bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of a Methodology for Safety Assessment of Existing Steel Jacket Offshore Platforms
Authors: Aggarwal R.K. , Bea R.G. , Gerwick B.C. , Ibbs C.W. , Reimer R.B. , Lee G.C. 
Published: October 2008

ABSTRACT
This paper describes a methodology for assessment of the safety of existing steel jacket offshore platforms. The methodology is based on a four-level evaluation process. The first two levels consist of screening of the platforms into one of three categories: "fit for service", "unfit for service", and "marginal", based on qualitative evaluation and simplified quantitative analyses. The higher levels of assessment require detailed computer analyses.
Capacity of the platform and potential consequences associated with the loss of serviceability of the platform are key parameters in this methodology. The capacity characteristics are expressed through a Reserve Strength Ratio (RSR = Ultimate Capacity / Minimum Reference Force). The consequences are expressed through evaluations of life, property, resources, productivity, and environmental implications associated with the proposed platform operations.
A study is currently (1990) underway to present this methodology in the form of a computerized knowledge-based expert system. The organization of the prototype expert system is presented.

INIRODUCTION
Steel platforms have been in use for more than 40 years in the Gulf of Mexico and other offshore areas around the world. At present, there are more than 4,000 offshore platforms in the United States. In the Gulf of Mexico alone in 1987, there were 3,080 platforms, of which 73-percent were in water depths up to 100 ft. and 27-percent were in water depth more than 100 ft. [1].
The structural configuration of these platforms ranges from single-well caissons to multi-leg jackets. In 1987, there were 1,969 wellhead platforms, 355 tender-assisted platforms, and 756 self-contained drilling & production platforms in the Gulf of Mexico [1]. The wellhead platforms are single well caissons or multi-well 4-legged jacket platforms. The tender assisted platforms are usually 4-legged jackets and the self-contained platforms are mostly 8-legged jackets. The design criteria of these platforms has changed significantly over the past 40 years. Many of the early platforms were designed for 25-year return period waves, whereas, since about 1969, the majority of platforms have been designed for 100-year return period waves. The American Petroleum Institute (API) first introduced recommended practices for offshore platforms (API-RP-2A) in 1969, to provide consistency in design, fabrication, and installation of offshore platforms. API has periodically updated the recommendations, and the 18th edition [2] now forms the general standard for design of Gulf of Mexico platforms
The present day Minerals Management Service(MMS), introduced the Outer Continental Shelf (OCS) Order No. 8 in 1979 [3]. More recently, the MMS introduced updated requirements, which largely follow the API guidelines with some additional requirements [4]. Present OCS requirements define the need for periodic assessment of existing platforms for their continued use (Clause 250.142 a)
Metal Annulus Seals for Subsea 'Wellheads: Important Systems Considerations
Authors: Boehm C.F. , Hosie S. 
Published: October 2008

ABSTRACT
The development of metal-to-metal annulus seals involves careful consideration of the environmental and operational requirements of these seals for sub sea wellheads. This paper discusses the development of such a seal with particular emphasis on the testing program which subjected the seal to realistic drilling conditions.

INTRODUCTION
Sub sea wellhead systems are exposed to a variety of severe environments. Some of the most critical wellhead system components are the annulus seals which seal or pack off the successive casing annuli as the well is drilled. True metal-to-metal seals are considered the premium approach for the most harsh conditions. Devising metal seal systems involves not only the usual evaluation of the seal environment, but particular attention to what constitutes a true metal-to-metal seal. Finally, qualification testing of such a seal involves careful consideration of fixture bias, those elements of laboratory testing which do not reflect realistic operational conditions.

