bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploratory Drilling on the Canadian Continental Shelf,Labrador Sea
Authors: Duval Bernard C.
Published: October 2008

The Labrador Shelf is still at a very early stage of exploration. The various factors which make exploratory drilling particularly difficult and shorten the operating season, like ice-pack, icebergs, meteorology, are discussed. After a first unsuccessful attempt in 1971 whith a conventional anchored-type vessel, the technological breakthrough occurred when PELICAN, a dynamically positioned drillship, was successfully used in 1973 and 1974, which resulted in two gas discoveries out of three wells drilled. A description of this operation is presented as well as possible applications to other areas.

1. INTRODUCTION AND GENERALITIES

The Labrador Shelf comprises an area in excess of 50,000,000 acres. It is tightly covered by federal oil and gas permits granted to 24 single. Companies and joint holder Combines.

Its northern and southern boundaries are respectively the 61° parallel (which corresponds to the latitude of Hudson Strait), and the 52° parallel (Strait of Belle Isle). It is bound to the West by the Labrador Marginal Channel, fringing the mainland made up by the Canadian Precambrian Shield. To the East one can take the 1500' bathymetric contour line as a practical limit.

Due to this particular situation between a channel and the continental slope there is neither shallow water nor gradual descent of the bottom from the Continent towards the oceanic depths. The "backbone" of the shelf is constituted by a succession of banks with an average water depth of 600 feet, separated by transverse topographical troughs and saddles (Figure 1). These banks are from North to South : Saglek Bank, Nain Bank, Harrison Bank, North and South Domino Banks. Their area varies from approximately 3,000,000 to 6,000,000 acres.

The Eastcan Group (1) holds titles over approximately half of the Shelf, including almost the entire area of the banks.

Various geophysical surveys and reconnaissance seismic work began as early as 1966 and 50,000 miles have been shot in the area since. As a result one can conclude that the Shelf is underlain by a basin in which sediments in excess of 30,000 feet at some places, have deposited. The maximum thickness is to be encountered in the North (Saglek), whereas the central and southern parts range from 5,000 to 20,000 feet.

The exploratory targets are blockfaults related to rifting movements which took place when Labrador and Greenland drifted apart during Jurassic and Cretaceous times. There are a number of well-defined structures to be drilled in the years to come and the stratigraphic objectives range in age from the Paleozoic up to the Tertiary. The Labrador Shelf is at a very early stage of exploration drilling. Among three wells drilled so far, two were located on banks (Leif and Bjarni) and one in a saddle (Gudrid).

To put the matter in a more regional perspective, it is interesting to recall that the most active exploratory area of Eastern Canada so far has been the Grand Banks -of Newfoundland to the East and South of the Island and the Scotian Shelf South of the Peninsula of Nova Scotia.
Inclined Pulout Forces for Embedded Plate Anchors
Authors: Colp John L. , Herbich John B.
Published: October 2008

Laboratory model pullout tests were conducted in a "rod analogy" soil model, dense dry sand, dense submerged sand, and Gulf of Mexico marine sediments at pullout inclination angles from 900 (vertical) to 450 and at two burial depths. Equations are, developed from the experimental data that 0can used for design purposes.

INTRODUCTION

The expansion of the field of coastal and ocean engineering has resulted in a corresponding increase in applications for floating equipment, anchored in shallow or deep water, many of which impose a stringent station-keeping requirement. One of the solutions frequently used in these applications is a taut-line mooring system. However, the design of these systems demands consideration of the problem of loads on the anchor that are always more or less inclined from the vertical, due to the forces ocean currents and wind often exert against floating equipment. The effects of such loap' inclinations are not well known, since the phenomena of the resulting seafloor soil failure caused by excessive inclined loads have not been observed and understood. Lacking this information, the practicing ocean engineer must estimate the holding capacity in his anchor system design very conservatively whenever inclined loads can possibly occur.

MODEL EXPERIMENTS

Test Series

The initial laboratory tests were designed to allow the observation in a two-dimensional array of particle motion, in a simulated, dense, cohesionless, granular material during pullout of a plate under the application of inclined loads. The failure phenomena that occurred during these modes of loading could be observed, which would aid in understanding them.

The second series of tests was performed in a three-dimensional tank of dense, air-dry Ottawa sand. Values of maximum pullout loads for varying conditions of load inclination, and depth of burial, were measured.

The third series of tests duplicated the second series except that the dense, Ottawa sand samples were submerged under fresh water. This series of tests was analogous to the second series, but showed the effects of submergence.

The fourth series of tests was performed in the same manner and with the same equipment, except that the soil sample was composed of actual seafloor sediments obtained from the Gulf of Mexico. 'lhus, the differences in pullout force and failure meclianisms that occur between a fine-grained marine material and the granular materials examined in the second and third series, could be compared.

