bluuebunny/crossref_metadata_2025_split huggingface dataset:
Early Subsea Production Systems Advance The State-Of-The Art
Authors: Van Bilderbeek Ben , Reimert L.E. 
Published: October 2008

ABSTRACT
Hydrocarbons have been found offshore in considerable quantity and quality. Whether this increasingly scarce commodity can be exploited to extend the age of fossil fuels depends on the development of offshore production systems.
During the summer of 1977, a modular template for a five-well early subsea production system was built in Aberdeen, Scotland. Shell Oil has purchased this system for installation in the North Sea. The system was designed eventually to be tied back and produced to a fixed platform.
A different type early subsea production (ESP) system, one using a unitized template, was employed by Petrobras as part of the Garoupa field development in the early part of 1978. Of particular interest is the unique 20-in. pile leveling system, which allows placement of the template onto the ocean floor in a horizontal position. As was the case for the Shell ESP system, these template wells also will be individually tied back to a fixed platform structure.
Various ESP systems have been employed and successfully operated in some of the most hostile offshore environments. One, therefore, can argue that the technological and economic viability of ESP systems has been proved, although general acceptance by a conventionally conservative industry cannot be claimed yet.
The ESP systems, subject of this paper, are specifically designed to render currently marginal fields economically viable and to extend hydrocarbon production into deeper waters. Another application for these systems is to provide cash flow during the early stages of a major field development when permanent production systems are being constructed.

INTRODUCTION
It will be known to most readers that the price per barrel of crude oil continues to rise to ever record levels. It may be less known that the cost of drilling and completion also is rising at astronomical rates.
Several reasons can be considered contributory to the rise in drilling and production costs such as inflation, politics, and, not least, field accessibility. The offshore industry is moving ever further offshore into deeper waters in their quest for finding economically viable hydrocarbon deposits.
The extreme high drilling and production costs for these deep-water offshore fields have prompted the oil industry to investigate alternative production systems that can provide substantial savings in over-all investment and development time required.
One such method has been called the early subsea production (ESP) system. Several variations of this approach are available, having in common the fact that the drilling stage of the field development can commence and continue while the production facility such as a bottom supported platform or a floating production vessel is under construction.
Two distinctly separate groups can be identified within these various systems:the ESP systems utilizing a floating production platform, andthe ESP systems tied back to a fixed or bottom supported production facility.
Test Of Various High Resolution Seismic Devices In Hard Bottom Areas
Authors: des Vallieres T. , des Kuhn H. , des LeMoal R. 
Published: October 2008

ABSTRACT
Research of operational high resolution geophysical methods for offshore soils and sub-bottom survey in a "seismically hard environment" led to a comparison study of a wide variety of shallow seismic instruments available on the market in the summer 1976.
Different seismic source (pingers, air-gun, miniflexichoc, surface or deep towed boomers and sparkers), streamers (mono and multitrace) and recorders (analog and mono or multichannel digital) were tested in glacial deposits off the East Coast of Canada The combination of the selected devices (source, receiver and recorder), led to thirty different data acquisition possibilities.
The on site performances and capabilities of each tool and the subsequent data processing possibilities led to an objective assessment of the different pieces of equipment to be used according to the type of soil encountered and the depth of investigation desired. When necessary, improvements were recommended.

1. INTRODUCTION
Offshore high resolution shallow sub-bottom profiling has always been a problem in the so-called "hard bottom areas" (coral reefs, morainic drifts, cohesive formations).
In these environments, a large amount of the emitted energy is scattered resulting in poor-penetration with conventional high resolution seismic tools.
In 1976, a joint venture between CFP (Compagnie Française des Pétroles), IFP (Institut Français du Pétrole) and SNEA(P) (Societe Nationale Elf-Aquitaine Production) associated in the GERTH (Groupement Europeen de Recherches Technologiques sur les Hydrocarbures) with the EEC (European Economic Community) support, decided to run a survey in such a seismically "hard" environment in order to test and compare the largest possible variety of seismic data acquisition devices and methods. The purpose was not to develop any new system or concept but to operate the existing tools, including experimental devices, available on the market. The tested instruments were basically selected according to the desired investigation depths (from a few metres down to 200 m). Only reflection methods were considered.
The tests were conducted in a morainic environment off the East coast of Canada on an acreage held by the Labrador Group of which Eastcan is operator. The average water depth was between 150 and 200 m. Several zones presenting specific soil conditions were preselected. In each zone the tests were run on the same lines to facilitate the comparison.

