bluuebunny/crossref_metadata_2025_split huggingface dataset:
Highly Compliant Column for Tanker Mooring and Oil Production in 1000-m Water Depth
Authors: Sebastiani G. , Brandi R. , Di Lena F. , Nista A. 
Published: October 2008

ABSTRACT
A two year research project has been carried out, devoted to the design of SPMs for temporary and permanent tanker mooring in 1000 m water-depth in the Mediterranean Sea. The main component is a very slender and highly compliant vertical column, tensioned at its top by a proper buoyancy chamber. The column is connected down to the base and to the upper buoyancy chamber through tapered steel terminators, thus ensuring full structural continuity and avoiding any critical mechanical ball joint. A small lattice tower placed on top of the buoyancy chamber supports deck and facilities.
The structure, designed as mooring/loading system, has natural period within the range of the wave periods so that it behaves in resonance conditions, yet the fatigue strength all along the column is adequate. This has been demonstrated through an extensive non-linear dynamic analysis and fatigue evaluation by spectral approach.
A two phase transportation/installation procedure and a telescopic assembling of the column have been proposed in order to accomplish marine operations on structures of reasonable size.
Furthermore, for the use of this concept as a permanent mooring, an original gravity yoke has been studied for the connection of the tanker to the top of the column.
The paper, after a description of the structure configuration, its performance and proposed marine operations, presents the main results of an extensive dynamic-fatigue analysis.
What is considered to be new, in this work, are the proposed simple but original structural concept, the installation procedure and the advanced nonlinear dynamic analysis carried out for a correct evaluation of the response of a compliant structure with several resonance conditions in the range of the wave period.

INTRODUCTION
The monopile concept was identified in a previous research project developed jointly by Tecnomare and Aker Engineering, where a design for a water depth of 350 m was performed. An extension of this concept to very deep waters is here proposed and discussed.
New problems arising from such an extension are mainly inherent to its great length and flexibility. This led to conceive an installation procedure where several individual substructures were eventually connected to each other by means of mechanical connectors. In in-service condition several frequencies were found within the wave frequency range, so that an accurate prediction of motion, stresses and fatigue accounting in resonant condition was necessary.

GENERAL DESCRIPTION

Configuration
The structure of the offshore mooring and loading terminal named Monopile is basically composed of the framed base structure, the very slender and high column, the buoyancy chamber, the upper tower and the head structure. The general arrangement is shown in Fig. 1, while in Table 2 the weight and buoyancy layout for the different parts of the structure is reported.
Optimization of Deepwater Steel Structures
Authors: des Deserts L , Deleuil G. 
Published: October 2008

ABSTRACT
This paper describes an optimization method for the design of fixed or compliant structures to be installed in large water depths and whose designs are dominated by the fatigue loading resulting from low period sea states. The method increases the range of application of jacket type structures, until the extreme environmental conditions generate prohibitive overturning moments at the mudline. The optimization of the geometry of the structure to minimize the hydrodynamic forces is complemented by a complete dynamic and fatigue analysis methods. The dynamic analysis can be either in the time domain or in the frequency domain and considers all wind, wave and current forces. Linear relationships between internal forces of the members of the structure have been established and permits the simplification of the overall fatigue analysis.
The method was applied on a jacket for 350 m (1150 ft) of water and the main results are presented.

INTRODUCTION
Oil production in deep water is a major objective of today's offshore industry. To minimize the cost of the equipment of a deep water field, it is necessary to design and build optimized offshore structures.
When the water depth increases, the governing criteria for the design of the structures to be installed differ from what they are in shallower waters.
The overall flexibility of any fixed or compliant structure increases with the water depth. Thus, the natural periods of vibration become close to the Mean period of waves. Then dynamic and fatigue effects become the governing criteria for the design of such structures.
The purpose of this paper is to describe a method for the optimization and the fatigue analysis of any deep water structure. In a first step, starting from a preliminary design fitting with all production criteria, the structure is optimized with respect to the hydrodynamic forces, in such a way that the wave period inducing the minimum external forces will correspond to the natural period of the structure. In a second step, the structure defined in the first step is fully analysed using a 3-dimensional model to verify its dynamic behaviour and to establish its fatigue life.
The fatigue analysis can be optimized by the use of the "correlations" defined in the dynamic analysis and permit a refined calculation of the hot spot stress areas.

