bluuebunny/crossref_metadata_2025_split huggingface dataset:
Special Mooring Systems Using Remote Controlled Quick Disconnects For Beaufort Sea Drilling Operations
Authors: Lasch James E. , Pearlman Michael D. , Riotte Erich C. 
Published: October 2008

Abstract
In the early 1970's InterOcean Systems, Inc. developed a remotely controlled rig anchor release (RAR*) to provide an anchored drilling vessel with the ability to remotely (by sonar signals) and rapidly disconnect its anchors without cutting the anchor cables. This paper describes the special mooring systems utilizing the RAR for Beaufort Sea drilling operations. These systems have been utilized by Canadian Marine Drilling, Ltd., the drilling subsidiary of Dome Petroleum in their Beaufort Sea operations.
Because of changing ice conditions which occur in the arctic, and because of the stringent Canadian government regulations, it was necessary and desirable for Dome Petroleum to provide special mooring systems on their drilling vessels which included an RAR on each mooring line. This system provides a rapid means of disconnecting in the event pack ice forces the drilling vessel off the well.
Several mooring configurations were tried, modified, and simplified to improve their performance over the course of the four years (1976 through 1979) of actual field use. The paper describes the mooring systems, the RAR units, the installation, testing, recovery and re-installation techniques. The release units are equipped with a status monitoring system which is described together with the experience of, its use with the mooring system.
Economic and safety advantages are discussed. Future uses and potential value of the mooring systems are presented, with examples of applications in other areas.

Introduction
In the early 1970's InterOcean was approached by a drilling contractor to see whether or not it could provide a quick release unit for floating drilling rigs, in particular, semi-submersibles. With its long experience in remote controlled release mechanisms InterOcean Systems developed the RAR which is used in the North Sea, in the Laborador coast area and in the Beaufort Sea drilling operations.
With the beginning of drilling operations in the Beaufort Sea using drilling vessels, numerous special needs were recognized. Among these was the need for special mooring systems for these drilling vessels.
The prevailing ice conditions in the Beaufort Sea and the stringent Canadian government regulations dictated a special system to hold the vessels on position and yet permit rapid disconnection from their anchors in the event of moving pack ice.
InterOcean had developed the rig anchor release (RAR) which proved capable of surviving the rigors of the mooring lines on drilling vessels. Thus, this system was selected and has been used on the Beaufort Sea drilling operations since the drilling program started in 1976. The mooring systems have undergone modification to meet the changing needs in this hostile environment and the RAR has proven sufficiently adaptable to meet the changing requirements.
Originally, the drillships were equipped with underwater fair1eads for each mooring line. These were to reduce the contact of the ships mooring system with the ice.
Seismic Source Decomposition
Authors: Stoffa Paul L. , Ziolkowski Anton L. 
Published: October 2008

Abstract
We exploit the differences that exist between the radiation fields of a point source and an array to design a marine seismic source with desired power spectral and directional characteristics, whose far-field time signature is known precisely from measurements.
The desired power spectral characteristics are created by firing a series of point source units sequentially, such that their time signatures do not overlap. The effective power spectrum of the whole series of signatures can be made equal to the sum of the power spectra of the individual signatures, and can therefore be designed to suit the desired application by an appropriate choice of source units.
The key to the subsequent processing of the recorded data is to measure the pressure wave generated by each point source unit with a hydrophone placed closeby, but in the linear radiation field. The position of this hydrophone relative to the source unit must be known accurately in three dimensions. The depths of the source units and their relative spatial positions at the instants of firing must also be known. From these measurements the far-field signature of the sequence in any azimuth can be deduced, and the impulse response of the earth can therefore be recovered from the recorded reflection data.
The desired directional characteristics can be created by arranging the source unit separations such that each source unit reaches the desired position at the prescribed firing instant. The deconvolution of the derived sequence of signatures simultaneously performs the source array simulation.

