bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Modelling of Cyclic Pile Capacity in Clay
Authors: Nadim F. , Dahlberg R. 
Published: October 2008

Abstract
A numerical procedure for evaluation of the response of a single pile in clay under static and/or cyclic axial loading was developed. Under combined static and cyclic loading, two separate but compatible models representing respectively the static and cyclic responses are established. The procedure is fast and efficient as it attempts (o model an equivalent pile response for the entire design storm, rather than follow the pile response through every load cycle.

Introduction
Significant efforts were made during the past two decades to improve the methods for evaluating the axial capacity of offshore piles (e.g. Refs. 1-5). As a result of these efforts, the 17th edition of API RP2A (Ref. 6) design guidelines completely revised the recommended procedure for evaluation of axial pile capacity in clay. Furthermore, in the commentary to API RF2A (17th edition or later), the necessity of separately evaluating the effects of pile length flexibility and cyclic loading on the pile capacity are pointed out.
During the period 1980-1990, the Norwegian Geotechnical Institute (NGI) performed several comprehensive pile testing programs in overconsolidated (Refs. 7-9) and soft, normally consolidated clay deposits (Refs. 10-12). The tests covered a wide range of static and cyclic loading combinations and provided the basis for the numerical model described in this paper.
A number of factors should be considered in modelling of cyclic axial loading of piles, The most important of these factors are:type of cyclic loading (one-way vs. two-way, loadcontrolled vs. displacement-controlled) and number of load cycles,soil properties and variation of soil strength andstiffness with depth and in the lateral direction,pile length and flexibility,initial stress distribution along the pile under static loads prior to cyclic loading, and 5) compatibility in terms of cyclic and average displacements and stresses.
The numerical model described below for analysis of static and/or cyclic axial loading of offshore piles accounts for aH these factors.
This paper includes the results from recent verification and case studies by NGI and Det Norske Veritas. In these studies, the prdlcted and measured behaviors of instrumented large diameter and model piles are compared. The paper also includes a comparison between the developed numerical model and the RATZ program developed by Randolph (Ref. 13).

Soil-Pile Interaction
The soil-pile interaction model is based on the so-called concept (Fig. 1): the mobilized shear force t, around a given pile segment is only assumed to be a function of the vertical displacement z, of the mid-point of the segment. The t-z springs in the model are non-linear. They are generated by numerical integration in the radial direction of the mobilized shear strains in each soil layer (Fig. 2a).
Salt Distribution in the Louisiana South Additions Area from 3D Seismic Data
Authors: Jamieson G.A. 
Published: October 2008

Abstract
This paper outlines some preliminary observations based on a large interpretation project that was carried out with a grid of 3D time migrated seismic data, covering over 7,500 mi2 of the South Additions region of offshore Louisiana. Depth migrated data, covering a smaller subset of the study area, was also utilized in the interpretation. Top and base of salt were interpreted and the resulting maps have identified patterns of salt and weld geometry that show some regional trends.
Historically, 2D time migrated seismic has been the primary dataset of most of the published regional salt studies. This paper focuses on areas where 3D time migrated data potentially shows most improvement over 2D data, specifically in the subsalt regions. In particular. relationships between basesalt keels, welds, basins, regional faulting and basement architecture are investigated. A generalized model is outlined to help explain the current salt geometry in the study area and comparisons are made with recently published salt evolution models.

