bluuebunny/crossref_metadata_2025 huggingface dataset:
SS: Offshore Wind Energy Special Session: Inspection Guidance for Offshore Wind Turbine Facilities
Authors: Sheppard Robert Edward , Puskar Frank , Waldhart Chris
Published: July 2010

With the expected introduction of wind turbine facilities for the generation of electricity to the US Outer Continental Shelf (OCS) waters, there is a need to evaluate how the long term operations of these facilities can be ensured through Integrity Management (IM) activities, particularly inspections. There is a long operational history of IM in the Gulf of Mexico, offshore California and Alaska, and around the world for fixed and floating oil and gas platforms. Both prescriptive and Risk- Based Inspection (RBI) methodologies have been established and implemented. This experience provides a foundation for implementing similar integrity management programs for offshore wind turbine facilities. This paper describes a guidance document developed to assist operators and regulators in developing IM programs for offshore wind farms, the incorporation of existing guidance for subsea structures, above-water structures and access systems, along with guidance from subject matter experts regarding critical inspection areas, inspection techniques, and inspection intervals that are unique to wind turbine facilities. This work was funded by the US Department of the Interior, Minerals Management Service (MMS).

Development Approach

An integrity management program is designed to ensure the safe and efficient operations of a facility over its service life. It is comprised of three primary activities:Inspection activitiesContinuous monitoring activitiesEngineering evaluation and data management

This basic framework has been used extensively with offshore oil and gas platforms worldwide. Coupling this with inspection and monitoring practices unique to wind turbine facilities (both onshore and offshore) provides a basis for developing guidelines for an offshore wind turbine integrity management program.

These guidelines and the approach used in their development are documented in MMS TA&R Project 627, " Inspection Methodologies for Offshore Wind Turbine Facilities?? [1]. Information from regulatory standards, industry recommended practices, and subject matter experts was used to divide a typical offshore wind turbine facility into specific systems and structures with similar inspection scope, frequency and approach. The highlighted critical inspection locations were coupled with practical inspection realities (e.g., what can be accessed and how can areas be inspected) important to developing a successful integrity management program.

This paper provides an overview of the MMS TA&R Project 627 [1] including:Description of a typical offshore wind turbine facilityPotential failure modes and inspection techniquesRecommended integrity management guidelines
Structural Repair at a Production Platform by Means of a Composite Material Patch
Authors: De Marco Meniconi Luiz Claudio , Porciuncula Ivan Neves , McGeorge Dag , Pedersen Arve
Published: July 2010

This paper shows work performed through a Joint Industry Project (JIP), aimed to enable repairs made from composite materials to be applied to metallic structural components of offshore platforms in general and FPSOs in particular. The basic motivation was to provide a repair methodology that would cause a reduced impact to platform operations, particularly in classified areas. The focus on FPSOs derived from the fact that most of them are converted tankers, originally designed for overhauling in suitable docks from time to time. That is no longer possible once they are deployed as floating platforms, intended to stay in place for twenty years or more. An important prerequisite was that the repair procedure had necessarily to have the approval of the Classification Society of the platform. The project was conducted in three phases. The objective of the first phase was to develop a qualification procedure for the repair of relevant defects with adhesive patches and to demonstrate its feasibility with simple examples. Along phase two a Project Recommended Practice for Patch Repair was issued and more qualification tests were performed. Phase three consisted of a practical application of the Recommended Practice, accomplished within Petrobras by a repair at a ballast tank of the production semisubmersible platform P-20, in operation at Campos basin. The repair was accomplished by means of carbon fiber reinforcements within a vinylester matrix. This paper describes the P-20 repair case and the design of the bonded repair. A brief overview is presented of the installation of the repair, quality assurance issues and needs for future follow-up. The experimental and theoretical studies performed in support of the repair trial are briefly described. The successful repair trial demonstrates the utility of bonded repairs in managing the integrity of offshore steel structure assets.

Introduction

This paper shows the result of several years of research aimed to develop a cold repair technology for marine structures based on bonding of composite materials. The main objective was to minimize impact on the operational routine of a floating production platform, even if the repair takes place in a classified area. The work was done by means of a Joint Industrial Project (JIP) coordinated by Det Norske Veritas (DNV). The sponsors of the JIP were Petrobras, Petronas, Statoil, Norsk Hydro, Shell and ConocoPhillips. The role DNV plays on the usage of composite materials in offshore is well known, through the documentation it already produced on the subject. DNV is also the Classification Society of some production platforms in Brazil, making it easier to have the necesssary approval for a field trial of the technology.
Seismic Modeling Analysis and Characterization of a Gas Hydrate and Free Gas Mixed System in Green Canyon, Gulf of Mexico
Authors: Zhang Zijian , McConnell Daniel Russell
Published: July 2010

The Bottom Simulating Reflector (BSR) has been used extensively to interpret possible gas hydrate from seismic data. However, a BSR is not found in the Green Canyon (GC) 955 of Gulf of Mexico, where gas hydrate deposits were predicted and confirmed through drilling. The stratigraphic facies where gas hydrates are indicated by Logging Wile Drilling (LWD) drilling in GC955 have a complex amplitude response of high negative and high positive amplitudes showing both continous and discontinous character with different modes of stacking and complexity, e. g. low positive over high negative, high positive over high negative, etc. Rock physics-based modeling, with basic parameters guided by the existing well data, are used to decipher the complex amplitude signatures to discriminate gas hydrate sands from gas prone sands.