Two-Dimensional Tests

The two-dimensional tests utilized a plexiglas tank 3 ft high by 4 ft wide by 3/4 in. thick. The tank accommodated an array of approximately 150,000 steel rollers 1/8 in. in diameter and 3/4 in. in length. 'they were stacked with all of their cylindrical axes parallel and with their ends constrained by the plexiglas faces of the tank. 'the ends of the rollers were large enough so that photographs of the array taken through the plexiglas plainly show each roller and its displacements.
Geotechnical Properties of Sea-Floor Sediments off the Coast of Southern California
Authors: Noorany Iraj , Kirsten Oskar H. , Luke Gregory L.
Published: October 2008

Near surface sea floor soils were obtained, with a sampler attached to the tracked underwater vehicle RUM, from eight regions off the coast of Southern California. The soils represented the continental shelf deposits as well as deep sea floor sediments. The geotechnical properties of these soils, including grain-size distribution, index properties, strength and compressibility, were determined.

Introduction

This paper describes the geotechnical properties of 28 sediment cores from eight areas on the floor of the Pacific Ocean off the coast of Southern California. The water depths ranged from 46 m. (25 fathoms) to 1199 m. (655 fathoms). The cores were taken by a 7.30 cm. in diameter, 56 cm. long sampler attached to the manipulator arm of the RUM (Remote Underwater Manipulator), a research vehicle of the Marine Physical Laboratory of the Scripps Institution of Oceanography, University of California. The sediment cores were stored in a 50C refrigerator and were tested at the Soil Mechanics Laboratory of San Diego State University, San Diego.

Sea-Floor Sampling by RUM

The RUM (Fig. 1), is an unmanned tracked vehicle developed for sea floor explorations in water depths up to 2440 m. (8000 ft.) deep. An umbilical cable connects RUM with a surface support platform ORB (Oceanographic Research Buoy) which provides the power and controls RUM. Various features of the RUM/ORB system are shown in Fig. 2. RUM has been instrumented for a number of underwater measurements (2). Among these are a remotely controlled sediment corer (Fig. 3), in-situ vane shear device and a cone penetrometer (3,4) which have been used in waters as deep as 1830 m. (6000 ft.).

Sampler Locations

The RUM/ORB system was deployed at eight different areas off the coast of Southern California during the months of January, February, March, May and June, 1972. The soil samples described in this paper were obtained from the upper 60 cm. of the sea-floor sediments. The eight areas explored were: La Jolla Canyon, La Jolla Fan, the continental shelf off Bird Rock, the edge of the continental slope west of Bird Rock, the continental shelf off the coast of Point Lorna, the edge of the continental slope west of Point Lorna coast, top of the Coronado escarpment, and the floor of the San Diego Trough.

Index Properties

The index properties of the samples are summarized in Table 1. The grain size distribution was determined from hydrometer test. The specific gravity of solids was measured by the pycnometer method, and the plasticity indices (liquid limit, plastic limit and plasticity index) were determined from Atterbert Limit tests. The liquidity index, in Table 1 is defined by the following equation.
High Seas Oil Recovery Systems Development and Testing
Authors: Leary John F.
Published: October 2008

The nature of high seas oil spills required the development of special devices which would operate and recover oil in the rough water environment. The importance of fast response to these situations dictated certain size and weight requirements and the oil spills predicted, dicated the recovery rate capability. These specifications are outlined and a history of events leading to the development and test of prototype systems is discussed. Certain of the oil recovery techniques are mentioned. Devices carried to prototype or advanced laboratory model level are discussed Examples are: the Free Vortex, the Weir- Basin, and the Disc-Drum. Attention is given to the theory of operation of these systems. Oil tests and sea tests of these devices are discussed. The capability of these systems as a result of recent design changes and tests is covered.

INTRODUCTION

The increased size of oil tankers, the density of traffic on the high seas, increased offshore drilling for oil and recent incidents of oil spills have all pointed to the urgent need for oil pollution control. In the event of a massive spill on the open sea, the Coast Guard will play an important role in the control, recovery, and disposal of this oil. It is the purpose of this paper to discuss the Coast Guard's approach to the solution of the problem of recovering spilled oil from the surface of the sea. Many oil recovery techniques were studied and tested. Those most promising ideas were constructed into prototype systems scaled in size to meet the rates of recovery of oil which would combat the size spill anticipated. Two such recovery devices were constructed and tested in inland pools with oil and on the high seas in calm and rough conditions. The Disc-Drum and the Weir-Basin techniques have proven quite capable of meeting the oil recovery rates projected. One of these devices, the Disc-Drum system, has been able to withstand all the rigorous testing thus far completed. A third technique, the "Free Vortex", is still undergoing research and development. This system has recently shown considerable improvement and may yet become a very useful tool as an oil recovery device both for high seas use and inland waters.