2. TESTED DEVICES
The 1976 program allowed the testing of nine seismic sources, five types of streamers and seven different recorders (fig. 1 & 2).

2.1. The sources
The tested sources can be divided into five main types :
Four different sparkers were used :a high powered sparkarray : near surface towed, 3 to 9 electrodes, energy up to 21 kJa multielectrode sparker (MES)(l) : near surface towed "comb" like sparker using an array of 3 sets of 144 electrodes. Power from 1 to 3 kJ.
Shallow Water Drilling With Adeep Water Drillship
Authors: Magill James M. , Macan John J. 
Published: October 2008

ABSTRACT
A working procedure has been developed and successfully used to enable a deepwater drillship to drill in shallow water. The paper describes how by a combination of recessing the wellhead and B.O.P. below the sea floor, in a sea-floor cellar, and by shortening the slip joint the deep water drillship CHANCELLORSVILLE was used to drill two wells in the Gulf Coast, in approx. 55 ft. of water. Experience gained during the first well was used to develop a more efficient procedure which was adopted for the second well.

INTRODUCTION
Until now, offshore drilling in shallow water depths has been greatly dependent upon availability of bottom supported drilling units, principally jack-ups or submersibles.
The concept that a drillship or drill barge employing innovative techniques, could be used economically in place of a jack-up in shallow water was not readily accepted until recently when Samedan Oil Corp. initiated its program to drill in shallow waters.
With the demand for bottom-supported rigs greater than the available supply, AOI proposed to use its drillship CHANCELLORSVILLE with a seafloor cellar as portrayed in Figure 1.
The typical minimum water depth for a drillship has been generally considered to be about 100 ft. This limitation is based upon factors requiring adequate spacing between drill floor and sea floor to physically accommodate the wellhead. BOP, ball joint, and slip joint.
Sufficient length of the riser system from ball joint to drill floor is necessary to allow movement (offset) of the vessel in the horizontal plane resulting from the combined actions of wind, waves, and current. Typical acceptable offset has been about 5% of water depth, or an offset which would limit the ball joint angle to about 5°.
Ball joints are capable of angles up to 10°. However, other considerations restrict allowable to a significantly lesser angle. Passage of drilling tools through the ball joint, and wear at the ball joint as drill pipe is rotated must be considered.
Sufficient vertical stroke of the slip joint should be present to enable the vessel to heave under the action of waves, and also for tidal changes.
Sufficient clearance between the vessel's hull and the BOP fixed to the sea floor should preclude contact when the vessel exhibits motions both vertically and horizontally from wave action.
As shown in Fig. 2, placement of the BOP and slip joint for CHANCELLORSVILLE in the normally designed manner would require a minimum water depth of about 99 ft.

Modification Needed
To work in water depths less than 88 ft. required certain modifications to the normal placement of equipment.
It would be possible to accept reduced water depth by merely setting the slip joint for reduced but acceptable downstroke. For example, 10 ft. downstroke would enable operation in water depths of about 76 ft.
Sea Bed Instability From Waves
Authors: Yamamoto Tokuo 
Published: October 2008

ABSTRACT
The pressures and the effective stresses in seabeds induced by waves are treated analytically based on Biot's three-dimensional consolidation theory. The wave induced pressures and stresses in a bed are strongly influenced by the permeability and the shear modulus of the soil, the compressibility of pore water, and the thickness of the bed. As a design example, a stress analysis is made for the North Sea design wave and seabed conditions. The numerical results indicate that the North Sea design waves will liquefy the top up to 2 m of the sand beds and induce the sliding failures in the top up to 8.0 m of the sand beds. The theory has been verified by a laboratory experiment for the wave induced pressures.

