bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of Wear in Compliant Tower Pile Systems
Authors: Johnson G.S. , Hasle A.E. , Figgers R.F. 
Published: October 2008

ABSTRACT
One of the technical issues that must be addressed for compliant towers is the wear that may occur due to the relative motion between the piles and pile guides. This paper presents a method for adapting! accepted analytical procedures for wear of mechanical systems and applying them to compliant towers and other offshore structures. This method is used for the Compliant Concrete Tower in North Sea fatigue conditions to show that wear is expected to occur, but can be limited by proper material selection and design and construction detailing.

INTRODUCTION
Pile supported compliant towers have been proposed and are being considered for use in various deep water fields throughout the world (Ref. 1 to 4). These towers obtain optimum "de-amplified" dynamic response by maintaining a structural period on the order of 2 times the wave period. This high period is achieve through the axial flexibility of the foundation system, which consists of long pile/sleeve units. Each of these units is guided along its entire length between the mudline and the attachment point to the structure.
As the tower sways due to wave loads, axial couples are developed in the pile/sleeve system. Relative motion occurs between the pile/sleeves and guides, giving the potential for wear at those locations. For the Compliant Concrete Tower (Fig. 1), the critical location for wear is at the guide nearest the mudline, where the normal force on the Pile is a maximum (Fig. 2).

DEFINITION OF WEAR
Wear is defined as a change in the surface contour, such as a groove formed in a flat surface or a flat spot on a curved surface, that results when two bodies are pressed together and relative sliding occurs. Zero wear is not defined to be the complete lack of wear; rather, it is wear of such a magnitude that the surface finish in the wear track is not significantly different than the finish in the unworn portion. Roughly, this corresponds to a depth of the wear scar on the order of one-half the peak-to-peak value of the surface finish.

WEAR CALCULATIONS FOR OFFSHORE SYSTEMS
Once a detailed design of the pile guides at the base has been completed, the appropriate method for determining wear potential will be through testing. However, at earlier stages of the design, simpler methods are required to ensure that wear concerns will not damage overall feasibility of the compliant tower concept.
Although wear is not a typical problem with offshore designs, it commonly occurs with mechanical systems, and accepted methods of calculating expected wear have been in existence for many years. The preliminary analytical methods presented in this paper are adapted from procedures presented by Bayer, et.al., (Ref. 5) for wear caused by loading of constant magnitude and frequency. This approach has been modified for offshore load conditions by using a discretized wave environment over the life of the platform and determining accumulated wear, as is done in a standard fatigue analysis.
The Relevance of Interaction Rules in Evaluating the Growth of Multiple Fatigue Cracks
Authors: Morgan H.G. 
Published: October 2008

ABSTRACT
Flaws introduced during fabrication or developing in service rarely occur singly. Contained in the popular codes used to assess the integrity of structures are rules defining how arrays of multiple flaws should be treated. The current US and UK codes adopt the same philosophy, - simplification of the flaw array into a single larger flaw of assessable shape. Recent experience in using these rules has suggested that in many cases, they may result in assessments that are excessively conservative, possibly resulting in premature rejection or repair of plant.
Although a number of solutions for Fracture Mechanics parameters relevant to interacting flaws have been derived, little has been done to investigate the mechanisms of crack interaction. This paper describes a series of fatigue tests performed to investigate by direct observation how crack growth rate and shape development are affected during interaction.
The results are encouraging in that only weak effects have been observed with no indication of grossly increased crack growth rates. A methodology for assessing simple flaw arrays is proposed which assumes individual growth until crack tip contact or overlap occurs, at which point crack shape is adjusted to a smooth semi ellipse and crack growth evaluation continued.

INTRODUCTION
Manufacturing or service-induced flaws rarely occur in isolation and are often clustered together in critical areas of a structure or plant. A common problem therefore in assessing plant integrity or remanent life is the determination of the behavior of groups of flaws and their influences on one another.
In structures subject to fatigue loading, or where failure by fracture is a possibility, Fracture Mechanics methods are increasingly used to calculate the growth rate, shape development and stability of crack-like flaws. It is the influence of the proximity of another flaw on the effective value of the stress intensity factor operating at a crack which will modify the way in which it grows.
The problem of flaw interaction is dealt with specifically by two of the currently used assessment codes which give guidance on the use of Fracture Mechanics, - ASME section XI Division 1:1986 (1) and BSI PD 6493:1980 (2). In these documents, multiple flaw arrays meeting specified criteria are "recharacterised" into single flaws of simple, easily handled shapes for which standard solutions exist. The criteria for interaction are nominally and loosely based on a particular increase in stress intensity factor (typically 20%) in the ligament between flaws, although the solutions used to calculate this are not given or referenced in the documents.

