bluuebunny/crossref_metadata_2025_split huggingface dataset:
Jet-Induced Trenching Operations: Mechanisms Involved
Authors: Vanden Berghe Jean-Francois , Capart Herve , Su Jason 
Published: October 2008

Abstract
The paper examines the response of sandy sea beds undergoing trenching by steadily moving underwater jets as mounted on jet trenching machines.
While much can be learned from trencher operation data, visualization of the sediment motion is difficult in field conditions.
This motivates the use of small-scale laboratory experiments. The focus is to examine the trenching process and posttrenched sand bed. The processes observed include erosion and entrainment by the jet-induced longitudinal current, infill due to the breaching of the trench walls, and overspill resulting from lateral escape of the turbulent flow out of the trench. These processes are expected to act as well in the field where they may control burial depth and sediment loss from the trench.
The experimental observation were used developed a model based on the gravity- and jet-driven turbidity currents theory.
This model describes the flow of a turbulent layer of water and suspended sand along the sea bottom. It incorporates the following physical processes:entrainment of ambient water and sediment particles into the current;damping of turbulence by stratification associated with the sediment suspension;interaction of the current with sloping topography.
Combined with a breaching model simulating the lateral infill of the trench, this model is able to assess the trench depth and the likely shape of the trench based on the tool travel rate, pump pressure and soil type.
The results of the above work will permit a better understanding of the mechanisms controlling the performances of pipeline burial operations by jet trenching. The proposed model will help the engineers in assessing the performance of the jet trenching machines.

Introduction
During the last years, the offshore industry has used more and more often the jetting power to create trench in the seabed.
The objective of these operations was generally to bury cables or pipelines under a protective layer of sand.
There exists different configuration of these tools. It could be a high power jet moving above the seabed or a ROV (remotely operated vehicles) equipped with jetting swords liquefying the seabed. The ‘product’, cable or pipeline, is first simply laid onto the sea bottom. The vehicle then uses the jetting system to inject high-speed water into the sand bed (see Figure 1). The jets scour a temporary trench, travelling with the vehicle, which allows the cable or pipeline to descend into the sea bed before being buried under the re-depositing sand further downstream of the trencher.
Interaction Model for Steel Compliant Riser on Soft Seabed
Authors: Aubeny Charles Paul , Biscontin Giovanna 
Published: October 2008

Abstract
The use of catenary steel compliant riser (SCR) systems has increased as hydrocarbon production has progressively moved further offshore and into deeper waters. The issue of fatigue damage caused by cyclic interaction of the riser with the seabed has gained prominence with the widespread use and lengthening of the spans. The problem involves a number of complex factors including trench configuration, non-linear soil stiffness, breakaway of the riser from the seafloor, and degradation of soil resistance during cyclic loading. This paper presents a soil-interaction model capable of modelling these complexities, using input parameters that can be obtained with reasonable expenditure. Model simulations for typical offshore soft soil conditions indicate that the model is capable of realistic predictions of cyclic bending moments. Degradation of soil resistance has a major effect on cyclic bending moment, particularly when uplift motions at the riser touchdown point are large.

Introduction
The introduction of these compliant floating systems for offshore hydrocarbon production has led to the development of new designs for the riser pipes, with the catenary steel compliant riser (SCR) often being system of choice. Fatigue stresses associated with extreme storms, vessel movements, and vortex-induced vibrations are critical to SCR performance. The zone at which the SCR contacts the seabed, the touchdown zone (Fig. 1), often proves to be a spot where bending stresses are largest and therefore a critical location for fatigue (Bridge et al., 2003; Bridge et al., 2004). Analyses typically show fatigue damage to be sensitive to seafloor stiffness, which at present cannot be estimated with a great deal of reliability. It should be noted that the vertical scale in Figure 1 is exaggerated for illustrative purposes and typically ratio of trench depth to trench length is small (say 1%) so the problem may be reasonably treated within the framework of a small deflection beam analysis. However, uplift at the touchdown point (TDP) is sufficiently large that the end moment associated with axial tension in the riser should be considered in the analysis.
All Electric Subsea Tree System Development
Authors: Halvorsen Vidar Sten , Koren Eivind 
Published: October 2008