DISCUSSION

A massive oil spill is one wherein millions of gallons of oil are released, possibly due to a casualty of a tanker at sea or an emission of oil to the sea from an offshore drilling rig. The classic example of the kind of spill referred to is the Santa Barbara Channel offshore oil spill which caused costly damage to beaches, wildlife, recreational marine facilities and other valuables along the shore. The primitive unprepared techniques used in an attempt to recover the oil were extremely inefficient, ineffective and very costly. It is commonly agreed that if spills could be contained and recovered and not allowed to reach the beaches it could save millions of dollars in beach cleanup and restoration costs. Oil recovery from the open water is, therefore, a highly desirable objective.
Computer Simulation of Offshore Oil Spill Cleanup Operations
Authors: Cochran R.A. , Fraser J.P.
Published: October 2008

ABSRACT

Computer simulation provides a powerful tool for use in selection and design of oil spill control equipment. This paper describes an oil spill simulation program which enables the user to assess the effects of weather and of the performance characteristics of oil spill control equipment on the recovery of spilled oil. Results of a sample case are shown which indicate the trends which might be expected from variations in the number of skimmers used, their ability to operate to different maximum wave heights, other skimmer performance characteristics, length of time spent on the job, and size of the spill.

INTRODUCTION

Anyone faced with purchase of oil spill control equipment has a serious problem: How much of what type of equipment is needed? Until recently, there has been no logical answer to this problem. Purchase of oil spill control equipment has, at best, been based on educated guesses. The purpose of this paper is to present a better method by which we can select equipment for oil spill containment and recovery. The performance of oil spill control equipment in calm water is easy to assess. However, the performance generally deteriorates as the weather becomes more severe. If the weather becomes very severe, it may be necessary to shut down operations or to seek shelter. The most important weather variable which affects the performance of oil spill skimmers and booms is the wave height; we can usually determine a characteristic wave height above which a given skimmer cannot operate. Similarly, the maximum wave height above which a given boom will not contain oil can be determined. Thus, we can characterize the performance of oil spill control equipment in terms of wave height. Historical (statistical) weather data for any given offshore location can usually be obtained. These data can be used to generate realistic synthetic weather synopses, using the theory of Markov chains.1,2 In turn, the weather synopses can be used to deduce corresponding oil spill recovery synopses, using a computer simulation program we have developed.3 In any run, using the oil spill simulation program, the computer keeps track on the weather, which can affect not only the ability of skimmers to recover oil or booms to retain spilled oil but also the ability of equipment to mobilize and leave shelter for the job site. The program also keeps track of the spreading of oil on water and (if desired) evaporation of the lighter components, and from this information the computer deduces the area1 extent of the oil spill and the resulting average oil thickness. This information is needed because the recovery efficiency (oil: water ratio) of any skimmer depends on the oil thickness. Booms or surface tension modifiers can be used to contain the spilled oil. The end result of the computations in any single computer run is the amount of oil recovered in that run. For our simulations, we usually generate 100 different weather synopses (thereby giving a statistical distribution of weather simulations) and compute the oil recovery for each.
The "stump" A New Dimension In Dredging
Authors: Batchelder George W.
Published: October 2008

Hydraulic dredging equipments has changed little since Liddy, Von Schmidt and others started pumping dredged spoil about one hundred years ago. The basic elements of the hydraulic dredge are simply a barge or ship's hull, a dredge pump, power plants, maneuvering spuds and lines or engine propulsion, suction line (cutterhead) and ladder, and a discharge line. In spite of various refinements and innovations, hydraulic dredges are about the same as they were when the Panama Canal was built.

Approximately one hundred hydraulic dredges are manufactured each year. Their sizes vary from the small six-inch portables to the 36"- 42" superdredges. Modern dredges have more compact power plants, more efficiently designed pumping systems, swell compensating equipment and space-age electronic equipment for controls and navigation - but this is not enough. Although both the venerable old dredges and the modern dredges have tremendous capacity and are the most efficient earth-moving equipment in the world, they are not capable of meeting the great bulk of today's dredging requirements. Today's requirements include working in the pen sea to cut, clear, and deepen channels and harbors to depths of eighty feet or more. There is a recognized need for dredges to work offshore in ocean mining projects, in land reclamation, and on beach nourishment projects. Planners and engineers have designed offshore nuclear plants, airports, artificial islands, and deep-water ports, taking for granted that the dredging industry was keeping abreast of the times and their requirements and that costs would be nominal. The truth is that there are not enough dredges capable of doing this type of work, and the price is not nominal. It is too expensive. These facts will no doubt be brought out in the National Dredge Study now being completed for Congress by the Arthur D. Little Company.

In the past dredge owners have been able to modify and make innovations to their existing fleet, incorporating the best available technology, in order to tackle various types of projects, most of which were in safe, sheltered waters. A dredge owner therefore has not only a large initial investment in the dredge, but the additional cost of upkeep and renovation. In his own best interest he must operate, maintain, and modify that dredge as long as he can keep it operational. However, many of these dredges are becoming really obsolete, and their owners cannot compete with operators of modern specialized equipment.