Introduction
In the seismic experiment the measurable response x(t) is regarded as being composed of the impulse response of the earth g(t), convolved with the far-field signature of the seismic source s(t), plus some noise n(t). Thus:
(1) x ( t ) = s ( t ) + g ( t ) + n ( t )
where the asterisk * denotes convolution.
The object of initial data processing of the measurements is to recover the earth impulse response g(t) from the measurable quantity x(t) with as high a degree of fidelity as possible. In order to do this there are three basic requirements which must be met :The signal-to-noise ratio must be large.The frequency bandwidth of the generated far-field signature s(t) must be broad.The shape of the far-field signature s(t) must be known. This means that both the amplitude and phase as a function of frequency must be known.
All these three requirements are met if the seismic source produces a high-energy, broad bandwidth signature of known shape. In attempting to meet the first two requirements at sea, with seismic source arrays, it is usually the case that the third requirement is not met. In this approach we aim to meet all three.

Marine Seismic Source Arrays
The marine seismic sources currently in use are of two types: point sources and arrays. Point sources are those which have dimensions which are small compared with the wavelengths of seismic radiation which they generate.
Controlling Iceberg Roll/Stability During Towing Around Drillships
Authors: Benedict C. Peter , Lewis John C. , Dinn Gary J. , Learning Frederick R. 
Published: October 2008

Abstract
Positive and effective management of icebergs around drill rigs on the Canadian East Coast is limited by deficiencies in iceberg handling icebergs roll under tow. Anchor handling tugsare delayed by three to six hours while redeploying towing gear. The troublesome bergs are normally in the range of 50-500,000 tons. Conventional floating polypropylene towing hawsers compound latent instabilities by applying a torque component (other netlike towing geometries control roll for only smaller bergs but tangle during deployment and recovery).
Field iceberg survey data was collected and on the basis of Lagragian computer analysis a large sample of simulated bergs were towed from random stable floating positions. Through these energy formulations the maximum "critical" tow force (before roll) was computed and the results showed:Calculated critical forces agreed with apparent bollard pull normally causing roll.Critical force varied widely for a specific berg depending upon tow bearing.Critical forces change completely when the iceberg settles to a new attitude.Iceberg drafts vary as much as 25% depending upon attitude.
This paper presents:The results on instrumenting iceberg tow forces on the Aquitaine site during the 1980 drilling program,An operational procedure for predicting critical tow forces on the basis of pre-tow surveys.

Introduction
Canadian East Coast drilling is limited to as few as 60 days per year by ice conditions. Only after pack ice clears in July does the short 60-120 day operating window open for offshore drilling.
In the most northerly active acreage Aquitaine et al. are drilling in 1200 feet at the Hekja site in the Davis Strait with the Ben Ocean Lancer1 In preparation for testing Hekja, improvements in equipment and procedures in 1980 enhanced environmental control in these areas:telemetering current data to predict and compensate for the onset of up to two knots current,automated iceberg plotting and trajectory predictions,computer prediction of maximum allowable bollard tow force for iceberg towing with,tensiometer monitoring of actual bollard pull.
This paper reports the results achieved in items c and d.
Around the drillships iceberg are cleared away by standard towing procedures, 3. Near Hekja, the Zapata supply vessels FREEDOM SERVICE and PIONEER SERVICE were used to circle each berg with 3/4 mi. of floating polypropylene rope, catching the forward end and gripping the iceberg at the rear water line. Following the attachment procedure (taking about one hour) the captain would apply 10-110 tons of bollard pull. A major difficulty then arising is that many bergs are of low stability and will roll, slipping the tow hawser.
Snap Loads And Bending Fatigue In Diving Bell Handling Systems
Authors: Liu Francis C. 
Published: October 2008