Introduction
Improved understanding of halokinetics in the Gulf of Mexico has relied heavily on improvement in geologic modelling and in particular, seismic data quality. 2D data has been the workhorse of regional studies. but 2D seismic sections are typically affected by out-of-plane interference. Due to the often extremely complicated geometry of salt masses, these effects can be significant. Further advances in regional understanding have resulted from a change in the way 3D data has been utilized in Gulf of Mexico exploration. Traditionally, 3D has been a tool of the oil companies development/ exploitation departments. Over the last 10 years, with the advent of non-exclusive 3D seismic data numerous large multi-block survey have been acquired such that the Texas/Louisiana shelf is now almost completely covered by 3D time migrated seismic data. In addition, many survey shot over the last few years have changed acquisition and processing parameters to maximize subsalt resolution. One such change has been an increase in cable length. commonly to 6 kms. Depth migration is another important technology that is being increasingly used for regional work improving the imaging and positioning of both saIt and subsalt reflectors. The industry is, therefore, in a position to use large quantities of very high quality 3D data for regional studies.
This paper illustrates some preliminary observations of salt and weld geometry and their relationship with sedimentation faulting and basement architecture. Weld features, including the now topical vertical ones, arc often the most ambiguous and subjective part of a complete regional salt inteqxetation. However, they are, in many ways, the most important as they ndicate the path of salt movement and also help pinpoint the likely position and geometry of paleo-intersalt basins and sandprone fairways.
The Atlantic Frontier - An Introduction
Authors: Fyfe T.B. , Osborne P.L. 
Published: October 2008

Abstract
The Atlantic Frontier, the area between the UK and the Faroe Islands, is characterised by relatively deep water and a harsh environment presenting significantchallenges for the UK oil industry. Over twenty years of exploration have yielded four discoveries, three of which are considered significant (Clair, Foinaven and Schiehallion). This paper describes thehistory of exploration and the three principle discoveries and summarises the current development plans for each. BP and Shell's strategic goals and business approach are also outlined. Pace is the key attribute which typifies our current approach to developments in the Atlantic Frontier in pursuit of our intent to establish a major new hydrocarbon province.

Introduction
This paper presents a general description of the Atlantic Frontier and serves to introduce the papers that follow in this section (Ref. 1-3) which discuss in detail the principle developments. It describes the location and unique environment of the area, recounts the history of exploration, summarises the principle discoveries and finally reflects on the strategy and business approach adopted by BP and Shell in exploiting the basin.

Location and Environment
Location. While the eastern ‘Atlantic Frontier’ can be said to extend from northern Norway to the west of Ireland and beyond, the focus of activity has to date been in the area more commonly known as ‘west of Shetland’. This area stretches from between the Shetland and Orkney Islands (to the north of the Scottish mainland) to the Faroe Islands, some 450 kilometres to the north west (Fig, 1) The area is split between UK and Faroese designated waters (to the south-east and north-west respectively) with a zone in the middle, referred to as the ‘White Zone’ which is still in dispute between the two Governments and is therefore effectively unavailable to the industry for exploration. The vast majority of activity to date (including all exploration drilling and all discoveries) has been in UK waters. BP/Shell's activity in the last three years has focused on the southern end of the basin, in and around UK Quadrant 204.
The Faroe-Shetland area is characterised by relatively deep water. The continental shelf, withwater depths to 200 metres, extends some 100-150 kilometres to the north-west of the Shetland and Orkney Islands. Thereafter the sea bed deepens quite steeply reaching a maximum of about 1200 metres in the centre of the Faroe-Shetland Trough before rising again towards the Faroe Islands. These water depthsmay not be excessive when compared to the Gulf of Mexico or the Campos Basin offshore Brazil, but they are considerably greater than experienced in the North Sea where the deepest water development in the Norwegian sector is Troll at some 320 metres and in the UK sector is Magnus at less than 200 metres. One of the key challenges for the UK oil industry is to access the technology necessary to exploit deep water discoveries.
The Validity of Morison Equation Extensions
Authors: Shafiee-far M. , Massie W.W. , Vugts J.H. 
Published: October 2008

Abstract
This paper presents results of an experimental work for investigating the hydrodynamic interaction of slender oscillating cylinders, Laboratory tests have been carried out to study wave-current-structure interaction by oscillating a vertical cylinder in the cross-flow and in-line direction with a (steady) flow and/or waves. Inclusion of a wide variety of flow conditions has been an important objective. The present paper deals with results of cylinder oscillations parallel to a current and concentrates on the in-line force component. Validation and suitability of various existing mathematical formulations for describing hydrodynamic interaction have been evaluated for the range of dimensionless parameters included in the laboratory test data.
The data refute the independent flow field approach to the prediction of hydrodynamic forces, and it is concluded that a modified form of the Morison equation which also happens to be linear shows promise for the universal prediction of hydrodynamic forces.

