A Cost Effective Newbuild Semisubmersible Floating Production Platform

Abstract

ABSTRACT Semisubmersibie based Floating Production systems (FPS) have been extensively used in offshore field developments worldwide. Most have been converted from existing drilling semisubmersibies. Faced with a rapidly dwindling inventory of existing platforms to convert, the industry near cost competitive new build units. this paper presents the principles and development of just such a platform. It will be demonstrated that this new build platform is cost and schedule competitive with a conversion for a deepwater Gulf of Mexico development. INTRODUCTION Monohull or semisubmersible based FPSS converted from existing vessels, featuring low capital mat and cycle times to first oil, permit operators to economically develop small to medium sized fields in deepwater or remote regions [1,2]. Historically, field developments employing floating production systems were focused mainly in Brazil, West Africa the Far East and Australia. More recently, Operators in the U.K. and Norwegian sectors of the North Sea and Atlantic Frontier have accelerated the use of floating production systems to exploit their more remote, deepwater or marginal fields. This increase has been fueled by the growing confident and coat reductions in subsea and riser systems [3]. A case point is the development of the Njord field in the Norwegian North Sea by Norsk Hydro in about 1000 ft. of water by subsea tiebacks to a 45,000 tonne newbuild floating drilling production unit the Aker P45[4]. Semisubmersible based production or drilling and production units, in combination with subsea wells, have been used worldwide to commercially develop small to medium fields (50 to 100 million barrel reserves) in a wide range of water depth and environments [5]. With the exception of 3 newbuild units, most have been converted from second or third generation semisubmersible Mobile Offshore Drilling Units (MODUS) The availability of suitable candidates for conversion was never a problem, until recently. The soaring demand for deepwater exploratory and appraisal drilling has depleted the pool of candidate rigs for conversion and also raised acquisition prices. There is a perception that a newbuild unit will cost a lot more and will have a significantly greater cycle time to first oil than a conversion. It is the intent of this paper to clearly demonstrate that a newbuild production semisubmersible, adapted from and employing the principles embodied in the Aker P-45 floating production unit can be eonunereially competitive with a converted semisubmersible FPS for a deepwater GOM application. DESIGN APPROACH Figure 1 illustrates the fimdarnental departure from the traditional approach to building semisubmersibles, that will achieve the design objectives of low cost and accelerated schedule for a newbuild FPS.