Introduction
Recent at-sea tests conducted by the Civil Engineering Laboratory (CEL) 1 have found that a suspended object with a low submerged weight and a large virtual mass such as a diving bell is highly susceptible to snap loads in a single lift line system. Tensions as high as seven times the payload weight were measured 'in sea state 2. Such high tensile loading could cause a catastrophic failure in the handling line when the breaking load is exceeded. Since the snap load is basically an impact load, the amplitude is expected to be proportional to the payload mass and the relative velocity of the payloadwith respect to the surface excitation velocity. Therefore, higher snap load tensions are expected for diving bells which have larger volumes and/or operate in higher sea states.
Bending fatigue is another problem that is closely associated with the design and selection of a critical lift system such as the diving bell handling system. With such systems, protracted payload suspension over a sheave in the water column is expected. In this mode, the line may fail under repeated snap loads of much lower level than the rated breaking strength of the rope. For fiber and wire ropes, bending fatigue is directly related to external fiberto- sheave abrasion and to internal fiber-to-fiber abrasion. No analytical method is available to predict the fatigue life of a rope/sheave system. Laboratory testing is the only means to generate design data. This paper presents the results of an investigation conducted in 1979 to examine the probability of snap load occurrence, the amplitude of snap loads, and the safety of existing diving bell handling systems. A computer analysis, a sea test, and a laboratory simulation test were made for the U. S. Navy Two-Man Open Diving Bell (ODB). Computer methods were also applied to analyze the handling system of the Deep Diving System/Personnel Transfer Capsule (PTC).
The Open Diving Bell (ODB) is essentially a shallow-depth submerged elevator in the water columnto accommodate divers equipped with air/gas supply equipment or hoses. The ODB consists of a hemispherical acrylic dome structure over a diver's transfer stand. It permits compressed air diving to 190 feet and mixed gas diving to 300 feet. For mostoccasions, the diving bell is operated in sheltered areas such as harbors. However, its applications are not limited to calm waters. The ability of the topside deck hands to work safely and effectively will be the controlling factor in stipulating the maximum operational sea state. The ODB manual2 calls for a handling line of non rotating rope capable of handling aload of 4,300 pounds with a safety factor of five. In the past, the diving bell has been handled by a system consisting of the ship capstan, any available standard sheave blocks, and a variety of ropes including 5- to 6-inch-circumference nylon 2-in-l braids and 1/2- to l-inch-diameter wire ropes.
An Advanced Design Deep Sea Mining System
Authors: Welling Conrad G. 
Published: October 2008

Abstract
In October and November 1978, an advanced design deep sea mining system was tested on the ocean floor at approximately 5000 meters depth. The test was conducted from the Glomar Explorer which had been modified to accept the special design system. The miner design, using the latest available technology, was configured to test concepts that provided for efficient operations. The concept included all the functions believed necessary for efficiency with a multiple of sensors to provide real time information to a control station on board the mining ship. The operators in the control station in turn operate the miner by remote control. The miner is self-propelled with variable speed and fully maneuverable. Controls include: speed and direction, depth of mining cut, rate of pickup, and slurry feed rate. Other controls include: washing and crushing of the nodules, lights for T.V. cameras, high resolution sonar and electrical power.
The system can be divided conveniently into seven basic subsystems: the miner, the flexible link, the buffer equipment section, the vertical pipe with cables, the ship platform, the ship control system and the miner control center.
The at-sea test was made to obtain operational and engineering data on the system. While certain deficiencies were encountered, none were considered basic. Sufficient information was obtained to prove the basic system was viable and would provide the necessary mining efficiency.