FLAW RECHARACTERISATION.
The rules governing the amalgamation of flaws are broadly similar in both documents, the rules in ASME XI generally being based on flaw depth or height and those in BSI PO 6493:1980'on flaw length. Recharacterisations are defined for coplanar and non co-planar surface breaking and embedded flaws. Each of the codes contains cases not addressed by the other.
Offshore Placer Drilling Technology: A Case Study From Nome, Alaska
Authors: Bronston M.A. 
Published: October 2008

Abstract
A drill system configuration capable of working in the arctic offshore environment was developed to evaluate the placer gold resources contained in the glacio-fluvial sediments offshore Nome, Alaska. This system is capable of working on the shore fast ice during the winter months and is deployed on a drill ship during the summer. Transfer of the drill between its summer and winter configurations is accomplished with a minimum of modification to the design.
The system is designed around the Becker drill, a percussive, reverse circulation drill capable of penetrating the indurated glacial sediments present in the offshore Nome environment. This drill has operated effectively to depths in excess of 50 meters below sea level.
Since early 1987, in excess of 2000 holes have been drilled using the system. The drill system, often operating in extreme weather conditions, has averaged approximately 10 holes per day of drill production. The ore reserves defined during these drilling programs have resulted in the recovery of greater than 70,000 fine ounces of gold to date, by the mining vessel Bima.

Introduction
In recognition of the rising interest in offshore exploration and mining technology, this paper describes a placer drilling system configuration which has operated successfully in the arctic offshore environment near Nome, Alaska (Figure 1). Since March, 1987, 2073 holes have been drilled during four programs, two summer and two winter. An average of 9.3 holes per day have been completed to an average depth of 10 meters per hole. The drill has also been used to conduct standard penetration tests for dredge design studies.
The system is modular, during the summer a ship is used as a platform, and during the winter under most conditions, annual or perennial sea ice may be used as a platform. The drill, a Becker AP-1000 diesel hammer drill, was originally mounted on a tracked carrier for work on tundra and other rough terrain. The drill was removed from the tracked carrier due to handling and weight considerations and mounted on a skid specifically designed to serve as a drill support structure in either summer or winter configuration.

Review of Previous Drilling Programs
Three drilling programs were completed in the offshore Nome area prior to 1987. Two programs were completed on the annual ice by mining .companies during the winters of 1964 and 1967 (Daily, 1964; Daily, 1969; Wojcik, 1974), and one was completed by the U.S. Bureau of Mines (U.S.B.M.) using a drill ship in 1967 (Nelson and Hopkins, 1972).
The Becker drill was used in both mining .industry drilling programs. These programs were conducted during the winter from the ice using a skid mounted drill, towed by a bulldozer.
A Subsea Wireline Service System
Authors: Cobb C.C. , Dines C.A. , Headworth C.S. 
Published: October 2008

ABSTRACT
The costs, safety and complexity of performing downhole service operations on subsea completed wells are major concerns of offshore operators. Service costs in particular often become the deciding factor when determining the feasibility of developing small subsea fields. Of particular interest are slickline and conductor line operations. In the past, these operations were usually performed on subsea wells using a semi-submersible rig and a rigid riser.
This paper describes a subsea wireline service system in detail. The system includes a subsea lubricator stack that attaches directly to the subsea tree. The wireline unit, control systems and deployment equipment remain on the deck of the vessel. The system is designed to be deployed from a relatively small vessel such as a diver support vessel (DSV). However, operations can also be conducted from a semi-submersible rig, workboat or moored barge. A riser is not required. System components, deployment and retrieval procedures, scope of work and emergency disconnect system are described in this paper.

INTRODUCTION
In many areas of the world, especially in the North Sea, the trend in offshore field development is towards subsea completions. The number of subsea wells is expected to double by 1994, with as many as 1000 by the year 2000. Several factors have influenced this trend.Cost - subsea wells are generally more economical than platform wells.Marginal production from undeveloped fields - most of the remaining undeveloped fields are small with limited potential which cannot justify the expense of platforms.Harsh environmental conditions - high Tides, extreme currents and ice make platform construction impractical.Deep waters - some undeveloped fields are in areas where extreme water depths exceeding 1300' make platform construction cost prohibitive.
Subsea wells are completed as single well satellites or in multiwell templates. Production can be into a floating production system, platform mounted system or a shore-based facility.
Subsea well completion designs do not differ significantly from platform-based wells. The corollary to this is that well servicing requirements will, in general, be the same for subsea wells as for any other offshore well.
Conventional riser-based methods of reentering subsea wells are time-consuming and costly, and therefore not: compatible with the operating cost levels dictated by the majority of subsea developments.
The system discussed in this paper was developed over a number of years, and has been successfully used to carry out a comprehensive range of wireline operations from floating vessels in the North Sea. This system was originally designed to be deployed from a diving support vessel (DSV).
ROV Tooling and Interface Design for a Subsea Satellite Template
Authors: Jolly A.D. , Hughes E.W. 
Published: October 2008

ABSTRACT
This paper describes the ROV intervention tooling and interface designs for the Troll Osberg Gas Injection (TOGI) template. The ROV tooling and interface hardware successfully completed shallow water tests in January 1989 and are presently undergoing final integration testing.
The paper is significant because the TOGI template is the deepest underwater production template ever installed in the North Sea. The template's dependence on cost effective and efficient ROV support has caused an increase in the level and sophistication of ROV tasks and hardware and these advances are applicable to many other deep water installations.