METHODOLOGY

GENERAL
The basic tool for structure optimization is a set of computer programs performing a dynamic analysis and computing the response of the structure to waves wind and current.
The main computer program works in the frequency domain or in the time domain and calculates the response of a lumped mass model of the platform. The hydrodynamic forces can be computed on all members of a jacket type platform.
Hutton TLP Marine Operations
Authors: Hart H.J. , White G.J. , von Fischer E.L. 
Published: October 2008

ABSTRACT
This paper reviews the Planning and execution of the Marine Operations for the Hutton TLP including:Well Template InstallationSite PreparationFoundation InstallationTemporary AnchoragesMatingMajor TowsTLP Installation Planning the work to meet project objectives resulted in the utilisation of a number of new techniques and advanced equipment applications. These included underwater pile hammers and special acoustic equipment to provide positioning information during underwater operations. However, the detailed planning which preceded each operation significantly enhanced the effectiveness of the equipment employed. Further, it contributed materially to the attainment of First Oil only twenty two days after TLP installation.

INTRODUCTION
The 'towing, mating and installation of the Hutton Tension Leg Platform (TLP) involved extensive marine operations ranging from conventional sea tows to the first-ever installation of a TLP. To ensure the success of some of the more complex marine operations, special methods and unique equipment applications were required. A number of these are addressed in papers presented at other OTC sessions.
This paper provides an overview of all of the principal marine operations associated with the TLP, highlighting those which required something more than a conventional approach. Figure 1 shows the relative locations of the operations covered, including:Hutton Field, Offshore OperationsInshore OperationsInverness Firth AnchorageMoray Firth AnchorageHull T?OWDeck TowMating The paper stresses the importance of effective management in the success of marine operations including the specific areas of advanced planning, contingency planning, co-ordination with regulatory agencies and the supervision of contractors. The overall marine operations schedule is included as Figure 2. Marine Operations on the project critical path were the Hull Tow, Mating, TLP Tow and Installation.

WELL TEMPLATE INSTALLATION
A 32 slot template for pre-drilling wells (Figure 3) was the first structure to be placed at Hutton. The template, measuring 33.2m long by 11.6m wide by 6.6m high and weighing 400T in air, was installed in two phases:

Phase 1
In April 7981 the template was transported to the field and within 24 hours of arrival at Hutton was placed on the sea bed. The template?s final position was within 5.Om of the geographic target. This accuracy was achieved by using a newly developed subsurface acoustic positioning system integrated with surface electronic navigation equipment. The subsurface equipment was developed from an existing transponder which operated in a short base line mode and transmitted data on position, orientation and levelness. This system became an integral part of the systems developed for foundation and TLP tether leg installation.

Phase 2
A semi-submersible drill rig was used to complete the template installation.
Effects of Shallow Reflectors on Amplitude vs. Offset (Seismic Lithology) Analysis
Authors: Gassaway G.S. 
Published: October 2008

