bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sea Bottom Scouring in the Canadian Beaufort Sea
Authors: Hnatiuk John , Wright B.D. 
Published: October 2008

ABSTRACT
Echo sounding, side scan sonar and seismic profi1ing records have shown that the continental shelf of the Canadian Beaufort Sea has been subjected to extensive scouring by ice features. The scouring phenomena is extremely important in the design and protection of offshore well s and future pipelines. Analyses of records collected by industry and government in the early 1970's and reported by Hnatiuk and Brown in 1977 have been refined with the inclusion of additional data collected by industry and government in 1975 and 1976. Here, the results of the information synthesis are presented in terms of regional maps showing relevant scouring parameters and their variation with location and water depth. A quantitative evaluation of scour return period is al so presented on the basis of sedimentation assumptions. This information is compared with a recent analysis of sidescan scour mosaics collected repetitively over four areas ranging in water depths from 45 to 150 feet and with time interval s ranging from 2 to 7 years between the repetitive seafloor maps. The rate of addition of new scours determined from the repetitive mosaic approach supports the regional assessment of Beaufort Sea scour but suggests more episodic and a really frequent scour events along with more active scouring in water depths approaching 150 feet. This information is discussed in terms of the Beaufort Sea ice regime.

INTRODUCTION
The continental shelf of the Beaufort Sea which extends some 75 to 100 miles from shore to a water depth of 600 feet, has long been considered to have the potential for major accumulations of hydrocarbons. During the period 1963 to 1969, permits to explore were issued for the majority of the Canadian mainland shelf. Offshore drilling commenced from artificial islands in late 1973 and oil was discovered in 1975. Subsequent drilling from artificial islands, caisson islands and drillships has confirmed the presence of major reservoirs of oil and gas, many of which will likely be developed for production.
Gouging or "scouring" of the seabed by sea ice pressure ridges or glacial ice features has been a concern in exploratory drilling operations and will be of even greater concern when gathering lines, pipelines and subsea development well s are being designed. Two critical aspects of the concern are depth of scour and return period. Currently when drillships are operating in areas of active scouring, "glory holes" or excavations are prepared in which the blowout preventors are placed for protection from the ice.
The first good records of sea bottom scouring in the Canadian Beaufort Sea were obtained during the summer of 1970 (1). These side scan sonar and echo sounder records plus those obtained during 1971 and 1972 were analyzed through Projects funded by members of the Arctic Petroleum Operators' Association (2,3) and reported at the 1976 OTC (4).
Landtesting the Underwater Manifold Centre for the Central Cormorant Field
Authors: Brady M.M. 
Published: October 2008

ABSTRACT
This paper describes the commissioning on land prior to installation of the Underwater Manifold Centre (UMC) for the Central Cormorant field. The test programme was unique in its scope and depth requiring 15 months and £11 million to complete.
Included in the paper are guidelines to assist future projects as well as summaries of technical results and a list of the principal problems that were encountered. Management practices utilised to guide the programme to its successful completion are emphasised throughout.
Finally, the paper concludes that the landtest programme was a cost-effective and indispensable step which resulted in the UMC being installed in May, 1982 with full confidence, especially in the essential high technology components.

INTRODUCTION
When subsea production systems are placed on the seabed where human access is limited, special steps must be taken to ensure they operate properly and that maintenance requirements are kept to an absolute minimum. For the complex UMC project with a 25-year design life, this involved designing and manufacturing components to have extremely high reliability. This, in turn, entailed establishing specifications and standards that far exceeded those used for normal oilfield equipment.
A first step in achieving these specifications and standards was to have adequate Quality Assurance (QA) and Quality Control (QC) programmes during the design and manufacturing phases of the project. However, experience, for example from Exxon's SPS pilot test, has shown that a further step is required. The production system must be debugged and thoroughly tested as an operating unit after it is assembled. This involves putting the system 'through its paces' on land and taking any corrective action before placing it on the seabed. Nevertheless, not all problems will be solved, and some maintenance back-up must be provided, which is described in other papers on the UMC.
Landtesting of the UMC was considered an indispensable step for the Central Cormorant Project. This paper describes the landtest exercise with the purpose of providing guidelines for future projects of a similar nature; and various sections focus on: programme objectives; planning; project organisation and test site facilities; technical results and problems; monitoring progress; and programme costs.
As these topics indicate, this paper is organised round management considerations since they were fundamental to the success of achieving the objectives and are transferable to other situations. Still, the paper carefully summarises primary technical results and lists the principal problems uncovered during testing. More detailed accounts of technical aspects are available in companion OTC papers on the UMC.