Field data are reprocessed conventional 3-D seismic data. Three scientific wells provide the basic constraints for the rock physics-based seismic modeling. The rock-physics modeling suggest that high positive amplitude and moderate to high peak/trough ratio are associated with high concentrations of gas hydrate; high negative amplitude and low peak/trough ratio will be associated with a gassy zone or a gas zone with low concentrations of gas hydrate above. The output of this modeling to the 3-D seismic data that traverse the scientific and industry well control points (wells) is consistent with drilled results and reveals variations in the depth of gas hydrate sands and gassy sands suggesting that there are localized non-equilibrium environments within the gas hydrate stability zone. The agreement with the drilled data suggests that a new and useful seismic attribute can delineate gas hydrate filled sands.

Introduction

A major challenge in gas hydrate exploration is the mapping of the distribution and concentration of gas hydrate deposits. As a gas hydrate indicator, the BSR has been used extensively in seismic interpretation of gas hydrate (Shipley et al., 1979; Hyndman and Spence, 1992). A BSR is parallel to the seafloor reflector and has the opposite polarity. Recent studies suggest that BSR is caused by a sharp drop in compressional velocity in the underlying gas zone (Singh et al., 1993; Mackay et al., 1994; Zhang and McMechan, 2006). Numerous expeditions have shown that the presence of a BSR does not correlate to high concentrations of gas hydrate above the BSR (Lu and McMechan, 2002; Tréhu et al., 2003). Thus, it is necessary to investigate better methods to image high concentrations of gas hydrate with seismic data. This paper reports a successful example of the application of rock physics based modeling to derive a seismic attribute, that when applied to conventional 3-D seismic data, identifies high concentrations of gas hydrate in Pliestocene clastic deposits in the Gulf of Mexico.
Converting Existing LNG Carriers for Floating LNG Applications (FLNG, FSRU, FSO)
Authors: Franklin David , Reeve Henry , Hubbard Brad
Published: July 2010

Despite the recent economic downturn and reduced need for LNG, long-term demand will be strong and opportunities to convert existing LNG carriers (LNGC) into floating LNG plants are growing. Costs, schedules, and permitting challenges for onshore LNG production facilities have trended upward making it difficult for project developers to get financing. Cost reduction strategies across the LNG value chain have resulted in significant changes in LNG shipping. To increase fuel efficiency, LNGC capacity has doubled in the past 30 years, and propulsion technology has migrated from steam to high efficiency diesel and dual fuel engines. Smaller, less efficient LNGCs are being displaced by new ships and the owners of the older LNGCs are seeking new roles for their vessels. This paper explores the opportunities and challenges of converting existing LNGCs for Floating LNG Liquefaction FPSOs (FLNG), Floating Storage and Regasification Units (FSRU) and Floating Storage and Offloading Vessels (FSO) service.

The costs of onshore LNG terminals with storage facilities, protected jetty, and cargo transfer equipment have increased sharply whereas converting an LNGC for liquefaction, regasification or storage creates a self-contained LNG terminal that can reduce overall LNG terminal cost by 30% to 50% compared to onshore alternatives.

Converting LNGCs into floating LNG plants raises myriad design challenges when developing a project. Specific project requirements will lead LNG project developers to choose the appropriate LNGC for conversion. Below is a partial list of topics, taken from experience, that require engineering study. These will be discussed further in this paper.Delivery flow rate and composition requirementsProducts to be marketedProject location specificsGas pre-treatment or LNG processing requirementsAppropriate ship type and size from available vesselsLiquefaction or regasification technologiesEquipment space requirementsVessel motion impact on process and storageMooring and berthing systemsOffloading configuration and methodsFitness for service and life extension, Class requirementsRequired utilities and integration with ship systems
DeepStar Jules Verne Subsea Processing Road Map
Authors: Lowry Timothy , Ray Tony
Published: July 2010

This paper presents the technology development road map prepared for the DeepStar Jules Verne Subsea Processing Study. DeepStar, the study sponsor, is a joint industry technology development project focused on advancing technologies to deliver increased production and reserves for its member's deepwater assets.