1. Introduction
Many types of slender marine structures in the offshore industry are affected by hydrodynamic interaction. This interaction must certainly be considered whenever the level of structural motion is not negligible.
The present work forms a part of an ongoing study of hydrodynamic interaction of slender cylinders carried out by the Workgroup Offshore Technology of the Deft University of Technology. Tests have been carried out to study flow-structure interaction experimentally by oscillating a vertical cylinder in the cross-flow and in-line direction with a (steady) flow and/or waves (regular and irregular); see table 1. The purpose is to obtain an unbiased set of laboratory measurements of the total interaction between the hydrodynamics (wave and current) on the one hand, and the moving cylinder on the other,
Various existing as well as new mathematical formulations for describing this interaction can be evaluated objectively using the data. Details of the experimental program may be found in references I and 2.
This paper considers the hydrodynamic interaction with the in-lineoscillation of the cylinder superimposed on a steady towing speed. This is a flow situation similar to that for a cylinder oscillating in a current or a combination of waves and current with a fixed cylinder,

2. Morison Equation Extensions
The in-line force arising from the oscillatory flow around slender fixed cylinders is usually represented by the Morison equation:
(MATHEMATICAL EQUATION AVAILABLE IN FULL PAPER)
where:p is the fluid density,D is the cylinder diameter,u is the flow velocity
The hydrodynamic drag and inertia coefficients, CJ and Q, are determined from experimental measurements.
The fluid force arising from an oscillating cylinder can also be expressed by a Morion equation by using the added-mass coefficient Ca, instead of inertia coefficient, The added-mass coefficient is generally assumed to be related to the inertia coefficient by:
(MATHEMATICAL EQUATION AVAILABLE IN FULL PAPER)
Marine Installation of FPSOS
Authors: Kok B.G.J. , Lanting D. 
Published: October 2008

Abstract
Global demand for Mobile Production Systems - including FPSO systems - continues to display sharp growth. This reflects the fact that they generally offer the most flexible and cost-effective fast-track route to first oi.l This paper outlines the experience gained during the marine installation and hook-up of the FPSO Uisge Germ and makes observations concerning developments in mooring leg [ethnology, In the Summer of 1995, the Uisge Corm was ready for installation in the North Sea. Prior to the arrival of the FPSO, the mooring legs were installed and tcstcd. During the installation of the mooring legs, a DP work barge was utilized. An anchored pupilage was employed for Use testing and a spread of anchor handling tugs accomplished the hook-up,

Introduction
All market forecasters envisage some sharp growth in tJre global demand for Mobile Production Systems (MPS) of various types, including FPSOS, semi submersible units, TLPs and jack-ups.
By the end of 1994, some 78 MPS units of all types were operational worldwide, including 17 in the North Sea - the area wtith the highest regional concentration. By the close of 1995, these figure had increased to 92 and 21 respectively. By the year 2000, it is possible what a to[al of 150 MPS units will be installed and operational.
These figures - as is the case with all statistics - are Open 10 debate. But the fact remains that MPS solutions we certain to occupy a more prominent position over the next decade. As we enter USC second half of the 1990s, the industry is taking stock, reviewing experience and taking a closer look at how the future for MPS developments may unfold.
Around 25 per cent of the MPS units currently operational are FPSOS. The majority are converted rankers operating in the relatively shallow water plays of South East Asia, Australia, West Africa and USC Middle East. The jack-up option rends to prevail offshore Australia, but jack-up MPS units are also operational in the shallow waler areas of the Gulf of Mexico and offshore West Africa. hi deeper water areas, including the Nothern Sea and US Gulf, some TLPs are now operational. In the YSSW Sahead, If-p developments in the US Gulf and offshore Brazil are forecast to increase significantly.
Offshore conditions largely dictate the selection of MPS type. Offshore Australia lends itself to jack-up and FPSO solutions, Offshore Brazil's deep water requires a semi sub-baaed approach. The US Gulf has a mix of jack-up and semi sub units, together with a few operational ?flPs South East Asia and West Africa have a mix of mold systems - FPSOS, semi subs and jack-ups.
The present MPS population in the North Sea represcn[s the greatest mix of types, but with the FPSO the exception until relatively recently. The first custom-built FPSO was installed in the Alba Field in 1993. More FPSOS are about to follow, including Foinaven (west of Shetland), McCullough, Durward /Dauntless, Teat, Njord and Balder.
FPSO's and Installation Contracting: A Concept for Deep Water Development
Authors: Schippers J. , Ripping M.A. , Lange F.C. 
Published: October 2008