SEAL ENVIRONMENT
In drilling a well, particularly sub sea, many conditions occur which could cause scoring damage in the wellhead bore. Wear protectors (wear bushings, bore protectors) are installed and retrieved after each successive drilling operation and can cause damage. Additionally, casing, casing hangers, associated running tools, and test tools are introduced into the wellhead bore and can, if debris is present or vessel offset severe enough, cause scoring damage. The frequency of such damage and its severity is indicated in Figure 1-A. A survey of used wellheads was conducted and the results of typical damage is shown in Figure 1 (1).
When a seal assembly is installed, its outer surface can be damaged because typically the metal seal element's outside diameter is virtually the same as the running tool and the hanger maximum diameters. Assuming a single trip casing-cementing, seal-setting system is run, there is virtually no protection as the seal assembly progresses down the riser bore, through the flex joint, annular BOP element, and past the ram cavities into position in the wellhead housing. Certain factors can make this trip more hazardous:Excessive vessel offset causing severe flex joint angles.Used or worn annular BOP elements, which typically extend into the primary bore of the BOP stack.Rams which have "drifted" into the primary bore of the ram presenters or have bit damage.
Adverse flex joint angles and protrusions into the primary bore of the BOP stack provide ready agents for damage to the metal seal element's outer surface. This type of damage is most often of a vertical or near vertical nature across the sealing area surface. The metal seal element's inside diameter and the hanger neck sealing surface generally do not suffer scoring damage in the course of running and cementing casing. However, the possibility of entrained solids or cuttings causing an erosive type damage is possible during circulation especially if silky/clay or "gumbo" as commonly found in some locations is present.
Vertically Constructed and Installed Jacket for the Gyda Field
Authors: Harris G. , Stone G.C.H.B. 
Published: October 2008

ABSTRACT
This paper examines the design, construction, 10adout, transportation and installation aspects of the Gyda Jacket. The jacket is a vertically constructed and installed six leg structure with vertical piles in 66 meters water depth. The jacket lift weight was approximately 8200 tones.
The concept was made possible by the new generation of heavy lift crane vessels, which opened the horizons for lifted jackets in the range of 8000 to 10,000 tones.
The new design features are discussed, which included the use of steel castings and the elimination of all internal stiffening of tubular joints. The major features and experiences gained during construction and installation are also discussed, particularly vertical piling. Comparisons are made with conventional barge launched jackets to demonstrate the cost and weight savings. The paper concludes with the major lessons to be learnt for future projects.

INTRODUCTION
The Gyda field is located 28 km. south-east of Ula and 43 km. north of Ekofisk in the Norwegian sector of the North Sea.
The estimated recoverable reserves are about 200 million barrels of stock tank oil, over a production life of 20 years. The planned production race is 60,000 barrels per day of oil and 1.9 million m per day of rich pipeline gas. 32 well slots are to be provided comprising 19 production, 11 water injection and 2 spare. The reservoir requires water injection at an average rate of 65,000 barrels per day.
The development is a single platform comprising four major topsides modules. The Living Quarters, Process/Utilities and Drilling modules are mounted directly on an eight leg Cellar Deck. This Cellar Deck stabs directly into the conventional piled steel jacket.
The jacket stands in 66 meters of water and the seabed comprises 10 meters of level sand with layers of clay beneath. The maximum design wave height is 25 meters and the jacket was designed for all the usual load combinations, including boat impact and earthquake. The jacket was designed for a total operating load of 26,500 tones.
The jacket is 76m high and has a plan area of 54.0m × 25.0m at the top and 58.0m × 38.0m at the base. The jacket is a six leg structure incorporating around 250 members and 109 nodes, see figure 1. It is supported by a total of 20 vertically driven piles 2134mm diameter, four 70m length, at each corner leg, and two 75m length at each centre leg.
The jacket accommodates a total of 32 conductors, eight are 500mm in diameter and tied back from the sub sea wellheads at the drilling template. The remaining 24 are 685mm diameter platform run conductors. There are 13 caissons, of various diameters and termination elevations descending from the topsides facilities, and 4 pre-installed risers.

PROJECT SCHEDULE
The overall project schedule is shown in figure 2. The concept engineering took place in the latter half of 1986. The front end engineering ran from the 5th January 1987 to the end of June, When detailed engineering commenced on the 1st July 1987.
USCG and the TLWP Facilities
Authors: Folse K.A. , Hanke T.A. 
Published: October 2008

ABSTRACT
This paper relates the experience of conoco Inc. in obtaining United states Coast Guard (usa) approval for facilities on the Tension Leg Well Platform (TrnP) located in Green canyon Block 184 in the Gulf of Mexico. Information is presented on the:chronology of key usog communications and TrnP project milestones,evolution of the list of "ship's services" on the TrnP which required usa:; approval,interaction between Conoco and usog on these "ship's services" to 0btain usa:; approval, andvarious certificates and documentation required for the TrnP.
This paper excludes items curler the jurisdiction of the Minerals Management Service (MMS).