The purpose of the Jules Verne Study was to:Evaluate the technical maturity of an all subsea processing development of a subsalt, high pressure, high temperature, black oil field in the Gulf of MexicoIdentify the gaps related to the all subsea processing developmentPrepare a program of projects (Road map) to close these gaps

Gaps for the following subsea systems were identified during the Jules Verne Study:Boosting (single phase liquid, gas compression, multiphase)Controls / Instrumentation (to identify technologies required for an all subsea processing development)Power Transmission / Distribution (high voltage umbilicals, connectors, penetrators, transformers, variable speed drives, circuit breakers, switchgear, etc…)Subsea Separation (gas-oil-water separation—including sand management and produced water treatment)

Other supporting systems were also evaluated, including, raw seawater injection systems and subsea chemical storage / injection systems.
Qualification of Dynamic Deep Water Power Cable
Authors: Slora Bjorn Roger , Karlsen Stian , Lund Sjur , Osborg Per-Arne , Heide Kristian
Published: July 2010

The exploration of new oil- and gas fields tends to go to deeper waters. Electrical power is mainly required for subsea processing equipment. In addition there is a growing demand for Direct Electrical Heating of pipelines, also in deeper waters. Consequently, there is a growing demand for dynamic deep water power cables in the offshore industry.

Hence, Nexans initiated a development programme to qualify a dynamic deep water power cable for 3000 m water depth in accordance to DNV-RP-A203.

Power cable conductors are made of pure Electrolytic Tough Pitch (ETP) copper due to its excellent conductivity. Due to its mechanical properties it is found imperative that the cable design relieves the copper stress in deep waters.

A double armoured three-phase power cable concept was selected for the qualification programme. An ingenious design, with special emphasis on controlling the lay-angles and radial displacement, has shown to be crucial in order to achieve the desired stress distribution in the cable and preventing mechanical over-loading of the copper conductors.

The electrical integrity of the manufactured prototype cable was intact after tensioning to 2040 kN, which corresponds to 13 000 m static water depth.

Careful examination and comparison of results from testing and cross sectional analysis has verified that the stress distribution in a dynamic deep water copper cable can be properly determined.

The study has documented, by cross section analysis and dynamic analysis, that the prototype cable will withstand the extreme loads and more than 300 years in operation at 3000 m water depth with good margins.

As the final step in the qualification programme a full scale flex test will be performed to verify that the cable is capable of withstanding the extreme and fatigue loads during a service life of 30 years.
SS - Gas Hydrate : Study for the Estimation of Seabed Stratum Deformation in Methane Hydrate Production
Authors: Ogisako Eiji , Nishio Shinya , Denda Atsushi , Oka Fusao , Kimoto Sayuri
Published: July 2010

The simulations and numerical analyses of triaxial compression tests on soil samples recovered from the East Nankai trough have been performed by the elasto-viscoplastic constitutive equation. And the numerical analyses of the laboratory model tests on ground deformation in methane hydrate production were carried out by finite element method. From the comparison with the experimental results it is proved that the simulations can express well the behavior of experiments and the numerical analysis results can well reproduce the deformation behavior of ground in the model tests.

Introduction

Methane hydrate is currently being eagerly examined as a next-generation energy resource in Japan to replace oil and natural gas. The Research Consortium for Methane Hydrate Resources in Japan was established to undertake research in accordance with Japan's Methane Hydrate Exploitation Program prepared by the Ministry of Economy, Trade and Industry. To produce methane gas from methane hydrate safely and without damaging the environment, it is necessary to address many wideranging environmental issues. One of them is to assess seabed deformation during methane gas production. In the above Consortium we are investigating the deformation of seabed ground which may occur due to the production of methane gas from methane hydrate.

Geotechnical properties of seabed ground have a significant effect on the deformation behavior. Soil samples were recovered from the East Nankai trough which is expected as one of the fields of natural resources of methane hydrate. We performed the soil index tests, consolidation tests and triaxial compression tests on these soil samples and estimated the geotechnical properties of soil samples based on the results of these laboratory tests. Then we identified the material parameters for the elasto-viscoplastic constitutive equation which can express the mechanical properties of the seabed ground and we performed simulations of triaxial compression tests on soil samples by this constitutive equation. Further we developed a simulator for the estimation of seabed ground deformation using the above constitutive equation. We carried out the laboratory model tests on ground deformation in methane hydrate production and we performed the numerical analyses of these model tests by this simulator.

