bluuebunny/crossref_metadata_2025_split huggingface dataset:
Design of a 25.5-in Titanium Catenary Riser for the Åsgard B Platform
Authors: Nygård M.K. , Sele A. , Lund K.M. 
Published: October 2008

Abstract
The Åsgard B semi-submersible production platform is located on the Haltenbanken in the North Sea in 305 m water depth. A free hanging 25.5" (ID) titanium riser has been demonstrated to be a robust engineering solution for a large diameter riser from a semisubmersible platform in this water depth. Pre-engineering covering all main aspects was carried out during the spring of 1999. The purpose of the riser is to accommodate the launching of a multi-diameter pig from Åsgard B and to serve as a gas export riser. The riser is presently a backup solution to the base case of subsea pig launching.
Presently, there is no other application of a catenary riser in titanium. So far titanium has only been applied to one top tensioned riser, and components, such as stress joints in a limited number of risers. A limited number of free hanging steel risers have been installed in deep water. Isolation joints have been provided at both ends of the titanium riser. In addition to the riser pipe itself the use of titanium is therefore limited to the taper joint in the pontoon support and parts of the isolation joints. Taper joints in titanium as well as the components in steel are considered proven technology. This accommodates the use of proven designs for all components.
In spite of not being critical to performance some technical issues are recognised as areas where further technical development is desirable. The most important aspect is considered to be the qualification of welding and NDT procedures. The most highly stressed welds need to meet strict requirements for initial defects. The requirements are determined through fracture mechanics analysis. It is believed that there is a potential for relaxing these criteria by further screening and grouping of available fatigue data in order to reduce uncertainties inherent in the current data.
A base case with a uniform 28 mm titanium wall thickness has been developed, with alternatives allowing for a nonuniform wall thickness. The base case gives simpler purchasing logistics, while the advantages of the alternatives are to reduce the required amount of titanium, to simplify production and to reduce the interface forces applied to the platform.
A well suited fabrication site which accommodates a straight riser of approximately 700m is located at Aker Verdal in Mid-Norway. Procedures for assembly of the riser, utilizing two weld stations, have been developed.
Load out, tow out and installation methods which are insensitive to varying weather conditions have been developed. Surface towing may be applied for the tow out. To limit weather window restrictions provision has also been made for mid water tow out. The installation procedure has initially the riser suspended between two tugs. One end is transferred to the platform whereafter the rear tug moves over onto a different heading to position the riser in the anchor in a cranked configuration. Contingencies for bad weather have been developed for all phases.
Correlation for Design of Laterally Loaded Piles in Soft Clay
Authors: Matlock Hudson 
Published: October 2008

Abstract
A program of research on laterally loaded piles for offshore structure has included field test with an instrument pile, laboratory model testing, and development of correlation for design. The work has been sponsored by a group of five oil companies.
Three loading condition are considered to be particularly pertinent to the design of laterally loaded pile in soft normally consolidated marine clay. These are (1) short time static loading, (2) cyclic loading such as would occur during the progressive build-up of the storm, and (3) subsequent reloading with forces less than previously maximums.
Good general agreement exist between conventional static-loading ultimate-resistance concept and experimental results, provide due allowances are made for the reduced vertical restraint at shallow depth, where it is insufficient to cofine plastic flow to horizontal planes. Force-deformation characteristic based on approximate theory produce satisfactory agreement between computed and experimental behavior of the pile-soil system.
The mechanism of cyclic loading characteristic are qualitatively illustrated by typical results from laboratory model studies. Deterioration in resistance because of cyclic loading is most severe at shallow depth and with large lateral deflection of the pile. A correlation based primarily on result with the instrumented pile tested at Sabine, Texas, gives satisfactory prediction of pile deflection and moment over a wide range of loading condition.
Estimates of response for reloading after cycling at a higher load made by considering that most of the lateral soil resistance is estimated for deflection smaller than those previous attained.
The correlation are summarized and recommendation given for their use in design.

Introduction
The ability to make reasonable estimates of the behavior of laterally loaded piles is an important consideration in the design and construction of many offshore installations. This is particularly true in the Gulf of Mexico where large lateral forces are produced by winds and waves associated with hurricane and where the foundation materials in the critical zone near the mudline are often found to be very weak clays.
A program of research on laterally loaded piles sponsored by five oil companies is the primary basis for the correlation in this paper. At this time it is intend only that the results be summarized in a form directly in design, but publication of the background research is planned for the near future.