Abstract
New floating production facilities are employed in increasing water depths. The major challenges for deep water installation activities are: vessel lifting capacity, sufficient crane wire to reach the seabed, vessel mooring / station keeping ability, a stable working platform, survey and positioning methods, and pile driving at great water depths, A large working deck space is an auxiliary advantage. This paper describes the key experiences gained on various FPS(0) related installation projects such as the Auger TLP foundations, the Enserch Garden Banks mooring system and the preparations for Mars and Run/Powell TLP installations.
The option of using a semi submersible crane vessel as a deep water hybrid / multi-purpose development unit will be described. The concept is based on a simple, deck supported modular and interchangeable arrangement.
The philosophy adopted is to provide the Field Operator with an opportunity to take a staged approach to developing a specific deep water field. In this approach wells are drilled and brought into production sequentially, thereby allowing the Operator to develop plans and optimize process facilities as more information about the reservoir is obtained. In addition, the early cash flow finances subsequent development.

Introduction
There is considerable experience related to the installation of floating units at various water depths.
With respect to the possible cost effective use of Semi Submersible Crane Vessels (SSCV'S)on floater projects one should consider possibilities where the use of key capabilities of SSCV'Sare optimized in the totat concept. Some examples to provide an impression are:Use of heavy lift capability during assembly, e.g. Nome turret Iifi of 4500T.Use of large deck space, e.g. Enserch Garden Banks FPF mooring leg installation.Use of station keeping capability, e.g. Mars TLP installation.Use of deep water hoisting capability, e.g. Auger templates and piles.Subsea pile driving, e.g. Teal mooring piles, Auger foundation piles.
Some specific experiences are briefly highlighted further in this paper to illustrate the potential of using SSCV'Sand the results that have been achieved.
Based on these experiences Heere Mac has developed its ?hybrid mission'. A concept which is considered to give an alternative view point to development of deep water oil fields and is meant to increase options within the market, not only for our company or for the oil companies themselves, but for the floating production market as a whole.
The challenge involved in finding a cost effective method of developing the deep water fields requires some changes in philosophy for future FPSO%. Key items in the technology already used for FPSO installation in deep water have shown that the elements are available to develop the hybrid mission concept in the near future.
Management of the Ekofisk Cessation Project (ECP)
Authors: Gabrielsen Jenny 
Published: October 2008

Abstract
This paper describes the major issues which have been addressed in the conceptual phase of the project in order to manage the project in a controlled manner.
These issues are.Establishment of a philosophy and strategy for the Cessation Process.Clear definition of the Cessation Phases, activities and interfaces.Establishment of a strategy for identification, execution and Implementation of required special studies.Establishment of a quality plan.Establishment of terms and definitions to be utilized in the project.Establishment of a plan for external communication.

