Design Methodology for Converting a MODU into a FPU

Abstract There are many idle mobile offshore drilling units (MODU) that present potential opportunities to reduce the cost of field development. This paper summarizes the background and proposes a design methodology that can be applied when companies look into the potential of modifying semisubmersible MODUs to floating production units (FPU). The focus will be on the relevant commercial aspects that need to be taken into account, followed by the engineering efforts required for modification of the hull and main marine systems and the replacement of drilling systems by process topsides. There are some key differences in the design drivers for semisubmersible MODUs and FPUs that need to be taken into account when considering a conversion. This further governs the requirements for modifications and upgrades of a semisubmersible MODU in order to operate as a FPU. Based on the above, a case study has been executed. Expected required modifications and upgrades are outlined in the paper. Further, some options for improving payload capacity are presented and discussed in terms of cost, payload increase and overall impact on the FPU design. There are several technical and commercial aspects that affect the viability of converting semisubmersible MODUs to FPUs, including but not limited to: production capacity/profile, environmental conditions, existing infrastructure, mooring and riser system requirements, contractual model, CAPEX for MODU and conversion scope. On the basis of the above, and an overall assessment of the current market and availability of MODUs, a qualitative feasibility evaluation has been performed and is presented in the paper. The need to reduce the cost of deepwater projects is vital if projects are to be sanctioned and move forward. We must find innovative ways to drive out cost if the industry is to survive. Conversion of MODUs to FPUs may prove to provide an opportunity to achieve this.