Both modern and specialized dredges have profit and performance advantages over the old dredges, which have consequently remained idle. Inflated costs and high interest rates make it too costly to upgrade many of the old dredges to competitive levels. The technology in dredge design that is evolving allows the dredge longer wearing time on replaceable parts and easier and faster servicing. This allows a dredge to work continuously for a greater percentage of the time and to use smaller crews, thus reducing project costs and increasing profits and competition.
Field Testing and Analysis of Laterally Loaded Piles om Stiff Clay
Authors: Reese Lymon C. , Cox William R. , Koop Francis D.
Published: October 2008

Two nominally 24-in. diameter piles, instrumented for measuring bending moments, were driven into stiff clay and subjected to lateral loading. A nominally 6-in. diameter pile was also instrumented for measuring bending moments. It was driven at the same site, loaded, pulled, redriven, and reloaded. Short-term static and cyclic loading was employed on both 24-in. diameter and 6-in. diameter piles. The water table was maintained a few inches above the ground surface during the testing program. The results of the tests were analyzed to obtain families of curves showing soil resistance p as a function of pile deflection y. Based on the experimental p-y curves and on theory for the behavior of soil, procedures for predicting p-y curves for stiff clay were developed. The procedures were used and predictions of pile behavior at the site were made. The predictions compared favorably with actual behavior.

Foreword

The research described in this paper was sponsored by Amoco Production Company, Chevron Oil Field Research, Exxon Production Research Company, Mobil Oil Corporation, and Shell Development Company. Shell Development Company was the operator of the project.

Location of Test Site

The field studies on which this paper is based were made at a location five miles to the northeast of Austin, Texas adjacent to US Highway 290. The surface soils in this area consist of stiff, preconsolidated clays of marine origins. These clays are referred to as the Taylor group and studies showed that unconfined compressive strengths of 2 to 10 tons/ sq ft were not uncommon in zones near the surface. These clays have a secondary structure, such as fissures, joints or slickensides, that was desirable because of the wide occurrence of this type of soil in nature. The secondary structure was expected to result in a less favorable behavior of the clay; therefore, a possibly critical soil condition could be investigated.

Preparation of Test Site

On December 15, 1966, a pit 45 ft wide by 50 ft long by 3 ft deep was excavated at the test site. A plan of the test area is shown in Fig. 1 with the locations of all soil borings and test piles. After the excavations was completed the pit was flooded with water to saturate the near surface clays and to simulate conditions that would exist in clays on the ocean floor. This initial inundation was done some five months before the installation of the first test piles and some six months before lateral loading of test piles. In April 1967, two soil borings, borings 5 and 6, were made to investigate the influence of some four months of ponding on the water content of the clay. These borings indicated an increase in water content with an accompanying decrease in shear strength for clays in the first few feet below the pit bottom. After borings 5 and 6, the pit was lowered an additional 2-1/2 ft. This additional excavation was done on April 21, 1967 and the pit was again inundated.
A 4000-Foot Riser
Authors: Heuze Louis A.
Published: October 2008

I. ABSTRACT

TOTAL-Compagnie Francaise des Petroles (C.F.P.) has developed, in association with Institut Francais du Petrole (I.F.P.) and ELF-Aquitaine, a dynamic and some static calculation programs for studying the behavior of part, or the totality, of a drilling riser.

This paper:–gives the conclusions of the theoretical studies about the relative influence of every parameter necessary for full determination of a riser,–gives some qualitative test results about different equipment proposed by manufacturers and liable to solve one of the most important problems that are–lastly, presents three systems that have not yet been realized and that could represent solutions for some problems examined in this study.

II. INTRODUCTION

Let it immediately be pointed out that the value 4,000 feet in the title only refers to the magnitude of the water depth now aimed at, not only by TOTAL, but also by all the major oil companies.

At the present time, many wells have been drilled over a water depth between 500 and 1,000 feet, the present record is held by SHELL at 2,000 feet, and about twenty drill ships or semi-submersibles have been ordered and should be equipped for depths between 2,000 and 4,000 feet.

This paper focuses on the risers for this latter category of drilling supports.

III. STATEMENT OF THE OBJECTIVE OF THE STUDY

It is understandable that the riser is one of the most important problems to be solved for deep sea drilling, and that the solution, if any, is to satisfy every condition of security, on pain of seeing the whole project fall into jeopardy.

That is why all the French companies joined together to spend several tens of thousands of dollars for creating very sophisticated static and dynamic calculation programs, for testing equipment such as buoyancy materials or riser connectors, and for developing new technology where existing techniques could not be extended.

IV. MEANS AND CONCLUSIONS OF THE THEORETICAL STUDY OF THE RISER

Dynamic Calculation Program

This program is bi-dimensional and calculates, statically or dynamically, the forces exerted and the stresses inside the riser, whether connected to the well head or disconnected.

