bluuebunny/crossref_metadata_2025_split huggingface dataset:
Offshore Gas to Liquids
Authors: Rodvelt Sigmund , Schanke Dag , Fosen Per Eirik 
Published: October 2008

Abstract
This paper gives a technical description of two concepts for offshore conversion of associated gas to synthetic hydrocarbons (syncrude) by the Fischer-Tropsch process.
The solution represents an alternative to flaring or injecting associated gas and thus provides a means to exploit new oil fields in an environmentally sound way.
Two concepts are presented, a 4300 b/d syncrude plant on a Multipurpose Shuttle Tanker (MST) and 14500 b/d syncrude production on a dedicated ship. Both have been designed for the harsh weather conditions in the Norwegian Sea.
Studies have shown that the concepts are technically feasible and indicate that the safety requirements for offshore installations can be met.

Introduction
Flaring of gas has become an environmental issue with high degree of focus among approving authorities as well as the oil companies. Handling of associated gas for oil developments has therefore become a more critical issue than before. This has led the oil and gas industry to seek solutions that can handle the associated gas in an acceptable manner both economically and environmentally.
Excluding cold venting and flaring as alternatives, two main technical concepts exist for handling associated gas; injectionof gas into a reservoir or conversion to a transportable product. The attractiveness of the latter is heavily dependent on field location and type of reservoir. Gas can either be reinjected into the oil producing reservoir or into a separate reservoir nearby. In cases where gas reinjection has a positive effect on oil production, gas conversion is of limited interest during the injection period. For later recovery of the injected gas, gas conversion may represent an alternative. In the case where gas is merely disposed of into a non-producing reservoir or even affects oil production in an adverse manner, gas conversion may be competitive.
Conversion of gas to transportable products can generally bedivided in two groups. In the first group, gas is processed to "transportable gas" in the form of LNG, CNG or gas hydrate. The second approach is to convert gas chemically to another product, either methanol or synthetic hydrocarbons ("syncrude").
In particular LNG has the potential to handle relatively large amounts of natural gas and several concepts have been presented in recent years (ref. 1,2). CNG and gas hydrate are relatively new concepts generally aiming at smaller capacities (ref. 3,4). Although technically simpler and less costly than chemical conversion, all three gas-to-transportable gas concepts share the disadvantage of needing separate product logistics.
On the Design and Installation of an Innovative Deepwater Taut-Leg Mooring System
Authors: Ma Wei , Huang Ken , Lee Ming-Yao , Albuquerque Sergio , Palazzo Fabio Gondim 
Published: October 2008

Abstract
The aim of this paper is to identify important design parameters and consolidate installation experiences from the recently installed deepwater taut-leg mooring system for Petrobras' P-27 semi-submersible floating production system offshore Brazil. The P-27 mooring system consists of 12 anchoring lines with polyester ropes and vertically loaded plate anchors (the World's first practical installation of VLAs). This paper emphasizes the innovative aspects of using polyester ropes for a permanent mooring system.
Synthetic ropes have recently been employed in several offshore deepwater installations. Among various synthetic rope materials, polyester rope is the most popular due to its light weight, high strength, low elastic modulus, and relatively low manufacturing cost. On the other hand, synthetic rope is still in its early stages of practical offshore applications, and there are concerns regarding design methods, design criteria and installation techniques.
This paper addresses these concerns by comparing dynamic mooring simulation results of the polyester mooring system with those of typical steel wire/chain mooring systems based on the P-27 design parameters. Discussions on the handling, installation, inspection and maintenance of the polyester mooring system included in this paper are based on the actual execution of the P-27 project. It is found that conventional mooring analysis and installation techniques can be conveniently adapted to provide a consistent performance evaluation and deployment strategy of the polyester taut-leg mooring system.

Introduction
With the recent rapid growth in deepwater production projects offshore Brazil, American Bureau of Shipping (ABS) is actively involved in the classification of several conversions including semi-submersibles and tanker-based FPSOs (Floating Production, Storage and Offloading) for Petrobras. Most of these floating platforms will be moored in ever increasing water depths. In deep water, the conventional catenary mooring systems become less stiff and have a larger horizontal spread, with much higher mooring component costs and payload penalties. To cope with these challenges, Petrobras is leading the offshore industry in utilizing new mooring systems for stationkeeping of these platforms, which include polyester ropes and/or VLAs in conjunction with the taut leg mooring systems. It is predicted that the use of these new systems will grow in the near future for deepwater mooring applications [Ref.1 & 2]. ABS is responsible for the classification of the P-27 for Petrobras. This paper will demonstrate the innovative aspects of using polyester ropes and VLAs for this permanent taut-leg mooring system through parametric studies.
Benefits of using assisted DP for Deepwater Mooring Systems
Authors: Wichers Johan , van Dijk Radboud 
Published: October 2008