ABSTRACT
Reflection amplitude .versus CDP gather offset analysis has become a major new tool in the exploration seismologist's arsenal. During the last few years several articles have been published on this topic, i.e. W. Ostrander (1982), G. Gassaway and H. J. Richgels (1~83-84), Graul et al (1983), and G. Gassaway (1984). These methods would be easy to implement if the observed amplitudes were solely related to the reflection coefficients at the elastic boundary. This is because the seismic (P-wave) reflection amplitude at an elastic boundary is a function of seven parameters. These seven parameters are three elastic constants in each media and the angle of incidence (Richter 19~8). These elastic constants are functions of mineralogy, lithology, and pore fluids, (see Simon &Wang, 1971; Toksoz et aI, 1976; and Garmichael, 1982). In fact, several methods have been developed to invert the observed amplitude variations in a GDP gather to the elastic constants and lithologic estimations, (Gassaway &Richgels, 1~83; and Hilterman in Graul et al, 1983).
However, mental reflection upon the problem leads one to a whole list of items that ultimately affect the observed amplitudes. This list can be subdivided into those items that are easy and those that are difficult to correct. Some of the items that are easy to correct are:spherical spreading of the wave front,geophone and shot arrays,free surface effects,geophone sensor not parallel to the emerging ray path, (particle motion), anddata processing programs.
Among those items that are more difficult to correct are:inelastic attenuation,anisotropic effects,transmission losses at overlying reflectors, andthin bed tuning effects. It has been our experience that transmission effects are an order of magnitude greater than the others.
This paper addresses transmission losses and comes to the conclusion that changes in transmission losses in the shallow reflectors can totally mask the true reflection coefficient versus angle of incidence Changes at the objective horizons. Therefore, it is concluded that correct "amplitude versus offset" interpretations must include a correction for the transmission losses at the shallow reflector boundaries.

INTRODUCTION
The analysis of amplitude versus offset within a CDP gather has created practical ways of estimating elastic coefficients. From the elastic coefficients, further estimates of lithologies and pore fluids are made. The resultant practice of "seismic lithology" has been developed. Ostrander (191:$2) proposed that gas bearing sands should show a strong increase in amplitude with offset on a CDP gather. He showed many examples where this was the case. Figures #1 and #2 show a shallow gas zone which conforms to Ostrander's model. The amplitudes show a strong increase with increasing offset. These two figures also show a second gas zone Which does not show the expected amplitude increase with offset.
The JEFF(A) Arctic Logistics Demonstration Program
Authors: Stocking W.B. , Edwards J.J. 
Published: October 2008

ABSTRACT
The JEFF (A), a self-propelled air cushion vehicle (ACV) leased from the U. S. Navy in June of 1983, has successfully completed one year of engineering testing and logistics demonstration in the Prudhoe Bay and Harrison Bay regions of the Beaufort Sea. The results of this demonstration program are embodied in a compilation of operational data covering effects of low temperature on unique ACV systems and components; selection of fuels and lubricants; cole' weather warm-up procedure, methods and effectively. of maintenance techniques, facilities and maintenance personnel; training of ACV operators; craft cargo procedures and craft navigation in low to zero visibility. The rigorous documentation of the day-to-day operational history of a self-powered ACV operating in the arctic provides a substantial amount of data both for the design of .future ACV's to be used in the arctic and the conduct of transportation studies in support of offshore drilling activities.
This paper deals with a developmental craft which was modified to meet arctic requirements and details the operational experience gained during the demonstration period with specific coverage of craft performance and discusses the interaction of the JEFF (A) with the indigenous logistics network of the North Slope. The paper also discusses the impact of the air cushion vehicle as a viable logistics alternative to currently used arctic vehicles.

INTRODUCTION
As the price of oil decreases, increased emphasis is placed on the economics of the individual elements of bringing oil to the marketplace. Oil-bearing geographic locales such as the arctic can effectively be shut down to oil exploration and production if cost elements don't "add up". The objective of this paper is to review, based on some near-term experience, the benefit that can be achieved in the cost of the oil exploration and production through the use of an air cushion vehicle to provide required logistics support. While not an exhaustive, long-term demonstration, the near-term JEFF (A) Arctic Demonstration Program reaffirmed the applicability to arctic logistic operations of air cushion vehicles in general and demonstrated the value of an air cushion vehicle configured as the JEFF (A) in specific. The ten month demonstration period provided exposure to a wide variety of environmental conditions and allowed an adequate amount of interaction with the in-place logistic network to assess compatibility requirements.
Offshore, within the land fast ice zone or near the barrier islands, the relatively smooth ice surface, broken infrequently by leads or rubble, offers a convenient highway for the transport of exploration gear. When the ice thickens naturally as winter progresses, or where a combination of continued low temperature and artificial flooding create "ice roads" with reasonable load-carrying capability, land-bound transporters such as trucks and rolligons with sleds or trailers can begin to roll.
Hydrodynamic Forces on a Pair of Cylinders
Authors: Bokaian A. , Geoola F. 
Published: October 2008