Appendix A describes:–the external actions that are considered by the program,–the simulation of the connections at the top and at the bottom of the riser,–the hypotheses and the principle of the calculation.

The riser is defined as the assembly of several stumps of which it is necessary to specify:–the length of each one,–the O.D. and thickness of the resistant section, that is, the section considered for calculating the stresses,–the mass per meter of length, the hydrodynamic diameter D that is considered for calculating the drag forces,–the diameter D considered for calculating the buoyancy,–the modulus of elasticity.
Inertially-Aided Dynamic Positioning
Authors: Buechler David L. , Hanna Jonn. T.
Published: October 2008

Integration of a commercial inertial navigation unit into a dynamic positioning control loop for offshore drilling rigs will provide improved operation and a self-contained backup in the event of signal loss from the primary acoustic or taut wire systems. Tests have demonstrated an average position error buildup of less than two feet per minute for up to one hour of pure inertial operation.

INTRODUCTION

The accuracy and reliability of the dynamic positioning system for deep water drilling rigs are strongly dependent upon the sensors in the control loop which measure the rig position and velocity. The prime reference for position control of the rig is an acoustic beacon, mounted near the well head, whose signals are picked up by receivers under the rig. This reference is usually augmented by taut wire angle sensors which are also tied to anchors on the ocean floor. Other more remote position references, such as Loran C or navigation satellites, are unreliable and less accurate, and therefore not normally considered for primary reference control. While the riser itself is a potential reference, its dynamic motion in deep water needs to be better understood.

As the drilling rigs begin to operate in depths of 2, 000 to 6,000 feet, the ocean bottom acoustic and taut wire references become less reliable because of transmission noise and the increased possibility of their complete loss. There is a strong desire by the operators of the dynamically positioned rigs to have a 'sky hook' available to provide a temporary reference should these signals be completely lost, and to provide a smoothing medium to suppress their high frequency measurement noise. An inertially stabilized platform can provide such a reference when integrated properly with other position references.

An inertial reference unit and digital computer together form a dead reckoning navigation system. The velocity is determined through the integration of accelerometer outputs; another integration determines the system position. The constants of integration, which are the initial velocity and position, must be supplied to the system. In addition, the platform alignment with respect to the earth must be known by the computer in order to establish a reference coordinate system in which to make the measurements and perform the computations.

On board the drilling rig, the inertial reference unit (IRU) platform can be leveled to the local gravity vector to provide a vertical reference to the acoustic pickups.
Wave Induced Oscillations of Tension-Leg Single Buoy Mooring System
Authors: Kirk C.L. , Jain R.K.
Published: October 2008

This paper presents analysis of the response of a tension-leg single buoy mooring system subjected to regular wave excitation. The buoy consists of a cylinder anchored to the sea bed by parallel chains. The nonlinear equations of swaying and pitching motion are derived from Morison's formula with the addition of the dynamic pressure force acting on the base of the buoy. A numerical solution is achieved by assuming that the swaying motion influences the pitching motion but not vice versa Time histories of the response of three sizes of buoy are given and the conditions under which pitching motion will lead to slackening of the anchor chains is determined.

INTRODUCTION

A tension leg single buoy mooring system (S.B.M.) is essentially a cylindrical buoy anchored to the sea bed by pre-tensioned chains or cables. A tanker moored to the buoy is able to transfer. oil from a submarine pipeline through a rubber underwater hose to the buoy's swivelling cargo manifold and finally through a floating surface hose to the tanker. The swivelling arrangement on the buoy permits the tanker to swing freely through 360 degrees thus preventing any twisting of the underbuoy hose.

The design of an S.B.M. for operation in severe sea conditions like those of the North Sea requires reliable estimates to be made of the maximum expected dynamic response of the buoy, the dynamic loads imposed on the anchor chains and their points of attachment with the buoy, and the stretching of the underbuoy hose. In addition to extreme wave loading cases the response of the buoy to smaller waves is of interest from the point of view of 1atigue of the anchor-buoy linkages and wear of eye connections as mentioned in Ref.1. Swaying motion is an important parameter in tanker mooring operations and in landing helicopters on manned buoys. Sway will also be the primary cause of stretching of the underbuoy hose whereas pitch may give rise to slackening of the anchor chains. In tensioned chains which slacken and then snap tight, dynamic loads may occur which are considerably greater than the maximum static loads. Goeller and Laura, Ref. 2, in tests on stranded steel cables found that forces greater than nine times the static load were developed in the snap condition.

