Reducing Drilling Operational Risk and Non-Productive Time Using Real-Time Geomechanics Surveillance

Abstract

Abstract Mud weight optimization is a key driver in attaining optimum wellbore stability while drilling horizontal wells. This paper demonstrates the role of geomechanical knowledge prior to and while drilling to address wellbore stability related issues to help reduce drilling risk and non-productive time (NPT). To maximize gas production from a tight carbonate reservoir, horizontal drilling and multistage hydraulic fracturing methods have been adopted. For several wells, maintaining wellbore stability has been a challenge without prior geomechanical knowledge of the field resulting in undesired drilling events such as tight hole excessive reaming, stuck pipe, and difficulties while making trips. Even in wells with pre-drill geomechanical analysis for mud weight recommendations, uncertainty in the pore pressure due to depletion along the horizontal section of the wellbore, drilling with one recommended single mud weight (MW) posed great challenge to manage wellbore stability. In this paper, statistical analysis of data is used to investigate root causes of wellbore stability related issues for a number of horizontal wells drilled in the direction of the minimum horizontal stress. The analysis suggests that wells drilled with little understanding of geomechanical properties along the wellbore path encountered significant NPT's compared to those wells where understanding of rock mechanical behavior and in-situ stresses was utilized to make recommendations prior to drilling. In some cases it helped reduce NPT to less than 2% even in exploration wells. Among the successful wells, results from a case study describing the real-time (RT) geomechanics workflow was used to optimize MW enabling drilling the well to the planned target depth. The uncertainty related to pore pressure and intervals of high porosity which creates a significant risk of differential sticking were addressed by incorporating RT data and updating wellbore stability models and providing recommendation to the field operation. The paper demonstrates the role of geomechanics and its impact to drilling operations aimed to reduce operation cost and increase drilling efficiency by eliminating geomechanics-related wellbore stability problems.