Simplified First Order Motion Analysis of a Moored FPSO
D J Smith
Abstract: This paper presents a simplified method based on a barge shape, for predicting the first order motion response of a typical moored floating Production Storage and Offloading (FPSO) vessel. The technique is suitable for use on a spread sheet and provides rapid optimisation for any given vessel and environment combination. Results are presented from a three–dimensional diffraction program showing that a barge shape can be used to estimate the motions of a FPSO at an earlier stage of the design process.
Dynamic Seals in HP/HT Wells
R Shepherd and A Stevenson
Abstract: Emerging completion technologies are placing increased demands on seal systems required for downhole use. The move towards higher production pressures and temperatures (HP/HT) means that seal design could become the limiting factor for the exploitation of HP?HT wells in the North Sea and elsewhere. Current dynamic seal design practice is not supported by a fundamental base of knowledge, although there is experience and empirical data at existing operating conditions. The basis for predicting seal behaviours under conditions more extreme than those currently experienced is therefore limited. For this reason MERL has designed and built a new instrumented dynamic seal test facility to investigate the behaviours and mechanisms of failure of seals, under realistic conditions simulating downhole service. The test facility that exists is unique in Europe and its function is illustrated by reference to typical results.
Avoiding the use of Exotic Materials in Pipeline Design
D H Demetriou
Abstract: The continued exploration and development of deepwater offshore oil and gas fields presents greater technical challenges to the pipeline engineer. Such wells tend to produce very corrosive wellstream fluids at high wellhead flowing temperatures. This paper will examine aspects of pipeline materials selection based on corrosion resistance requirements. A review of alternative pipeline materials is presented, together with limitations on the use of each material for corrosive service. Finally, the paper will demonstrate how a re–evaluation of the traditional predictive models for assessment of corrosion rates, in wet CO2 gas pipelines, can avoid the use of high alloy carbon steels, or exotic materials.
A Technique for Monitoring the Settlement of Fouling Organisms at Exposed Subtidal Locations — Technical Note
IS Thompson et al
Meeting Reports
Underwater Research and Discovery
M Breen, C Johnston and S Marine
Offshore Mechanics and Arctic Engineering
DT Brown
Book Reviews
Remotely Operated Vehicles of the World
Reviewed by John Bevan
Anchor Handling Tugs and Supply Vessels of the World
Reviewed by John Bevan
Survey Vessels of the World
Reviewed by John Bevan
Underwater Technology Vol 22 No 2
Winter 1996–97
A Personal View
The future is subsea but not us for humans
Dr Rex Gaisford
Technical Papers
The Design and Evaluation of a Phase–Steered Parametric Sonar System Intended for Sediment Characterisation
JC Cook, AD Goodson, PA Lepper, B Woodward
Abstract: The ultimate aim of the European Commission’s MAST–II REBECCA project was to study the viability of characterising sub–bottom sediment structures entirely by acoustic means. Part of the system developed to attempt the realise this aim was a parametric sonar system. The mode of operation was to insonify the sea bed at different incidence angles, using a variety of transmitted acoustic pulses, and subsequently to examine reflected and forward–scattered signals. The paper describes firstly the transmitting system designed and developed at Loughborough University. It then presents the results of static calibration tests in Lock Duich, Scotland and further results obtained during sea trials on two French research vessels off the coast of Brittany, when the parametric sonar array was integrated into a two–fish with an attached hydrophone streamer. The sonar transmits a phase–steerable primary beam centred at 75 kHz and generates in the water useful secondary signals at typically 3 kHz to 7kHz, with a narrow sidelobe–free beam (2.5° x 2.5°), at Source Levels up to 196 dB re 1 mPa at 1m at 5 KHz.
Weather and Climate Variability Since Prehistoric Times and Recent Indications of Continuing Fluctuations in the N.E. Atlantic
N Lynagh
Abstract: Weather and climate are in a constant state of variation. The time–scales over which these variations take place range from minutes to millennia and even longer. Human experience of these variations spans only a very short period of time. As a consequence, a change which is actually part of a long–period variation about the mean can easily be mistaken for a trend in the mean itself. In recent decades significant variations in the wave climate of the N.E. Atlantic Ocean have been identified. It is important to try to identify whether these changes are a variation about a steady mean or whether they are indicative of a shift in the mean itself. An examination of the varying climate of storm systems in the N.E. Atlantic helps to provide an understanding of why the wave climate appears to have changed.
