TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractOver the last two years Noble Denton has been undertaking a Joint Industry Project (JIP) to investigate how to improve the integrity of the moorings used by Floating Production Systems (FPSs). The JIP has surveyed the world wide performance of all types of FPS mooring systems including FPSOs, semi submersible production units and Spars. Wide ranging support from 23 sponsoring organizations including operators, floating production contractors, regulatory authorities, equipment suppliers and inspection companies has enabled access to a significant pool of data. This paper utilizes the JIP data to discuss the following:• Causes of system degradation • Consequences of mooring failure • Key areas to check on a mooring system • Fatigue implications of friction induced bending • Options for in-water inspection • The importance of connector design • Methods to detect line failure • Contingency planning A few pioneering floating production units have now been on station for many years. Review of inspection data from these units shows that selective repair may be needed to maintain the design specification right up to the end of the operational life. It has been found that wear can be faster on leeside, as opposed to windward lines and that certain weighted chain designs are susceptible to damage.The likelihood of line failure and the implications need to be better appreciated. Following failure, it may well take several months to implement a full repair, due to a lack of spares/procedures and possible non-availability of suitable vessels. However, it has been found that carefully planned and coordinated inspection operations can detect potential issues early on before more serious deterioration takes place. In general, mooring monitoring/instrumentation and access for in-water inspection seem not to be as advanced as might be expected for a system which is safety critical. Hence good practice recommendations are included which can be applied to both existing and planned future units.

The gathering momentum for the use of polyester ropes for long term production system moorings in deep water has instigated a thorough review of their fatigue performance. The traditional view of designers has been to use spiral strand steel wire rope T-N curves to assess the fatigue performance of polyester ropes on the basis that available evidence indicates that the latter's fatigue performance is superior to spiral strand wire rope. The authors have examined all the available fatigue testing data and the proposals for polyester specific T-N curves and have identified a number of issues pertinent to the derivation of fatigue design data for fibre ropes and propose an improved design curve. This paper systematically identifies the various issues and proposes a rational way of including the available data (including runouts) for the development of a T-N curve for polyester ropes. The new data was used to re-visit the fatigue life and reliability for an example West of Shetland FPSO moored using polyester ropes (Ref.1).

This paper describes key findings from Phase 1 of the Deepwater Installation of Subsea Hardware (DISH) JIP. The objective of DISH Phase 1 was to identify key gaps in the offshore industry's technology for installing subsea hardware in water depths beyond 2,000m, by comparing present-day capabilities of the installation industry with likely deepwater installation requirements of oil and gas operators over the next 10 years. Technology gaps were identified by interviewing engineering and installation contractors, oil and gas operators and specialist suppliers; by carrying out a literature review study; and by holding a Phase 1 Mid-Flight Workshop to identify and prioritise the key gaps. The results were further refined before finalising the Phase 2 work programme. A review of the capabilities of wire rope lifting systems showed that self-weight will make conventional wire rope systems inefficient for water depths in the range 2,000m to 3,500m, and impractical on most installation vessels. The industry will therefore have to turn increasingly to deepwater fibre rope deployment systems. Key challenges are to establish the industry's confidence in fibre rope deployment systems, and to provide key information about the engineering properties of man-made fibre ropes and of the loading on such systems. Lack of knowledge of fibre rope behaviour was considered to be a fundamental, show stopper', which will inhibit the adoption of fibre rope deployment systems for ultra-deep water installation. DISH Phase 1 is now completed, and Phase 2 was launched in January 2002, based on the priority technology gaps and challenges identified during Phase 1. Background The DISH JIP was instigated following a pan-industry Workshop held in November 2000. At that time hydrocarbon developments were being planned in water depths close to 2,000m, and deeper fields were already being considered. Speakers from major installation contractors and BP believed, however, that established techniques for lowering and installing heavy items on the sea floor may either prove impractical or uneconomic in water depths beyond 2,000m, such as in emerging areas of the Gulf of Mexico. Furthermore, the deepest fields so far developed have been in relatively benign ocean environments, and the installation methods used to date are not necessarily transferable to harsher environments. A number of technical advances will therefore be needed to make some deepwater developments economic and practical. These issues were discussed further in a paper presented at a SNAME Workshop in February 2001 [1], which summarised possible technology gaps in the areas of lifting and lowering technology, load control and positioning, metocean effects and weather window requirements. General Approach DISH Phase 1 aimed to identify key technology gaps by comparing present-day capabilities of the installation industry with likely deepwater installation requirements of oil and gas operators over the next 10 years. The goal of achieving a common understanding spanning operators, contractors and suppliers worldwide, across the whole industry, was considered to be particularly important.