Outline of Triaxial Compression Tests

The digging of wells was carried out in deep sea at the East Nankai Trough. We performed triaxial compression tests on core samples recovered from the Nankai Trough Well (Nishio et al., 2006). The triaxial compression tests were carried out in K0 consolidation undrained condition. The depth of core samples used in tests is 8.5-225.0m below the seabed surface. The samples used in the tests are mainly cohesive soil.
Large scale condition monitoring for a subsea gas compression system pilot
Authors: Eriksson Klas Goran , Staver Knut Ola
Published: July 2010

A pilot for a subsea 12,5 MW Gas compressor system is built, and will be operated in an onshore test pit environment for 2 years before being evaluated and deployed subsea. Several new components have been qualified during the pilot project, e.g. subsea UPS, subsea High Voltage Circuit Breakers, subsea Variable Speed Drives, Active Magnetic Bearing system and electric valve actuators. During these 2 years of pilot testing, a large number of parameters will be monitored and logged (in the order of 1 million data stored per second). After 2 years, there will be logged appr. 250 TByte of data. The intended use of this data is to obtain detailed knowledge on the behavior of the various components, to observe gradual degradation in performance over time, and for trouble-shooting and diagnostics in case of upsets. For the final subsea plant, the goal is to have a system for Condition Based Maintenance, based on the knowledge gained during the pilot testing. This paper describes the plant, the various data sources, the data network collecting the data, the storage system and the retrieval / visualization / analysis system.
Lessons Learned From Observing Walking of Pipelines with Lateral Buckles, Including New Driving Mechanisms and Updated Analysis Models
Authors: Bruton David A.S. , Carr Malcolm , Sinclair Forbes , MacRae Ian
Published: July 2010

Pipeline walking is a phenomenon that causes global axial movement of a whole pipeline. Pipeline walking has been observed on a number of pipelines to date and if left uncontrolled can lead to potential failures at connections or risers.

Designing to control or mitigate pipeline walking can result in significant changes to field layouts and high installation costs associated with pipeline anchors, which have been installed on a number of recent developments. It is therefore essential to be able to assess whether walking is a potential issue early in the design process.

Walking is a stepwise ratcheting mechanism that occurs during changes in operating conditions, particularly during shutdown and restart operations. A number of contributory mechanisms are known to cause pipeline walking:Sustained tension, applied to the end of a pipeline by a steel catenary riser (SCR);Seabed slopes, along the pipe length, defined by route bathymetry;Thermal transients, defined by changes in fluid temperature and thermal loading during shutdown and restart operations;Multiphase flow behavior during shutdown and restart operations.

This last multiphase flow mechanism has only recently been identified from observation and measurement of operating systems and is not addressed by previously published analytic pipeline walking models developed by the SAFEBUCK JIP, published at OTC in 2006[1]. This fourth mechanism is described along with a discussion on the impact of multiphase flow on pipeline walking, axial friction response, anchor loading and route curve stability. A new analytic modeli is presented to assess pipeline-walking rates due to this behavior.

This paper also illustrates pipeline-anchoring solutions that have been employed to control pipeline walking on a number of deepwater developments and discusses the issues with these control methods, including the increased potential for route-curve pullout. The paper also investigates the complex interaction between pipeline walking and lateral buckling. It is known that lateral buckles along a pipeline can significantly influence both pipeline walking and end expansion predictions. The complex cyclic interaction is explained and methods for predicting the cyclic response either analytically, or using FEA techniques, are described. i Errata - This revision includes updates to equation 11.
Bottom Current Measurements at GoM Furrows for the Cascade and Chinook Fields Development
Authors: Lima Jose Antonio , Ribeiro Eric Oliveira , Daniel Jeremiah , Ivanov Leonid I.
Published: July 2010

This paper presents near-bottom current profile measurements in furrows located east of the Sigsbee Escarpment in the Cascade-Chinook field development flowline route from the facilites to the Chinook manifold in the Walker Ridge region of the Gulf of Mexico in water depths greater than 2500 meters. These furrows are deep channels aligned with the southwestward direction and in a variety of configurations with typical dimensions of 5 to 10 meters depth and 15 to 50 meters width. The measurement systems were custom designed bottom frames with acoustic current profilers and turbidity sensors deployed by Remotely Operated Vehicle (ROV) to accurately position the frames in predetermined positions inside the furrows. An innovative approach was developed to address cost effectively the technical challenge of the scheduled regular 4-month data recovery. To reduce costs, it was elected to deploy an acoustic modem from a vessel to download data from the subsea frames in lieu of recovering and redeploying the frames with the use of an ROV.

In general the Sigsbee Escarpment region experiences a complex deep water flow regime not completely evaluated or understood as yet. The steep gradients of the continental slope act as a wave guide for many flows associated with conservation of potential vorticity such as the Topographic Rossby Waves (TRW). The propogation of these waves and their flow affects the bottom currents in the furrows and on the sea floor. Spectral analysis of the bottom current measurements indicated a 12-day coherence peak that may be associated with TRWs. Speed values above 0.30 m/s were measured at the first bottom bin and the direction of the flow was most frequently aligned with the furrow's main axis.

Introduction

The production facilites of Petrobras America Inc. (PAI) Cascade and Chinook fields in Walker Ridge Block 249 and adjacent blocks are close to the base of the Sigsbee Escarpment. There is limited knowledge of the currents at the site in this complex bed form. PAI launched a rigourous current measurement program at the site which included measurement of current in the furrows, to develop an appropriate current profile design criteria for the project. This paper provides the preliminary data analysis of measurements taken over a 12 month period by PAI Contracor, the Woods Hole Group (WHG).