Introduction
The Ekofisk field was discovered in 1969 in the southern part of the Norwegian Continental Shelf, Today twenty-six platforms are installed in the Greater Ekofisk Area in water depths of approximately 240 feet (73 m). A re-development of the Ekofisk Field, called Ekofisk-II, is now in progress. When Ekofisk-H comes on line in 1998, two new platforms will be installed and twelve of the existing platforms will cease operation, see figure 1. According to proposed new Norwegian law the operator, on behalf of the license group, shall present a p[an for cessation of production to the Norwegian authorities 2-5 years before platform operations cease. In this cessation plan the licensee will examine the various disposal options that may be relevant to the particular platforms and pipelines, The four opt]ons to be examined are continued use in petroleum activities, other uses, abandonment in place and removal. For each disposal option considered in the cessation plan, technical. economical. safety, environmental, fisheries, sea and air traffic considerations have to be discussed. The licensees will in the cessation plan recommend a final disposal option to the authorities. However, the final decision for how to dispose of the installations lies with the authorities.

Philosophy & Strategy
In accordance with the Ekofisk-II Plan for Development and Operation (PDO) submitted in December 1993 the Ekofisk cessation philosophy is to decommission the installations when normal operations cease, make them tidy and safe and store them in situ until disposal is acceptable to both the authorities and licensees. This philosophy still applies, see figure 2.
The authorities are in agreement that the disposal solution and timing need to be agreed on a case-by-case basin The assessments which are made in the conceptual and feasibility phases of the Ekofrsk Cessatton ProJect will provide the necessary basis for preparation of the cessation plan for the twelve platforms which will cease operations as a consequence of Ekofisk-II.
Based on the Ekofisk cessation philosophy, the strategy when installations cease operation is to decommission and render them cold for a period of time and to defer disposal as long as practicable. The main factors which determine the optimum timing of final disposal are the operating cost associated with a cold installation and the possible change in disposal cost as time elapses (see figure 3).
Fast Response System for Large-Volume Acid Stimulation
Authors: Gilson Bill 
Published: October 2008

Abstract
Historically, the conventional approach to large-volume offshore acid stimulation has been to use a vessel dedicated to offshore stimulation services or 10use a semi-permanent installation on the rigor platform. This approach often results in long term commitment to an offshore vessel restricted to stimulation work or a great reduction of the valuable space on the rig or platform for an extended time. Both of these options usually require continuous, large capital outlays with periods of little or no use.
The fast response stimulation package (FRSP) described in this paper provides a 25- bbl/min, centrally controlled, modular, acid-stimulation system with 50,000-gal acid storage capacity, 25-bbl/min, computer-operated blending equipment, acid-resistant manifold modules, and high-pressure pumping units. All processes are monitored and operated from a central control cabin. The FRSP can be quickly installed on an offshore work vessel or drilling rig of sufficient size to perform matrix acidizing and acid frac, and then be removed between jobs. The equipmenthas recently completed acid-stimulation services in a five-well program in 30 days, deliveringupto41,000 gal of blended acid at rates of 0.5 to 17 bbl/min from two different drilling rigs. This equipment has provided for greater versatility and better use of operator assets while providing specified requirements for stimulation services.

Introduction
When the operator requested an acid-stimulation package for the project in West Africa, there were numerous requirements. Some of the more important requirements are listed below:Perform acid-stimulation services from either of two offshore rigs or on an offshore workboat.Be able to set up at the jobsite in less than 2 days and demobilize in 1day.Do not exceed 15 MT lift for any one piece of equipment when used on one of the rigs offshore.Provide 40,000 gal of raw HCI.Establish a pumping rate of 25 bbl/min with no less than 1,800 hhp.Be able to batch-mix all the acid before the job to include up to 40,000 gal of flush and 10,000 gal of pad acid, allowing for additional additives during delivery to the well, such as gelling agents.Accomplish all these tasks without sacrificing dependability, safety, or versatility, or increasing adverse affects to the environment.
The service company responded with the FRPS, which provides a 25-bbl/min centrally controlled, modular, acid stimulation system with 41,000-gal raw acid storage capacity, 25-bbl/min computer-operated blending equipment, acid-resistant manifold modules, and high-pressure pumping units. Figure 1 is a photograph of one of the early jobs taken from one of the semi submersible drill rigs just before completing hookup.