The Next Generation Production Drilling Semisubmersible Based Deepwater Field Development System
Authors: D&apos;Souza Richard , D&apos;Barton David , Hatton Steve 
Published: October 2008

The traditional Production Drilling Semisubmersible (PD Semi) platform has served as a reliable production hub for developing medium to large deepwater fields that can be substantially drained from a single drill center. Several recent breakthroughs in well construction and completion technologies have significantly improved well rates and ultimate recovery, as well as drilling and intervention efficiency. There have been concurrent advances in drilling and production riser, mooring and process system technology, as industry continuously strives to drive down capital costs of deepwater field developments.

Most of these initiatives are unrelated, with specific and localized objectives. Taken independently, they provide incremental economic benefits when viewed in a field development context. The PD Semi (and other floating platforms) have been slow to realize the significant benefits that could be derived by incorporating some of these technologies, because of the historically segmented approach to design.

A systems engineering approach applied to a PD Semi based field development system is used to enable the identification and integration of "high impact" well construction, completions, drilling, riser, mooring and process technologies to create a new generation PD Semi platform. The result is a step change reduction in capital costs for deep and ultradeepwater developments as opposed to an incremental change achieved by simple extrapolation of current practice.

Introduction

The inflation-adjusted price for oil and gas has remained flat over the long term. The offshore industry is challenged to maintain or continuously reduce finding and development costs per boe, even as the quest for new hydrocarbon sources progresses steadily into deeper and more remote waters.

Several major hydrocarbon reservoirs have been discovered in the Gulf of Mexico, Brazil and West Africa in 1500 to 2000m. Operators have invested large sums in lease acquisition and seismic evaluations of prospects down to 3000 m. in anticipation of discovering rich hydrocarbon deposits. Significant exploration and appraisal drilling programs are in progress in the 2000 to 3000 m. water depth range.

Led by rapid advances in seismic, well construction and completions technologies, finding and development costs have fallen steadily in the last ten years. However, capital costs of surface production facilities have not kept pace. With today's proven field development systems, the size of recoverable reserves needed to justify development in ultradeepwater remains unacceptably high.

Production drilling or production only semisubmersible platforms with subsea trees have been selected in preference to dry tree platforms for several large deepwater developments in the North Sea, Brazil and recently the Gulf of Mexico (GoM). In ultradeepwater a conventional PD Semi with subsea wells is a proven and commercially attractive alternative to a conventional production drilling spar platform with surface trees. It also provides greater flexibility to accommodate reservoir uncertainty and lower technical, cost and schedule risk (Ref. 1).

This paper demonstrates the value of utilizing a systems engineering approach to identify "high-impact" emerging technologies. These span a broad spectrum of disciplines and enable the creation of a next generation PD Semi platform field development system.