ABSTRACT
Measurements are presented of forces on a pair of identical parallel circular cylinders with a scotch surface under a steady uniform flow. The drag coefficient of the cylinders was found to be a continuous function of the cylinders' spacing. With increasing the stream wise separation, whereas the transverse extent of the force field on the downstream cylinder indicated an increase, that on the upstream one showed a decrease. In the near wake, the lift forces attained peak values while the drag forces remained lower than the single cylinder value. The forces on the upstream body differed from those on an isolated body only if the two cylinders were as close as two diameters. Mutual interference effects were observed to be most significant at small separations.

INTRODUCTION
The resistance to fluid flow around a body is strongly affected by the presence of other nearby bodies. When two cylinders are in close proximity, the flow around the downstream body can affect that about the stream one and vice versa. Adjacent structural members subjected to fluid flow may generate an interaction which can cause the force on individual members to increase or decrease over the single cylinder value. Examples include members of the jacket type drilling platforms, semi-submersibles, floating tubular structures, risers, and other tubular structures in offshore engineering; cooling towers and transmission lines in civil engineering and so on.
Characteristics of the flow around two interfering circular cylinders are a research topic much more complex than that concerning isolated bluff bodies. When two parallel cylinders are far apart and the rear (downstream) body is well outside the wake of the front (upstream) one there is no interference between them. The flows around both cylinders are the same as that around a single cylinder. The interference between the two bodies will start either when they are sufficiently close to each other or when the downstream cylinder is adjacent to or within the wake of the upstream one. A careful review of flow interference between two parallel circular cylinders in various arrangements in a cross-flow has been presented by Zdravkovich12. The quantification of the interference effects in terms of static forces on individual members, and vortex shedding frequency in terms of the governing flow parameters constitute the essence of the problem. This paper describes a series of experiments aimed at determining the lift and drag forces on two parallel and closely spaced circular cylinders with a smooth surface positioned at right angle to approaching flow direction.

EXPERIMENTAL ARRANGEMENT AND PROCEDURE
The investigation was conducted in a long rectangular horizontal flume, 0.3 m wide, 0.3 m high. The working section was situated at a distance of about 1 m from the upstream end of the flume.
Exploration 3D: A New Tool Of Cost Effective Information For Offshore Prospects
Authors: Ritchie W. , Major J.T. 
Published: October 2008

ABSTRACT
The present industry climate magnifies the need for lower finding and developing costs for new reserves. With most of the larger new non-OPEC reserves expected to be found offshore, involving high costs and heavy front end investment, improved information to reduce risk in the offshore arena is critical. The 3D seismic system has clearly demonstrated its value in the post-discovery stage. A cost-effective extension of this concept applicable to the pre-discovery stage is now available. The Exploration 3D method provides:–earlier, better quality information to locate potential reservoirs.–reduced cycle time to production–equivalent cost to alternative conventional seismic methods
The role of Exploration 3D is discussed for the Gulf of-Mexico environment.

