bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Critical Review of Transportation Analysis Procedures
Authors: Chianis J.W. , Mangiavacchi Andrea 
Published: October 2008

ABSTRACT
In recent years, with increased emphasis upon deepwater field development, the size and weight of offshore platforms have increased significantly. Consequently, platform transportation has become of great importance, reinforcing the need for a better understanding of the problem. In the past, for relatively small structures, platforms were analyzed for the combined effects of gravity and inertial loads only. The barge was usually assumed to be rigid, implying no structural interaction between the barge and the platform. For the larger and heavier platforms built today, a more sophisticated analysis must be performed. In this analysis the complete platform/barge system is considered. This method accounts for barge flexibility and the resulting platform/barge structural interaction. This paper examines both procedures and highlights the critical aspects and pitfall s of each.
Numerical results from a recent study are presented to illustrate the differences in the two procedures. Specifically, several design related questions pertaining to barge flexibility, motion and force phase relationships, tie-down force distribution, platform stresses, fatigue, interpretation of results, and conservatism of results are addressed.

1.0 INTRODUCTION
There are two important considerations in the transportation analysis of offshore platforms. From a navigational standpoint, the mission is considered successful if the platform/barge assembly completes the trip from the fabrication yard to the installation site without mishap. This is ensured by enforcing a number of general stability criteria. From a structural standpoint, however, the platform is expected to reach its final installation site without suffering any major structural failure or significant fatigue damage as a result of the transportation phase.
Offshore platforms are usually fabricated in a horizontal position, and are then skidded onto a barge for the trip to the installation site. In its seagoing configuration the platform generally rests on skid beams, and is secured to the barge by tie-downs. In this position, the platform is vu1nerable to various structural problems for two main reasons:The platform is designed primarily for its In place upright position.The platform is quite flexible in the horizontal position. These problems are further compounded by the fact that some of the largest platforms designed today are in the range of 70D-1000 feet, while the largest launch barges currently available do not exceed 650 feet in length. This results in the platform overhanging the barge at one or both ends, as well as on the sides. Depending on the geometry of the platform and the barge, overhangs of up to 150 or 200 feet are possible.
A Rich Middle Triassic Source Rock in the Barents Sea Area
Authors: Bjorøy Malvin , Hall P.B. 
Published: October 2008

ABSTRACT
The scope of the work presented in this paper is an evaluation of the petroleum potential of the source rock which shows most promise for the Barents Sea area. The evaluation is based on analysis of a large number of samples from a Middle Triassic black shale deposit on the various islands of the Svalbard Archipelago. This investigation has shown that the shale is an oil-prone source rock. Analysis of samples taken from areas in the Barents Sea, indicates that this shale sequence has similar potential as a source rock throughout the area south of Svalbard. Integration of this data with the available geophysical and geologica1 data allows us to propose that the rich, oilprone Middle Triassic shale sequence also has a widespread distribution throughout the Norwegian Arctic.
The results of the geochemical analysis undertaken on Mesozoic deposits of Svalbard and from subsea outcrops in the Barents Sea area will be presented. In addition the significant geological data for the region will be included.
The geochemical data to be discussed includes; total organic carbon content, Rock-Eval pyrolysis values, vitrinite reflectance and kerogen analysis in transmitted light. In addition some data on the amount and composition of extractable organic matter in the Triassic shales will be mentioned.
Traditionally the Upper Jurassic shales have been regarded as the major source rocks on the Norwegian Continental Shelf. In addition to Jurassic source rocks there are some probable source rocks of Triassic age, particularly of Mid-Triassic age. Any oil and gas exploration in the Norwegian Arctic must take into account other possible source rocks from the Triassic, as well as those of Jurassic age which are regarded as the main source rocks in the North Sea. The presence of additional source rocks in the Barents Sea area increases the possibilities of oil and gas discoveries in this area.