The aim of this paper is to describe the mathematical model that was developed to study the response of an S.B.M. in sway and pitch to linear waves in deep water. Since a tanker does not remain moored to an S.B.M. in rough sea, the forces induced by tanker motion are not considered. The nonlinear equations of motion are derived by using D'Alembert's principle. It is assumed in the analysis that pitching motion does not affect swaying motion, but not vice-versa. This partial uncoupling facilitates the numerical solution. The justification for this procedure is based on the fact that the primary motion of the buoy is sway, with the secondary pitching motion occurring at a higher frequency.
A Submersible Diving System for Science
Authors: Fike John W. , Dolan Robert B.
Published: October 2008

As a result of the inventive ambitions of Edwin A. Link, Trustee and Vice President of Harbor Branch Foundation, Inc., a unique observation submersible with diver lock-in/lock-out capabilities has been developed. A second generation submersible christened the JOHNSON-SEA-LINK II in January 1976, it exhibits the characteristics of versatility, simplicity, safety, fast turn around between missions, ease of operation and comparatively low cost.

Framework, pressure hull, mechanical, electrical and pneumatic controls, as well as life support equipment, are divided into separate modular sub-systems. In all cases the removal of a module or a system for routine maintenance or repair is accomplished in minutes. Overlapping, cross-connecting or unitizing between systems has been avoided. The use of off the shelf components, when possible, and standardization of hardware helps to satisfy the five requisites. Extensive human engineering has provided a top to bottom, left to right logic to all control functions.

The objective of the submersible JOHNSON-SEA-LINK II is to provide the scientific staff of Harbor Branch Foundation, Inc. with a sophisticated oceanographic tool that will be operational 365 days a year. This paper discusses how that objective was met.

INTRODUCTION

The drive to preserve and improve our environment and the need to deal with the pollution problems created by prolific industrial technology are two of the major issues facing the United States today. Deterioration of the environment either real or within the realm of real possibility has generated concern and demand by a public that is growing increasingly aware of the threats. If it is accepted that the rivers and streams of the nation act, in part, as sinks, then it stands to reason the oceans are the ultimate sink, the final receptacle for the nation's unrecovered, untreated and unwanted waste and byproducts. What effect has it had, what are the capacities of these great bodies of water? Consider the importance attached to these questions by the Biological Oceanographers concerned with the oceanic eco-system. To measure the quantity of life and catalog the variety of life in the water column and on the ocean floor, there must be a base line with which to compare it. Since the eco-system can be rapidly altered by the introduction of an unnatural substance, sampling and observation must be by highly mobile means. The problems associated with the procurement of accurate in situ biological and physiological sub-surface data is well documented. It follows then that an important aspect of the requirements of the oceanographer and scientist is a means of rapid in situ investigation. Often the use of manned submersibles can offer many advantages for a quick and relatively inexpensive method of obtaining the much needed information.
A High Load Moderate Speed Deployment System for a Deep Ocean Bottom Working Vessel
Authors: Person Abraham
Published: October 2008

A working vessel for deploying and retrieving heavy loads in deep oceans is now operational. This is accomplished by lengthening or shortening a load-connected pipe string and by two pair of yoked, hydraulically powered cylinders that alternately support and transport the pipe string and load. This paper describes the deployment and retrieval system.

The system, known as the Heavy Lift System, contains four 19-foot stroke hydraulic cylinders and their power units and 8500-ton capacity connecting yokes for each pair of cylinders. Ancillary hydraulic equipment includes a pipe string engaging latch on each yoke, a 450,000 ft-lb pipe string torquing/ detorquing device on one yoke, a stationary support for "parking" and rotating the load and the hydraulic power units for these elements. In addition, the system includes an instrumentation and control suit to automatically or manually operate the complete deployment and retrieval functions.

The system has a stall load capacity of 8500 tons. It has been fully tested and successfully used to deploy and retrieve up to 7500 tons at 6 feet/minute in 17,000 foot depths.

INTRODUCTION

The GLOMAR EXPLORER is the surface support vessel for an operational system designed to work the ocean bottom. It transports the bottom equipment and provides the work platform from which the bottom equipment is operated, deployed and retrieved. Design parameters for deploying/retrieving were much greater than anything previously done from a vessel, and unique equipment had to be devised, tested, installed and operated. The resulting subsystem is called the Heavy Lift.

The mechanical link between the Heavy Lift and the bottom equipment is a rigid pipe string. Deploying/retrieving is similar to current offshore riser and drill string operations, i.e., add/remove a pipe stand then lower/raise the pipe string to the next tool joint. Initial pipe string design payload and depth was up to 4,000 tons and 17,000 feet. To minimize pipe string stress and thereby its weight, the work platform for the Heavy Lift was gimballed and heave compensated1. Platform space was limited and any equipment on the platform added to the gimbal-heave compensator loads. Compact and light Heavy Lift components were needed.

The design weather window for deploying/retrieving was' small and the necessary lowering/ raising rates could only be achieved by automation which, in turn, requires remotely controllable components. Finally, pipe stands weighed up to 40,000 lbs each, tool joint torque was up to 450,000 ft-lbs and, in spite of the gimbal-heave compensator refinement, the design payload for the Heavy Lift became 8,500 tons at 17,000 ft depths. High rates and high loads necessitated high powered Heavy Lift components.

