Abstract
Drilling experience and well data acquired during field exploration and development can be used to characterize the geomechanical properties of faults and its implications on risk assessment. We have built a geomechanical model based on the available logging and drilling data, along with failure observations from different offset wells. Modeling results have revealed a present-day stress field characterized by a transitional normal faulting to strike-slip stress regime. The large, seismically resolvable faults have been brought into a three-dimensional numerical geomechanical model to determine the stress conditions near these faults. The stress tensor is here combined with a failure criterion to assess the potential for fault instability.
Drilling through some of these faults is required to reach the main field targets. We have investigated the effective stresses acting on each fault surface in order to determine whether these faults are active under the current stress field. To understand the risk of losses while drilling, we have estimated the required downhole mud weight pressure to induce shear failure along the main fault surfaces. None of the faults considered in this study are active; however, drilling through these structures may reactivate some fault segments. MWD data has been successfully used to validate the model and highlight the importance of fault stability assessment to help control bottom hole pressures and mitigate the risk of losses while drilling.