Abstract
For the exploration and production in deeper water use may be made of semi-submersibles and ship shaped types of structures. In the production phase the floaters are normally permanently moored and the mooring system is designed to withstand the local extreme environmental conditions.
Due to the risers and mooring lines in deep water a considerable amount of damping can be induced to counteract partly the low frequency motions. The mooring system however has to take the ultimate forces to keep the vessel on station. In these water depths the length of the mooring lines may be considerable. The cost effect by reducing the mooring system in terms of less mooring lines or a lighter system by applying assisted DP is worth to consider.
As an example a 200 kDWT tanker based FPSO system moored by means of a turret system has been considered. A water depth of 1200 m has been taken. The heavy mooring system may withstand survival conditions e.g. 100-year storm condition.
The same tanker is now provided with a class 3 assisted DP system, consisting of 4 azimuthing thrusters. The size of the passive mooring system (no DP) can be reduced and may withstand a much lower seastate e.g. 1-year storm condition.
It will be shown that the light mooring system including the DP system may be equivalent to withstand the same survival condition e.g. the 100-year storm as the heavy passive mooring system. The results show the effectiveness and benefit in using DP to assist the mooring system in survival conditions.

INTRODUCTION
At present DP assisted tanker based FPSO units are used mostly for heading control. In these designs the location of the turret is located closer to midship than to the bow. Due to the osition close to midship the heading of the FPSO with regard to the environment may become unstable and heading control may be necessary, see Ref.1. For FPSO units with bow turrets permitting weathervaning, the application of DP assistance to reduce the mooring forces is worth to consider.
In deep and ultra deep water not only the costs of the long length of the mooring leg are large, but also the installation costs increase considerably with the water depth.
In applying assisted DP to reduce the mooring forces, the design of the mooring system may be reduced to a passive system to withstand the 1-year or 5-year storm. In higher seastate the DP system must be activated. The average percentage of times of the occurrence of seastates higher than e.g. a 1-year or 5-year storm is relatively small. If a passive mooring system is designed to cope with the 100-year storm, the mooring system will be a heavy one. This heavy system will encounter during the full life cycle a large number of oscillations and different load levels, effecting the strength and fatigue of turret and mooring legs.
In this paper an attempt is carried out to show the benefits of DP assisted turret moored FPSO units in deep water. For deep to ultra deep water computer programs are valuable design tools.
Wave Measurements Using Upward-Looking Sonar for Continental Shelf Applications
Authors: Fiseel David B. , Birch J. Richard , Borg Keath , Melling Humfrey 
Published: October 2008

Abstract
An upward looking sonar instrument the Ice Profiling Sonar (IPS), has been developed, and successfully used for obtaining time series measurements of ice keel depths over the continental shelves of the Arctic in support of scientific research. Since the winter of 1996/97, it has been extensively used off the coast of Sakhalin Island, Russian Federation, in support of offshore oil and gas research aimed at characterizing the seasonal sea-ice regime. The IPS instrument has now been modified to extend its capabilities to provide accurate measurement of ocean waves. The instrument uses a high frequency acoustic transducer (420 kHx). It has a very narrow conical beam (2 degrees width at -3 dB) to minimize the spatial smoothing of surface waves across the sonar footprint. With reduced power consumption, and an expanded internal storage capacity of 64 Mbytes (flash EPROM), the new instrument is capable of continuous measurements of wave amplitude at a sampling rate of 1 Hz over deployments of up to nine months duration. During March to April 1998, an evaluation of the performance of the modified IPS instrument through intercomparison with a wave-rider buoy, was conducted in open ocean conditions off the Pacific west coast. Instantaneous wave heights of up to 11.5 m were measured. The results indicate good agreement between the measurements obtained from the IPS instrument and those measured using the wave-rider buoy. The subsea IPS instrument is very well suited to wave measurement in areas where sea ice or shipping are hazards to surface installations.