Deepwater Geotechnical Investigations in the Gulf of Mexico
JH Pelletier, EH Doyle and RN Dutt
Abstract: This paper discusses Shell Offshore Inc.’s current deepwater Gulf of Mexico (GOM) geotechnical investigation practice. The development of the geotechnical investigation prognosis and its components are outlined. The paper discusses the range of water depths, site soils, platform types, investigation vessels , and in situ tools that have been used. Both standard and advanced laboratory testing schemes are presented and their purposes discussed. The importance of integrated geophysical studies for defining investigation scopes is highlighted. The use of the data for the design of surface and subsea development structure foundations and exploration and production wells is reviewed. The Mars Tension Leg Platform (TLP) site is provided as an example of an integrated geotechnical investigation. Finally, the paper proposes directions for advances and development in geotechnical investigations and associated technology for the 21st century.
Meeting Reports:
Climate Change Offshore N.W. Europe ― An Assessment of the Impact of Changing Meteorological and Oceanographic (Metocean) Conditions on Offshore Activities
INL Gallett, D Thomas and A J Fyfe
Using the Marine Environment for the Greater God
AG Senior
An Update on Subsea Tree Technology
SA Hutton and H Howells
Book Reviews
International Offshore Engineering
Reviewed by C Kuo
Titanium Alloys in Subsea and Offshore Production Systems
Reviewed by WD Loth
Underwater Technology Vol 22 No 3
Summer 1997
A Personal View
From manganese nodules to Working Time Directives
A Read
Technical Papers
Extreme Value Analysis of the Structural Response of a Single Point Moored Vessel
J Bowers, I Morton and G Mould
Department of Management and Organisation, Faculty of Management, University of Sterling, Sterling, FK9 4 LA, UK
Abstract: Offshore system design requires an estimate of the extreme environmental conditions, typically based on the 50 year period values. Where a single environmental variable dominates the system’s behaviour, a univariate extreme value analysis may be sufficient. However, many systems are dependent on several aspects of the environment and a multivariate extreme value analysis is required.
One approach is the use of a response function to transform a bivariate environment to a single variable describing a critical force in the offshore system. The resultant one dimensional problem is then explored using the standard techniques of univariate extreme value analysis.
This method, the ‘structural variable approach’ is applied in a bivariate extreme value analysis of a single point moored vessel and its dependence on wave height and period. The 50 year return period steady drift force determined by this method suggests that the vessel will experience considerably greater forces than might be expected from a simple univariate extreme value analysis based on wave height alone.
Erosion Damage Mapping in a Standard 90 Degree Take–Off Subsea Christmas Tree Assembly
G Parslow, D Stephenson, J Strutt and S Tetlow
Abstract: School of Industrial and Manufacturing Science, Cranfield University, Cranfield, Bedfordshire, MK43 0AL, UK
It is increasingly recognised that erosion arising from sand production can be a significant problem in the production of petroleum fluids. Since the quantitative analysis of the flow behaviour of entrained particles is extremely difficult, the traditional methods of estimating the rate of erosion occurring in well–head equipment has been based on the accumulation of experience and information on past equipment failure or damage. The ability to predict erosion rates in a new or modified system would provide the designer with an invaluable tool for estimating low erosion potentials within a cost effective and reliable design solution.
Here we present a set of results from an ongoing process of research examining erosion risk for various subsea component geometries. The set of data concerns a ‘T’ joint geometry, appropriate to both conventional and horizontal subsea Christmas tree configurations and demonstrates our use of a multi–layer paint erosion indication technique to produce highly visual and accelerated maps of erosion damage occurring in a three dimensional component model. The paper also serves to introduce our exploratory investigations of computational fluid dynamics and fluid/particle flow dynamics visualisation as tools for modelling the erosion patterns observed.
Report of the Marine Technology Foresight Panel Working Group on Exploitation of Non–Living Marine Resources
C P Summerhayes, R Coles, B. Wheeler, M Baker, DS Cronan, R Burt, G. Griffiths, N Veck, D Anderson, H Young and M Murphy
Abstract: As a contribution to the UK Government’s Technology Foresight programme, which aims to set priorities for research funding for the future through dialogue between industry, academia and Government, we have examined the non–living marine resources part of the Marine market sector. Under this heading we identify substantial potential for growth in three target market areas:
A offshore information and forecasting services
B seabed survey in support of engineering of all kinds, military activity and transport
C exploitation of deep waters beyond the edge of the continental shelf
Although the UK is already strong in several marine markets and in the science and technology necessary to underpin continued market success, we believe that substantial additional benefits will accrue to the UK if it increases its efforts so as to acquire a large fraction of the developing global markets in these three areas. We have prioritised the technologies in which further investment in R&D is required if the UK is to achieve these benefits.