Figure 1 provides a general view of the eastern Sigsbee Escarpment and furrows fields on the vicinity of Cascade and Chinook fields, located on Walker Ridge area.
Demonstrating the Feasibility of Steel Catenary Risers from a Cylindrical FPSO in Harsh Deepwater Locations
Authors: Aarsnas Jan V. , Major Fredrik , Rooney Phelim , Muren Jan
Published: July 2010

The cylindrical FPSO is now in operation at three offshore oilfields, on in Brazil and two in the UK Central North Sea. It is furthermore selected for a field development in the harsh and sub-arctic Norwegian Barents Sea. Full scale monitoring of motions on units in operation has verified predictions, confirming very favorable motions when compared to shipshape FPSOs and even semi submersibles.

In 2009, a study was awarded by a major oil company to investigate the feasibility of applying Steel Catenary Risers (SCR) with a cylindrical FPSO at a location with deep water and very harsh environment. Results from the initial analysis proved feasibility and associated model testing has allowed calibration of first order and second order analysis methods and particularily have lead to a better understanding of second order and heave coupled pitch motion effects.

Adaptation of the cyclindrical hull to improve its characteristics as a host platform for steel catenary risers has been the incentive for the case study outlined in this paper. Platform and riser optimisation should be field specific, but the results presented for a very harsh environment, demonstrate the feasibility of steel catenary risers with a cylindrical FPSO at any location, worldwide.

In this paper, the focus is on demonstrating how a cylindrical FPSO/SCR design spiral can progress towards meeting the challenges of a harsh environment with competitive hull/riser combinations.

Introduction

The cyclindrical FPSO/SCR challenge is to provide an SCR hang-off location with motions, as follows, even in very harsh environments.The maximum downwards vertical velocity in 100-year design conditions should be less than 2,4 m/s (1,9m/s in 100 year conditions is achieved)The long term distribution of all motions at the riser hang-off shall provide a robust SCR fatigue life (achieved with low amplitude heave RAO within Tp range with high % occurrence)Angular motion should stay within a range of +/- 25 degrees at hang-off (achieved 18,1 degres)Horizontal offsets envelope within 2,5% of waterdepth in 100 year conditions with intact mooring (achieved 2,3%)

A cylindrical FPSO with SCR hang-off in a moonpool is demonstrated to meet the above criteria with margins, even for very harsh environments. The Cylindrical FPSO is arranged so that the SCR hang-off is located very close to the centre of the FPSO, within a moonpool, and thus the predominantly heave induced vertical motion at the riser hang-off meets SCR hang-off motion targets. Mooring systems are developed to meet the offset criteria.

The case study responses are reported for a 16" gas export riser, based on API standard seamless pipe dimensions with 5 mm corrosion protection coating, resulting in an "OD/weight submerged" ratio with 148 kg/m3 contents of 3,0 m2/tonne. Equivalent 123/4" and 103/4" production SCRs with contents 800 kg/m3 and high insulation are outlined for benchmarking.
The Medgaz Ultra Deep Water Pipeline Project
Authors: Chaudhuri Jay , Pigliapoco Mauro , Pulici Massimo
Published: July 2010

Recent completion of the marine pipeline linking Algeria and Spain across the Mediterranean Sea, with a 24-inch pipeline, as part of the Medgaz Gas Transmission project, successfully overcame the challenges of 2,155 metres water depths, deep water cable crossings and sea bed post trenching activities. This paper summarizes the various key design considerations addressed to meet the demanding requirements of the ultra deep Medgaz pipeline together with the engineering challenges met by Saipem in planning and executing the laying of the 24-in. gas pipeline in the Mediterranean Sea ultra deep water.

Design issues discussed include route optimization, efforts in relation to mitigating geohazards and challenging seabed topography characterising both Algerian and Spanish continental slopes. The intrinsic difficulties in performing intervention works in ultra deepwater, stimulated the application of advanced analysis methodologies for the assessment of in-service buckling and long term freespan fatigue. The installation of the Medgaz marine pipeline presented numerous difficulties which were of more complex nature than for the normal laying of a trunk line. Crossing of the Alboran Sea (the particular area of the Mediterranean Sea), (see Fig. 1) with a 24-inch pipeline that reached a depth of 2,155 metres was, without doubt, the most complex part of the entire works, involving two large semi submersible pipelay vessels: Castoro Sei and the Saipem 7000. The paper presents an overview of the main aspects of pipelay technology facing long trunk lines in ever great water depths and outlines the many engineering challenges faced as well as the solutions adopted that contributed to an effective development in pipelay technology. The presentation reviews also the post-lay intervention work using the Beluga deepwater trencher, the Innovator Remotely Operated Vehicle guiding ultra deep water laying and crossing of five existing seabed cable. Resolution of the many technical problems faced during the execution of the Medgaz Marine Pipeline project has proven the soundness of the engineering solutions adopted for the implementation of this ultra deep water pipelay project.

