Over a period of several years, both John Brown and Aker Engineering have executed a number of studies and design contracts for production facilities in water depths beyond 750m. This chapter presents a designer's view of the issues raised by some of these studies with respect to the technically interesting highlights and how they fit within the context of extended well testing, early production, production and export for a future deepwater field development. Extended well testing and early production facilities are considered in terms of monohull systems, but the main thrust of the paper is a description of improvements in TLP technology which make these vessels less expensive and hence more cost-effective for hydrocarbon production in both moderate and deep water. The chapter highlights commercial factors and raises for discussion the general circumstances under which extended well testing the early production may be applied and the logic of combining these phases with the final production and export.

INTRODUCTION

A scenario is set (see Fig 1) in which extended well testing, early production, production and product export would each play a significant role in securing an early return on investment, thereby making a deepwater development more attractive. Early production is assumed to be by a monohull Floating Production and Storage Unit (FPSU) with a Single Anchor Leg Mooring system (SALM), and critical features of design and installation of such a system are discussed. A Tension Leg Platform (TLP) is assumed to be central to the long-term production requirement with the FPSU providing at least a medium-term export route. Specific features of TLP design improvement are described, and a brief discussion is presented on the main points of difference between steel and concrete vessels. Quantitative figures are presented which indicate how TLP design has advanced and come of age. Finally, the costs of major aspects of deepwater FPSU and TLP project are set out so that the need for further design improvements or project development can be seen in an overall context.

Fig 1 Development by TLP and FPSU.(available in full paper)

Early Revenue By Phased Development

It will take at least 4 years from project start up to finally install and commission on site a full permanent production and drilling platform for these water depths. Our studies have shown that this schedule is feasible for such a TLP on a fast track basis.

Since there will not be a pipeline for oil export, a storage and offloading facility will be required to be on site ready when the main platform comes on stream. Our studies have shown that such a floating monohull unit can be made ready in about 2 ½ years. There is therefore a overlap of 1 ½ years, during which time it makes economic sense to use this as an early production (EP) system to offset capital expenditure with early oil revenue. Satellite wells can be predrilled during construction of the storage and offloading facility to which can be added a basic temporary process train to allow limited production from a few satellite wells.

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