This paper describes the application of casing drilling technique for the top hole section in conductor sharing wells in a brown field, offshore Malaysia. Its objective is to describe the integration of the casing drilling technique and the conductor sharing design when used in conjunction. It is intended to share the challenges faced during the design and execution phases of the project, the solutions analyzed and applied; as well as the outcome and learnings.

In this case study, the conductor sharing design makes it possible to maximize the well capacity of the offshore drilling platforms by accommodating multiple wells per drilling slot. The casing drilling technique is implemented to manage drilling risks related to wellbore stability, losses and shallow gas. The feasibility for combining the two technologies is evaluated during the planning stage by reviewing the documented previous industry experience of the two technologies, combined or separate; while local knowledge is analyzed to ensure all drilling factors are considered.

Solutions to challenges such as wells interface inside the shared conductor, directional control, losses, cement design and placement techniques, well control, operational procedures and time and cost efficiency are analyzed. The execution results are analyzed by comparing design estimations and assumptions with field data and actual results. These data is translated then into recommendations and lessons learnt. The conclusions of this case study are presented as a set of design work, drilling practices and risk analyses processes and their results that can be replicated or considered in future wells design where conductor sharing and casing drilling are to be implemented together.

While several individual studies of particular conductor sharing wells configurations, casing drilling and well construction techniques are available, the present work discusses one of the few applications to date where conductor sharing and directional casing drilling technologies are combined to address specific offshore challenges. The team considers of paramount importance that the knowledge obtained on this very specific combination of two technologies is documented and shared within industry professionals to provide reference for future applications.

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