DEFINING THE OBJECTIVES
The UMC landtest objectives were defined in four areasIntegration testing,Verification of equipment fits and interchangeability,Collection of base-line data regarding the system's response, andTraining of operating and maintenance personnel.
Hydrodynamic Loading of Steel Structures
Authors: Ohmart R.D. 
Published: October 2008

ABSTRACT
Measured jacket brace member axial loads are compared with predictions based on conventional static structural analyses. The measured to predicted load ratios are shown to be lognormal1y distributed. Slightly conservative predictions are obtained, on the average, using drag and inertia coefficients of 0.7 and 1.7, respectively, and with no consideration of current or marine growth.
Total wave load (shear) distributions can be directly inferred from the member load distributions. A parameter study indicates that the addition of large currents and levels of marine growth, especially if the drag coefficient is increased because of roughness, results in extremely conservative wave load estimates.

INTRODUCTION
The calculation of stresses in an offshore structure requires the analysis of a structural model subjected to appropriate load sets. For the static case, these sets include gravity loads (live and dead) and environmental loads, i.e., those due to wind, waves, and currents. The wave induced stresses can be divided into two components. The first is due to the local loading on the member itself and the second is due to the overall deformation of the structure under the integrated load on the total structure. Since the local loadings decrease exponentially with depth, lower members in the structure are stressed primarily by structural deformation.
Wave loads on a template-type structure are calculated based on the semi-empirical Morison equation. It may be written as(Available In Full Paper) where dF/d1 is the force per unit length, p is the density, D is the member diameter, u is the fluid velocity, and CD and C are the drag and inertia coefficients, respective1y. Though several laboratory and field wave force measurement programs have been conducted to determine the coefficients, the selection of appropriate values from the wide range of those published remains a subject of debate. The adequacy of the Morison equation, the many assumptions and uncertainties involved in the prediction of wave loads, and most of the force measurement program.
Though the existence of currents in wave fields has long been acknowledged, little is known concerning their influence on the wave field and on the resulting hydrodynamic forces. A depth varying current further complicates an already difficult problem. Therefore, the conventional method of including the current effects on wave loading is by superimposing the current profile on the wave velocity field generated in the absence of current. Further, it is often assumed, and sometimes required, that the current be considered co1inear with the direction of wave propagation.
The effect of marine growth on fixed platforms has been discussed by Heaf. Marine growth influences the loading of a structure in at least five ways:increased member diameters;increased drag coefficient because of the roughness;increased mass and added mass leading to a lower natural frequency and hence an increased dynamic amplification factor;increased structural weight; andthe effect upon hydrodynamic instabilities, such as vortex shedding.
Unsteady Aerodynamic Loading of a Tension Leg Platform
Authors: Armstrong B.J. , Barnes F.H. , Drabble M.J. , Grant Ian 
Published: October 2008

ABSTRACT
A model study has been made of the aerodynamic loads experienced by a typical TLP superstructure Details are given ofextreme quasi-static aerodynamic loads induced under extreme conditions;the aerodynamic admittance function relating the spectrum of drag force to the wind gust spectrum.