Introduction
The design of the Advanced Deep Sea Mining System evolved over a period of years. Systematic studies involving operations research and system analysis were used to determine the necessary functions required for efficient operations. Mining involving large tonnages is basically a materials handling problem. In order to obtain high efficiency the system must be designed to operate under steady state conditions, avoiding where possible fluctuations in material flow rates. This implies full responsive controls for a large integratedsystem. Of course, this does not represent anything unique. Many examples can be cited in land mining operations such as the continuous coal mining machine vs. drill and blast.
The basic problem facing the future nodule miner is the remoteness and size of the nodule ore body and, therefore, the difficulty of obtaining detailed information on its physical nature. Even though extensive prospecting and exploration of the Pacific Clarion-Clipperton nodule belt has taken place, one can only describe the ore body on a statistical basis. There are sufficiently large variations in nodule grade and abundance and bottom topography to place rather extensive demands upon the operationalcharacteristics of the miner.
In the initial phases of making design trade-offs, it became apparent that there was economy of scale in design, that is, designs that achieved annual tonnages of three to four million dry tons per year had considerably lower unit costs per ton than those designed at approximately one million tons.
A Study on Estimating the Relief of Magnetic Basement
Authors: Suh Sang Y. , Hyun Byung K. 
Published: October 2008

Abstract
A new method of estimating the relief of the magnetic basement is designed. In the method, the pseudo-gravimetric anomaly, which is vertical derivative of the pole-reduced magnetic potential, is calculated. The pseudo-gravimetric anomaly is downward continued up to the predetermined mean depth of the basement, and then converted to the equivalent distribution of surface densities. The variation of surface densities at the mean depth gives the relief of the magnetic basement. A model study for a two dimensional case is also given.

Introduction
The problem of magnetic interpretation to geophysicists may be said to consist in finding the distribution of magnetized material whose magnetic field is given on a plane surface. Therefore, we are confronted with the inverse problem of potential field theory, i.e., of determining the source from its potential.
An approach to solve the problem is to select the dimensions and magnetic properties of a subsurface model so that its magnetic effect agrees as closely as possible with the observed anomalous pattern. This procedure is relatively simple. But it becomes more complicated if more than one simply shaped body is evidently responsible for the measured anomalies which anybody trying this has experienced for himself.
Hahn (1965) has introduced a method of estimating the relief of a layer with homogeneous magnetization and a surface relief capable of producing the measured anomalies. The magnetized bodies within his task of geological investigation are assumed to be crystalline rocks showing a sufficiently high degree of metamorphism, and/or intermediary to basic igneous rocks. The complex of these rocks may be represented by some sort of a layer with a more or less constant magnetization and a surface relief which is responsible for the magnetic anomalies. His method gives the relief by using the concept of "relief wave" assuming the direction of the magnetization is same as that of the earth's field.
In this paper, we would like to introduce another approach to find the relief of such a layer, without assuming the direction of the magnetization. This does not mean that the present method gives the solution without knowing the direction but it rather means that we can find the solution, at least theoretically, if the direction of the magnetization, which may be different from the present earth's field, is known.
Our method uses "pseudo-gravity" the concept of which can be found in some literatures (Baranov, 1957). The pseudo-gravimetric anomalies, which are slight modification of Bhattacharyya's pole-reduced magnetic potential, are downward continued up to the predetermined mean depth of the basement. These are converted to an equivalent stratum, i.e., an equivalent distribution of surface densites. The variation of surface densities at the mean depth gives the relief of the magnetic basement.
Flash Butt Welding for Large Diameter Pipes
Authors: Muesch Hermann , Langer Jochen , Dueren Carl F. , Luegger Horst 
Published: October 2008

Abstract
For economic reasons, large-diameter pipes with wall thicknesses of up to 40 rom are most suitable for Jmethod deep-water pipelaying. The welding process chosen is a modified flash butt welding process with inductive preheating. The suitability of this process was proven by means of a prototype machine designed for welding X 60 pipes of 3011 diameter and 40 mrn wall thickness.
Numerous tests were carried out in order to optimize the welding parameters and to analyse the various influencing factors. The results have shown that the modified flash butt welding process incorporating a process of inductive normalizing the weld regionproduces high quality welds which fully meet the requirements of offshore pipelining. A condition is, however, that only pipes with a high degree of purity are employed.
Good reproducibility of the results is guaranteed thanks to the welding machine being automated with a preprogrammed welding process.

