bluuebunny/crossref_metadata_2025 huggingface dataset:
3D TROMSO Survey Planning: Cost efficiency through seismic data quality.
Authors: Savini Luca , La Bells Giovanni , Ronchitelli Giovanni , Seldal Jan
Published: October 2008

The approach described in this case history allows for the firs(hrclirrrr of a ‘full 3D’ dataset in order to solve the interpretation problems of [he area at reduced COSI.

The structural definition of the main prospects in the area was unclear. mainly due to the poor quality of 2D seismic data, The committed 2D seismic survey would have probaby supplied a seismic-data set of slightly better quality, but on the other hand. there would not have been a suitable improvement in the imaging of the main prospects. In an attempt to overcome these problem, an ‘Explorative 3D’ survey was planned.

In order m ensure a proper quality of the .3D dataset an integrated approach to the acquisition and processing planning was adopted.

Acquisition was carried out utilizing ‘skipped configuration’ capable of acquiring 12 CMP lines for each sail line with a considerable reduction in cost.

Introduction

The area under investigation. located in the Barents Sea PL 20I on Blocks 701 8/3 - 7019/1, is characteristic by a complex lacating setting.

Several 2D seismic surveys had shot in the Blocks in question in the past, Nevertheless. the quality of the previous data doesn't allow for a proper definition of the main plays to be made. The main geophysical problems are linked to the pattern of reflection and refraction multiples and the dipping noise that masks the primary events. The analysis of the area suggested that a new 2D seismic acquisition would not have supplied sufficient improvement in the imaging of the main prospects. A different approach was therefore considered. The approach, which we call ‘Explorative 3D’ allows for the production of a ‘full 3D’ dataset at reduced cost.

The study started with the analysis of the previously acquired 2D data and with the reprocessing of part of it. By selecting an appropriate processing sequence, from the theoretical parameter study and the prospect geophysical constraints, an operaiorral proposal was presented 10 the partners,

The final implementation takes into account the theoretical constraints for the main target, the experience already acquired in this kind of ‘Explorative 3D’ and the overall budget constraints.

Acquisition was carried out utilising a quad streamer dual source configuration with a specific lay out capable of acquiring twelve CMP lines for each sail line. Such an approach requires proper handling of the data through special processing steps, such as the extensive use of flexibinning technique. Moreover, [he utilisation of special pre-stack deconvolution techniques in the TAU-P domain was also considered.
Geohazard 3D Lessons from European Experience
Authors: Orren R.J. , Hamilton I.W. , Eikum L.S. , Kinck J.J.
Published: October 2008

The paper discusses the use of 3D exploration seismic data for geohazard evaluation purposes. as based on a body of data from i] number of recent cases on the European continental shelf, Comparison is made with conventional high-resolution 2D site survey data, An assessment of the current impact of the technique on the market in Europe, which takes account of theviews of several operators.

Introduction

Over the past few years [here has been increasing interest in the use of exploration 3D seismic to improve the detection of shallow gas and other drilling hazards.

The Fugro/Geoteam companies in Europe, especially Geoteam AS in Oslo, have been contracted on a range of projects to interpret existing exploration 3D seismic data for assessment. This has been undertaken using data from several North Sea area for various clients. the majority to date on the Norwegian continental shelf.

Often the 3D data has been used in conjunction with acquisition and integration of conventional 2D high resolution (FIR) seismic site survey data, or other complementary seismicdata. but in some cases the shallow gas geohazard as assessment has been made, at the client's request. using only 3D seismic data.

To optimise the exploration 3D seismic data, reprocessing work is currently underway on one central North Sea site to attempt to improve resolution

To obtain a snapshot of the wider picture of the use of geohazard 3D in Europe, some views of operators have been sought. and the market impact this represents is discussed. A related activity has been the performance of a small number of trials conducted in full high-resolution 3D seismic acquisition for geohazard objectives. This approach is currently not standard geohazard survey practice and still in the development stage. it merits separate discussion and is outside the scope of this paper.

Geoteam Experience

Approach.

