A Geomechanical Approach for Drilling Performance Optimization Across Shales in Safaniya Field—Arabian Gulf, Saudi Arabia

Abstract

Abstract Mud-weight selection is a critical factor for ensuring wellbore stability while drilling, especially in the presence of unstable shale formations. This paper describes a geomechanical approach that has been used to optimize the drilling of these types of wells. In an offshore field, the 12-¼-in. sections are typically drilled across well-known, unstable shale formations that have caused numerous stuck-pipe incidents and wellbore-related nonproductive time (NPT) in most of the offset wells. During the planning phase, the formation evaluation data, casing design, and directional profiles are reviewed and analyzed. These data are then used to perform a geomechanical study to identify the safe mud-weight window. The outcome of the study is then used to produce a set of guidelines for drilling these wells across the problematic 12-¼-in. section. These guidelines were applied to wells from an offshore field in Saudi Arabia in which the troublesome section was drilled to the casing point in each well, with no observed wellbore-stability issues. There were no losses induced and no formation collapse encountered. The planned reaming trips were eliminated, which significantly reduced the cost of drilling and completing these wells. Based on the outcome of this study and the results, this process, based on geomechanical analysis, can be used as a reference for optimal mud-weight selection to mitigate wellbore-stability problems in nearby platforms in this field of the Arabian Gulf.