bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pull-out Parameters for Buried Suction Anchors
Authors: Wilson Quentin , Sahota Baldev S. 
Published: October 2008

ABSTRACT
Data obtained from a model of a self-burying suction anchor tested in a granular soil bed in the laboratory and from larger anchors tested at sea are presented. Scaling parameters for comparing the performance of buried suction anchors are proposed and discussed and a preliminary investigation made of an anchor group with a 1000 kN (225000 lbf) vertical pull-out capacity.
The procedures used and some of the problems encountered during sea trials with suction anchors are described.

INTRODUCTION
Suction anchors should be considered as a family of marine devices with capacity for resisting uplift force, each device having its own characteristics and field of application.
Anchors in the form of inverted suction cups have been investigated extensively and have been shown to be capable of application in sands, silts and clays 1,5,11. The use of large cup-type anchors as footings on a gravity structure has been proposed by Wang et al 10 with the intention that additional anchoring capacity should be developed by soil pore pressure reduction during extreme storm conditions. Large suction anchors have been tested by the Shell Rijswijk laboratory5,6 and the maximum allowable lateral force for a 3.8 metre (12.5 ft) diameter anchor reported to be 160 tonnes.
Cup-type anchors may be regarded as surface attaching devices, even though the anchor skirts penetrate the sea bed, since there is usually no soil above the anchor to contribute to pull-out resistance. A suction anchor with non-penetrating skirts of flexible material has been proposed by Schofield4 and investigated in the laboratory by Al-Awadi l Cup type anchors, which are of rigid construction, require some soil depth for penetration of the skirts but the non-penetrating anchors can be attached to slabs of rock or concrete.
The development of self-burying suction anchors of hemispherical shape has been described by Wilson and Sahota12 and it has been observed that, for a given anchor size and suction pressure, the buried anchors can develop greater pull-out resistance than the other types due to the effect of the soil above the anchor.
All suction anchors have certain features in common. A cavity within the anchor is connected to the water in the soil voids via a filter or porous part of the anchor body, so that a reduction in water pressure within the cavity, created by pumping, is transmitted to the soil pore water. The flow of water which develops between the surface of the submerged soil bed and the anchor filter creates a distribution of force in the soil, directed in the flow direction and at right angles to the equal-pressure or equipotential surfaces (Fig. 1). The flow lines and equipotential surfaces form a flow net which develops with time from initiation of pumping but which tends towards a steady state condition if no perturbations occur. The generally favourable increments in the soil effective stresses that are produced increase the pull-out resistance of the suction anchor.
Presentation of 3-D Seismic Results
Authors: Paturet Daniel , Chanliau Michel , Leflaive Remi 
Published: October 2008

ABSTRACT
The processed seismic data of a 3-D grid can be presented using conventional seismic sections along the direction of acquisition and a perpendicular direction. They can also be presented using any chosen direction.
Like in 2-D seismic it is possible to use colors to enhance the variations of certain parameters such as amplitude or frequency.
Constant time horizontal sections are very helpful for the Interpreter Since they allow a direct isotime contouring.
Tomoseis sections, where color is used to represent the instantaneous phase, give the dip of the seismic events and thus help and improve the above contouring.
A selected seismic horizon can also be flattened for studying some of its characteristics such as amplitude and frequency. It is then easy to obtain sections similar to the constant time sections, but parallel to this reference level. This process allows direct isopach contouring.
Examples of these different displays obtained from actual 3-D offshore seismic surveys will be presented.

INTRODUCTION
Seismograph prospecting for oil is now a little more than 50 years old. During the first decades, the interpretator had to pick the reflected events on individual records (fig. 1), to check whether they correlate from each record to the next, then to draw a vertical time sections (fig. 2), then to read the times of selected horizons and transfer such readings on a location map, then to contour the isotime - lines, so as to eventually obtain an structural image of the subsurface (fig. 3).
In the mid-fifties, with the introduction of the magnetic recording, some of these tedious tasks were taken out from our poor interpretator, who directly disposed of a vertical time sections along the acquisition lines (fig. 4). The digital recording and processing, surprisingly enough, although it launched tremendous possibilities in the field of signal enhancement, dit not appreciably help in the data handling at the interpretation stage. It is only very recently that efforts were made to capitalize on the computers capabilities, in order to supply the interpretation with documents on which he can directly visualize the geological Implications of his seismic Interpretation.
Such objective assumes that, first, there is a spatial 'continuity of the seismic data collected; it is what has been designated under the general name of "3D seismic". For offshore surveys, it amounts to shooting a large number of parallel lines, and relying on the sea currents to spread the measurement points on a regular grid (fig. 5) : surface position - (fig. 6) : subsurface position.