INTRODUCTION
Production systems are being installed in deeper waters than ever before and are requiring more unmanned intervention. In addition, production systems are becoming more sophisticated. These two factors are combining to expand the envelope of present remote subsea support, intervention tasks and hardware. The TOGI project represents an up-to-date example of present day ROV production intervention capabilities.
The TOGI ROV work packages are designed to be ROV independent so that they can be deployed and operated by work ROV's of opportunity. In order to accomplish this, the ROV tools are powered and controlled through a modular hydraulic power skid package, and the deployment of the tools is based on the fly-in method. The use of manipulators is minimized and all tool interfacing is done through the hydraulic power skid as shown in Figures 1 & 2.

TOOL DEPLOYMENT/DOCKING
Many previous remote work system tooling and work package designs relied on manipulator installation of the tools. Manipulators are necessary and useful tools for performing a wide variety of subsea work tasks. However, different manipulators have different operational envelopes and characteristics and it is extremely difficult to develop manipulator deployed tools that are manipulator/remote work system independent. At the same time, it is usually impossible to justify the complexity and expense of developing all remote work system interfaces and intervention hardware such that the need for manipulators is eliminated. For this reason, the TOGI remote work system tooling and production equipment interfaces were designed to provide both docking and actuation of various hydraulic and mechanical functions without the use of manipulators, while the operation of hydraulic isolation valves and the connection of surface hotlines were retained as manipulator tasks.
In order to ensure the manipulator based tasks could be accomplished by a variety of remote work systems, several full scale manipulator models were built to ensure that compatibility was maintained. The use of the models to determine final equipment location and physical interface design has been proven to be extremely beneficial.
As stated above, the best method of ROV tool deployment, in most cases, is by physically flying the tool into position with the ROV. This is commonly referred to as docking.
Accuracy of Offshore Subsidence Measurements With Seabed Pressure Gauges
Authors: Mes M.J. 
Published: October 2008

ABSTRACT
Phillips Petroleum Company Norway successfully pioneered the development, installation and application of pressure gauges to measure offshore- platform subsidence as a function of time.
Four pressure gauge systems were installed in the Greater Ekofisk area. On each of the 2/4-E Tort 2/7-C Edda and 2/4-F Albuskjell platforms one system was installed, serving as platform bench mark references. One system was installed on the 2/4-H Hotel platform, for which the subsidence must be measured as a function of time. These systems are described.
The theoretical accuracy as well as the apparent accuracy from prototype data prove that with pressure gauges we can measure the progression of subsidence with a relative uncertainty of +/− 9mm

INTRODUCTION

Background
Phillips Petroleum Company Norway is the operator for the Ekofisk Field, located roughly in the center of the North Sea. Figure 1 shows a geographical location map. Several platforms, located near the center of this field, are connected by bridges. This group of platforms is referred to as the Complex. The field was discovered in 1969 and has produced oil and gas since 1971.
In November 1984 it was discovered that subsidence takes place in the central Ekofisk field. Several measurements systems were, used to obtain information on the total amount of subsidence and the subsidence rate. An experimental measuring system based on pressure gauges was installed.
This system consisted of pressure gauges suspended from the Hotel and Tor platforms. A sketch of this experimental system is shown in Figure 2. Over ten weeks of uninterrupted, usable data were obtained and interpreted. It was decided that the measurement system was attractive for further development. Permanent Pressure Gauge Subsidence Monitoring Systems were installed on the? 2/4-H Hotel, 2/4-E Tor, 2/4-F Albuskjell and 2/7-C Edda platforms during the summer of 1987.
Sea bed pressure gauges (SPG) serve the following requirements:they track the progression of subsidence accurately so that a reliable rate of subsidence is computed.Data collection and data interpretation is economic and not labor intensive.The SPG system provides continuous measurements so that discontinuous subsidence can be seen.
New Critical Service eRA Alloys
Authors: Rizzo F.J. 
Published: October 2008

ABSTRACT
Over the past few years, there has been increasing activity in drilling oil and gas wells to depths greater than 20,000 feet. Because of this, extremely hostile environments such as those in Mobile Bay are encountered. Materials selection for these systems has become a problem. Standard alloys will not hold up under the expected operating conditions. High alloy CRA compositions are being evaluated for these applications. This work describes how the use of powder metal processing of 625 (UNS N06625), 625M (UNS N07626) and C-276 (UNS NI0276) and the unique properties of these materials can be helpful in solving many of these problems.

