bluuebunny/crossref_metadata_2025_split huggingface dataset:
Global Analysis of the Terra Nova Riser System
Authors: Allen Sam , Kassner Chris 
Published: October 2008

Abstract
Flexible riser systems are critical for the use of floating production systems in harsh shallow water environments. The use of flexible risers in such environments is driven by large vessel offsets, large vessel motions, and harsh shallow water environmental conditions. Where turret disconnectability is required in ice-infested waters, the riser system must be able to accommodate not only the normal FPSO motions, but also the disconnection and freefall of the spider buoy from the FPSO, and the spider buoy motions in the disconnected position. The Terra Nova riser system is the first large capacity disconnectable riser system in the world and the systems successful design and installation have demonstrated the ability to utilize flexible pipe technology for this type of application.

Introduction
The Terra Nova field development is located in 94 meters of water off the East Coast of Newfoundland, Canada in the Grand Banks Offshore area. The region has a harsh environment with intense storms occurring frequently in winter and the presence of pack ice and icebergs.
Terra Nova is an FPSO development. The Terra Nova FPSO has an overall length of 292.2 meters (277.0 meters between perpendiculars) with a nominal crude oil storage capacity of 960,000 barrels. The first phase of field development utilizes four remote drill centers connected to 34.4 km of static flexible flowlines and umbilicals. Eleven dynamic risers and four dynamic umbilicals provide the link between the static pipelines and the FPSO. Considering future development, the entire riser system accommodates for 14 dynamic risers and 5 dynamic umbilicals.
The selection of a floating production design for Terra Nova, the seasonal presence of ice, and the possibility of an iceberg encroaching on the field introduced basic functional requirements for the field's development. These main requirements were the design/fabrication of an ice strengthened vessel and a facility capable of disconnecting from its risers and mooring chains;thus enabling the vessel to move off location to avoid a potential collision with an iceberg. Pursuant to these functional requirements and the overall design requirements, this paper details the challenges imposed on the global design of the Terra Nova riser system and its associated equipment. Furthermore, a synopsis of the riser installation in year 2000 is provided along with lessons learned from the design and installation of the Terra Novariser system.

Riser Configuration Selection
Three types of riser configurations were considered for the Terra Nova riser system. The first of these configurations was the Pliant Wave® (Fig. 1). The riser's wave configuration is shaped via a distributed buoyancy module section. Following this section the riser is anchored to the seabed via a tether that is connected to a swivel clamp on the riser and a gravity base on the seabed. The riser then descends to the seabed and ultimately is terminated at the flowline connection.
Protection Against Underscour
Authors: Posey Chesley J. 
Published: October 2008

ABSTRACT
This paper summarizes the results of several investigations of underscour, which can endanger offshore structures. Reproduction at model scale of an unusual pattern of scour first observed by divers led to improved understanding of the phenomenon, indicating the use of graded reverse filters for stopping erosion completely. Model tests, special severe erosion studies, and experience with offshore installations show how effective and economical protection can be obtained.

INRODUCTION
The foundations of offshore structures must be secure if catastrophic losses are to be avoided. Where such structures are built, the bed of the sea is likely to be sand or loosely compacted alluvial material. If the bottom level has remained constant, there must have been an equilibrium between the erosion and deposition of material occasionally moved by the velocities normally occurring there. The local velocities next to parts of a structure having circular or less well streamlined cross-section, in contact with or penetrating the bottom, must be more than double the average, and hence will have much greater capacity to move material Underscour is the inevitable result. Research dealing with scour at bridge 'piers and abutments might seem to provide a safe basis for estimating its depth, since in open waters the strong currents do not come from the same direction for long periods of time. Measurements made around a Padre Island offshore drilling platform which had become alarmingly unsteady, however, disclosed a type of erosion which was entirely different from what the bridge-pier analogy would predict (Ref. 1). The volume of material removed was many times greater, and it had disappeared in a comparatively short time. The present paper summarizes briefly the results of a number of investigations which have dealt with various phases of the problem.

