Analysis of the rapidly growing mobile offshore production system (MOPS) market provides a revealing statistical description of technical fleet characteristics and commercial/contractual approaches toward ownership and operation of MOPS units. Based on a proprietary database of existing and planned MOPS units, in-house studies, and a review of published sources, this analysis correlates fleet technical and commercial data with the characteristics and requirements of various field applications and geographical areas. Current MOPS market trends are illustrated by reviewing units recently installed or under construction. MOPS unit design and key component technologies are becoming more mature, but applications continue to show a high degree of innovation and further development of some components is needed to extend MOPS use into very deep water. Future applications will likely reinforce the present trend toward FPSOS and provide increasing opportunity for broader contractor participation, responsibility and ownership. The MOPS market will remain vital and expanding into the next century and will continue to be characterized by a diversity of technical solutions and commercial arrangements. Introduction Mobile offshore production systems (MOPS) constitute the most rapidly expanding segment of the worldwide offshore field development market. The expansion in MOPS applications that began several years ago and is still accelerating is being accompanied by great vitality in technical advancements and commercial arrangements, as well as by the entry of many new participants into the market. And while rapid growth is always disorderly and confusing, the MOPS market is beginning to mature in certain respects as the relative merits of various technical solutions and commercial arrangements are sorted out. It is no longer necessary for an offshore operator contemplating use of a MOPS to approach the selection process by reinventing the wheel. It is, however, still necessary to define what is included in the MOPS category when presenting analytical results, since different investigators hold different assumptions. For this study, mobile offshore production systems include all readily movable vessels or structures that are directly engaged in the production and/or processing of oil at an offshore field location, This MOPS universe thus includes ship-shaped monohull floating production, storage and offloading systems (FPSOS), semisubmersible-based floating production systems (FPSS), and jackup production units (JPUS). The five existing and two newbuilding TLPs and the two Spar units on order are omitted from specific consideration as having more in common with fixed bottom-founded platforms than with MOPS and in being owned exclusively by oil companies. The first TLP will conclude its 12th year of service at Hutton field this year with no indication that it will be redeployed any time soon. if operators begin toselect some of the mini-TLP designs for actual applications, these units would fit our conception of a MOPS.

No abstract

This paper discusses the advantages and disadvantages of semisubmersibles and large tankers (150,000 to 250,000 DWT) when used as floating production and storage systems. Primary technical considerations which are discussed include:Mooring LoadsProduction RisersVessel MotionsCrude Storage and OffloadingSystem ReliabilityField Shut-In ParametersCapital ExpendituresLead Times The data included is based on computer simulation, model tests, and industry successes in meeting similar challenges. INTRODUCTION In the past decade several fields have been produced in the North Sea with semi submersible drilling units which were converted to production units. As a result of the proven suitability of semi submersible production units in hostile environments (Argyle & Buchan Fields), many people believe that only semi submersibles are suitable for those locations. With the increasing use of converted tankers as floating production, storage and offloading units, it is appropriate to evaluate their suitability for more hostile environments. SYSTEMS EVALUATED Five basic configurations which are considered in this paper are:Converted Semi; Shuttle Tanker. This includes a semisubmersible drilling unit (modified with production equipment), with continual offloading to dedicated shuttle tankers.Converted Semi; Storage Tanker. This includes a semi submersible drilling unit (modified with production equipment), a permanently moored storage tanker, and periodic offloading with shuttle tankers.Custom Semi Production and Storage. This includes special design and construction of a large semisubmersible, with periodic offloading with shuttle tankers.Production and Storage Tanker; SPM. This includes a very large crude carrier (VLCC), or a converted tanker (150,000 to 250,000 DWT), permanently moored with an articulated tower or single anchor 1eg mooring (SALM) with a rigid yoke, and periodic offloading with shuttle tankers.Production and Storage Tanker; Turret Mooring. This includes a converter a tanker or VLCC permanently moored with a turret mooring system, and periodic offloading with shuttle tankers. For each case, it was assumed that major pipe1ines are not in place, necessitating the use of shuttle tankers. MOORING LOADS Typical mooring loads (without shuttle tanker attached) are shown on Figure 1. The mooring forces are significantly lower for the tanker based unit which weathervanes than for a semi submersible exposed to beam seas. Therefore, a much greater factor of safety can be maintained with similar mooring systems, or the size of the tanker-based mooring can be reduced in order to minimize capital expenditures. The mooring loads for the tanker may be slightly larger than shown when the wind, waves and currents are not collinear.