Requirement for Analysis and Design
There are many different ways in which piles or caissons may be subjected to effect of lateral forces. One such case is show in Fig 1a represent a pile and a leg of a jacket-type structure.
The structural analysis problem amounts to that of a complex beam-column on an inelastic foundation. For pile separated by spacing of several diameter or more, the Winkler assumption is useful to facilitate the analysis. This means that the soil is considered as a series of independent layers in providing resistance p to pile deflection y (Fig 1b)
The Continuous Sweep VIBROSEIS®Method
Authors: Broding R.A. 
Published: October 2008

ABSTRACT
A procedure has been developed for the VIBROSEIS® method of seismic exploration wherein the sweep or pilot signal is applied continuously to the vibrator during the acquisition period.. This method allows for increasing the duty cycle of the vibrators to as high as 1000/0. An increase in vibrator utilization is equivalent to increasing the vibrator power. A description of the method is given and examples of sections obtained with the continuous sweep method are compared to sections obtained with the normal sweep/listen method.

INTRODUCTION
In the VIBROSEIS method, the power output or resulting signal-to-noise ratio is directly proportional to the vibrator "on" time. This results from considering that the peak power in the pulse compression process is the pulse compression ratio.
(available in full paper)
or, the signal-to-noise ratio is proportional to the vibrator 1\ on" time.
In considering data processing costs, the time required for correlation is important.
Thus, in considering a maximum "on" time for the vibrators, we must also consider a minimum correlation time. A first consideration for maximizing the lion" time is to lengthen the sweep time. However, this also lengthens the correlation time.
The sweep repetition rate cannot be faster than the section time of interest. This is necessary to meet the requirement for having a unique pilot signal, i. e., for never repeating over the section time or depth of interest. Thus, the maximum sweep length time for a minimum correlation time is the desired section time.
In marine VIBROSEIS operations, the time for data acquisition is the time required to traverse one station interval. With a ship speed of 6 knots or 10 feet per second, the time for data acquisition using a 228-foot interval is then 22.8 seconds. Normal procedures of equal sweep and listening periods, do not permit two acquisitions per interval when the section time is 6 seconds or more. Therefore, it is common to shorten the listening period to reduce the cycle time and so permit two acquisitions to be obtained. For example, using a sweep length of 6.8 seconds and a 4. 5-second listening time, two acquisitions require 22.6 seconds or essentially the maximum time allowable at 6 knots for a 228-foot interval. The effect of shortening the listening period is to restrict the usefulness of the last part of the sweep on deep events. In effect, this produces a time variant filter with an increasing frequency or upsweep such that the high frequency end of the sweep is not available for that portion of the section that is greater in time than the listening period. This procedure is very useful for increasing the vibrator duty cycle without deteriorating the data quality. However, the method is restricted depending on the sweep used and the section time desired. Therefore, the method of continuous sweeping has been developed to permit a major increase in vibrator duty cycle or "on" time.
A Jackup-Installed Platform for Marginal Fields
Authors: Bunce J.W. , George P.J. 
Published: October 2008

Abstract
An innovative platform for marginal oil and gas field developments is described. Its principal features are that it can be installed by a jack-up drilling rig as part of the drilling program, it does not require foundation piles and has superior boat impact resistance when compared with other designs. This paper describes the design of the structure, with particular emphasis on jack-up installation aspects, boat impact resistance and foundation design. A number of practical applications are described.

Introduction
A large number of innovative platform structure designs have been developed in recent years that are cheaper to construct and install than conventional three or four legged steel jackets.
Ref. 1 gives a good summary of the range of platform designs currently available.
The platform designs usually comprise a superstructure supported on a single vertical caisson (monotower) with bracing near its base that attaches to piles driven into the sea floor. Such structures are simpler than conventional jackets, making them cheap to construct. They are also lighter, so they can sometimes be installed by a jack-up drilling rig rather than by a specially chartered crane vessel, making them cheap to install. The guyed caisson platform design introduced here is believed to have advantages over these established designs in that it is still cheaper and easier to construct and install.
In addition, it has superior resistance to boat impact forces, which will usually govern the design of small platforms in moderate water depths. Further, some of the conductors and risers can be on the outside of the central caisson, without the requirement for a boat impact frame. This allows the conductors to be spaced well apart, which leads to a good layout of the wellheads and production equipment in the superstructure and aids drilling operations. For multiple conductors it also has the effect of reducing the wave loads and the self-weight of the structure.