INTRODUCTION
During the early stages of exploration for oil in the North Sea region there were lengthy discussions concerning the probable source rocks for the oil and gas, especially in the Northern North Sea. The geochemical techniques used in the late sixties and early seventies were rather crude and the errors introduced by this, at least in part, led to the conclusion that Paleocene shales were the source rock for the Ekofisk oi1 it was 1ater estab1ished that Ekofisk oil, as with other hydrocarbon accumulations found in the Central Graben (Fig. I), was sourced from the Upper Jurassic - Lower Cretaceous Kimmeridge Clay Formation. The situation in the Viking Graben (Fig. 1) is far more complex. It is generally accepted that most of the oil and gas found in the Norwegian sector of the North Sea has been sourced from shales of Jurassic age. Potential source rocks have been identified in shales from Upper, Middle and Lower Jurassic. In some areas potential source rocks have been identified in shales of Cretaceous and Lower Tertiary age, but it is believed that these are of minor importance.
Stimulated Self-Burial of Submarine Pipelines
Authors: Huisbergen C.H. 
Published: October 2008

ABSTRACT
Under certain conditions submarine pipelines bury themselves down to two diameters below the original sea bed. A field example is presented, and an analysis is given of the possible mechanisms involved. Seeking a wider application of this phenomenon, a stimulated self-burial method is introduced, using fins attached to the pipe. Tentative laboratory tests show promising results.

INTRODUCTION
The answer to the question whether a specific pipeline on the seabed should be buried or not depends on a variety of arguments, stemming from corporate engineering practice, government regulations, international conventions, etc. All these arguments are somehow used in cost/risk analyses, where factors of widely different nature play a part, each with their own margin of uncertainty. The accumulated uncertainties may create such an amount of maneuvering room that the original question may be answered either way. There are quite some uncertainties involved with a pure technical natural including such items as:pipeline resistance to impactspipeline/bed interaction under currents and wavesdefinition of adequate pipeline stability under hydrodynamic forces and the related design criteria adoptedlast but not least the burial techniques themselves. All items just mentioned are subject to a continuing development of theoretical, empirical and technical know-how, thereby possibly affecting the outcome of the burial question.
An interesting development in the area of pipeline burial was the recent discovery of the act that pipelines bury themselves down to three pipe diameters under certain circumstances. A surprising example of this phenomenon in the Dutch North Sea sector will be presented hereafter.
Needless to say that this is an important asset in attempting to minimize the capital cost, especially for marginal oil and gas fields. In fact this phenomenon has recently led the Dutch authorities to relax their pipeline burial regulations. Meanwhile, specific research is being conducted in the framework of MATS (Netherlands Marine Technological Research) aiming at a better understanding and subsequent predictability of self-burial for specific pipelines. However, there are natural limits to the self-burial potential of pipelines, depending on pipeline characteristics, hydraulic conditions, and the nature of the sea bed.
In order to broaden the applicability of self-burial, and to cope with conditions where plain pipelines would not or not fast enough bury themselves, the Delft Hydraulics Laboratory has investigated the feasibility of a new method (patent pending), called stimulated self-burial. The method essentially seeks to stimulate controlled local erosion by using plastic fins attached to the pipeline. Laboratory tests showed promising results so far, which may lead towards a cheap new pipeline burial method, thereby shifting the answer to the original question in positive direction.
High-Resolution Seabed Mapping: New Developments
Authors: Klein M. 
Published: October 2008

ABSTRACT
This paper describes several new developments in the evolution of side scan sonar sea bed mapping systems. A new advanced microprocessor-controlled tuning improves record quality. New deep tow vehicles allow for relatively high speed medium depth towing or low speed full ocean depth towing. Detailed bottom topography can be overlaid on the side scan sonar/sub-bottom profiler data to enhance record interpretation.