PRESENTATION OF 3-D SEISMIC RESULTS
Another necessary condition is to have relocated the seismic energy where it has been reflected, and not where it has been recorded. This is migration stage of the data processing, the effect of which can be seen by comparison of fig. 7, 8, 9 (7 : grid stack - 8 : 3D migrated grid stack - 9 : 3D migrated grid stack 500 m apart, whereto the deep seismic event of fig. 7 has moved).
Analytical Approach To The Design Of Atension Leg Platform
Authors: Chou Frank S.F. , Ghosh Susobhan S.F. , Kypke Dean A. 
Published: October 2008

INTRODUCTION
The economics of offshore petroleum production have changed radically over the past few years, and reservoirs thought too deep or small now contain the financial incentive to justify their development. The various techniques and concepts previously developed to exploit such conditions pave also become economically feasible, such as the Tension Leg Platform (TLP).
The costs of TLP systems can be justified for use in the deep water reservoirs which are currently attracting attention because, at the water depths being considered, TLP's are less expensive than alternative structures. The results of a comparative study done by Daily, Karsan and Kypkel, illustrated on Fig. I, compares the qualitative cost between conventional fixed structures, Guyed Towers and Tension Leg Platforms.
The cost comparison crossover points for the offshore structure alternatives shown on Fig. 1 depend on environmental factors as well as water depth. The severity of the sea environment, seabed conditions and topography possible seismic activity, projected life of the field and desireability of platform reuse are all cost factors. In general, the cost crossover points move to the left, i.e. to shallower water depths, with an increase in degree of any of the environmental variables other than water depth.
It is in the deeper water depths that the TLP cost curve increases at a lesser rate than conventional structures, because the platform structure does not change as you move into deeper and deeper water. In other words, fixed platforms and guyed tower structure size correlate with water depth; the deeper the water, the larger the structure size required. In fact the inability to attain the structure size and proportions required by conventional platform design probably set the upper limits on the water depths in which conventional systems can operate. Thus the cost curves for these two structures will increase more- rapidly than the TLP in deep water reservoirs, for once a TLP platform is paid for, nothing will change except the amount of the mooring system to be bought and the cost to install it.
The mooring system is the common concept linking all TLP design. TLP's are basically buoyant structures restrained at a draft greater than that required for hydrostatic equilibrium by use of a vertically oriented, taut mooring system. This mooring system is quite rigid axially while being relatively flexible transversely. TLP design studies by Peres and Kypke2 and Capanoglu3 show that the mooring system configuration effectively eliminates heave motion, and the horizontal offset can be limited to an acceptable percentage of water depth.
The TLP has been developed as variations to one or more of the basic configurations noted in Fig. 2, and the individual components of a TLP drilling and production system are noted schematically in Fig. 3. These components will be found in a variety of shapes, locations, and applications on anyone of the TLP variations developed to date.
Evaluation Of Internal Corrosion On Marine Risers By Divers Using Acoustical Holography Techniques
Authors: Stankoff Alain , Guenon Yves , Thomas Gerald 
Published: October 2008

ABSTRACT
The proposed paper describes a method producing a three-dimensional acoustical image of the internal face of the riser. Inspection is carried out by a diver operating only at the moment from a lock-out submersible. An array of ultrasonic transducers is applied on the outside surface of the riser, and generates a sequence of focused Shear wave beams, which are reflected back to the transducer array by the defects on the other face. The point by point electronic scanning allows to construct a 3-D image of a 150 mm by 100 mm section of the riser. Each image includes approximately 5000 acoustical points, each one corresponding to a 20 mm by 5 mm by I mm riser element. Depth extension of defects in the metal is given to - 1 mm. All data are recorded on digital tape and processed by computer at the surface after each dive to produce detailed inspection documents. Approximate time for inspection of a I square meter riser surface (100 images), in operational conditions, is 3 hours.
Extensive laboratory tests are reported showing the capabilities of the method in evaluating the internal corrosion and especially the corrosion due to pitting. At the issue of these tests, the system is found to provide a detailed representation of the corrosion or erosion with satisfactory depth resolution. Several parameters are extracted from the data to characterize the corrosion status and to allow evaluation of the safety of the riser.