Platform General Description
Figure 1 shows an example of the structure design for a central North Sea site in 60m water depth with a 5,000kN topsides operational weight, 9 well slots and an export riser. The platform is unmanned and requires only limited access during normal operation.
The platform comprises a superstructure supported above the wave crest level on a guyed caisson founded on a shallow spud-can on the sea floor. Six of the conductors are supported on the outside surface of the caisson through guides; the export riser and other conductors are inside the caisson. The caisson is 2500mm-diameter fabricated from high strength steel plate with maximum thickness 50mm.
Three pairs of wire rope guy lines are attached to the caisson. One end of each line is attached to the caisson near the top, above the water surface with the other end attached to an anchorage at the sea floor. Anchorages may be vertical load plate anchors, suction anchors, piles or anchor blocks, depending on the soil conditions and the loads to be resisted.
A New Seabed Penetrometer
Authors: Meunier J. , Sangouard D. , Lhuillier B. 
Published: October 2008

Abstract
There is today no operational system able to perform geotechnical measurements with standard 36 mm CPT cones in deep sea with a depth of investigation of 20 to 30 metres below the sea-bed. The advantage of the new system is that it will allow surveys in deep sea in a more cost-effective manner.
GEOCEAN-SOLMARINE, a French Marine Contractor with deep water geotechnical tools capabilities and IFREMER, a French Research Institute for exploitation of the sea, joined to design and build a new seabed penetrometer which will be operated by GEOCEAN-SOLMARINE for industrial operations and by IFREMER for scientific applications. The IFREMER's version is now under assembly. The first tests at sea of the penetrometer are expected for mid-2000.

Introduction
The current trend for offshore oil developments is to move into deeper water. There will therefore be a growing need for reliable soil design parameters in deep water, for the design of structure foundations, for the anchoring of floating production and storage systems, for pipeline laying and for slope stability problems.
Scientists are also interested in in-situ measurements for different topics: sediment characterisation, slope stability, environmental studies, hazard mapping, stratification logging, indication of stress history and lithology deposits,...
The tool designed by GEOCEAN-SOLMARINE and IFREMER is a frame which is lifted over the seabed and which remains during the duration of the measurement. The penetrating system is based on a flexible rod which is pushed by friction into the soil. For scientific applications, the tool is called "Penfeld", the penetration force is limited to 40 kN which allows a penetration of 20 metres into the soft soils encountered in deep seas. Several locations can be investigated during the same deployment of the system. The industrial version called "DS7000" will be built with higher capacities.
In a first step, the penetrometer will be equipped with a conventional cone including the measurements of point resistance, shaft resistance and pore pressure. Further a new cone will be developed specially devoted to high pressure environment, including differential pore pressure and complementary sensors such as a gamma-densimeter and a thermometer.

Need of sea bed measurements in deep sea
The offshore activities are now moving from the continental shelf to deep seas. This change modifies the needs in soil surveys.
On the continental shelf, the main object of the surveys for foundation design of platforms was to obtain information on the soil for the design of the piles for the anchoring of platforms. The piles were 50 metres, 100 metres long, even more. A typical survey consisted generally in a cored borehole over all the length of the pile, and an instrumented borehole, using a wire line Cone Penetrometer Test performed by length of 3 metres.
In order to perform such a survey, a geotechnical vessel with facilities in drilling was needed.
These methods are operational only in water depths less than 200 metres.
Subsea Intervention From a NonDrilling-Rig-Type Vessel
Authors: Franklin Robert , Collie Ian , Kochenower Chris 
Published: October 2008

Abstract
Deepwater technology has been creeping up the learning curve as the different oil and gas operators move out into deeper and deeper water depth. With the new technology comes new ways of performing older more routine jobs. EEX became the first company to decommission and abandon a deepwater development project. Being first, they had to find new and better ways to do the work. The use of a non-drilling intervention vessel that was self-powered and dynamic positioning simplified the project and allowed EEX to save money and time over the estimated time and money required for a conventional drilling rig and derrick barge approach to the problem.