Introduction
Measurement of waves at continental shelf depths has been addressed with a variety of ocean instrumentaticns (Stewart1). For some applications, such as where information on the waves encountering an offshore platform are required, rigmounted sensors offer the beat solution. However, often wave data are required before the oil and gas platforms are in an idea, or for the purpose of providing inputs to, or validation of, wave models. For these applications, accelerometers operated within surface buoys are used with data relayed to receivers at shore stations, or via satellite. However, wave buoys are prone to damage from the large waves themselves, from ice if it is present in the area, from vessel traffic or from vandalism. As well, under extreme wave conditions, wave buoys are prone to errors arising from limitations in the response of the accelerometer due to pitch and roil of the buoys (Sky et al.2) and possibly due to the buoys not following the waves themselves under such examines conditions.
An alternate approach is to obtain wave measurements from the comparative safe and calm conditions of the bottom of tie ocean. Bottom-mounted, internally recording instruments, that sample the wave-induced fluctuations of pressure and velocity, are widely used for this purpose.
Deepwater Mooring and Riser Analysis for Depths to 10,000 Feet
Authors: Ward E.G. , Haring R.E. , Devlin P.V. 
Published: October 2008

Abstract
The purpose of this paper is to identify technology needs for analysis tools and methods for designing Floating Production Systems in depths to 10,000 feet. The authors and their colleagues specifically addressed analysis tools and experimental methods needed to establish design values for surface vessel motions and dynamics, riser motions and loads, mooring systems and loads, and the coupled response of the vessel, risers, and moorings for deepwater Floating Production Systems. The identified technology needs were prioritized, and suggested approaches to achieve the desired results are presented.

Introduction
The industry has developed design analyses tools for deepwater Floating Production Systems. These tools were first calibrated and validated with model tests, and in some cases field data and experience from Floating Production Systems installed water depths to 3,000 feet are being used to validate design analyses. As the industry progresses to deeper and deeper depths, these design tools cannot be directly validated or calibrated against data due to limitations in capabilities to conduct directly scaled model tests, and the natural lack of field data or experience in these new depths. The good correlation observed to date provides a strong basis for extrapolating these analysis tools to these new depths. However, data to calibrate or validate these tools in these newdepths, or to identify aspects requiring refinement or further development, are needed. When planning for Phase IV of the DeepStar joint industry project, the Mooring and Riser Committee recognized this need and made it one of the highest priorities for work to be accomplished during 1998–1999.
A workshop process was selected as the most effective means of obtaining input from many experts. Experts representing a broad range of expertise, experience, and perspectives were invited to participate along with Texaco DeepStar JIP members. Some 65 people from 40 companies and institutions participated in the two day workshop, which was held on October 29–30, 1998. Technical presentations and a survey of ongoing relevant research were used to introduce and focus the workshop sessions. Three workshop sessions provided the opportunity for all participants to introduce and discuss technology needs in the areas of FPS motions, FPS risers, and FPS Moorings. Some 70 technology needs were identified and discussed. The technology needs in each area were prioritized, and the final workshop session developed an overall prioritization of the needs identified. This project was conducted by the Offshore Technology Research Center of Texas A&M and the University of Texas on behalf of Texaco's DeepStar Joint Industry Program.
Efficient Integrated Analysis Methods for Deepwater Platforms
Authors: Løken Arne E. , Sødahl Nils , Hagen Øistein 
Published: October 2008

Abstract
Deep Water Floating Production Systems is an integrated dynamic system of risers, moorings and a floater responding in a complex way to loading from wind, waves and currents. The great challenge in selecting the proper strategies for efficient analysis is addressed in terms of analysis techniques and principles of selecting analysis approach. Available analysis methods are discussed with emphasis on treatment of important non-linear effects. A large potential for reduction of the computational efforts involved has been identified based on a careful selection of response model and method of analysis. Efficient analysis will therefore to a large extent depend on the analysts? experience regarding physical system behavior and insight on available analysis methods. A userfriendly computer implementation of advanced as well as simplified methods is hence the basis for cost efficient analysis of Deep Water Production Platforms. Structural reliability analysis is a consistent way of handling uncertainties. This methodology provides a probabilistic basis for decision making under uncertainty with due consideration of cost. Application of methodologies for tension leg platforms, semi-submersibles, deep draft floaters and more conventional ship shaped units are discussed.

Introduction
Efficient Analysis Methods for Dynamics of Floater, Risers and Mooring Systems often constitute the balance between due consideration of different factors affecting reliability and cost of predictions versus the need of the industry. Important questions may be raised such as: How to allocate given resources so that best accuracy is achieved? How to obtain required accuracy by adequate use of resources?
The following efficiency factors for method selection can be summarized as:New designs and design environment for deep water.Design code requirements.Method used can be a function phase of project (i.e. Research and Development, Design and Verification etc.).Physical and statistical model approximation versus confidence to the estimates.Method tailor made for specific object.Tailor made Numerical Solution Methods.Experience feed back from model tests and full-scale information.User-friendly pre-processors and post-processors including graphics.Use of maintained and verified software with cost share and many users. The most important change when working in deep waters up to 2000 meters and beyond is the change in riser and mooring systems, materials, length, weight and increased exposure to fluid forces, see Refs. 1 and 2.
Integrated Mooring & Riser Design: Analysis Methodology
Authors: Connaire Adrian , Kavanagh Kieran , Ahilan R.V. , Goodwin Paul 
Published: October 2008