Abstract
This paper will present work that has been completed over the last several years to develop an all electric Subsea control system ending with an all electric tree. The work is now conducted in a joint StatoilHydro-FMC Technologies R&D program; Subsea MMX.
All electric systems provide CAPEX savings from reduced umbilical, OPEX savings from eliminating fluid consumption, and environmental benefits from eliminating emissions of hydraulic fluids.
The basis system discussed in this paper is currently in use for Subsea Choke Control and Manifold Valve Control, and it won the OTC Technology Award in 2006. This system is now further refined for application on safety critical applications like Christmas Tree valves with improved redundancy and fault tolerance in order to meet requirements for safety and availability.
This paper will discuss the analytical development and review of the safety critical electric tree system, as well as describe the technical solutions developed. The development have taken into account the standardisation efforts by the Subsea industry regarding control system interfaces and are compatible with the IWIS and SIIS RP standards.

Introduction
The Electric Tree system was derived from the already field proven All Electric System that so far have been controlling choke and manifold valves on the StatoilHydro operated fields Statfjord and Norne.
North Sea Offshore Cathodic Protection
Authors: Mackay W.B. 
Published: October 2008

1. Abstract:
General principles of cathodic protection are given. Specific design for fixed structures, mobile rigs and sub-sea pipelines in the North Sea are discussed.
The paper compares test results obtained and parameters used in the North Sea with results and design figures obtained and used in other regions and circumstances. It is concluded that North Sea conditions demand specific cathodic protection considerations.

2. Introduction:
In the North Sea the offshore structures are mainly fixed platforms, sub-sea pipelines and mobile rigs with a few mooring buoys and storage tanks. The cathodic protection of structures designed for the North $ea is _ almost totally by sacrificial anodes with impressed current systems playing little part. Impressed current systems, where fitted, have suffered three major defects:Have not been of rugged enough construction to stand up to physical conditions.Have not had sufficient maintenance and supervision given to them in use.Have not been designed to give adequate current distribution and polarization protection.

3. Cathodic Protection by Sacrificial Anodes

3.1 General Requirements :
This requirement is that the anodes will polarize the steel to a point where the steel will not corrode (or corrode only at an acceptable rate) for an acceptable period of time at an acceptable cost.

3.2 Anode Material:
Bare or coated steel structures in sea water may be protected with aluminums or zinc anodes. Sub-sea pipelines which rest in the sea bed should be protected with zinc as at present aluminums alloys have not been developed to the stage where they can be guaranteed to work satisfactorily in a mud environment.
It must be noted that the composition of the aluminum or zinc anode material is critical in order to give a gored capacity and so that physical disintegration or passivity will not occur. Because of the critical nature of the alloying elements and their dispersion within the material rigid quality control is required during manufacture. In order to meet anode specifications high grade primary metal must be used.
It should be remembered that unit weight of aluminums anode alloy gives out approximately three and a half times the ampere hours of the unit weight of zinc anode material. In order for the materials to equate commercially then tile zinc anode needs to be three and a half times as cheap as the aluminum anode on a cost/unit weight basis.

3.3 Anode Potential:
Anode potential is the difference between the potential of the anode and the specified reference or half cell. In marine cathodic protection the half cells used are the silver/ silver chloride half cell, the copper/copper sulphate half cell and the zinc reference electrode.
The significance of anode potential is that the higher the potential the greater the anode output with the associated benefits for this. In addition the higher the potential the quicker the rate of polarization of the steel to which the anode is attached.
Detailed Geotechnical Investigation Around In-Place Mat Foundation Including T-Bar and CPT Comparisons
Authors: Audibert Jean , Neubecker Steve , Stewart William Pratt 
Published: October 2008