Discussion
As the Gulf of Mexico development activity moves out into the deeper waters, operators must find more cost-effective ways to exploit the oil and gas resources. Service companies must also change to meet the challenges that are found in the deepwater Gulf of Mexico. In 1998 EEX Corporation (EEX) recognized that the Garden Banks 388 Field, in 2,100 feet of water, was maturing and would be reaching its economic limit by mid-1999. Management at EEX began reviewing the techniques needed to properly decommission and abandon the field.
In shallower waters, the decommissioning and abandonment of a producing field has evolved from the use of large rigs and extensive management / logistics procedures to a more stream lined procedure with a turnkey or specialist in the decommissioning and abandonment process. The end result is the same, sometimes better, but the time required to complete the task and the cost of the operation is cut dramatically. In many of the cases the wells can be plugged and abandoned with a coil tubing unit and a wireline / logging unit, rather than using a large drilling or workover rig. The larger drilling / workover units could take one to two weeks to rig up and place in operation and many found that the equipment was overkill for the nature of the operation. Coil tubing and wireline / logging units often can be rigged up in a matter of hours and the plugging and abandonment operations could be completed in less time than it took to rig up the larger units. To say the least the time and cost savings were significant. EEX felt this same evolution was possible in the deepwater environment.

Decommissioning
EEX wanted to be able to have the FPF and the FSR decommissioned and brought back to the dock, by late August or early September, to avoid the peak of the hurricane season. By doing so, it would reduce the risk of damage to equipment or the loss of valuable time due to possible bad weather.
The Floating Production Facility (FPF) was used to decommission the production equipment, riser, manifold, jumper lines, flowlines and sales lines running to Eugene Island 315. Seawater was used to flush the system and it was pumped into the wells to push the wellbore fluids into the formation and establish the injection rates for each of the wells.
Fatigue Curves for Polyester Moorings - A State-of-the-Art Review
Authors: Banfield S. , Versavel T. , Snell R.O. , Ahilan R.V. 
Published: October 2008

Abstract
The gathering momentum for the use of polyester ropes for long term production system moorings in deep water has instigated a thorough review of their fatigue performance. The traditional view of designers has been to use spiral strand steel wire rope T-N curves to assess the fatigue performance of polyester ropes on the basis that available evidence indicates that the latter's fatigue performance is superior to spiral strand wire rope. The authors have examined all the available fatigue testing data and the proposals for polyester specific T-N curves and have identified a number of issues pertinent to the derivation of fatigue design data for fibre ropes and propose an improved design curve.
This paper systematically identifies the various issues and proposes a rational way of including the available data (including runouts) for the development of a T-N curve for polyester ropes. The new data was used to re-visit the fatigue life and reliability for an example West of Shetland FPSO moored using polyester ropes (Ref.1).

Introduction
Synthetic fibre ropes have undergone a rapid testing and development phase over the last five years through a number of Joint Industry Projects (Ref. 2,3,4 and 5) and other studies. Ref. 2 is a recently launched JIP which utilises the latest materials with marine finish, terminations and rope designs.
Due to their good behaviour in fatigue, testing fibre ropes to quantify their fatigue life can be an expensive process and individual tests at loads representative of FPS conditions are predicted to run for man-years even when accelerated several fold. Thus, most fatigue testing has been conducted at high load levels and accelerated rates to produce data within reasonable time and budget.
This paper will review the data to show the true potential of polyester fatigue life and to provide a realistic design T-N curve.

Terminated Rope Breaking Strength
Rope strength is defined as Minimum Breaking Strength (MBS) with terminations and is guaranteed by the manufacturer. The average measured breaking strength will typically be 10% higher based on the most recent technology.
As shown in Table 1, a material, rope and termination review of the public domain data shows considerable scatter in the margin of ABS (Actual Breaking Strength) over MBS between -7% to +36%. This illustrates that care needs to be taken in analysis of data when selecting the basis of rope strength and that a common basis for strength can reveal new information. The column titled theoretical ABS is calculated from the yarn content to give the theoretical strength of the rope to allow for terminations, variability (manufacture of rope, not terminations) and obliquity (effect of the lay angle). This gives a strength expected using a well made, designed and terminated rope with a high quality fibre. This now gives a margin well within 10% for the spliced ropes, with the exception of number 5 for which the terminations may not be reflecting the true potential of the rope.