INTRODUCTION
The subject of wave induced pressures and stresses in seabeds is important with regard to the design of foundations for various ocean and near shore structures, such as gravity type breakwaters, offshore oil storage tanks, and drilling rigs like EKOFISH at North Sea. The subject is also important when one considers the problems of the flotation of buried pipelines and the burial of rubble mounds, tetorapods, and other blocks by waves. However, the subject is not well understood because the dynamic behavior of soils is difficult to express mathematically.
When the water waves propagate over a porous bed such as a sand bed, the flow of fluid is induced in the porous medium and the porous medium itself is forced to deform. Thus, the bed response to water waves is actually a combination of fluid and solid mechanical effects.
There have been numerous investigations of the problem of the flow induced in a porous bed by water waves, including Liu (1973), Massel (1976), Moshagen and Tørum (1975), Nakamura, et al. (1973), Putnam (1949), Reid and Kajiura (l957) and Sleath (1970). However, they all assumed that the porous beds are rigid and non deformable. In addition, all except Moshagen and Tørum (1975) and Nakamura, et al. (1973) assumed that the pore fluid is, incompressib1e. The fluid motion in the porous bed is usually expressed by Darcy's law which, with the assumption of a rigid bed with isotropic permeability and incompessible water, leads to the Laplace equation for the pore water pressure. The consequence of this theory is that the pore-water pressure response is independent of the permeability of the bed material. The approach taken by Nakamura, et al. (1973) and Moshagen and Tørum (1975) is based on the assumption that the water is compressible while the porous bed is non deformable which leads to the heat conduction equation for the pore-water pressure. The conclusion from this assumption was that the pore-water pressure response is strongly dependent on the permeability of the bed material. This approach provides no information on the wave induced stresses in seabeds.
Explosive Welding - The Deepwater Pipeline Connection/Repair Solution
Authors: Redshaw P. , Stalker A.W. , Allen K. 
Published: October 2008

ABSTRACT
After briefly describing the physical aspects of explosive welding in general terms, this paper outlines how the underlying principles are applied to the making of pipeline connections under water. Using the same basic weld geometry, two general connection types are available - a pipe flange and a sleeve weld. The associated systems of pipe preparation, flushing and drying, dewatering, welding, and subsequent inspection receive attention, and in all cases the minimal requirement for operator skill is emphasized. Results of mechanical property tests are presented for particular pipe sizes. Finally, practical applications are proposed with emphasis on the suitability of the technique for all water depths.

INTRODUCTION
During the early 1970's, the ability to make planned connections and undertake repairs on pipelines in deep water was seen as one potential problem area, and following a comprehensive examination of a number of alternative joining systems, it was decided that explosive welding offered several positive advantages. It is basically a very simple operation, requiring a minimum of equipment that, once the parameters have been developed for a particular set of circumstances, gives very reproducible results. There is no demand on the manual skills of divers operating in saturation diving conditions and preliminary indications are that the process is relatively insensitive to water depth. All these factors would suggest that explosive welding offers great potential as a pipeline-joining technique that could eventually be a remote operation controlled from a submersible. Thus, in 1973 a work program was initiated to develop an explosive welding technique for pipelines that would offer to the oil industry both a technically acceptable solution and one that would afford a considerable economic advantage over other currently available systems.
This paper describes the joining process that has culminated from this program and that has achieved full process approval from the major classification societies operating in European waters. In addition to the actual welding process itself, there is a range of ancillary engineering operations equally relevant to the success of the over-all operation and these also receive attention.

EXPLOSIVE WELDING TEDHNOLOGY
The process depends on the use of explosives to accelerate metal components into a high-velocity oblique collision. The physics of the process have been amply described elsewhere (Conclusion 4) and will only receive brief attention in this discussion.
In order to achieve a weld, two conditions must be satisfied:the impact pressure must exceed a certain value (at least 10 times the yield stress); andthe collision-point velocity must be subsonic.
The impact pressure depends on the velocity of the flyer pipe, and since the acceleration of the flyer takes a finite time, it is usual to arrange for a gap between the components in order to satisfy the first criterion.
Development Of An Alignment System For The Three-Part COGNAC Platform Jacket
Authors: Piter E.S. , Sterling G.H. , Cox B.E. 
Published: October 2008

ABSTRACT
This paper discusses the system incorporated into the three-part Cognac "A" Platform jacket to guide the sections into lateral alignment as they were positioned offshore. A brief description of the alignment appurtenances and data on the in-place misalignment are given.