Abstract
The Maleo Producer is a converted Bethlehem JU250 mat-supported jack-up unit, which was installed in July 2006, on a soft, normally consolidated clay foundation some 40 km (25 mi) south east of Madura Island and approximately 25 km (16 mi) south of Puteran Island, offshore Indonesia. The unit was connected to a wellhead platform, and gas production began in late 2006. An initial site investigation performed in 2003 indicated that the undisturbed soil conditions consisted of a soft normally consolidated clay profile, with an undrained shear strength of 2 kPa (40 psf) at the mudline, linearly increasing with depth at a rate of 1.22 kPa/m (7.83 psf/ft) down to a depth of around 14 m (46 ft), below which a slightly stronger clay was encountered. The issue of on-bottom stability of the unit and its resistance to overturning were questioned by the classification society (ABS) as part of the reclassification of the rig. The behavior of the foundation under extreme storm loads and seismic events could be more reliably predicted by the designer, and more readily accepted by ABS, if new soil data were available. Two types of soil data were required 1) soil data for foundation design and re-analysis under and around the mat and 2) soil data for seismic analysis of the installation. This paper describes the extensive site characterization undertaken to prove the stability of the Maleo Producer facility during both the design storm and seismic events.

Introduction
The Maleo Field is located in Indonesian waters about 40 km (25 mi) south east of Madura Island and approximately 25 km (16 mi) south of Puteran Island (Figure 1), within the Madura Offshore Production Sharing Contract (PSC) area.
The Maleo Producer is a converted Bethlehem JU250 mat-supported jack-up unit (formerly the CD10) ABS Class Number 7900120. The unit was installed in July 2006, and was connected to a wellhead platform. Gas production began in late 2006 (Figure 2).

Description of the Installation
The installation is in approximately 57-m (187-feet) water depth. The hull is supported on three cylindrical steel legs, 3.66-m (12-ft) in outer diameter. The legs are supported on an "A" shaped mat (Figure 3) that rests on the seafloor. The mat is 64 m (210 ft) long, 52 m (170 ft) wide and 3-m (10-ft) thick. It has 0.6-m (2-ft) deep skirts (extensions of the mat side walls) that extend along all edges of the mat (around the outside mat edges, inside the slot at the aft end and around the inside edges of the 18 m × 33m (59 ft × 108 ft) cut-out within the three legs beneath the hull (Figure 3).
A 14-in (366-mm)-diameter gas export seafloor pipeline connects the installation (from the starboard side of the mat) to the 26-in. (660-mm) East Java seabed pipeline approximately 7 km (4.3 mi) to the south.
Details of the structure's geometry, preload history, and design load conditions were provided by Stewart Technology Associates (2006 a&b), as documented in Ooley and Stewart (2008).
LNG Terminal Expansions; Working Successfully Within a Live Plant
Authors: Tennison Dan 
Published: October 2008

Abstract
This paper is based on the lessons learned during the two recent expansions of the Southern LNG import terminal in Savannah GA. It shows how the Project Management team planned and executed the expansions, and particularly how the team interfaced with Operations.
Possible applications of the information provided in this paper is for LNG terminal owners and operators who seek to perform similar expansions within an operating terminal, or similar mid-stream operating facility (gas processing, etc.).
The paper concludes with 4 major findings that will benefit the reader:Project Management and Operations teams are significantly different in their goals, work practices, structure, culture, and scope, which affect expansion projects. Project engineers may lack operating experience and perspective, which can limit their ability to " Design for Operability??. Operations personnel can have less project management perspective, but are the true authorities on running the plant safely and efficiently. Leveraging both strengths is the key to a successful project.The greatest risk on the expansion project occurs at the Project - Operations interface. This interface is best managed through planned and structured communication systems (meetings, reviews, reports, golf), tailored for a mutual success.Contractor management is challenging when working within a live plant. Tie-ins, notices, permits, interference, slow downs, etc. must be planned for early, and thoroughly addressed in the contract.Commissioning and turnover of the expansion is crucial from the stand point of Operations interface. The phasing in of Operations personnel with Project personnel (training, spares, warranty work, lessons learned, and close out) must be thoroughly planned beforehand.
Three major technical contributions to the knowledge base for the LNG industry are:The Post-Project Lessons-Learned exercise this project confirmed the effectiveness of our communications management approach.The Contracting strategy for the EPC contract included key contractor responsibilities and specified expectations and communications responsibilities that mitigated interface risks.The Project Team acquisition, development and leadership methods used were highly projectized to produce a purpose-built project organization.