A 3D seismic geohazard evaluation is typically commissioned before a site survey, to enable better planning and optimisation of the later data acquisition. It can, however, be performed alongside the interpretation of the 2D site survey data. to produce an integrated report.

3D evaluation is also leading, particularly in Norway, to a reduction in the amount of l-fR2D acquired. A complementary HR2D survey can then, if the site is suitable, be as limited as a crossed pair of lines at the location. 3D evaluation has also been used alone, if the area is sufficiently familiar, has suitable geology and has been densely sampled by previous drilling.

Methodology.

With reference to the usual types of supporting geological information (previous wells, regional geological information etc.) the 3D data is interpreted by picking significant horizons. from sectional and time slice views, and producing isochrons (i.e. structure maps) and reflection strength maps of these horizons. Modern workstations are utilised for the interpretation: Charisma in Norway, and Western OASIIS in the U.K.
Numerical Modelling of Cyclic Pile Capacity in Clay
Authors: Nadim F. , Dahlberg R.
Published: October 2008

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

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

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

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

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

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

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

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.
The Heidrun Field: Global Structural Design and Analysis of the Heidrun TLP
Authors: Botros F.R. , Wilson T.J. , Johnson C.M.
Published: October 2008

The structural analysis and design of the Heidrun tension leg platform presented many technical Challenge a that had to be overcome in a fast and efficient manner to meet the demands of a very tight schedule. Some are inherent in the nature of a compliant structure such as a TLP with its complicated interaction between the structure, the mooring system and the environment and the importance of proper weight and at ability control during the different phase a of construction and operation. However, many other a were unique to the Heidrun platform. The Heidrun hull is the first large offshore structure built entirely of high strength lightweight aggregate (LWA) concrete. The topside modules form an integral component of the structural system of the platform. The interface between the steel topside modules and the concrete hull proved to be a very complex engineering task requiring very detailed analyses, tight fabrication and installation tolerances as well as testing of a number of key components. Ringing loads were included in the structural design of the platform for the first time in an offshore structure. The transportation of the large topside modules, mounted transversely on barges, and their mating to the hull was unique. The reserve capacity built into the design to provide additional safety in the critical components of the structure. The paper presents an overview of the multitude of challenges encountered during the detail design of the platform.

Introduction

The Heidrun TLP introduced several structural innovations not seen previously on any offshore platform. Examples of these include the concrete Module Support Beams (MSBS) as a main structural member of the platform and for supporting the topside modules, unique solutions for connecting the topside modules to the substructure, exclusive use of high strength LWA concrete in the construction of the hull, design and fabrication of very large diameter columns, and design of the platform for the structural effects of ringing.

This paper gives an overview of the structural analysis and design activities required in connection with the development of the Heidrun TLP and concentrates on design aspects which are novel or required more extensive consideration due to the nature of the TLP configuration or construction method. A short description of the platform is provided followed by the most significant aspects of thehydrodynamic and structural analyses. Special analyses and some of the unique design considerations associated with the hull and topsides design are presented. For completeness brief descriptions are given of the construction sequence of the hull, the foundations and the independent design verification performed for the structural design.
US Voluntary Semp Initiative: Holy Grail or Poisoned Chalice?
Authors: Powell T.A.F.
Published: October 2008

Introduction

There are acknowledged differences in deregulation of offshore E&P safety by the US Minerals Management Service and the W(Health & Safety Executive. The US is part of the way through a patient reform of it's contemporary rules whilst the UK has almost completed the installation of a radically new and forceful regime.

Because both regulators share a common key aim, this paper explores the background to the status quo by going back to the beginning of this century to track oilfield and regulatory development on troth sides of the Atlantic.

The closing part of the paper identifies the nature of the current divide between the UK and US positions, which were once so close. At a time of consolidation for the HSE and a time of looking into the future for MMS, I speculate, at the close, on how the HSE might have responded to the choices confronting the MMS.

History of UK Oil Industry & Regulation

Early History. The E&P industry has always been dominated by the US. Some American companies can make money out of undertakings that most European companies would not glance sideways at, It is not just a question of scale and consequential opportunity, it is a matter of history - and, to a lesser extent, culture History, in fact, is the most important influence on the situation I describe in this paper.

