A Multi-disciplinary Design Approach for a Deepwater Field Development Solution
Authors: Poldervaart Leen , Van Cann Bram , de Bonnafos Olivier 
Published: October 2008

Depending on factors like environmental conditions, reservoir characteristics, number of wells and facility payload, a number of different floating production units are used in the major deepwater regions. For remote deepwater areas, FPSO's can be considered a proven and reliable field development solution. Subsea wells, drilled and completed by a MODU, can be tied back to the FPSO or a cluster of subsea wells can be manifolded and tied back to the FPSO. When dry completions are a preferred solution, a Dry Completion Unit (DCU) might be selected. Due to the limited payload, the DCU will most probably be connected to a nearby FPSO where hydrocarbon fluids will be processed. By integrating the drilling facilities and a dry tree platform into the FPSO unit, the DCU can be eliminated and drilling and work-over expenses significantly reduced.

For relatively benign environments a Dry Tree FPDSO has been developed, which allows full field development from a single unit. This Dry Tree FPDSO concept includes a number of different systems including floater, mooring, drilling, well systems, production and operations. In order to achieve an optimal integration of the different systems into a single unit, a multi-disciplinary development approach was used. In addition to the technical feasibility, this approach was used for the evaluation of the operability of the unit, the overall safety level and an economic evaluation for possible field development scenarios.

This paper will discuss the multi-disciplinary design approach for integration of drilling, production and dry completions into a single unit without scarifying integrity, safety or availability. Results from various engineering studies, safety analysis and economic analyses for different field development scenarios will be presented.

Introduction

In recent years, the offshore industry has seen an increase in global deepwater exploration and development activity. In their search for new energy resources, oil companies explored potential deepwater basins and a number of large discoveries have been made. Especially offshore West Africa (WoA) a number of large discoveries have been made in deep water blocks and the development of these large reservoirs (with recoverable reserves over 500 MMbls) requires vast investments. To be successful, the field operator will have to develop a cost-effective field development strategy, taking into account a number of external factors including the local government, future market conditions, environmental impact, associated risk level, etc. In order to achieve favorable project economics, a fast-track schedule might be preferred. When establishing a field architecture several (more or less proven) field development concepts are available. These include: compliant tower, TLP, FSO or FPSO, (truss) spar or semisubmersible. For each specific geographical area, the suitability of each concept is mainly governed by local infrastructure, waterdepth, environmental conditions and reservoir characteristics.

Where the Gulf of Mexico is faced with seasonal hurricanes (extreme survival conditions), offshore WoA and Brazil can be considered as relatively mild environments. The environmental conditions offshore WoA can be characterized as benign with an ever-existing swell coming from the Southern Atlantic.