Introduction

The pre-commissioning of the Medgaz pipeline, one of the most important projects in the subsea deepwater pipeline gas transport sector ever implemented in the world for its complexity and technological content, was successfully completed in March 2009, in compliance with the target schedule (Ref. 1).
Intermediate Fluid Vaporizers for LNG Regasification Vessels (SRVs) and FSRUs
Authors: Madsen Per Helge Sandaroe , Karsten Dag , Strande Reidar
Published: July 2010

This paper describes two different LNG Re-gasification systems with intermediate medium.

Steam heated system using Water/Glycol as intermediate are delivered to two SRV's dedicated for Massachusetts area in United States. These ship systems are not yet started, so only the delivered technology is described.

Seawater heated system using propane as intermediate medium is delivered for two FSRU's. One vessel is dedicated for Guanabara Bay, Rio de Janeiro and one for Dubai. On the Dubai vessel, Re-gasification system is not yet started. The system for Guanabara Bay was started successfully in September 2009. The delivered technology and operational experiences are described for this system. In addition, possible improvements for future projects are presented.

Introduction

There is firm demand for new LNG import projects in the world, particularly from developing economies. In the past, LNG has been imported to land based terminals, where LNG has been pressurized and re-gassed. Due to the fast growing need for LNG around the world, cheaper and more fast track solutions for supplying LNG has been developed during last decade. Instead of building the Re-gasification terminals with storage and Re-gasification utility on shore, the Re-gasification equipment has been put onboard LNG carriers, and high pressure gas is delivered to shore from the ship either via a floating buoy and submerged pipeline system from offshore location, or via loading arms on a jetty. In general, there are two types of Re-gasification vessels.

Shuttle and Re-gasification Vessels (SRV's) and Floating Storage and Re-gasification units (FSRU's)

The advantage with SRV's and FSRU's compared to on shore terminals are that they are flexible and have a short time from investment decision to start up.

Therefore, they open a ‘fast-track’ way of opening the energy market to natural gas, thus increasing diversity of supply, reducing costs and introducing environmental benefits.
The Kvitebjorn Gas Pipeline Repair
Authors: Gjertveit Erling , Berge Jan Olav , Opheim Birgit S.
Published: July 2010

On the 1st of November 2007 during a routine inspection, severe anchor damage was discovered on the 30?? Kvitebjørn rich gas pipeline, about 10 km from the platform at 210 m water depth. The damage constituted a localised dent and a 17deg buckle, but no leakage.

Since 1987 Statoil on behalf of the different pipeline transportation licences, has invested time and money into building up an effective repair contingency for the pipeline network from the Norwegian Continental shelf, in particular the large gas export pipelines.

The contingency repair method for the Kvitebjørn pipeline is based upon the use of two Morgrip couplings and a spool to be installed with remotely operated H-frames and a purpose build Coupling Installation Frame (CIF), constituting vital parts of the total Pipeline Repair System. The couplings were produced and tested back in 2005.

This paper will cover the initial damage description, the repair preparations, the actual remote repair methodology and lessons learned. The Kvitebjørn incident has shown how important it is to be prepared and it can be termed as a real baptism for the company's pipeline repair preparedness.

The 27th of January 2009, one year and three months after the damage discovery, the repair was successfully completed and gas export from the Visund and Kvitebjørn platforms resumed.

Kvitebjørn pipeline system

Kvitebjørn is a medium size offshore gas and condensate field located in the Norwegian sector of the North Sea about 140 km vest of Bergen on the vest coast of Norway, see figure 1. A 30?? gas and condensate pipeline carries the partly processed product to the Kvitebjørn/Troll processing plant onshore at Kolsnes just outside Bergen.

A 20?? gas pipeline from another oil and gas field, Visund, is also tied into the Kvitebjørn gas pipeline via a subsea T-connection about two kms downstream the Kvitebjørn platform.
SS: New API Codes: Updates, New Suite of Standards - API Bulletin 2HINS - Guidance for Post-hurricane Structural Inspection of Offshore Structures
Authors: Puskar Frank , Spong Robert
Published: July 2010

Timely and cost effective inspection of offshore structures following a hurricane is critical in order to safely re-man the facilities and bring production back on-line. Recent hurricanes Ivan, Rita, Katrina and Ike in the Gulf of Mexico (GoM) resulted in thousands of above and below water structural inspections of offshore structures to determine if they sustained damage. Several of the API Recommended Practices (RPs) for offshore structures provide guidance for such " special?? inspections, but the guidance is limited and general in nature. API Bulletin 2HINS (2HINS, short for Hurricane INSpection) complements those publications and provides additional guidance specific to structural inspection following hurricanes. The document is applicable to permanent fixed and floating structures in the Gulf of Mexico.