TWO TYPES OF EROSION
The first type, which we shall call bridgepier type, is localized around the pile or shaft where it enters the sea bed. Approach velocities a pier-diameter or two above the bottom are higher than those close to the bottom. They cannot, therefore, curve out to go past the pier at as small a radius as the lower velocities can. This gives rise to a "horseshoe" vortex, a strong three-dimensional boundary-layer phenomenon, which erodes a hole next to the pier (Ref. 2). If the bed material is cohesionless the scour hole is on the sides and upstream nose of the pier, providing, of course, that the direction of the bottom current remains the same for a long enough time. The shape is an inverted cone with base diameter several times that of the pier (depending upon pier shape and roughness as well as other factors) and with side slopes equal to the submerged angle of repose of the material. Scour holes of more complicated shape are formed if the bed material is cohesive. This bridge pier type of erosion is easily reproduced at model scale, using gilsonite, coal, or ordinary sand. Where there are a number of pipes or piles not too close together, each one has its own scour hole (Ref .3)
Cost-Saving Solution for Offshore Piles in the Egyptian Mediterranean
Authors: Gilchrist J.M. , Wali I.M. , Ragab H.G. , El Ashmawi A.S. 
Published: October 2008

Abstract
Rosetta P1 is a fixed, steel offshore gas production platform situated in 63m of water some 80km north east of Alexandria in the Mediterranean Sea. The platform, which weighs around 3200tonnes, has four 54-inch diameter, 1.5-inch wall thickness tubular steel piled foundations, one located at each of the four jacket legs.
The foundation strata contain a very dense sand layer between 57.5 and 63.5m penetration, ideal for terminating the piles in. However, conventional API RP2A methods of pile design would have resulted in at least 3 of the 4 piles being driven to over 90m penetration to achieve the design capacity of 32MN. A solution evolved from two main aspects of design:State of the art soil mechanics provided justification to increase the limiting unit end bearing capacity to 15MN/m2 from the currently recommended API value of 12MN/m2.The introduction of a steel cruciform insert into the pile toe to bridge the gap between the lower coring pile capacity and the higher plugged pile capacity.
The solution enabled the piled foundations to be accepted and certified at 60m penetration and resulted in project budget savings of about USD 1.5 million.
This paper provides a detailed account of the solution and the resulting project benefits.

Introduction
The Rosetta offshore gas field lies in the Mediterranean Sea, offshore east of Alexandria, Egypt. Rashid Petroleum Company (Rashpetco), a joint venture between The Egyptian General Petroleum Corporation (EGPC), British Gas (the operator), Shell and Edison, is developing the field.
The Rosetta Gas Field Development Project comprises an offshore platform, an offshore pipeline, an onshore terminal and two onshore pipelines.
During the course of the offshore platform foundation design, it was determined, by conventional API RP2A methods, that the piles would be required to be driven to depths of over 90m to achieve the design capacity of 32MN (Fig. 1). However, soils data from the geotechnical survey and the results of various field tests performed at site revealed a dense, strong sand layer at approximately 60m, ideal for terminating the foundation piles. If any unnecessary conservatism in conventional design methods could be removed, considerable savings could be achieved. In an effort to optimise the design and save costs a detailed review of conventional design methods was launched.
The identification of certain limiting values defined by API RP2A were determined to be the most significant design constraint. Accounts provided by practitioners and researchers alike suggest that more recent advances in geotechnical testing tools and methods provide better quantitative assessments of soil behaviour and should allow the extension and application of these values in design. A discussion of empirical findings in recent practice and research, which led to the relaxation of conventional limiting values adopted in the Rosetta piled foundation design, are presented in this paper.
Seabed Borehole Mining: Why Not?
Authors: Abramov Grigori Greg 
Published: October 2008

Abstract
This Paper is dedicated to Borehole Mining (BHM), the method of remotely extracting rock material through boreholes by high-pressure water jets. The technology is based on in-situ jet cutting of rock mass, creating slurry, and delivering it to the surface.
Remote operation in this case scores significant advantages over traditional mining methodology, the most important of which are: total personnel safety, high mobility, minimal environmental impact, and low capital/operational cost. Since these advantages, such regions as the World's Offshore and Polar Zones become the most appropriate BHM's application areas.

Introduction
On-land developed, Borehole Mining is well known in the "Continental" engineering community. The recent BHM's list of successfully extracting minerals includes Coal, Uranium, Iron Ore, Titanium, Zirconium, Kimberlite, Bauxite and several more. This list also includes stimulation of water, oil and gas production. The depth of operation just exceeded 1 km. In addition to exploration, mining and stimulation, the array of BHM application also includes environmental and underground construction areas, river banks reinforcement and several more.
Despite widespread acceptance of the theory behind BHM, and its recent and verifiable track record in the field, few offshore specialists or professionals are aware of the explosive financial potential of Borehole Mining. Meanwhile, no known obstacles prevent application of BHM from the water surface. Owing to aggressively pursued standardization, the list of required equipment includes only a vessel or a floating platform, with a pump station and the Borehole Mining Tool. This paper is to introduce the "ground" Borehole Mining technique and experience and present the opportunity of BHM application from water surface.