INTRODUCTION
An overview of the Jolliet Project management, design, fabrication and instal1ation1 is presented in the paper "Jolliet--The Project." A key element of the project is the TrnP located in Green canyon Block 184. This paper addresses a portion of the TrnP project activities, in particular, the approval by regulatory authorities of the various facilities systems on the TrnP.
At the time the Green canyon TrnP was approved to proceed, the concept was fairly new and as yet untried in the United states. conoco recognized the need to obtain regulatory authority approval to install the TrnP on the outer continental Shelf (OCS). Two regulatory agencies, the united states Coast Guard (usog) and the Minerals Management Service (MMS), would be involved in approval of the TrnP. Structures on the u. s. OCS were divided into fixed, which were curler the jurisdiction of the MMS, and floating which were unclear the jurisdiction of the USOG. The two agencies had agreed to a general division of responsibilitiesfor approval of the various systems on these structures.
The TrnP was designated a floating OCS facility and, therefore, curler usog jurisdiction. he usog took the position that existing rules for M0bile Offshore Drilling Units (mro's) more closely approximated the TrnP and would be used as a startin3' point for review. Also, the usog would review and approve all "ship's services" marine engineering systems to 46 CFR Chapters F and J. The USOG stated that because of differences between mro's and the TrnP, they would remain open to discussion on any issue for which requirements were not specific.
The MMS had jurisdiction over drilling and production systems (industrial systems). The requirements of the MMS for fixed platforms were familiar to conoco, but the detailed assignment of jurisdiction over TrnP facilities to either USOG "ship's services" or MMS industrial systems was not clear early in the TrnP design phase.
Wave-Loading Experiments on Elements of Jackup Legs at Large Scale
Authors: Schuurmans S.T. , Lagers G.H.G. 
Published: October 2008

ABSTRACT
Results of wave loading experiments on chord sections and isolated bays of two typical jack-up leg designs are discussed. The tests were carried out at a large scale (approx. 1:2 for chords and approx. 1:4 for bays) in regular and random waves with large wave heights (up to 2.4 metres). This large scale is necessary to obtain flow conditions which are representative for full scale offshore conditions.

INTRODUCTION
Wave induced forces are a major contribution to the overall loading on a jack-up platform. They play an important role in the design of a jack-up platform or in the analysis of existing jack-ups, when their fitness for use at a specific site is considered.
While a large amount of experimental data has been gathered on smooth and rough circular cylinders in planar oscillatory flow and in waves, very little information is available fromtests with jack-up legs in such conditions. Itis generally assumed in the jack-up industry that the wave loading on jack-up platforms canbe based on experimental data obtained in stationary flow in wind tunnels. In view of the application of such platforms in deeper water and more severe environmental conditions, this situation is not satisfactory.
Therefore, a joint industry project was carried out to improve knowledge and understanding of the wave loading on jack-up legs. The basic objectives of this project were:to determine wave forces on typical jack-up legs under representative wave conditions and with the smallest possible scale effects andto achieve results for engineering applications which have a more general bearing than on the tested legs only.
This paper describes some results of wave loading experiments on elements (chords and isolated bays) of jack-up legs, carried out within the scope of this joint industry project. In view of the second objective, smaller elements (chords) were tested beside larger elements (bays) to enable determination of interaction coefficients. Bracings were not tested separately in this programme, because a large amount of literature is already available on circular members in stationary and oscillating flow. For the extrapolation of the laboratory data to full scale offshore conditions, it is essential to obtain these data in post-criticalflow conditions. To achieve the required Reynolds- numbers, the tests were therefore carriedout at a large scale (approx. 1:2 for the chords and approx. 1:4 for the bays) in regular and irregular waves with large wave heights (maximum wave height in irregular wave trains up to 2.4 metres).
This paper concentrates on the execution and the results of the wave loading experiments. In future publications, attention will be focused on the composition of elementary results to bay and leg results and the comparison of the composed results with measured results to check on interactions.
Wave Run-Up and Wave Forces on a Truncated Cylinder
Authors: Niedzwecki J.M. , Duggal A.S. 
Published: October 2008

Abstract
The results of a small scale experimental study to investigate the wave run-up and wave forces on a truncated cylinder, representing a single TLP leg, are presented. The investigation examines the wave run-up and in-line wave force conditions resulting from both regular and random waves. Surface adhering wave gages and a shear type load-cell design were developed for use in the study. Time series data around the cylinder and the sensitivity of the observations to wave steepness and scatter parameter are presented. For the random wave cases, attention is focused upon the relationship between the front and back of the truncated cylinder. Information on the transfer function, coherence, phase and total force are presented and discussed.