Compact, low weight, remotely controllable and high power components were achieved by designing hydraulically powered mechanical equipment. These were integrated with an electronic control system to meet the Heavy Lift subsystem functional requirements during automated operations.
Development of Automatic Underwater Welding With Local Cavity Formation Method
Authors: Tamura Mitsuru , Nishio Yasuhiro , Wada Hirokazu
Published: October 2008

This paper describes the development of automatic underwater welding system based on an unique localized dry environment by a fluid curtain.

With only the welding machine submerged, the system is operated by remote control in the ocean in connection with materials supply and supervision of works, thus considerably reducing its reliance on diving and underwater operations.

In this process, a stabilized gaseous zone can be created only around the welding spot just underneath the welding torch by inclined water jet stream from the outer circumference of the double nozzle. Then various gas shielded arc welding methods such as TIG, MIG and C02 arc welding are performed in the dry environment. (Fig. 1, 6, 11, 12)

As the initial plan, a submersible automatic welding machine has been produced, and the trial test of this system has been successfully performed on objects submerged in a large cistern while supervising and controlling-their welding conditions by TV monitoring from outside the cistern. (Fig. 15, 16, 17) Welding results have proved excellent, being not much different from those undertaken in an ordinary environment on land. (Fig. 13, 14, 18)

INTRODUCTION

From the viewpoint of natural resources development and utilization of space, recognition and concern have been rapidly elevated with regards to the importance of ocean development and thus the conception of super giant ocean projects such as various offshore plants, sub-sea production systems, etc. are being mapped out actively.

For the construction of these gigantic structures, full-scale underwater fabrication techniques are indispensable.

Among these the underwater welding technique is expected to play the most vital role. Thus early development is earnestly desired by various fields concerned.

Up to the present, the two currently available underwater welding are the dry and wet methods.

For the sake of obtaining reliable weld, it is unquestionably desirable to be welded in a dried environment. Dry method; however, requires a special chamber that entirely covers the work, which brings limited use in the shape of object as well as extremely high cost. Wet method on the other hand, has depended much upon submarine work by divers. And because of many points which are still at issue with respect to reliability, efficiency and workability, underwater welding has not yet been put in full-scale practical use.

Recent developed local cavity methods are noted because of their better handiness than that in the dry technique and also the much better reliability than in the wet processes.

The authors have developed a unique local cavity formation process by a fluid curtain and its application to welding, cutting and painting underwater.

This method utilizes the effects of shutting off the water invasion by the momentum of fluid jet and smooth exhausting of cavity gases by flow entrainment.

This paper describes the principle of cavity formation, cavity formation conditions and its application to welding.
Steels for Different Sections of Offshore Structures
Authors: de Boer Harald , de Meyer Lutz , de Schonfeldt Henry , de Thiele Manfred
Published: October 2008

Steels of different mechanical properties and weldability should be used in different sections of offshore structures with regard to their configuration and stress conditions.

Normal strength steels have a good weldability and a high efficiency in welded joints, when fatigue stresses occur.

High strength steels with 355 N/mm2 minimum yield point are weldable fine grain steels with a wide range of applications. However, plates of more than 30 mm thickness must be preheated before welding to avoid cracking. For complicated structures which are loaded by fatigue stresses, like nodes, the weldability and toughness, in particular in the z-direction of plates, have been improved. A high resistance against lamellar tearing was obtained by inclusion control. The development of a high strength steel which is crack free weldable without preheating was achieved by consistently lowering the carbon content, balanced by an increase in manganese. The properties of these two steel types may be combined in one steel which needs no preheating and is resistant against lamellar tearing.

High strength steels with yield points between 400 and 690 N/mm2 can be used in sections where static stresses dominate.

The principles of steel selection with regard to different stresses during manufacture and service are demonstrated schematically for a semi-submersible drilling unit and have already been successfully applied.

INTRODUCTION

Drilling rigs and production platforms for the offshore technology have to meet different requirements depending on their field of operation. This applies also to the steels used for these structures. The Gulf of Mexico will demand other steels than arctic waters and it would be of poor use to build a complete offshore structure out of one type of steel, because there will be different kinds of stresses. The stress analysis shows that those sections which are exposed to wave forces, are mainly affected by fatigue stresses, whereas parts of the platform itself are mainly statically loaded (Figure 1). The quotient out of the minimum and the maximum stresses represents the ratio of the fatigue stresses. As important as this stress ratio is for the design of offshore structures, as important is the weldability of steels for their construction (1). In addition to the weldability the reliability of a structure is a main factor when selecting materials. Under these conditions there may be applied successfully three categories of steels in one structure:minimum yield point below 300 N/mm2minimum yield point about 355 N/mm2minimum yield point between 400 700 N/mm2

Most of the plates needed for offshore structures are 15 - 75 mm thick.