Many people know that the US oil industry is nearly J50 years old, Fewer people know that the UK industry is 100 years old. 1a 1896, before the proper application of rotary drilling in the US, and the Spindle top gusher, a commercial gas development on the English south coast supplied a hospital and railway station with heat and light. However, the UK E&P industry didn't come to much for a long time and, with no production to speak of, in 1914 the UK Government took a stake in what was to become BP in order to secure supplies for the oil burning Naval fleet during World War 1

After the War the government attempted to ginger-up the exploration scene by offering monopoly licenses - effectively licensing people rather than leasing areas, which it had no powers to do, except on Government or Crown (belonging to the Storke) land. This proved only modestly successful: The Duke of Devonshire, one of the few to try their luck started the only ?significant' development near to his family seat at Chatsworth House in Derbyshire and for a while produced 1700 gallons per week.

Tile 1930's was most important, In 1934 the Crown took all undiscovered reserves into it's ownership and the Governmentpassed law' 10 appoint lease operators (licensees) - thereby creating the concept of sharecroppers, of which BP was to be the dominant party, and at the same time bringing the UK and US Federal lands systems very close together.
Applied Research Reduces Air Pollution from Platforms in Offshore California Waters
Authors: Konczvald A. , Shackell G.C.
Published: October 2008

The monumental task of reducing air pollutants generated from offshore oil and gas platforms while preserving safety and production safeguards is difficult. Recently, a group of scientists have pioneered the 'smokeless oil spill burn' concept using Enhanced Burning Additives (EBA), while the Minerals Management Service (MMS) entered the 8th year of monitoring the safe operational practices under air pollutant reducing measures such as water injected turbine generators and the use of new fuels on platforms along the Californian Pacific coast. This paper presents the conclusions of this trial period of selecting the right, technically feasible concepts.

Application

Our recommendations are applicable to any offshore platform, The field data have convinced MMS to endorse only the cost effective and safe technologies, The solution lies in avoiding the incompatibility of existing platform processes with new air toxics minimization measures.

Results, Observation and Conclusions in the category of 'Energy Savings', only Engine Retrofitting, Partial Electrification and Computerized Process Optimization have proved to be acceptable. In the category of 'Air Toxics Reduction Technologies', only the New Fuels, Smokeless Burns and the 8 new Desulfurization Methods showed reliable results.

Significance of Subject Muller:This paper presents a couple of revolutionary solutions in the groups of ozone precursor reduction and the natural gas desulfurization techniques, Information on Smokeless Burning and on the RAPRENOX process have not been addressed in such details before due to pending research and patent phases.

Introduction and Regulatory Background

Due to the Clean Air Act of 1990, the U.S. EPA has taken the power of offshore air quality regulation from the MMS and transferred it to the local Air Pollution Control Districts (APCD) of coastal county governments. The APCDS have developed a fee based system as a function of the mass of air pollutants generated by each platform and offering offsetting volumes if the operator chooses to reduce the same type of pollutant within a coastal city, or if it participates in the conversion of heavy diesel engines to natural gas engines in buses and trucks or engine replacement in resident fishing boats.

The platform operator companies have tried to reduce the air pollution fees and have turned to new research applications. First, the energy savings from on-site electric power generation, partial electrification and supplying near-shore platforms with onshore electricity have reduced the air pollutant output significantly.

Second, the computerized process optimization techniques have reduced waste of energy and improved safety, Finally, changes in operating routines have led to the development of computerized safety features such as toxic and explosive gas leak sensors, linked to the platform command room. Other routines have been modernized, and treated in detail under the flare related paragraph
A Method to Estimate the Limiting Sea States for a Docking Operation
Authors: Beldi A. , Chopelin P.
Published: October 2008

A safe docking operation of a jacket against an existing structure at seafloor level, with or without crane assistance implies a sufficient knowledge of the jacket motions and the impact load. This paper describes the method in use to estimate the limiting sea states for a docking operation. This method uses a simple way to calculate the impact load. Allows the evaluation of the impact load between a jacket and a pile or a template to be done analytically and to estimate the limiting sea states. A correlation between the field data and the analysis results is done for the Nkossa project.