INTRODUCTION
In the past few years, side scan sonar systems have evolved into sophisticated sea bed mapping systems. Microprocessor technology has been used to provide two-axis scale correction of the sonar data in real time. Low frequency systems are available which can cover swaths of many kilometers with low resolution, and medium and high frequency systems are available which cover smaller areas in more detail. Corrected strips of sonar data are placed side by side to produce a fully corrected sonar map of the sea bed. Figure 1 shows a sea-bed mosaic made with a 50 kHz side scan sonar. Because these sonar maps resemble aerial photographs, they are far easier to interpret and utilize than the older, uncorrected sonar data. As the sonar mapping technique gains increased acceptance, new developments are continuing to improve the quality of the maps and the efficiency of data gathering. Figure 2 shows the shipboard portion of a typical sea bed mapping system. The system allows the sonar records to be annotated with data such as event mark numbers, navigation coordinates, time, date, etc. in order to facilitate assembly of sonar mosaics. A keyboard allows manual entry of additional data. Parallel or serial (RS-232) ports are available to accept navigational and other data from external sources.

ADVANCED HANDS-OFF-TUNING®
Side scan sonar system designers have always been faced with a difficult situation regarding the dynamic range of the sonar echo signals. During the course of a sonar sweep, the signals may vary in level over a wide range, on the order of 120 db. The hard copy graphic recording media however, typically only have a dynamic range on the order of 20 to 40 db. A variety of automatic gain control systems and time variable gain systems have been developed to deal with the problem.
Manually tuned time variable gain controls allow the operator adjust the gain curves to produce reasonably uniform sonar records under most conditions. Unfortunately, these systems tend to need relatively skilled operators to achieve optimum results.
Other systems have been developed which set up a fixed time variable gain curve based on theoretical calculations of the various factors which affect the sonar signal. These are called predictive systems. The factors taken into considerations include the sonar spreading losses, attenuation losses and the bottom backscatter functions. Some systems also include a calculation for the vertical beam angle of the sonar transducers.
Strain Identification and Quality Control in Welded and Bolted Unions Using Nondestructive Optical Methods
Authors: Bryden I.G. , Grant I. 
Published: October 2008

ABSTRACT
A method of identifying and measuring strain concentrations is described and demonstrated which uses a laser light source and photographic recording. The method is shown by application to a T-junction weld to be simple to use and having a number of distinct advantages over commoner techniques.

INTRODUCTION
Strain measurements are commonly made at regions where high distortion is suspected using strain gauges or photo elastic coatings. Both of these methods require some knowledge in advance of where strain concentration might be expected. They also require careful surface preparation to enable reliable measurements to be made.
This paper describes the application of a simple optical method for identifying and measuring strain concentrations which requires no surface preparation. The area of the strained sample in view is easily altered enabling rapid scanning of large structures. A further advantage of the optical method is that it can be applied to any part of a complex node or union where 1ine-of-sight access exists to possible problem regions.
The optical method, " speckle photography", is demonstrated here through its application to a welded "T"-junction between two a.15m diameter pipes. The principles of the method are also presented together with the relevant theory. The single beam speckle method is shown to be the most suitable optical method for engineering applications since it has no need of high quality optical components or a vibration free environment.

EQUIPMENT
Figures 1 and 2 show the apparatus used to obtain the strain measurements. The laser used in this work was a 15mW Helium neon type which was mounted rigidly onto a 1m × 1m × 25mm aluminum plate fitted with adjustable feet. Also mounted on this plate were an optical spatial filter for expanding and 'cleaning' the beam and an adjustable mirror for directing the light onto the equipment to be tested. The camera used was a standard 35mm single lens reflex type fitted with 210mm telephoto lens. The lens was fitted with a narrow band diffraction filter tuned to allow only light of wavelength 533 ± 5nm through. This allowed tests to be performed in subdued lighting rather than total darkness. The camera was mounted on a heavy duty video tripod either directly or via a horizontal travel micro positioning device.