Special metallurgical procedures for the production of particular grades within these categories will be described with regard to their application. Some of these steels have been proved in service whereas others have been recently developed.
Response Of Concrete Gravity Platforms To Earthquake Excitations
Authors: Watt Brian J. , Boaz Irvin B. , Dowrick David J.
Published: October 2008

The earthquake response of typical concrete gravity structures in a 100 to 200m water depth range was evaluated using response spectrum and Fast Fourier Transform solution techniques. A series of parametric studies showed:The analysis method has a marked effect on magnitude and distribution of computed foundation and structural forces.Correct modeling of the foundation compliance, especially radiation damping, is essential.At the lower end of the soil stiffness range, foundation instability governs and at the upper, structural strength.

INTRODUCTION

One of the specialty sessions at the 1975 OTC was dedicated to the subject of earthquake engineering offshore. It was evident from the state of the art presentations at that time, that few if any investigations had addressed the question of the response of concrete gravity type platforms to earthquake influences. This is hardly surprising since the first production platforms of this kind were installed in the North Sea in the summer of 1975 and to the authors' knowledge, none has yet been ordered for an offshore region characterized by high earthquake risk.

One of the chief advantages of the concrete gravity platform is its potential for carrying payload to location and the very limited amount of offshore work required. The advantage of this in a short installation weather window, like that of the North Sea, is only now becoming fully appreciated. The Gulf of Alaska has similar weather characteristics to the North Sea but also is associated with a high earthquake risk. This paper presents a part of an overall investigation into the feasibility of constructing and installing concrete gravity platforms in the Gulf of Alaska. This was conducted from September 1974 through April 1975. At the time the study commenced, there were sound geological reasons for anticipating the presence of suitable founding conditions at or close to the mudline but only limited numerical data existed.

OBJECTIVES

It would be logical to assume that the intensive nuclear power development programme in the 1960's would have generated ample means for evaluating earthquake problems experienced by massive concrete structures. While this is undoubtedly true with respect to an understanding of the basic phenomena and the provision of some of the methodology, certain factors must be remembered. In the first instance, the size in terms of both mass and geometry of a typical gravity production platform is significantly greater than that of a nuclear reactor installation. Secondly, the superstructure of the former is relatively flexible. Thirdly, the interaction with the surrounding water represents a further level of complication in the case of a submerged structure. Finally, in a typical nuclear reactor design situation the emphasis is on the detailed evaluation of a particular site whereas the type of investigation undertaken in this Gulf of Alaska study was geared more to the identification of which type of site would be satisfactory from all view points.
System Model Development of Two Fast Current Oil Removal Systems
Authors: Ard Roswell , Ayers Ray , Beach Robert
Published: October 2008

Presently, the effective removal of oil spills is limited to current speeds of about one knot. There are several high risk areas of the country where currents are in excess of one knot. To be able to effectively recover spilled oil in these areas, the Coast Guard has initiated a program to develop suitable systems. This program and the results to date are discussed herein along with its projected future direction.

INTRODUCTION

The most common technique available today to control oil spills is the floating boom that supports a vertical skirt extending down into the water to form a barrier to the passage of the oil. At currents in excess of about one knot, the oil slick will not be contained by the boom and will flow beneath the barrier as the oil droplets are entrained by the escaping water. This phenomena applies to any oil recovery device that establishes a relative velocity in excess of about one knot between the oil and the water. The effectiveness of these devices is even further limited by the action of winds and waves.

A large number of oil spills occur in rivers, estuaries, and bays with velocities in excess of one knot. Today, the only way of cleaning up spills in these situations is to wait until it is caught by back water areas and then apply conventional clean up techniques. Another aspect of this problem is the slick that has spread out over a vast area. To recover this type of spill effectively requires the capability of rapidly picking it up with a speed of at least three to four knots in order to effectively maneuver.

The opinions or assertions contained herein are the private ones of the writer and are not to be construed as official or reflecting the views of the Commandant or the Coast Guard at large.

The National Oil and Hazardous Substances Pollution Contingency Plan gave the Coast Guard the responsibility of removing oil discharges on the waters of the United States. Since the fast current problem existed in many of these waters, the Coast Guard initiated a program to develop a suitable oil spill recovery system.

INITIAL RESEARCH

The initial part of this program consisted of two parallel efforts. One of these efforts was to investigate the feasibility of various processes to recover oil in a fast current situation. The other was to determine suitable support systems and the environmental factors that would be encountered in trying to pick up oil in a high current situation.

Process Feasibility Study

A study by Texas A &M investigated the behavior of a floating oil slick subject to various external mechanical influences and to the action of current and waves. Oil diversion schemes, rapid removal techniques, and energy absorption barriers were evaluated. Energy dissipation and rapid removal by lifting appeared to have the most promise for fast current oil recovery.