Field Application of Software Model and Wellbore Strengthening Materials for Drilling Depleted Reservoirs and Mechanically Weak Formations in Gulf of Suez

Abstract

Drilling operations might require increasing mud weight beyond formation's fracture gradient margin which may lead to downhole losses into formation and other potential problems resulting in Non-Productive Time (NPT). This paper describes successful application of wellbore strengthening software (WSS) to simulate formations’ strengthening process by increasing Hoop Stress while drilling depleted reservoir sand or mechanically weak formations. The software model takes into consideration well design, basic rock properties and in-situ earth stresses. The paper also defines design of mud formula and lab procedures verifying the designed wellbore strengthening materials (WSM) blend and successful application in field. Design and selection of mud formula are main pillars of successful formation strengthening procedure to match with induced fractures width. Unlike other software models that use generic particle size distribution (PSD) data, software in this study takes into consideration PSD of specific batches of WSM to simulate wellbore strengthening process and recommend the optimum WSM blend, concentrations. Based on mud formula design from WSS, lab tests were conducted to verify concentrations and selection of WSM and accordingly formulas were applied successfully for complicated drilling operations. Static and dynamic formation strengthening techniques were applied successfully in multiple wells. Based on software results and recommendations, Techniques’ application managed to strengthen weak formations up to 121% of original fracture gradient, decreased section drilling time by 20% which resulted in drilling costs reduction by up to 24.2 %. As a result of this successful application in many critical wells, WSS results are now integral to operator's well plan to enhance wellbore pressure integrity of weak intervals, in following drilling operations. The presented study is based on an innovative approach to strengthen weak and depleted formations in critical drilling operations using exact PSD data of WSM batches, formation properties and customized software model, an optimum concentrations blend can be selected to strengthen wellbore and hence it can be customized for every application where optimum formation strengthening is required.