Background

Regular structural inspections are a part of the in-service operating procedure for all offshore structures. The API RPs for the different types of fixed and floating structures provide guidance to develop In-Service Inspection Plans (ISIPs) to meet this need. These documents also typically identify the need for " special?? inspections following major events such as extreme storms like a hurricane or an accident like a severe collision. The goal of these special inspections is to determine if a structure sustained damage that affects the safety of personnel working on the structure, the primary structural integrity of the asset and its ability to perform the purpose for which it was intended. However, within these documents the guidance for special inspections is limited and generally up to the discretion of the owner or regulatory authority, particularly where and what to inspect.

Recent experience in the Gulf of Mexico has shown many structures exposed to hurricane level winds did not sustain damage [Energo 2006, 2007 & 2010]. As a result some structures did not require inspection. Alternative methods such as comparisons of the hurricane conditions at a site to the structure's environmental design conditions can be used on a case-by-case basis to provide adequate basis and justification when inspections on a structure are needed or not needed, especially below water inspections. The use of engineering assessments in lieu of an inspection is particularly useful for deep water fixed structures or floating structure where below water inspections, or internal hull inspections for floating structures, can be dangerous, time consuming and costly.
Taking the gas lift valves to a new level of reliability
Authors: Carlsen Jorn Andre , Stokka Øyvind , Kleppa Erling
Published: July 2010

Gas lift valves are an integral part of the tubing in gas lifted wells. Many operators use tubing with premium threads for these wells. Additional safety equipment, including the packer and the downhole safety valve, has been subjected to a program intended to prove its capabilities as a safety device. This is not the case with standard gas lift valves, developed and delivered according to the governing standard, ISO 17078-2. On the contrary, this standard states that the valves are only intended to be a flow check and not a pressure safety device. This paper discusses the development of a new validation standard, where the intention is to prove the equipment's safety capacity, as well as new equipment developed to meet these challenges.

Introduction

Most operating companies design their wells according to external or internal regulations with respect to safety equipment and safety levels. Each component needs to meet material standards and specific equipment standards. The standards will also describe production requirements as well as acceptance testing procedures for the equipment in question. New equipment typically has to be qualified to a certain validation procedure described in a standard issued by an external standards organization and often to additional internal company requirements.

Barrier Philosophy

The safety philosophy of preventing uncontrolled release of hydrocarbons is often referred to as barrier philosophy. The barrier philosophy for a given well typically depends on region, nationality and operating company. The Norsok D-10 is an example of a standard describing elements preventing hydrocarbon or pressure release to the atmosphere and it defines well barriers as; " Well barriers are envelopes of one or several dependent well barrier elements preventing fluids or gases from flowing unintentionally from the formation, into another formation or to surface. The well barrier(s) shall be defined prior to commencement of an activity or operation by description of the required well barrier elements to be in place and specific acceptance criteria.??
SS: Metocean: The Gulf of Mexico Current Simulation - A 32-year Run of 1/12o HYCOM
Authors: Wang Wensu , Esenkov Oleg E.
Published: July 2010

Drilling and production operations in the deepwater regions of the Gulf of Mexico can be impacted by strong currents from the Loop Current and its associated Eddies (LCE). The position of the Loop Current is variable as is eddy propagation across the Gulf. Consequently the specification of design currents for locations in the deepwater Gulf requires extensive knowledge of the LCE system.

An improved 1/12o HYbrid Coordinate Ocean Model (HYCOM) of the Gulf of Mexico was run for a 32-year period to simulate ocean currents in the Gulf by implementing a "Hybrid Boundary Condition" that combines original and high-inflow open boundary conditions. The improved model results show a realistic Loop Current penetration, eddy path variability and other eddy statistics. Eddy current extremes compare well with the best existing database in the U. S. lease area. The currents from the 32-year model run broaden our knowledge base of the LCE system and provide a database of current conditions for design of structures in the Gulf of Mexico. Bottom currents near the Sigsbee Escarpment were also examined. The results show that characteristics of these bottom current events match those of observed currents, but the magnitudes of the modeled current events are lower than the observations which is most likely due to a lower vertical model resolution near the bottom.

1. Introduction

In the deepwater region of the Gulf of Mexico, LCE is a dominant feature which produces high currents that can adversely impact exploration and production activities. At times, the Loop Current flows almost directly from the Yucatan Strait to the Florida Strait. Over time the Loop Current grows and extends further into the Gulf, and then instabilities in the Loop lead to a "pinching off" of eddy as shown in Figure 1. The detached eddy will slowly propagate west until it finally dissipates. The process may take over a year.

