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Early in the DeepStar program, both subsea pressure boosting and subseaseparation were identified as potentially necessary components for implementingdeepwater subsea production. The initial goal for the entire DeepStar programwas to have the technical capability to implement a deepwater Gulf of Mexico(GOM) subsea production system by 1996. Thus, the current status of subsea pumpand separator development was reviewed to determine whether such equipmentwould meet DeepStar technical requirements, and could be implemented by the1996 target date. Assessments were made of the system arrangements and costsfor implementing subsea pumps or separators relative to alternativeapproaches. This paper addresses a number of technical aspects and cost implications ofthese pumps and separators. It notes the field development circumstances thatfavor implementation of subsea pumping and subsea separation, but also suggestspotential system design alternatives to these components. Introduction Oil production from deepwater reservoirs in the Gulf of Mexico may requirein-field pressure boosting in order to achieve satisfactory flow rates over thelife of the field. Satellite subsea production systems, such as proposed forDeepStar, are prime candidates for pressure boosting, particularly as theoffset distances lengthen and production pipeline friction losses increase. Subsea multiphase pumps, as well as subsea production separators withliquid-phase pumps and gas compressors, are being developed for satellite fieldpressure boosting applications. The multiphase pump systems are generallysimpler systems than the subsea separators, but face technical problemsinherent in pumping gas-entrained liquids of varying gas content (up to 100%gas in some applications). Subsea separation overcomes these multiphase pumpingproblems and significantly reduces pumping power consumption; it can alsopotentially relieve hydrate problems by separating produced gas from producedwater. However, subsea separators are generally more complex and costly thanmultiphase pumps, and have to demonstrate reliable, low maintenance separationfor site-specific well fluids.

This paper presents a methodology for estimating the fatigue life of elastomer/steel flexelements.Flexelements are laminated composites usually consisting of between 10 and 25 elastomer layers, each bonded to a rigid laminar reinforcing shell.Such flexelements are used as TLP tendon flexj oints, and drilling riser ball joints. Test programs have been devised to qualify flexj oints for use in specific TLP structures, e.g. Hutton, Jolliet and Snorre. The present program has undertaken a systematic study of flexelement fatigue life characteristics.References and illustrations at end of paper.--------------- 225..-~.

This paper discusses the development of a large diameter threaded connector for tension leg platform (TLP) tendons. The connector is designed to join sections of 48 inch (1.22 meter) outside diameter, 1. 625 inch (0.041 meter) wall thickness pipe that make up the TLP tendons. This work is part of a broader research effort aimed at demonstrating the use of large diameter tendons. Use of large diameter, buoyant tendons results in TLP designs that are relatively insensitive to water depth.Elastic and plastic finite element analyses were conducted on various axially and radially preloaded connector concepts to study ways to reduce stress concentration factors (SCFs), improve static strength and resistance to jump-out, and evaluate sensitivity to machining errors.The results favored a radially preloaded connector concept. The resulting design has a weight of only 2.4 times the corresponding unit weight of the tendon pipe, a low SCF (less than 1.4), and a static strength greater than the tendon pipe. It also can be machined using conventional, computer controlled machines.A comprehensive testing program aimed at verifying the structural and functional performance of the connector was carried out.

Offshore production terminals and deepwater risers are seeing increasing use by the offshore oil industry. The structural design of these units presents a unique challenge compared to other offshore systems. Development of design loading conditions and fatigue histories is especially interesting due to the complex interaction of nonlinear riser and vessel dynamics, the statistical nature of maximum loads and the need to consider directionality as well as the magnitude of environmental loading. This paper presents a complete procedure for predicting design loads and fatigue histories for production risers and offshore terminals. The emphasis will be on systems wherein a dedicated vessel is connected to the riser by a rigid mooring arm. A number of structural design configurations will be surveyed. Techniques for preliminary sizing, dynamic analysis, model testing and fatigue analysis will be discussed. The application of this procedure to several specific design cases will be summarized.