INTRODUCTION
During the early phases of the Cognac design, the decision was made to fabricate the Cognac Platform in three separate sections (Reference 1 and 2), (Figures 1, 2, and 3=Available in full paper). The Base Section was launched from a barge in an upright position. It was then lowered to the seafloor and anchored by 24 large diameter skirt piling (Reference 3). This section was 178½ feet in height measured from the centerline of the bottom horizontal to the top of the upward looking mating flanges.
The Mid Section was fabricated and launched in a horizontal position, ballasted to vertical, lowered and set on top of the Base Section. This brought the total height of the jacket to 498½ feet. The Top Section, which was 527½ feet in height, was fabricated and installed similar to the midsection and extended the platform so that the jacket :walkway was 14 feet above the waterline.
The primary mating components were the ten jacket legs through which large diameter tubular connection pins were installed and grouted in place (Figure 4). These pins extended through all three jacket sections and terminate just above the mudline at the bottom of the Base Section.
Two of the jacket legs (Rows XL and X4) terminate at approximately 400 feet below the waterline. The other eight legs extend above the waterline.
At each mating interface, the jacket legs terminate with large mating flanges that contain a rubber seal for containment of the grout as it was pumped into the jacket leg/pin annulus.
Other items which were fabricated as an integral part of each jacket section, and had to line-up after installation, included eleven pipeline pulltube risers, sixty straight conductor pipe guides and two curved conductor pipe sleeve guides. The proper alignment of these items was not necessary to insure the structural integrity of the platform; however, each of them could be utilized only if properly aligned.
Precepts to be followed during the design and selection of the jacket alignment system were developed and alternate alignment systems were studied. Relative cost comparisons were made, taking into account the impact on the construction schedule that each system would have.
The two most important functions of the alignment system were:To provide a guiding system that would allow the upper jacket section to be set down upon the landing supports of the lower section and released from the lowering lines without structural damage resulting from an underwater collision between the mating jacket sections.To provide a method of aligning the corresponding jacket legs of the mating sections to an accuracy that would allow installation of the leg connection pins.
Permafrost Beneath The Beaufort Sea: Near Prudhoe Bay, Alaska
Authors: Sellmann P.V. , Chamberlain E.J. 
Published: October 2008

ABSTRACT
The occurrence and properties of subsea permafrost near Prudhoe Bay, Alaska, were investigated by drilling and probing. Nine holes were drilled and 27 sites were probed with a cone penetrometer. The deepest drill hole was 65.1 m below the seabed, while a depth of 14.1 m was reached with the cone penetrometer. Engineering and chemical properties were determined from core samples and point penetration resistance data were obtained with the penetrometer. Thermal profiles were acquired at both the drill and probe sites.

ABSTRACT
Temperatures below 0°C were observed in all the drill and penetrometer holes logged, although frozen sediments were encountered only occasionally. Seasonally frozen sediments were observed near the seabed at each site. The degree of ice bonding, or strength, could be related to seabed temperature and was greatest in shallow water (&lt;2 m). The penetrometer resistance and thermal data indicated that deeper ice-bonded sediments occur, for example approximately 12.7 m below the seabed in 2 m of water off the Sagavanirktok delta.
Of eight holes drilled offshore, it appeared that four encountered bonded permafrost. In general, the position of the ice-bonded permafrost interface was extremely irregular. The depth below the seabed to this interface at various distances from shore along the line studied was 28.8 m at 1 km, 65.1 m at 3.5 km. 44.1 m at 6.8 km, and 29.5 m at 17.2 km.
Shallow, overconsolidated marine sediments were found in the upper fine-grained section at all of the drill sites investigated; the degree of overconsolidation varied considerably among the sites. This fine-grained section was up to 10 m thick and covered sands and coarse gravels.

INTRODUCTION
Scientific and engineering investigations conducted by several nations bordering the Arctic Basin have documented the existence of subsea permafrost. Many questions concerning distribution, and particularly the properties, of these perennially frozen sediments still remain.
The earliest quantitative studies commenced around 1953 in the USSR. The Soviet investigations have continued, with emphasis on field observation and theoretical studies.1
Few studies were conducted in North America prior to the extensive activity stimulated by petroleum exploration in the arctic regions. Early direct observations and theoretical models of subsea permafrost by Lachenbruch and others2,3 were based on studies made near Barrow, Alaska. Lewellen4,5 followed these investigations with drilling and probe studies in the same region.
In the Canadian Beaufort Sea, probably the first evidence of permafrost and ice-bonded sediment was obtained during an Arctic Petroleum Operators Association drilling program.6 Shearer et al.7 observed the occurrence of bingo-like features on the outer shelf. Hunter et al. followed these studies with an extensive investigation of the distribution of ice-bonded permafrost. These studies, which were largely based on examination of seismic records, showed extensive subsea permafrost.