The high currents associated with the LCE can be as high as 2-3 m/s at the surface and they can penetrate into the water column to several hundreds meters below the water surface. LCE currents can be greater than hurricane generated currents as shown in Figure 2 which presents current vertical profiles generated by LCE, winter storms, and hurricanes (API, 2009). The high currents increase loads significantly on offshore structures, including floating hulls, mooring lines, and risers.
SS: Fiber Moorings, Recent Experiences and Research: Analysis, Design and Installation of Polyester Rope Mooring Systems in Deep Water
Authors: De Andrade Omar P. , Duggal Arun S.
Published: July 2010

The purpose of this paper is to describe the authors' recent experience with the analysis, design, and installation of polyester rope mooring systems for deep water applications. Among the latest research activities, this article describes a series of full-scale tests performed on polyester rope provided for several spread moored systems offshore Brazil and West Africa. One of the main purposes of the performed tests was to determine non-linear stiffness characteristics of the rope; but other parameters used in the design and optimization of the polyester rope mooring system were also investigated.

Introduction

The past decade has seen a steady increase in the number of polyester rope deep-water mooring system for oil and gas exploration, especially floating production facilities. Brazil has always been in the frontier of the application of synthetic mooring ropes. Industry forecasts point to a strong increase in the number of such systems, considering the latest deepwater discoveries made offshore Brazil. Due to the past and present history of success in the use of polyester rope for the mooring of deep water floating system offshore Brazil, it is a general consensus that this trend will continue into the future and expand to other producing regions such as The Gulf of Mexico and West Africa as it can already be observed.

There are many obvious advantages in using polyester ropes on deep water mooring systems. We could mention a few of them such as: lighter weight, desirable elastic characteristics and superb fatigue performance; on the other hand when engineering and installing such a system there are specific issues to be appropriately dealt with by the designer and the installation personnel. This paper will discuss some of the peculiarities associated to the design; analysis and deployment of polyester rope mooring system for deep water applications.

The main topic of discussion in this article is a practical way to model the elastic stiffness of polyester mooring ropes in order to have a simple and reliable model that produces reasonably conservative extreme mooring loads and vessel-offsets. Such numeric model describing the elastic behavior of the polyester ropes have a significant impact on mooring system for floating facilities for deep water applications, with a specific application to the mooring of FPSO's.

Typical Polyester Rope Mooring System for Deep Water FPSO Applications

Fig. 1 depicts a typical deep water FPSO spread moor system. Each anchor leg is constituted by two segments of chain, one located at the bottom and the second close to the surface; joined by a single or multiple segments of polyester rope. In case of the mooring system shown on Fig. 1 we can see three (3) segments of polyester rope joined by two (2) short segments of chain.
SS: Fiber Moorings, Recent Experiences and Research: Fiber Rope Tether Manufacturing - Current Best Practice and a vision for the Future
Authors: Rowley David S. , Leitte Sergio
Published: July 2010

Polyester Mooring Tethers are gaining wide acceptance in the Gulf of Mexico, Brazil and other areas of deepwater mooring operations. This paper looks at current rope manufacturing, developments in splicing technology, length accuracy measurements systems, rope manufacturing length and breaking strength limitations, and developments in synthetic polymer raw materials.

Current areas of deepwater rope research and development include improvements in jacket cut resistance, improved termination designs between rope and rope or rope and chain or wire, higher integrity sand barriers and stiffer materials for next generation mooring lines at ultra-deepwater depths. These developments are necessary to allow the deployment of fiber rope moorings in harsh environments such as the Arctic, into ultra-deepwaters and conversely into shallower water applications, and to embrace alternative deepwater installation techniques, such as pre-lay on the sea bed.

In recognition of the need to give naval architects and installation contractors' more options and ideas to develop alternative, cheaper and quicker methods of installing mooring systems, the future for Fiber Rope Tethers is reviewed. Of particular importance is the need for longer, stronger, lighter and more robust Fiber Rope tethers, composite rust free lightweight connectors to complement the rope's characteristics, installation using low cost anchor handling vessels and rental deployment systems, pre-laid moorings deployed on the seabed months before hook-up, and better ways of bedding in creep and use of lower pre-tensioning loads in mooring ropes.

Introduction

Polyester rope mooring tethers are gaining wider acceptance in deepwater mooring operations. The benefits of polyester rope moorings are compelling: lighter, easier to handle and with excellent mechanical properties to withstand the loads and elasticity demands of deepwater mooring.

As mooring lines move to greater water depths, and further offshore, however, the engineering integrity of the mooring rope and its splice are critical to effective station-keeping. With improvements in anchoring systems design and chain quality, the focus is now on the mooring rope, and its connectors, to deliver the mechanical performance needed for ultra-deepwater moorings.

Splicing Technology

Polyester mooring ropes are a key component of deepwater and ultra-deepwater mooring systems. The mooring line is made up of one or more lengths of rope joined together by connectors. The longer the rope, the greater the number of connectors needed, including rope-to-rope, rope-to-chain and rope-to-wire connectors.