The IS0 Offshore Structures Standard will provide the Industry with a single Standard providing design guidance for almost all types of offshore structure. Work on the Standard has progressed to a point where the IS0 Sub-committee undertaking the work can inform the Industry in overall terms what to expect when the new Standard is published and the timeframe for publication. This paper outlines the objectives and scope of the Standard. It will describe the organisation developed to undertake the work, the international representation and contribution from a large group of people, and how a concensus is being developed within this diverse group of contributors. The paper will outline the document structure and Standard format which has been developed to encompass the interests of different geographic regions whilst maintaining a consistent application of the basic design process. The Standard is being developed by building on existing Industry practice from appropriate worldwide sources. The relationship between the IS0 Standard and existing documents from API and other sources will be described. Application The Standard will apply to all types of structure on a worldwide basis. Results and Conclusions The purpose of this paper is to inform the Industry of the Standard. Significance The IS0 Standard will become the primary technical guidance replacing existing Industry structural practices and standards. Introduction This paper is the first of four complimentary papers which aim to inform the Industry of the work being undertaken under IS0 Technical Committee 67tSub-Committee 7 Offshore Structures. This paper outlines the overall process behind the development of the Standard. Paper 8423 deal with the Fixed Steel Structures Part, 8422 with Fixed Concrete Structures and 8420 Floating Structures Background to the work of IS0 TC 67tSC 7 The Oil Industry operates on a truely international basis and is under close scrutiny by host governments and regulators, each with their own views on technical issues appropriate to their region. Our Industry has a strong culture of self help and self regulation and has built up, notably through API a suite of Industry based standards. Whilst within the confines of the Oil Industry API, ASTM etc. standards are recognised and applied world wide they do not have the same authority as national Standards and many countries have their own regulations which supplement or replace API documents. The Industry therefore currently faces a multiplicity of regulations according to host location. The International Standards Organisation set up 50 years ago is accepted world wide as the publisher of globally applicable standards. In the late 1980's the Oil Industry, primarily guided by the Exploration and Production Forum and API, took a decision to convert it's standards into IS0 Standards and formed seven sub-committees under the parent IS0 Technical Committee 67 (which oversees the Oil Industry standards effort). Subcommittee 7 was formed to address Offshore structures. Other sub-committees address Linepipe, Pipelines, Drilling Fluids and Cements, Drilling and Production Equipment, Casing, tubing and Drillpipe and Machinery. Scope of IS0 TC 671 SC 7 The scope of work is:- Offshore Structures used in the Production and Storage of Petroleum and Natural Gas.

The ISO 19900 series of standards addresses the design, construction, installation, integrity and assessment of offshore structures. In the early 1990's industry stakeholders drafted a long term plan to develop and maintain an international set of standards to supercede a growing number of local and regional standards. Existing standards generating bodies and government agencies including API, DnV, BSI, NPD, HSE and others combined with industry leaders to embark on developing a comprehensive set of offshore structure standards that would provide uniformity in methods and procedures across the world. Coupled with the core standards, individual countries/organizations could utilize the ISO standard supplemented by local regulatory and/or design conditions to assure appropriateness of facilities.