1. INTRODUCTION
Southern LNG owns and operates an LNG receiving terminal near Savannah GA. The terminal was built in the late 70s, operated for 3 years and was decommissioned for 18 years until being re-commissioned in 2000-2001. Shortly thereafter, the first expansion was planned. This expansion coincided with the initial years of operations of the newly reactivated plant, and had to be taken into account from a risk and scope standpoint. The project team worked closely with the Operations staff to plan and execute the expansion successfully. Lessons-learned from the first expansion has been applied to the subsequent expansion, now underway at Elba.
Imaging Downed Platforms
Authors: Taylor Michael , Davis Jonathan Peter , Lynch Richard Douglas , Philips Tom , Beck Richard D. , Burhke Mark  K. , Tomaszkiewicz Wojciech , Simpson Richard , Butcher Ron , Openshaw Graham 
Published: October 2008

Abstract
The Downed Platforms project deals with seven platforms containing 59 wells which were toppled during Hurricane Katrina in water depths ranging from 86 to 135 feet. Visibility at these depths is limited at best. A way to visualize the entire platform to aid in planning decommissioning activities was developed. This paper describes the various techniques used to image the platforms, including offshore field work, post processing, and analysis.
The technologies and techniques described in this paper could be applied to imaging of complex subsea structures, seabed surveys and hazard assessment, and processing of complex multibeam datasets.
This project employed new methods for acquiring sonar data which has conventionally been used for mapping the seafloor from a horizontal or near horizontal platform. The results in this paper will highlight the need to consider alternative methods of acquiring data and discuss the reality of deploying these methods in the field. Results from the project will be used to demonstrate the success of these methods.
This project delivered the highest quality datasets possible which removed significant uncertainty and allowed detailed planning to proceed. The paper will showcase a new method for acquiring detailed three-dimensional datasets, the benefits of deploying different imaging devices and highlight the importance of using available technology to minimize uncertainty.

Background
The 2005 hurricane season was the most active on record and hurricanes Katrina and Rita inflicted major damage to Gulf of Mexico (GoM) production facilities on the outer continental shelf (OCS). Seven platforms were completely destroyed in the Grand Isle 41/43/47 field, or " downed??. All platforms located in the Grand Isle (GI) and West Delta (WD) lease areas are in water depths from 86 to 135 feet. The locations were GI 40B, GI 40F, GI 41A, GI 47C, GI 48D, WD 69C, and WD 69K (Figure 1), which are all within 20 to 35 miles west of the centerline track of Hurricane Katrina.
Methodology to Establish the Fitness for Continued Service of a Damaged Export Pipeline in 1000 m of Water
Authors: Raghu Damodaran , Swanson Richard C. , Alexander Christopher Richard 
Published: October 2008

Abstract
Deepwater pipelines are critical arteries that transport gas and oil production from the Gulf of Mexico to onshore transportation hubs. The yearly hurricane season in the GoM has a serious impact on the reliability of this infrastructure, as evidenced by the severe damage experienced, and subsequent difficulty and delay returning to full service. The difficulty arises from the various challenges in damage, inspection and evaluation as well as the delay in analysis and procuring the repair hardware needed. Many of the damaged pipelines need extensive and time-consuming repairs depending on the severity and criticality. However, if sufficiently conservative and prudent analytical methodologies are used, many of the damaged lines can be inspected, analyzed and established to be fit for continued finite service. Employing a combination of repair and fitness for service analysis can effectively manage the risk of damaged deepwater lines, while in some cases, continuing operation.
In this paper, an approach is presented that can be used to analyze and establish the integrity of damaged lines. It reviews the various analysis methods available and integrates one or more of the methods to arrive at a unified approach. The approach is illustrated through an example of a 20" dented pipeline in 1000 m of water, where the fatigue life was estimated using FEA, simple dent fatigue equations and further validated using full scale testing. A decision tree that provides guidelines for deepwater pipeline damage evaluation and fitness for service is provided.

