Cement and Debris Milling by Wire. Innovative Approach to Remove Hard Debris from Wellbore

Abstract

Small platforms with a limited deck space is always presenting a new set of challenges for well re-entry especially for Wellbore Clean Out (WBCO) for debris management. The same issues faced in the PTTEP Sarawak well operation where field with more than 10 years of production where sand, scale etc is part of the main challenges in ensuring production sustainability from the wells. Well A was completed back in June 2019 as gas producer with 3-1/2" cemented monobore completion with 74 deg deviation and long tangent section. Post completion, well was having difficulties during re-entry for the initial offline perforation leaving the two bottom most sand interval temporarily left out for early production of the intermediate sand interval. During the attempt in getting into the target sand interval some debris collected shown some leftover soft cement debris settlement. After several years of production of the intermediate sand intervals, the production performance is showing sign of depletion with water loading thus requiring the access to the last two bottom reservoir. In view of debris and cement accumulation shallower than the target perforated interval, there is requirement to clean the HUD to bottom of interest depth. Due to the limitation of platform deck space, there were difficulties to deploy coiled tubing for this well thus electric line with tractoring devices was selected to convey milling motor, collection chamber and mill bit to remove the debris from the wellbore. The biggest challenges were to remove the metal debris settlement from previous perforation as it imposes risk of tools stuck during cement milling and WBCO. The job was successfully executed with total cleanout interval of 150 m at negligible amount of Non-Productive Time (NPT). This paper will describe overall job design from the planning phase, until the job execution phase which covers specific and unique procedure development associated to effort to eliminate the risk of tools stuck due to perforation metal debris settlement in the rathole. Detailed lessons learnt from the operation were captured for future similar operation in the field.