Petronas has successfully set a new milestone in the history of casing while drilling (CWD), pushing the limit with 20 inch to 1002m MD, deepest in the world to date in a recent Malay Basin operation. Objective of this case study is to share the success story of CWD application in PETRONAS. CWD has come to a matured stage, widely practiced and become a normal practice particularly in Petronas Malaysia operation. This case study paper will focus on how the challenges turned to opportunities, and the overall assurance process leading to this achievement. Challenges, planning, engineering, execution, lessons learnt & potential future enhancements will be the main key highlights in this paper.

Key objective of CWD utilization in this project are for drilling optimization and prevention of potential NPT contributed by wellbore stability. Offset wells' wellbore condition and issues has become the key reference to kick start the process, followed by objective prioritization, OCTG screening & selection, operating parameters, casing drilling fluid selection which lead to a successful CWD operation. Pre-planning and equipment preparation for this Level 2 CWD had been engineered to avoid any potential problems due to equipment malfunctions. This paper also analyzed potential future improvement which would extract more benefit from this technology. Integrated risks assessments and HSE considerations have been the highest priority, which cover all aspects in offshore CWD operation including well control and operational optimizations.

CWD allows drilling the borehole and cased off the wellbore in a single trip. Total time for an interval was reduced by eliminating the time for running casing and mitigating downhole problems with borehole instability. The section was drilled with an average ROP of 30 m/hr. In general, the CWD operation for this project saved 1.5 days or USD 500k from the well cost as compared to conventional drilling and casing running operations. The drillable casing drill shoe was drilled out with a PDC bit, eliminating dedicated trip. This has directly reduced the cost and improved operational efficiency for the project. Surface section losses has been identified as one of the potential risks based on offset wells. The clay smearing effect had assisted in plastering the potential losses zone which lead to smooth casing drilling and running operation. Other benefit was elimination of HSE exposure from conventional methods, such as manual handling of casing and its running equipment. No recordable accidents/incidents during the operation.

Major focus and input on this paper will be pivoted mainly on Well C which has been successfully drilled and cased at 1002m MD. However relevant input from Well A and Well B will also be included as reference and explanation, in the effort to seamlessly show the journey from initial stage until current stage of confidence in implementations. Comprehensive analysis and detail engineering planning, together with a full geological & subsurface review has increased PETRONAS confidence level to continue pushing the envelope further; exploiting the benefit of CWD. Relevant best practices, analysis, casing drilling job preparation & procedures will be beneficial for PETRONAS CWD operation in Malay Basin.

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