INTRODUCTION
The economic and safe design of offshore structures requires the availability of reliable codes of practice. Reference is often made to DNV and ABS rules in calculating the overall environmental loads on a structure due to the typical wind and wave climate. These rules base their load and moment calculation procedures on documented field and model tests of specific structures and their elements.
When compliant structures are considered, dynamic effects excited by the periodic nature of waves and the "gusting" structure of wind must also be considered. In the particular case of gust loading, the relationship between the statistical properties of the wind and the induced forces on the structure must first be defined by a suitable aerodynamic "admittance". This frequency dependent function has been shown in many studies to rely on both the structure and its environment 1,2,3,4,5 It cannot generally be defined a priori but requires model or prototype studies to be made for all but the simplest of structures.
In the present investigation, the relationship between the wind characteristics and the resulting forces has been derived for a superstructure geometry typical of a "tension-leg" platform (TLP) in a series of model tests.
The data presented here consists of (i) measurements in a steady uniform flow giving details of the overall drag force, lift force and pitching moment at model leg lengths corresponding to the extremes induced by a design wave, (ii) measurements of that element of the aerodynamic admittance function matrix which relates the unsteady drag force to the velocity fluctuations parallel to the free stream. This will be referred to as the "admittance function".
In both cases variation with the angle of yaw to the wind is considered. The effect of pitching of the structure is considered in the uniform flow while the effect of changing the length scale is examined in turbulent flow.
The resulting set forms a base of unsteady aerodynamic load data which may be used in the modelling of the dynamic behaviour of a TLP.

EXPERIMENTAL ARRANGEMENT
The experiments were conducted in a closed-return wind tunnel. The working section of the tunnel is 3m long and, in cross-section, is built on a basic frame which is 1.2m square. The working section is fitted with corner fillets so that its cross-section is octagonal. The tunnel produces a uniform flow in the working section with a turbulence level of 0.02% at 15ms1. The model used in the wind tunnel study has a design which includes the main features of proposed tension leg platforms. A plan view of the model in shown in Figure I, and the elevation views are shown in Figure 2.
Model Tests To Establish a Design Method for TLP-Tether Systems
Authors: Sekita K. , Sakai M. 
Published: October 2008

ABSTRACT
Model tests were conducted in regular and random waves with a view to establishing a design method for tension leg platform (TLP)-tether systems. Linearized and nonlinear analytical methods were used, and the calculated values were compared with measured values. The nonlinear method was used in analyzing a TLP tether system under such critical sea conditions as would cause the tethers to snatch a situation that should be avoided in the design of TLP tethers - and under unstable conditions with all tethers at one corner of the TLP broken off.
The results of these investigate are reported in this paper.

INTRODUCTION
The tether system is one of the important elements in ensuring the safety and reliability of a tension leg platform (TLP). These factors of safety and reliability are influenced to a great extent by the variation in tether tension due to the wave induced motion of the TLP. To determine the dynamic characteristics of the TLP, the authors used a dynamic response analysis system (part of the Offshore Floating-Structures Design System, OFDS, which was developed to evaluate the stability and dynamic motion characteristics of floating structures) and a method of analysis that considers nonlinearity due to the dynamic motions of the structure. Model tests were also conducted to prove the validity of these methods of analysis.

TLP ANALYSIS

Linearized Analysis
OFDS performs the following principal functions:Stability analysis.Analysis of static loads (wind, current and drift forces).Analysis of static equilibrium (offset value and mooring force).Analysis of the dynamic response of structures in waves.Structural analysis.
To evaluate the dynamic characteristics of the TLP, the fourth function above was used.
A TLP was assumed to be a rigid body with six degrees of freedom. Of the fluid force acting on the floating body, diffraction and radiation forces acting on its large-mass sections such as the hull and columns were analyzed by three-dimensional potential theory. The drag force on the TLP due to the relative velocity of water particles was obtained through linearization and iterative calculation.1,2
Forces that act on individual elements of a TLP can be expressed as:(mathematical equation available in full paper)
The right side of Eq. (1) contains the terms for the inertial force, damping, drag force, righting force and wave force. Mi and Mai are the mass and added-mass matrices of an element i, respectively. Ni is linear damping, Ki is the restoring force coefficient matrix, and U is the velocity matrix of the fluid. Di is nonlinear damping and Fi is structural weight and wind load. The wave force is calculated at a mean offset position due to wave drift, current and wind. The restoring force is a nonlinear force owing to a drawdown effect. For these reasons, a linearized motion equation is solved by iterative calculation.
Development and Evaluation of an Experimental Seawater Hydraulic Tool System for U.S. Navy Divers
Authors: Black S.A. 
Published: October 2008