1.Introduction
Due to the ever-growing demand for energy, offshore oil and gas exploration has been extended to areas with water depths up to 2000 m. The most economical method for handling gas is the pipeline. However, the pipeline is also frequently an economic and safe solution to the problem of oil transportation.
In recent years, various studies have shown that of all the possible pipelaying techniques, the J-method offers the most advantages for large pipe-diameters or depths below 600 m.
These studies were carried out by a West German team which received financial support from the Federal Minister for Research and Technology. 1/
The results of these studies were published in the OTC in 1979. 2/ The new pipelaying method requires an economic welding technique which ensures that the connections between large-diameter pipes with wall thicknesses of up to 40 rom are of a high quality. Of all the possible welding processes, flash butt welding was chosen and a prototype machine developed to demonstrate its suitability.
The following is a report on the findings and results of numerous destructive tests which were carried outon the girth welds.

2. Pipelaying Method
As the welding process developed is for flash butt welding large-diameter pipes specifically for J-method pipelaying, it is appropriate that this new pipelaying system be summarized.
In contrast to the usual method of laying a pipestring in the form of an "S" from lay barges using long stingers, the pipestring laid by the J-method is paid out into the water through the middle of the pipelaying vessel by means of an inclined ramp, the angle of which is a function of the water depth (Fig. 1).
The depth to which the J-method can be used is limited by the axial loads resulting from tension and bending in the J-curve and also by radial stress resulting from the effect of the water pressure on the pipe. Dynamic loading and oncoming flow also have to be allowed for.
Novel Underwater Strengthening System For Tubular Joints
Authors: Tebbett Ian E. , Robertson Donald A. 
Published: October 2008

Abstract
This paper describes the novel use of a cement grouted sleeve as a means of strengthening tubular joints on a southern North Sea gas production platform to provide additional punching shear capacity. Two joints of X configuration at the -15 m (50 ft) level consisting of 610 mm (24 in) diameter members have been provided with split steel sleeve and cement grouthas been injected into the void between the sleeve and original structure.
This strengthening system was chosen as an alternative to a fully welded repair or mechanical clamping devLces the main advantages being reduced diving requirements, simplification of underwater habitats and the ability to accommodate fabrication tolerances, lack of fit and member distortions and misalignment.
As present design codes provide information on the strength of or design method for such systems, a programme of laboratory tests, including simulation of installation procedures, was undertaken to demonstrate the validity of the design. Details of the tests and results are presented together with details of the chosen solution and notes on the field installation. Of particular interest is the use of underwater welding methods to provide mechanical shear connectors on existing tubulars. This allowed the use of significant ly shorter sleeves and greatly simplified their installation.

Introduction
Cement grouted sleeves have previously been used only as a means of strengthening, connecting and repairing simple tubular members in a jacket structure. This paper describes a case history in which grouted sleeves have been used as a means of strengthening tubular joints.
The application described concerns two X-joints on platform AR of the southern North Sea Viking Field gas complex. These joints had been shown by reanalysis of the structure to have an inadequate safety factor against punching shear failure.
A grouted sleeve solution was chosen in preference to other methods (e.g welding or mechanical clamps) for reasons identified in the paper. The strengthening system was successfully installed during 1980 and thissuccess has established such systems as viable strengthening and repair alternatives for tubular joints.

Background
The Viking Gas Field is situated in Blocks 49/12 and 49/17 of the southern North Sea. The field consists of two manned platform complexes and five unmann ed satellite platforms. The five original 'A' and 'B' Complex platforms were installed in the period 1970 to 1972, the compression platforms, AC and BC, and the satellite platforms were installed in 1974/1975.
The 'A' Complex consists of five platforms of various sizes and leg configurations, interlinked by bridges. Platform AR which is of particular interesthere is situated at the west end of the complex and is the only six legged platform in the Viking Field. It serves as the main riser platform for the field and also provides accommodation for 30 personnel.