INTRODUCTION
Monitoring and maintenance of marine risers are essential for operators of offshore oil and gas production platforms, as any damage to the risers can result in a partial or total shut down of the production, with significant economical consequences. On the other hand, marine risers are specially exposed: highly corrosive fluids, thermal gradients, collisions with service ships, constraints due to connecting sealines instabilities, etc...
The significant damage can manifest itself either as:A geometrical deformation, easily identified by a visual surveySome external corrosion evaluated through visual surveys and potential measurementsInternal corrosion or erosion frequently localized (pitting).Fatigue cracks.
These two later events are generally evaluated through techniques derived from on land surveys, poorly adapted to the needs of saturation diving :Internal corrosion is evaluated either with instrumented pigs, requiring a shut down of the production and providing a very coarse information unable to identify pitting, or, with manual ultrasonic tests which are time consuming and inappropriate to provide a complete survey of the suspected areas.Fatigue cracks, are visualized through magnetic particles inspections which are costly, due to the high quality cleaning required, and provide only a description of the surface outlet of the cracks.
Drillability Profiles Derived From 3D Seismic Surveys
Authors: Owusu Kwame J. , Gardner Gerald H.F. 
Published: October 2008

Abstract
A computer algorithm is outlined by which velocities can be derived from three dimensional multi-fold data, based on three dimensional migration before stack. The operation of the algorithm is illustrated with synthetic data for a layered model. It is shown that the velocities derived are practically the same whether the input traces are digitized with 16 bits or 1 bit. The practical significance is that velocity analysis can be extended by this method to areas where the data quality is poor by using 1 bit data. Sign bit digitization is, in effect, an extreme form of trace equalization. The reduction in amplitude information by using sign bits is compensated for by the vastly increased number of measurements spread over an area around the well. A practical application for the method is the construction of drillability profiles based on velocity measurements, with emphasis on the detection of formations with abnormally high fluid pressures.

Introduction
Three dimensional, multi-fold, seismic surveys generate a notable amount of data for the analysis of subsurface problems. A typical marine survey, for example, may have source points 100 ft apart along parallel lines that are 200 ft apart. Thus, if the data are recorded with a 48 channel streamer, each square mile surveyed contains over 250,000 seismic traces. Three dimensional processing combines all these data to form an image of each point of the subsurface.
Similar quantities of data can be acquired on land with the use' of 1024 channel sign bit recording systems. The amplitude recovered on correlating a Vibroseis sign bit recording with a sign bit representation of the sweep signal is remarkably similar to that obtained using 16 bit digitization for both the recording and the sweep signal. This property suggests that in some data processing routines the input data can be made sign bit with little loss in accuracy but with a great gain in data compression and reduction in computation time. An example of this was given by Cochran for CDP stacking velocity analysis.
In this paper, we explore a velocity analysis based on three dimensional migration before stack. The input data are migrated for a wide range of velocities using the Kirchhoff method of migration. No approximations are made. The computation is simplified by transforming time to a logarithmic scale, as explained below. The display, instead of being the usual plot of semblance as a function of velocity and time, is a plot of power as a function of depth Z and time T. Maxima in this plot are picked and velocity obtained from the relation V = 2Z/T.
The method of computation is illustrated with 16-bit synthetic data to which noise has been added. These data are also reduced to sign bits and the analysis repeated. The velocities inferred in the two cases are shown to be virtually identical.
Probabilistic Fatigue Analysis Of Offshore Pipelines During The Laying Operation
Authors: Stephens Denny R. , Mandke Jayant 
Published: October 2008

Abstract
When a pipelaying operation is performed in deep water, a joint of pipe may take 'one or two days to travel from the lay barge to the sea bottom. During this time, it is subjected to dynamic loads due to barge motion, waves, and currents. The oscillatory stresses induced by the loads may result in significantfatigue life damage to the pipe before it reaches the sea bottom.
This paper describes the application of probabilistic techniques to determination of fatigue damage to offshore pipe during the normal layingoperation. Spectra1, ana1ysis techniques of offshore structures as described in the now classical papers of Vughts and Kinra and of Maddox and Wildenstein, cannot be applied directly in this situation.
Because of the movement of a joint of pipe with respect to the lay barge, the relationship between stress cycle amplitude and wave height (i.e., the stress transfer function) for a joint on the pipe will vary with time. This, in combination with the random nature of waves, will result in widely varying stress histories, and therefore fatigue damage, for the joints of pipe when they reach the sea bottom. It 'is necessary that the bounds on this damage be determined for design purposes in order to know the fatigue life remaining in the pipe.

Introduction
Although the deepest pipeline installation to date has been in 2000 feet of water along the transmediterranean line across the Sicily channel, future installations in water depths up to 9000 feet are being considered at present. The candidate pipelaying methods applicable to these depths are the so-called "J" curve method and perhaps to a limited extent an extension of the conventional "s" method. Both systems have yet to be fully developed for application in these depths. When laying pipelines in deep water, a joint of pipe may take two or three days to travel from the barge to the sea bottom. The laying method and the pipe-joining technique that is selected will influence this travel time. During this period, every pipe joint is subjected to dynamic loads caused by barge motion, waves and current. The oscillatory stresses induced by these loads can result in significant fatigue damage to the pipe by the time it reaches sea bottom. This paper discusses the method of somputing the fatigue damage imparted to the pipe during the laying operation from a surface vessel.
Offshore pipelaying can best be described as an incremental process in which joints of pipe are added to an offshore pipeline suspended off of a lay barge. After a joint of pipe is welded to a pipeline, the lay barge moves forward and permits that joint and the previous suspended joints to move toward the sea bed. A typica1 barge and pipe1ine configuration is shown in Figure 1.
Ice Force Prediction Using a Limited Driving Force Approach
Authors: Vivatrat Vitoon , Krelder John R. 
Published: October 2008