Introduction
The prediction of wave run-up and the associated wave forces on coastal structures and deepwater platforms has been of interest to the offshore community for many years. During this time, the engineering applications have included the design of piers, lighthouses, conical islands, fixed offshore platforms, and more recently the design of tension leg platforms (TLP's). As the focus for engineering design has changed the analytical and numerical tools available have significantly improved (Kim and Yue, 1989). However, these tools have been calibrated with only a limited amount of laboratory and field data.
The objectives of this study were to:to provide new laboratory data on truncated cylinders subject to regular and random waves, andto examine this data utilizing variety of statistical analysis tools in an attempt to provide new insight into the wave run-up problem.
In what follows, a perspective of where the results from this study fit into the current open-literature is provided through a brief review of previous experimental studies. Next, a description of the experimental setup and procedures is presented. The results for the regular and random wave cases are presented and discussed in sequence in separate subsections.

Previous Experimental Studies
Previous experimental studies have generally focused upon 1.) very large diameter structures in shallow water including man-made islands, and 2.) single and pile groups extending from the seafloor through the free-surface. Table 1 presents a comparative view of many of the earlier studies. Of particular interest are the range of parameters which have been examined.
The first three studies, listed in Table 1, are concerned with the wave elevation distribution around large circular islands and lighthouses. The tests conducted were for a rather limited range of wave interaction parameters with a scatter parameter greater than 0.6 in all cases. However results from all three investigations showed good agreement with linear diffraction analysis. Isaacson (1978) proposed a cnoidal wave theory approach to estimating the run-up on large circular cylinders in shallow water and showed that, though the cnoidal theory underestimated the experimentally measured wave run-up, it provided better estimates than linear diffraction analysis.
A New Locating Towed System for Mapping Smal Buried or Exposed Sealines
Authors: Kuhn H.W. , Robach F. , Schnepp G. , Guilhamat B. 
Published: October 2008

ABSTRACT
Locating buried small diameter sealines (say &lt; 10") with conventional geophysical methods has always been a problem for the off-shore oil industry. Standard towed survey tools, based on reflection seismics or proton magnetometers, suffer from their lack of resolution and sensitivity. The towed magnetometer, developed by the CEA, thanks to its very high sensitivity (0.01 nT) and measuring rate, allows small diameter sealines to be accurately detected. Moreover, when simultaneous injection in the sealine of an electric low frequency signal is performed, even cables or flexible pipes with little magnetization are detected.

I. MAGNETOMETRY AND ITS APPLICATIONS
Measurement of the Earth's magnetic field using airborne techniques is a standard military approach for submarine locating, and for mapping natural resources in geophysics.
The measurement is based on the principle of proton or electron magnetic resonance which transforms the intensity of a magnetic field H to a proportional frequency F.
The relation is given by Larmor's formula:(Available In Full Paper)
The frequency detector then measures the total field.
The measurement can be made by a moving sensor which is either towed behind an aircraft by a cable which reduces the effect of the magnetism of the carrier, a relatively simple solution, or embarked on the aircraft, which then calls for appropriate compensation techniques.
A fixed magnetic observation station equipped with a total field magnetometer having a relative precision better than a millionth will record time-dependent fluctuations of the magnetic field. Diurnal variations, magnetic storms and pulses are related to the sun?s activity and amount to a thousandth of the Earth's almost constant internal field.
For high sensitivity measurements, a differential technique is used. This eliminates the time dependent fluctuations which are identical at two geographically close points. The use of such a differential technique is standard in aeromagnetic mapping, but in marine applications, it is exceptional.
In submarine archeology for example, the use of three magnetometers towed behind a boat can be used to obtain the differences in total field experienced by the sensors (figure 1). These differential measurements are insensitive to temporal fluctuations, and the interpretation of the anomalies detected can result in the discovery of ancient shipwrecks essentially made of wood.

II. SPECIFICATIONS OF A HIGH SENSITIVITY MAGNETOMETER
Magnetometers available commercially at present, are based on either proton or electron magnetic resonance and are known as proton magnetometers or optically pumped magnetometers. The magnetometers presented here have been developed by the French Atomic Energy Commission (C. E.A.) and are based on simultaneous proton and electron magnetic resonance (Abragam - Overhauser effect) (1).