Reports
Near Seabed Geophysics and Geotechnics: What can they do for your next subsea pipeline project?
B Tollin
Towards 2000: Metres or Millenium?
J Sommerville and M Cook
ASPECT ’96: Advances in Subsea Pipeline Engineering and Technology
A Kyriacou et al.
Tax Pounds and Toxic Seas: Deep Water Containment of Pollutants
INL Gallett
Book Reviews
Sea Change : A Message of the Oceans
Reviewed by DA Pilgrim
Dredging : A Handbook for Engineers
Reviewed by LJ Ayling
The Infernal Diver
Reviewed by RL Allwood
Underwater Technology Vol 22 No 4
Autumn 1997
A Personal View
The Marine Foresight Report D Goodrich
Technical Papers
Report of the Marine Technology Foresight Panel Working Group on Energy
D McKenzie
Introduction: The Marine Foresight Panel came about in 1995 to represent the cross–cutting interests of the Marine Markets as the sixteenth panel in the UK Government’s Technology Foresight exercise. The Technology Foresight process was set up as a national consultation exercise to bring together industry, academia and government to determine where the country should invest its science, engineering and technology spending.
In view of the range and scope of technologies which underpin the marine industries in the United Kingdom this Foresight Panel was made up of five sub–groups, reporting to the Panel Chairman and resulting in a Final Report made up of their findings. This paper is the second of two sub–group reports to be covered in Underwater Technology, selected for their interests to SUT members.
This report summarises the initial work of the Energy Sub–Group in identifying those areas in the fields of marine energy where there is high potential for innovative and economically significant developments to be initiated, within the Foresight time–scale of 20―30 years, through research and applied technology. Is Abyssal Seafloor
Isolation an Environmentally Sound Waste Management Option?
DK Young and PJ Valent
Abstract: This paper discusses the waste disposal concept of environmentally isolating industrial wastes (i.e. sewage sludge, fly ash from municipal incinerators, and dredged material) on the abyssal seafloor. Environmental acceptability of this concept is compared with alternative oceanic waste management concepts of containment and dispersion. Dredged material, containing contaminants with high particle affinities enabling potential toxins to be readily sorbed to sediment and be buried within the seabed, is ideally suited for abyssal seafloor isolation. Sewage sludge, with low bulk densities, is better suited for disposal by dispersion. Fly ash, containing high levels of heavy metals which can be mobilised under certain redox conditions, is a poor candidate for ocean disposal.
Marine Biological Mapping for Environment Management Using Acoustic Ground Discrimination Systems and Geographic Information Systems
J Davies, R Foster–Smith and IS Sotheran
Abstract: Effective marine environmental management requires base maps of biological resources. Remote sensing techniques are one of the most cost–effective methods of resource mapping. Sonar is the optimal method of remote sensing the seabed in turbid, temperate marine waters. Acoustic group discrimination systems provide a relatively simple, low–cost method of sea bed mapping but are designed to map the physical environmental variables of topography and seabed type. The BioMar project at the University of Newcastle–upon–Tyne has developed methods of analysing acoustic data in conjunction with biological information to produce biological resource maps. These methods utilise geographic information systems (GIS). These methods are described and illustrated with data from two case studies undertaken for the UK Government conservation agencies. Fuzzy Yaw Autopilots for Unmanned Underwater Vehicles Tuned Using Artificial Neural Networks R Sutton and PJ Craven
Abstract: This paper describes the application of neuro–fuzzy techniques in the design of autopilots for controlling the yaw dynamics of an unmanned underwater vehicle. Autopilots are designed using an adaptive–network–based fuzzy inference system (ANFIS), a simulated annealing turning methodology, and a fixed fuzzy rule–based approach. To describe the yaw dynamic characteristics of an unmanned underwater vehicle and realistic simulation model is employed. Results are presented which demonstrate the superiority of the ANFIS approach. It is concluded that the approach offers a viable alternative method for designing such autopilots.
Reports
Report of the Marine Technology Foresight Panel Working Group on Energy
D McKenzie
New Methods of Subsea Wellhead Control
W Andrews
Behaviour of Offshore Structures ’97
DT Brown
Denizens of the Deep: The Marine Life of the Atlantic Frontier
INL Gallett
Book Reviews
Regional Satellite Oceanography
Reviewed by DJT Carter
Sea Dumped Chemical Weapons: Aspects, Problems and Solutions