Abstract
This paper discusses the importance of environmental driving forces in determining ice loads on Arctic offshore structures. The concept of a limited driving force is discussed and methods arepresented to estimate the magnitude of the driving force.
Most techniques for calculating ice loads on structures assume that sufficient driving force is available to sustain failure of the design ice feature against a structure. This paper assesses limits to the environmental driving force in a first-year ice field by considering analytical models of ridge formation, wind and current driving forces and irregularities such as leads and tidal cracks. The predicted forces are compared to available in-situ measurements.
An example is presented to illustrate calculation of maximum rubble pile loads on a conicalstructure. Implications of the concept to selection of design ice loads for structures in exposed, dynamic ice areas are considered.
Average driving forces are estimated to be approximately 10-50 kips/ft for far-field, with some local concentration near fixed structures. These values for the average limited driving force should be considered only as order of magnitude estimates. However, they are sufficiently less than failure loads for many ice features to indicate that consideration of limited driving forces in an ice field may reduce estimated ice loads on Arctic structures.

Introduction
The design of safe, economical structures in the offshore Arctic requires accurate predictionof ice loads for a wide variety of ice conditions. Ice conditions offshore the northern coast of Alaska can generally be classified as a fast ice zone atransition zone, and pack ice. Near the shoreline the fast ice is relatively stable during the winter with limited movement and deformation. A transition zone, beginning at the outer edge of the fast ice, extends out into the Beaufort Sea where it merges with the arctic Pack. The transition zone, typically beyond 45-60 foot water depths, is characterized by more movement than the fast ice with intense ice deformation. Design ice loads increase significantly with water depth because larger ice features can occur without grounding, and the larger movements indicate a higher probability of encountering a large ice feature.
Gravel islands have been constructed and used for exploratory drilling in water depths of up to approximately 65 feet in the nearshore Beaufort Sea. As offshore development advances in the transition and pack ice zones, reducing the uncertainty in ice load prediction will provide more reliable and cost-effective designs.
The prediction of a design ice load involves several components. First, the design ice feature must be selected and the properties of the ice feature specified. The load required to fail the ice feature against the structure is calculated.
Analysis Of Physical And Mechanical Properties Of Deepsea Sediments From Potential Manganese Nodulemining Areas In The North Central Pacific
Authors: Tisot Jean-Paul , Gerard Bernard 
Published: October 2008

Abstract
The knowledge of geotechnical properties of potential manganese nodule mining areas sediments is necessary to study and determine in the best conditions the possibilities of collecting these nodules.
The sediments found in this area all along the geotechnical study fall into three categories. The most numerous are pelagic clay, but other materials from abiogenic origin can be found locally, that is to say: siliceous ooze or calcareous coze.
First, we are going to study. the sedimentologic description, then the index properties of the three soils. Furthermore, we shall describe the mechanical properties incluG Lng a synthesis of the laboratory test results.
A fact is obvious : the physical and mechanical properties of the three materials as well as their behaviour are very different.

:Introduction
Since 1970, AFERNOD has been studyinga2.25Million square kilometer area between the Clarion and Clipperton fractures (Fig. 1) in order to prospect the potential deposits of polymetallic nodules (LENOBLE, 1980). At the same time, theoretical and experimental works about harvesting these nodules have been conducted (GAUTHIER and CHARLES, 1979).
These works have shown that, whatever the systems used to harvest, an interaction between the nodule harvester device and the seafloor will appear. This interaction will mainly consist in a mechanical sollicitation of the sediment. HIRST and RICHARDS (1975), among others, have analysed this problem.
Therefore, since 1977 AFERNOD has decided to study the geotechnical properties of the existing sediments in the prospected area. When doing this researching work, we have tried to study the problem from different points of view.
The required samples have been obtained by of three different means :Box corer.Boomerang corer.. Piston corer.
A few soil mechanic tests have been done immediatly after the sampling on board; most of the samples have been stored and carried over to France to be studied in a laboratory.
The results shown here are a synthesis of the various experiments done on the whole of the samples picked up in a burial depth of one meter below thebottom.

Description Of The Sediments
Three types of sediments quite different one from the others have been encountered during the coring in the studied area.
The most frequently encountered sediment is pelagic clay very homogeneous and of a dark brown colour. Thissoil is mainly (80 %) composed of clay minerals (the fi'ne-st elements), the rest gel).erally have a biogenic origin (diatoms, radiolarias,.) and are more or less well preserved.