Introduction
The ability to reliably transport hydrocarbon products from the Gulf of Mexico outer continental shelf to refineries in the continental US is very critical to the continued supply of energy to the nation. The total hydrocarbon production, over 300 million STB of oil and 1100 million SCF gas constitute 30% of the US oil consumption and over 25% of the gas consumption1. In the Gulf of Mexico currently there are over 44,000 km of pipelines that transport oil and gas.
Over the last several years hurricanes, such as Rita and Katrina have had devastating effects on this pipeline infrastructure.
In many cases the damage has been severe enough to require extensive replacements. Operators of the pipelines are faced with the increased challenge of inspecting and quickly assessing the damage to establish appropriate repair methods, or in certain cases replacement. Owing to the complexity of deep-water pipeline infrastructure, viz. difficulty to access and inspect and the complex designs required to carry out repairs, operators have to develop relatively elaborate and detailed protocols for inspection, analysis and repair.
Marine Magnetotelluric (MMT) Data Interpretation in the Gulf of Mexico for Subsalt Imaging
Authors: Sandberg Stewart , Roper Tom , Campbell Tracy 
Published: October 2008

Abstract
A marine magnetotelluric (MMT) survey was performed to assist seismic and gravity methods in mapping the base of salt in a complex system in the Gulf of Mexico. For the salt complex investigated, 2D interpretation of MMT data provided an incorrect base of salt, when compared with well-derived data. When 3D inverse modeling was employed, not only the correct base of salt was determined, but additional detail of the subsurface was produced. Resistivity variation within the sedimentary host provides indication of lithologic variation that can be interpreted further. A preliminary correlation between low-resistivity zones and low velocity was also indicated. Separation of data-required subsurface resistivity of the model and resolution effects of the method, was also investigated.

Introduction
WesternGeco has an ongoing project to apply marine magnetotelluric, full-tensor gravity (FTG), and seismic interpretation to refine the base of allochthonous salt bodies in the Gulf of Mexico. The overall goal is to improve the resolution of seismic images of possible hydrocarbon-bearing sedimentary structures beneath the salt.
In this paper, we present some detail of the interpretation of a complex of salt bodies in the Garden Banks region of the Gulf. To map this salt, a total of 171 MMT seafloor stations were occupied in 2006, making it the largest MMT survey collected worldwide at that time.

The Marine Magnetotelluric (MMT) Method
Magnetotellurics (MT) is a natural-source, electromagnetic method of imaging structures in the subsurface. Natural variations in the earth's magnetic field induce electric currents (or telluric currents) under the earth's surface. Measurements of orthogonal components of the electric and magnetic fields at a receiver site constitute the data that are used to image the resistivity structure of the subsurface.
The MMT method generally refers to an MT survey in which the receiver sites are located at the seafloor beneath the seawater. The overlying seawater significantly changes the available signal strength at higher frequencies, and creates a current flow path above the receiver positions.

Approach and Previous Work
Electromagnetic investigations of the earth beneath the seafloor have a long history (Bannister, 1968 [active source]; Wannamaker et al., 1989; Heinson et al., 1993). Recently seafloor MT instruments have evolved to be capable of reliably measuring higher frequencies associated with structures shallower than the oceanic mantle and crust (Key and Constable, 2002).
Applying the MT method to mapping salt bodies for hydrocarbon exploration has been discussed in the literature. For example, Watts, et al. (2003) described an onshore example of how MT could be applied where the seismic method had difficulty because of velocity inversion associated with both salt and carbonate structures.