BHM Equipment and Technology
Few innovations in mining science have been so universally sought as a viable method of remotely controlled, automated subterranean excavation - the extraction of deeply buried natural resources while personnel and controls remain safely above ground. After years of design, laboratory tests, field trials, and actual operations, that dream has been realized, and is known today as Borehole Mining.
Originally developed as a remote underground exploration and mining method, Borehole Mining (or BHM) soon found applications in related areas such as underground construction, environmental projects, abatement solutions, and more. The extension of exploitability presently under review is mineral extraction below the seabed.
The BHM method is based on in-situ water jet cutting of rock mass, creating a slurry and delivering it to the surface. In Fig. 1 the schematic of the method is presented. The borehole mining tool 1 is lowered into the borehole 2 and high pressure water 3 is pumped down. At the bottom part of the tool, one portion of that water comes out through the hydromonitor nozzle 4 in a shape of water jet 5 and cuts the material 6 creating slurry 7. The other portion of high pressure water then comes to the eductor 8, which produces a vacuum.
An Innovative Deepwater Geotechnical Tool
Authors: Bienvenu V. , Bessonart J. 
Published: October 2008

Abstract
The today's challenge for the Offshore Industry is the fields' development in deep and ultra-deep seas.
A new generation of geotechnical tools for soils identification is being developed for these water depths.
If tools as cone penetrometers have already been largely studied for deep seas, no static sampler has yet been planned. MARINE GEOSYSTEM, a new established French Geotechnical Consulting and Services Company, has patented a new concept of geotechnical static sampler, capable to work by water depths up to 6000 meters with a modular depth of investigation up to 30 meters below seabed.

Introduction
With the increasing need of reliable soil information in deeper seas, a high level of new technologies developments and methods of work is expected by the Offshore Industry.
In the field of deep geotechnical surveys, the existing tools are well identified and classified under two categories, (1) the in-situ measurement performed into the soil and (2) the sampling.
The measurements of the in-situ soil characteristics are mainly obtained thanks to a cone penetrometer. Other tests as the vane test or the seismic cone may also be performed. The penetrometer technology is widely used on the continental shelf but has also been developed for deep seas (mini-cone, coil tubing systems") [Meunier and al, 2000].
Existing sampling equipments have been conceived including gravity corer systems.
The tool planned by MARINE GEOSYSTEM, called STARFISH, is mainly developed to perform a static penetration into the soil at constant speed, to come back to sampling specifications applied on the continental shelf.

Existing tools
All of the existing samplers dedicated to water depths greater than 1000 meters, excepted traditional wireline methods used on the continental shelf, do utilize a dynamic impact to penetrate into the soil.
The Giant Corer CALYPSO has been developed by the IFRTP (French Institute of Research and Technology for Austral Territories) and is operated onboard the scientific vessel Marion-Dufresne. It is one of the most referenced corers and can be fitted up to 10 tons and 60 meters long. The results achieved by the international campaigns of IMAGES Program confirm the exceptional performances of the CALYPSO corer [IFRTP, Calypso documentation].
The STACOR is a large diameter gravity corer developed by the French Institute of Petroleum between 1987/1990 [IFP, Stacor documentation]. The STACOR presents a true immobility of the piston during the penetration. Cores were taken in abyssal plains through more than 5800 m of water.
Others corers as the JUMBO piston corer (JPC) [Silva and al, 1999] or SELCORE (developed by SELANTIC) could be mentioned.
It was then important to develop a sampler offering the same type of specifications of what was performed and recovered on the continental shelf including recovery of a 4" (101.6 mm) static sample. With the STARFISH system the operations are entirely controlled (penetration speed, position and verticality of sampler") with a recovery from the mudline to a maximum depth of 30 meters below seabed.
Sensitivity of SCR Response and Fatigue Life to Variations in Hydrodynamic Loading at Low Keulegan-Carpenter Numbers
Authors: Imas L. , Triantafyllou M.S. , Thompson M. , Hsu T. , Young R. 
Published: October 2008

Abstract
Very little reliable hydrodynamic data exists for bare and straked pipes subject to oscillatory flows which describes drag and added mass behavior as a function of Keulegan-Carpenter (KC) and reduced parameter Beta (B) numbers, namely for KC below 4 and B above 6000. The ability to accurately predict the global motions response and fatigue life of an SCR riser operating at such low KC/high B numbers to a large degree depends on the appropriate selection of hydrodynamic coefficients for such an analysis. This paper presents the experimental procedure used in obtaining the drag and added mass coefficients at low KC numbers, consequent results and their use in a design analysis of an SCR operating at extremely low KC numbers.