PROCEDURE
In operation the camera was focussed on the object under test. The expanded laser beam was directed onto the test piece and the scattered light measured with a spot-light meter. The required values of the F number of the lens and the exposure time being noted. Once this was done the laser shutter was closed and the camera shutter locked open with the aperture set to the required value (typically f5.6). The first exposure with no loading on the test piece was then made by opening the shutter on the laser for the required period (typically 1s). Once the first exposure was made the load was applied to the object and the camera was shifted sideways by a known distance.
High-Resolution Deepwater Survey Sonar
Authors: Robinson G.R. 
Published: October 2008

ABSTRACT
As survey requirements moved into water depths greater than 2,500 meters, new technology was required to obtain high resolution geophysical data alone precise grid lines. This paper discusses a unique bottom referenced tow system that provides 100k Hz side scan and 3.5/7.O kHz sub bottom sonars; multiplexed over an 8,500 meter single coax tow cable. This design provides a stable towing platform that maintains a constant optimum height over the sea floor which requires minimum cable length 'alterations that affect the tow fish causing imperfections in the data. This system is meant to provide high quality, distortion-free mosiacs with uniform bottom and sub-bottom features recorded at a constant tow speed and height above the sea floor.
Because the towing concept is bottom referenced, the topographic features are lost as the tow fish flies over a high relief area at a constant height off the sea floor. With enhanced electronic techniques, combined with a depth sensor in the fish, the topographic detail of the sea floor is recorded on the sub-bottom record; thus, the survey packageprovides the complete high resolution record of the true sea floor and sub-bottom features with resolution and quality never achieved before.
Another important facet of this system is positioning of the tow fish. With 8,500 meters of cable out, it is imperative for record correlation to know where the tow fish is. A precise ultra-short baseline portioning system integrated with the tow fish telemeters the tow fish position back to the vessel. The position is then co-r-related to the vessel navigation system to allow position plotting along the survey grid.

INTRODUCTION
The offshore oil and gas industry is exploring for reservoirs in deep water exceeding 2,500 meters. As survey requirements move into these water depths, a new technology has been necessary to obtain high-resolution geophysical data of the sea floor. Improved techniques have been developed to acquire high-resolution, short-range side-scan sonar (100 kHz) and 3.5 or 7.0 kHz sub-bottom data in deep water environment. Extremely detailed records of the ocean floors geologic features have been gathered that compare to the data obtained in shallow water surveys.
Developments include the design of the deep-tow vehicle and associated electronics, special towing requirements, and navigation for precise positioning of deep-tow system. Also, a multiplex system was developed to provide for dataacquisition and control of electronics over long cable lengths.(Figure 1)

TECHNICAL REQUIREMENTS AND EQUIPMENT
The acquisition of high-resolution data in deep water requires attention to numerous aspects not normally encountered in shallow water surveys. Shallow or surface towed acoustic sources suffer from losses due to signal attenuation and beam spreading. These losses increase in severity with greater water depths.
Failure Analysis of a Calm Buoy Anchor Chain System
Authors: Shoup G.J. , Mueller R.A. 
Published: October 2008

ABSTRACT
In 1982, Philippines-Cities Service experienced a wear failure of a cateneary anchor chain mooring used to moor a CALM type buoy. In order to explain the failure, Cities Service conducted a comprehensive failure analysis and model basin test of the failed system, and in addition, performed comparative wear tests on U3 and U4 chain. The results of the investigation indicate that interlink motion and resulting wear are an important design criteria for mooring lines.

