UMC Design Review

ABSTRACT The Underwater Manifold Centre (UMC) was installed in the Cormorant field in the North Sea during May 1982 to develop a segment of the field which could not be reached from the two existing platforms. This paper describes the basic design layout and major sub-systems of the UMC and reviews the design philosophy and criteria employed to achieve safety, reliability and flexibility. Described is a second-generation system based on Shell and Esso's previous subsea technology and experience. The paper concludes that the UMC is capable of providing the necessary facilities to recover reserves in a safe and reliable manner. INTRODUCTION Subsea production systems are designed for a limited but essential number of functions, especially when compared with platform-based facilities. Combinations of compression, fluid processing, separation and multi-level facilities, normally associated with production of offshore oil and gas, are not yet considered suitable for subsea systems. Nevertheless, the basic functions provided by the UMC encompass the anticipated production and water injection requirements to produce the reserves. Design of the UMC was developed to provide the basic functions itemised below.A template structure for drilling wells;A manifold system for collecting and distributing fluids;A centralised base for supporting associated remote control, Through Flowlines (TFL), chemical injection and maintenance system equipment; andA connection base for pipelines and control lines to the platform and satellite wells. The first part of this paper describes the UMC's layout and its associated equipment. The second part discusses design aspects related to achieving a safe, reliable and flexible system. The scope of discussion is, however, limited to the UMC seabed related equipment and does not extend to include details of related platform facilities, pipelines or interfaces with drilling operations. The UMC design is a second-generation system which combines Shell's single satellite well capability with Exxon's template-manifold concept, there by extending the system's total capability. SUB-SYSTEM AND COMPONENT DESCRIPTIONS Figure 1 illustrates the general arrangement and sub-systems of the UMC. Principal sub-systems and components identified are:The template, consisting of large tubular steel frames;The manifold pipework and its protective roof;Electro-hydraulic control and distribution system;Two hydraulic accumulator units;Two chemical injection units;The Remote Maintenance Vehicle (RMV) track;Satellite well flowline and control-line connections located on 'side porches' andConnection facilities for the main pipelines and control cables going back to Cormorant 'A' platform located on the 'front porch'. Each of these items will now be described.