Introduction
The question of appropriate drag and added mass coefficients for risers operating at low KC numbers was raised early in the design of a steel catenary gas export riser connected to the Typhoon TLP (Figure 1). The Typhoon SCR is 18" in diameter, and the TLP is located in approximately 2100 feet of water. Drag and added mass coefficients were needed for the straked riser region, which extends several hundered feet below the riser attachment to the TLP, and the bare pipe region, which extends below the strakes to the riser touch down point. The Typhoon 18" SCR is particularly critical in terms of fatigue life at the touch down point due to the low water depth / diameter ratio, which is in fact the lowest of any SCR installed to date (Figure 2).
1Formerly with Advanced Marine Technology Inc.
For the most damaging fatigue seastates, motions of this riser are small, typically less than half a diameter. Figure 3 shows KC values for a typical fatigue seastate plotted along the riser length. From the figure it can be seen that most KC values are below 4.0.
The Typhoon TLP operating conditions relevant to the SCR fatigue life analyses are those of surge and sway in random seas, with underwater current effects considered negligible. Greatest fatigue life sensitivity was found to occur under conditions where significant wave heights varied from 10 feet to 1 foot, and the corresponding wave periods varied from 8 seconds to 2 seconds. In terms of SCR geometry and motions, the above conditions correspond to KC numbers between 4 " 1, and (reduced parameter) Beta numbers of between 20000 - 10000. The KC and Beta numbers are defined as:
KC = Vm*T/D
Beta = D2/(T*nu)
Vm is the SCR maximum oscillation velocity; T is oscillation period; D is riser diameter; and nu is the kinematic viscosity of water. The maximum value of SCR velocity is used, since both the sea-state and the vessel motions (hence the SCR forcing) are specified as random processes.
Hydrodynamic data, compiled in Bearman (1988), Sarpkaya (1986), Triantafyllou (1980), for bare and straked pipes in oscillatory flows does not provide pipe CD values (as a function of KC & Beta numbers) below KC ~ 4 and Beta ~ 6000.
An Algorithm for Determining the Uncertainty of Complex Multiphase Flow Models
Authors: Wilkens R.J. , Flach L. 
Published: October 2008

Abstract
An algorithm was developed for determining the implications of multiphase flow uncertainties. The specific method employed combines the classical uncertainty analysis of Kline and McClintock with multiple random variable probability theory. The initial results indicate that in addition to uncertainty prediction, the algorithm can also be used to statistically reduce the sharp discontinuities common in multiphase flow modeling, thus leading to improved simulation convergeance.

Introduction
Flow assurance and risk assessment are major issues in the offshore petroleum industry today. While there is a push for increasingly more complex flow models it is important not to lose the understanding of the accuracy of such models and their sensitivity to input parameters. Error bars for flow assurance simulations can greatly affect field planning, equipment sizing, and risk assessment.
At present, uncertainty calculations for multiphase flow conditions are not well understood and are rarely reported. Over short distances, uncertainties in prediction of pressure drop in the design stage can be large without causing significant production problems. However as multiphase transport in pipelines extends into tens of miles, a significant error can occur in predicting capacity. The method described can also be extended to the prediction of such values as corrosion rate, arrival temperature, and wax deposition rate.
In developing a method for determining uncertainty, it is desired that re-coding of the model not be necessary, implementation be simple, practical computational constraints be considered (e.g., no Monte Carlo approach). This led to an approach that was discrete and also was able to lessen the effects of sharp discontinuities. Specifically, existing model functions can be evaluated at selected intervals with the results being probability-weighted to arrive at a solution.

Statement of Theory and Definintions
Error bars represent the confidence interval for a given confidence level. When engineering results are specified, error bars are attached to the data to give the reader an idea of the level of uncertainty associated with the results. A list of values for common confidence intervals is given in Table 1. It is important to note that when the confidence level does not accompany the error bars, it is common to assume 2.15 - 1 odds. The values in Table 1 were generated using Eq. 1 in conjuntion with the Gaussian distribution.