well was drilled successfully in a controlled manner. In this paper, an experience is highlighted to demonstrate the effectiveness of customized geomechanical solutions. It discusses the implementation of geomechanics at a specific sub-surface condition to attain the best result. In this study, there was a high risk for wellbore instability while drilling through highly stressed formation in minimum stress direction. The task was approached in a systematic way with a core objective of ensuring practical implementation of geomechanics findings, and follow the recommendations to mitigate wellbore stability related issues. There were two options that were been evaluated in this paper to prevent and mitigate wellbore stability, the first one is to low mud weights together with wellbore surveillance using real-time technolog, the second on is to use higher mud weights using sealing polymer and proper mud system formulation to avoid differential sticking.