INTRODUCTION
Powder metallurgy (PM) technology has been in use for many years. It has only been in the last twelve to fifteen years that people have been using this technique to produce material for critical applications. This has occurred because of the advantages of PM processing, which include uniformity of microstructure and properties, the ability to produce near-net shapes, and the ability to make components from alloys which are difficult to fabricate.
The aerospace industry led the way to develop materials and processes for the manufacture of fully dense PM materials. There was a need for materials with very high strength-at-temperature .capabi1ities. Years earlier, the limit had been reached for materials made by the conventional cast and wrought or ingot metallurgy (IM) method. The approach with PM was to make high strength, homogeneous, near-net shape parts for turbine engine hardware. After ten solid years of successful flight experience and many thousands of components later, this technology is beginning to find its way into other industries.
In the oil industry, this technology is being used to make some of the new corrosion resistant alloys (CRA's). Many of these materials are highly alloyed which leads to segregation problems and fabrication problems with conventional manufacturing processes. With the PM approach, these problems are overcome. In critical service applications such as the sour gas wells in Mobile Bay, there are many areas where CRA's made via the PM route can fulfill the stringent requirements. This is an ideal situation to take full advantage of the flexibility of PM and a cost effective method to justify the use of the high alloy CRA's that will do the job.

PM HANUFACTURING PROCESS - POWDER
The PM process starts the same as many other material manufacturing operations do; with melting. When high alloy materials are being made, this usually means vacuum melting. Powder can be produced from any molten metal, but the type of CRA's being discussed herein require vacuum or inert gas handling to keep the residual elements as low as possible. At Crucible, this melting unit is a vacuum induction furnace with a nominal 5000 pound capacity. Attached to this equipment is an inert gas atomizer which is used to manufacture the powder metal from a molten stream. A schematic diagram of this system is shown in Figure 1.
Statistical Risk Methodology: Application for Pollution Risks for Canadian Georges Bank Drilling Program
Authors: Sharples B.P.M. , Stiff J.J. , Kalinowski D.W. , Tidrnarsh W.G. 
Published: October 2008

ABSTRACT
Risk analysis assessment techniques have not been applied previously to determining environmental risks at specific locations for offshore exploratory drilling programs in Canada. Rational analysis of the potential causes of failure, combined with probabilistic methods, provides a quantitative measure of the risk of an oil spill and consequent pollution from exploratory drilling which has not been available previously. This approach has demonstrated that the risk of oil pollution is very small much smaller than is perceived by the general public. Methods are also suggested by which operators can further reduce this risk.

INTRODUCTION
In recent years, there has been increasing public concern about protecting the marine environment from the effects of accidents in offshore oil and gas exploration and development activity. This concern attained a very high profile over a proposal for exploratory drilling on Georges Bank, a seaward extension of the continental shelf that projects into the Atlantic Ocean between Cape Cod and Nova Scotia. Georges Bank supports a rich fishery which is important to fishing interest in both Nova Scotia and Massachusetts. Much of this concern stems from the public's perception about the risk of environmental damage. When Texaco Canada Resources Ltd. (Texaco Canada) announced plans to seek regulatory approval to drill two exploratory wells on the Canadian side of the bank, the issue of risk to the environment was paramount in the minds of the interest groups lobbying against such activity. In the public debate over the issue, the potential risks of drilling activity on the bank became badly distorted.
Without site specific information to answer the concerns of critics, Texaco Canada was unable to respond directly to the allegations that its proposal presented an unacceptable risk to the environments and fisheries of the bank.
To provide a factual basis for discussing these risks, Texaco Canada contracted Energy & Maritime: Claims and Appraisals, Inc. (EMCA) and Noble Denton & Associates, Inc. (NDA) to develop a methodology to quantify the risks of an oil spill resulting in environmental damage, and apply it to the Georges Bank area. The objective of this study was to put the potential pollution risk in proper perspective and then develop recommended strategies for managing this risk.
Data were collected on blowout casualties, oil spill events and combined with an existing database on nondrilling hazards for the years 1955-1987. The goal was to present the hazards in a simplified graphical form, together with quantification of the probabilities of occurrence of the initiating events that could lead to an oil spill. Probabilistic techniques were used to verify the roost likely size of such an oil spill, if it were to occur, from both historical data and rational analysis. Information on previous accidents was used to assist in formulating appropriate hazard mitigation techniques.