ABSTRACT
The Naval Civil Engineering Laboratory has developed an experimental seawater hydraulic tool system consisting of a hydraulic impact wrench powered by a reversible vane motor, a rotary propeller cleaning tool powered by a unidirectional vane motor, and a diesel hydraulic power source. The reversible and unidirectional motors were laboratory tested. After 200 hours the reversible motor provided 3 hp output at greater than 70% overall efficiency. Vane springs failed and were replaced after 100 of hour?s operation. The impact wrench delivered over 1,100 ft-lb of torque to a 1-inch-diam bolt in less than 8 seconds when used by a diver. The propeller cleaning brush provided sufficient power to rotate a 7-inch-diam brush in water at speeds to 2,200 rpm with additional power to do useful work. The portable power source was tested for over 240 hours and found to deliver up to 12 gpm of filtered seawater at pressures to 2,000 psi. A description of system components, the results of test and evaluation and future plans are presented in this paper.

INTRODUCTION
The Naval Civil Engineering Laboratory (NCEL) is engaged in a continuing program to provide U. S. Navy divers with improved tools and techniques to increase their underwater work capabilities. Part of this effort is directed towards the development of powered hand tools. Most of the hand tools presently in use are powered by oil hydraulic systems. While these tools have provided the diver with the capability to conduct many useful tasks, the need for oil to power the tools presents unique disadvantages when used underwater:leakage to and from the environment inevitably occurs and the consequences can be destruction of system components and pollution of the environment,the need for dual-transmission hoses burdens the diver, anda fire and safety hazard exists with the use of oil in a high-pressure hyperbaric environment.
Since 1976, NCEL has been developing hydraulic systems that use seawater instead of oil as the working fluid. A seawater hydraulic system would provide the diver with easy to handle tools which are compatible with the environment and that have all the attributes of oil hydraulic tools. Early research in seawater hydraulic systems resulted in the successful developed of an experimental balanced vane motor. " The experimental motor produced 3.3 hp at 1,600 rpm with a seawater input flow of 7 gpm at 1,000 psi and operated for 50 hours before spring failure caused shutdown.
Based on the success with the experimental motor the development of an experimental seawater hydraulic tool system was initiated. The overall objective of this work was to produce a complete tool system that would serve as a laboratory test bed for use by technical personnel to demonstrate the feasibility of seawater hydraulic diver tools and to identify components needing development.
Polyethylene Coating Damage on an Underwater Pipeline in the Southern North Sea
Authors: Rippon I.J. , Finnegan J.E. 
Published: October 2008

ABSTRACT
Following a recent inspection, approximately 60 km of a 138 km methanol pipeline was found to be under-protected due to the premature consumption of the original zinc bracelet sacrificial anodes. The cathodic protection system had been designed to last 40 years accommodating uniform coating holidays of up to 3% of the total surface area. However, substantial coating damage (in excess of the design allowance) in localised areas has resulted in accelerated depletion of the system in less than 12 years.
A retrofit, sled anode, cathodic protection system was designed to furnish the current required to protect the pipeline for the next 30 years. This system is composed of a 330 kg, Al-Zn-In alloy, stand-off anode mounted upon a low profile sled. The design can provide a 3 amp current for 30 years, which will protectapproximately 200 metres of uncoated pipeline at a current density of 50 mA/m2 During the autumn of 1983, 50 of these sled anodes were installed on the main methanol line. The result was a 200 mV cathodic potential shift within 24 hours.