Abstract
The integrated design of deepwater risers and moorings has the potential to bring substantial benefits in terms of overall system response, cost and safety to a offshore development. Existing design methods, with their origin in shallower water design, have typically not considered design integration. The associated design assumptions need to be reassessed in deeper water, where substantial benetits can accrue from integrated design. The justification for integrated design methods lies in the importance of hydrodynamic loads, stiffness, damping, added mass and potential compliant effects of risers as partof a moored system and also in the need to recognise the precise station keeping requirements of riser systems.
This paper presents the work of a JIP managed by MCS International and Noble Denton Europe and supported by 20 participant operators, contractors, manufacturers and regulators, which has investigated methods of integrated mooring and riser design over 2 1/2 years between 1997 and 1999.
Several altenative innovative riser and mooring analysis methodologies, corresponding to varying levels of design integration, have been developed and investigated for five selected FPS/FPSO systems to evaluate alternative design approaches. The vessels were selected to represent recent state-of-the-art mooring and riser designs in water depths up to 2000m.

Introduction
A comparison of alternative methodologies for the analysis of integrated mooring and riser system designs, representing several different levels of design integration, are described, together with their design assumptions. Their results and relative merits are evafuated against the results of mooring model tests and original design calculations.
Finafly, observations are made on appropriate integrated design methodologies, particularly for deeper waters.
Each of the design methods under review represent increasing levels of complexity and integration of the mooring and riser design. The objective of their evaluation was to investigate the analysis methodology which is robust in representing actual conditions while still being a practical design tool.
The five vessels considered throughout the investigation include a Central North Sea (CNS) FPSO in 150m water depth, a West of Shetland (WOS) FPSO in 400m water depth, a Northern North Sea (NNS) semi-submersible located in 350m water depth, a Brazilian FPSO in 1000m water depth and a generic Gulf of Mexico (GOM) floating production unit (FPU) located in 1700m water depth. The vessels and their associated mooring and riser systems, which are briefly described in Table 1, incorporate a variety of water depths, mooring system types, riser system designs and environmental conditions.
JIP-DEEPER: Deepwater Analysis Tools
Authors: Nestegård Arne , Krokstad Jørgen R. 
Published: October 2008

Abstract
New technical challenges arise when moving to deeper water locations for oil exploration. In order to meet some of these challenges, Det Norske Veritas and Marintek are jointly carrying out a three year research project on Deep Water Analysis Tools - DEEPER under the auspices of the Royal Norwegian Council for Scientific and Industrial Research.
The DEEPER project aims at improving existing procedures for design and verification of deepwater floating production units with emphasis on development of software analysis tools. The most important technical challenges treated in the project are:Strong current loading and viscous forces due to the longer exposed risers and moorings implying that flow induced vibration phenomena may increase.Interaction between mooring/riser dynamics and floater motions requiring coupled solution of mooring dynamics and floater motions. Other aspects covered by the project are improved methods for prediction of low-frequency floater motion, ringing of deepwater tension leg platforms and improved statistical methods for prediction of extreme floater motion and related non-linear responses. The project results will be included in a handbook with practical procedures for use by engineers when analysing deepwater floating structures.
A status and review of methods, corresponding computer tools and analysis procedures developed in the project will be presented. Applications on a deepwater SPAR, TLP and FPSO. will also be included.

Introduction
The Royal Norwegian Council for Scientific and Industrial Research (NFR) has invited Det Norske Veritas (DNV) and Marintek to carry out a Joint Industry Project on "Deep Water Analysis Tools" (DEEPER). The project was started in November 1996 and will terminate December 1999. The total budget is 16 MNOK, of which 40% is financed by NFR. The remaining funding comes from oil companies and engineering companies. The work is carried out by DNV and Marintek. The project also supports three Dr. students, one at University of Oslo and two at Norwegian University of Science and Technology.
The project aims at improving existing procedures for design and verification with emphasis on development of software tools. The need for improved analysis capabilities is emphasised by the fact that depth limitations of existing laboratories make it difficult to carry out model tests with required accuracy for design verification of deep water installations (above 800–1000 m). To enhance and improve existing software tools for use in both the design and verification phase of a deepwater development, is therefore deemed necessary in order to maintain the overall safety and meet the cost reduction challenge of the industry. Supplementary, the so-called hybrid verification techniques, utilising numerical simulations closely linked with model tests can improve the verification reliability even more, see Ref. 1.