INTRODUCTION
In 1982, Phillippines-Cities Service installed a CALM type mooring terminal near Palawan Island in the South China Sea. A 100,000 DWT tanker was soft moored to the CALM for use as a permanent storage facility for the Matinloc Oil field. The system was to remain in service until a rigid arm system under fabrication could replace the CALM type mooring.
As a consequence, the anchor chains were sized for the rigid arm system. Since the CALM buoy did not have sufficient buoyancy to support all six chain legs (standard 6-leg spread with 60° between adjacent chains), only 4 legs were connected. To further reduce weight and maintain adequate safety factors, U4 chain was used in the uppermost portion of the catenary near the buoy. Figure 1 shows the resulting anchor chain pattern which later failed. Table 1 summarizes the important parameters of the mooring at the time of the failure.
Approximately two months after installation a typhoon passed near the Matinclo field generating 40–70 knot winds and 3U ft. maximum waves for a period of about three days. The maximum storm intensity was less severe than the design storm for the tanker connected to the buoy. During the storm two chains failed by excessive interlink wear and the remaining two chains were worn about 50% through. Figure 2 shows one such failed link. On all chains the wear occurred at the junction between the fixed stopper link and the first tree link in the catenary. This point experiences the majority of relative motion between the buoy and the catenary.
Historically, accelerated wear rates have not occurred on similar CALMS; however, the Cities terminal was unique in several ways. Grade U4 chain relatively new product of high strength chain) was used in the wear zone where large interlink relative motions occur. Also, the buoy anchor chain pattern was asymmetric with distinct strong and weak roll stiffness axes and surge stiffness axes. Clearly, either the metallurgical composition of the U4 chain is unusually susceptible to wear as compared to U3 chain; or the asymmetric hookup of the buoy generates such large forces and motions that any anchor chain steel would wear at an accelerated rate, regardless of grade.
A failure analysis and review of existing metallurgical data showed that an experimental wear test program was needed to define the wear characteristics of both U3 and U4 chain. Model basin studies were also performed to quantity the force-motion time history at the wear point.
New Generation Arctic Drilling System: Overview of First Year's Performance
Authors: Loh J.K.S. , Stamberg J.C. , Cusack K.P. 
Published: October 2008

ABSTRACT
This paper is a follow-up to OTC 4481:- Kulluk - An Arctic Exploratory Drilling Unit, presented at the 1983 OTC. A comparison between the original design basis of the rig and the first year's operational results is presented. The items compared are the towing performance, mooring system performance, the hull structure, and the drilling system. The towing and mooring system comparisons cover both open water and ice conditions. Ice management by icebreakers and logistics problems are reviewed.

INTRODUCTION
The Conical Drilling Unit Kulluk was designed by Gulf Canada Resources Inc. and built in the Tamano Works of Mitsui Engineering and Shipbuilding Co. Ltd. The Kulluk was delivered on schedule on April 2, 1983. After loading equipment and supplies, the Kulluk was towed out of Tamano on April 15, 1983. The schedule that was presented in the original paper was attained within one day of each milestone. This was achieved despite a year when the ice condition was abnormally severe.
This paper will compare the first year's operational results with the rig's design criteria.
The areas covered will be:environmental conditionshull shape effects, both in a moored and in a towed condition; open water and ice covered water conditionshull structural concernsdrilling system.
The paper will also describe some of the planned improvements for the Kulluk's operations.

Environmental Conditions
The Kulluk was designed to the following conditions:

A. Operating
Water depth - 24-55m Air temperature range -50°C to +20°C
Open Water - one year return storm2.8m significant wave height 8 second peak period45 km/hr. sustained wind0.5m/sec. current velocity Ice Conditions1.2m ice thickness55km/hr. sustained wind0.3m/sec. current velocity

B. Survival
Open Water - 100 year return storm7.3m significant wave height 12.5 second peak period110 km./hr. sustained wind0.7 m/sec. extreme current velocity Ice Conditions
The mooring system must be capable of releasing from the anchors prior to the loads reaching 50% of rope breaking strength.

Mooring System

A. Open Water
Many of the pertinent design features of the Kulluk mooring system apply to both open water and ice conditions.
The Kulluk mooring system has been designed for use in the Canadian Beaufort Sea in water depths between 24m and 55m. It consists of a 12-point mooring system with 90mm wire mooring lines, mooring winches and high holding power anchors. The 12 anchors are radically dep1oyed at equal angles. The lower fairleads are well below the ice surface on the bottom of the hull to avoid ice contact. This mooring system enables the Kulluk to respond to ice forces from any direction.