INTRODUCTION
Following a recent inspection of all pipelines associated with the Viking Gas Field, all the gas pipelines were found to be in an acceptable condition, but a substantial proportion of the methanol pipelines were found to be in need of remedial action.
This paper deals only with the methanol lines, however results of the gas line survey are given for comparison. It addresses the possible causes of observed damage and the remedial work carried out on this polyethylene coated 3 methanol pipeline.
The work will be of interest to other operators with lines of similar age and coating type.

FIELD DESCRIPTION
The Viking Gas Field is located 86 miles due East of the Lincolnshire coast in the southern North Sea (Figure 1). The field consists of two main complexes (A and B) and five unmanned satellite platforms (Figure 2).The satellite platforms, the B Complex and the A Complex are connected by infield feeder pipelines. The main gas export pipeline is a 28" line of 138 km in length between the A Complex and the shore terminal.
Current winter production figures for the field are:Dry gas present peak production: 750 MMSCFD Condensate average well production:4 bb1s/MMSCF
Connate water average well production:less than 1 bbl/MMSCF
To prevent the formation of hydrates, methanol is injected into the gas stream at various places. The methanol is pumped from shore along a 31/2 pipeline piggyback to the 28" gas line, and distributed throughout the field by piggyback pipelines. The produced gas, condensate, water and methanol are separated at the shore terminal. After storage and make-up, the methanol is pumped offshore as required.
Engineering and Construction of Mukluk Island
Authors: Ashford R.A. 
Published: October 2008

ABSTRACT
This paper describes the design, planning and construction of Mukluk Island, the largest and most exposed artificial gravel island in the Alaskan Beaufort Sea.
The Island was constructed in two stages, with gravel being hauled over ice road from a shore-based pit to a natural island and stockpiled in winter and then transported by barge to site the following summer. The unusual construction techniques adopted to ensure successful project completion in unpredictable arctic conditions are described.

INTRODUCTION
Mukluk Island is located in South Harrison Bay at the junction of OCS Sale 71 lease blocks 191, 192, 205 and 206. It is 150 miles north of the Arctic Circle, 60 miles west of Prudhoe Bay and 20 miles north of the Colville River Delta in 48 feet of water. It is the first gravel island to be built in Harrison Bay and the site is the most remote, most exposed and the deepest water location of any island built to date in the Alaskan Beaufort Sea.
From the date of the lease sale on October 13, 1982, Sohio Construction Company had one year to pl an, design and construct Mukluk Island, including obtaining the thirty-three necessary permits from various regulatory authorities.
Within that year, inspite of unusually severe ice conditions in the Summer of 1983, Mukluk Island was successfully completed and the dril1ing rig moved onboard.

CONSTRUCTION PLANNING
Preliminary design of the island indicated that a steep 1 vertical to 3 horizontal side slope would be feasible. For a 350-foot diameter work surface, the volume of gravel would be approximately 1.25 million cubic yards including an allowance for losses. Gravel was known to be available onshore close to Oliktok Point, approximately 30 miles from the Mukluk site. Methods of transporting this quantity of gravel within the next year were investigated.
Consideration was initially given to conventional winter construction by hauling gravel over ice road all the way to Mukluk. This scenario had to be abandoned because of permit schedule restrictions and the need to carry out the geohazard survey prior to commencing construction.
Other possibilities, such as the use of an Arctic drilling structure, converted VLCC, or summer dredging an island using an offshore borrow source were a1so ruled out because of permit schedule restrictions.
Construction of the is land by barge haul directly from shore was not practical due to the greater distance involved and shallow water depth close to shore. We calculated the available barge capacity was insufficient to haul this distance with barges only partially loaded because of the draft 1imitation. Also, the docking facility at Oliktok Point would be used for incoming Sealift module offloading and would therefore not be available for much of the summer.