INTRODUCTION
Over the last 15 years, the oil market has undergone, and continues to undergo, major structural changes. Worldwide oil demand has fallen from its 1919 peak of 51.2 million barrels per day (mbd) to 44.7 mbd in 1983. On the supply side, higher oil prices spurred non-OPEC production growth from 35% of worldwide production in 1973 to 56% in 1983.
The reserves from which non-OPEC production emanates have been found mainly offshore in the recent past and most experts believe the bulk of significant new non-OPEC reserves will continue to be found offshore.
Today, in the presence of severe price pressures and declining reserve bases, oil companies are thus faced with finding new reserves in a high cost, high risk offshore environment where 26% to 41% of future oil demand is projected to lie.
The costs at stake are significant in the offshore environment. Table 1 shows the cost relationships of the major expenditure segments. Drilling and structures account for approx 70% of total expenditures or $26 billion in 1984, projected to grow to $40 billion over the next three years. The U.S. share is projected to grow from 20% to 25% over this same time period.
The introduction of tools which have a direct impact on time and cost effective utilisation of drilling equipment and structures becomes, therefore, ever more important. We will discuss a new tool, Exploration 3D, which directly supports and expedites the decision processes by providing cost effective, timely quality information to the oil company at the stages when it can be of most value.

GULF OF MEXICO ENVIRONMENT
The brightest spot for increasing U.S. reserves is in the Gulf of Mexico. In addition to maturing areas offshore Louisiana and Texas, the flexure trend in the Gulf of Mexico's deeper waters is growing in attractiveness. The role and use of Exploration 3D will be illustrated in the Gulf of Mexico environment.
In the last five years, 3200 offshore tracts have been leased. With the advent of area-wide leasing in 1983, independents as well as the majors have participated in the Gulf of Mexico search.
Corrosion Reduction In Production Tubing With the Aid Of ,A Phase Equilibrium Model
Authors: Reinhardt J.R. , Powell T.S. 
Published: October 2008

ABSTRACT
A model is described which predicts where the corrosion of production tubing, due to condensed water in gas condensate wells, is most likely to occur. The prediction is made by combining flash equations and thermodynamic equilibrium principles within a computer algorithm for use with a personal computer.

INTRODUCTION
Corrosion attack of the production tubing of a gas condensate well may cause the tubing to fail at an unexpected, early date. The tubing could then be replaced but at considerable expense due to the unscheduled workover and the loss of production.
One of the major factors-for corrosion is liquid water being in contact with the surface of the tubing (1). The liquid water allows small electrical circuits to be completed between small anodic and cathodic areas on the surface. The small anodic areas are the surface areas being dissolved (i.e., corroded) and this reduction of the thickness of the tubing wall leads to tubing rupture.
Many other factors are also important for corrosion to be possible. One factor is that some component, such as hydrogen sulfide, is reduced in the water to give an aqueous solution which can transport the electrical charge. Another would be the actual contact of the liquid water with the surface. The relative amount of condensed hydrocarbon may prevent the condensed water from effectively contacting the surface. A volume ratio of liquid water to liquid hydrocarbons of about 0.3 is believed necessary before the vertical tubing surface becomes sufficiently water-wet so that corrosion is possible (2).
The purpose of this paper is not to look at all the factors which contribute to corrosion, but to present a model which predicts where the tubing could become water-wet. Once this zone of tubing is identified, the corrosion engineer may decide what actions to use to reduce the potential for corrosion. Some suggested actions include:using a more corrosive resistant tubing through this zone,injecting an inhibitor below the zone to place a protective coating on the tubing surface, andinjecting an additive below the zone to change the phase equilibrium so that water-wetting is not possible.

THEORY
The first step in developing the model is to imagine that the entire length of the production tubing is divided into sections as seen in Figure 1. Each imaginary section is then considered to be an individual flash chamber. The entire length of production tubing is, thus, replaced by an imaginary string or stack of discrete flash chambers. The flow streams leaving each flash chamber are recombined into a single stream that becomes the feed stream for the next flash chamber. This system of separated and recombined streams continues up through the total stack of flash chambers. The stack of chambers could be extended to include the flash across the perforations at the bottom of the well and the primary separator at the surface.