The assessment of the impact load requires little calculation and if provides a simple velocity criterion which can be used during the dotting operation. It is available for any operation including elastic impact (Jack-up installation, compliant jacket installation in deep water). The information in this paper provides useful help for similar marine operations.

INTRODUCTION

The installation of a jacket over a pre-installed structural requires a reliable analysis of the impact between two guides:a female guide (a bell) belonging to the jacketa male guide (a pile) belonging to the structure

Later in this paper we will describe the method in use to analyze the docking problem. It provides a velocity criterion to limit the motion of the bottom of the jacket. This criterion will be used in the field installation as an aid to making the decision to start the docking operation.

The period of time required in order to ensure that the docking operation takes place safely depends on the load impact caused by the encounter of the female guide with the male one, To decrease the risk of damage, permissible sea states are often used to limit the jacket motion. The ETPM impact load calculation method uses some simplification hypotheses allowing a calculation by hand. The method has now been used by McDermott-ETPM in a number of jacket installations. It is illustrated in this paper by the Nkossa project. A generalization of this method to a numerical algorithm is presented. The numerical algorithm will take into account all the forces acting on the bodies.

PROJECT DESCRIPTION

The Nkossa project involved installation of two similar jackets, NKFI and NKF2, by McDermott-ETPM for ELF Congo. The NKFI jacket (approx, 6000 t) was fabricated at McDermott-ETPM Jebel Ali Yard in the United Arab Emirates and towed to site on the launch barge Intermac 627 (14000 km voyage). The jacket was to be installed in 170 meters water depth over a pre-drilled template. Following launching, the jacket self-upended and was moved towards the template. Then, the ballasting and docking operation was made without crane assistance.

The NKF1 jacket was maintained over the template by connections with the POIARIS barge and two tugs (Fig, 1). This connection system allows an easy approach over the template and an appropriate orientation of the jacket.
Re-qualification of Ekofisk Pipeline Systems
Authors: Tangeland Tor G. , Collberg Leif
Published: October 2008

Re-qualification is an engineering service which will increase in importance and extent in the future, as the installations get older. A re-qualification is are-assessment of the design, but with changed design parameters. In some cases the original design requirements may be un-realistically conservative. The first part of the paper contain an introduction to the Ekofisk Field and a description of the generic justification for performing pipeline re-qualification assessments and explanation of the methodology which can be used The second part of the paper contain a description of the Ekofisk re-qualification performed for 19 pipelines and 29 risers. To enable the re-qualification to be performed new approaches had to be developed for the, (1) loads, (2) capacities and (3) deterioration evacuations and predictions. The paper contain selected results from the re-qualification assessment for some of the pipeline systems.

Introduction

Ekofisk is located in the south part of the Norwegian part of the North Sea. The field is one of the world's largest offshore oil and gas fields, it was discovered in 1968 and the first production started in 1971. The original design lifetime of the installations was 30 years.

The greater Ekofisk area is made up of eight oil and gas fields. The Ekofisk Center Complex serves as a production and transportation hub both for the Ekofisk fields and several other gas and oil fields. Approximately 85.000 m 3 (530.000 bop) of oil are being piped 354 km to the Teesside terminal in England, and around 56 Standard million m 3 (2 billion standard cubic feet) of gas are piped 441 km to the Emden terminal in Germany each day by the two Norpipe pipelines operated by PPCON.

When Ekofisk started production the recovery factor was estimated to be 17 to 18 percent, Presently the factor is more or less doubled to around 35 percent. The original operating license for the Phillips Group lasted until 2011. Due to the increased recovery it will take longer to produce the field and therefore the license has been extended to 2028. This implies that the Ekofisk installations are needed for a significant longerperiod than original designed for.

The Ekofisk Field has experienced seabed subsidence due to compaction of the producing formation. In addition to the vertical deformation, which is leas important for the pipelines, the compaction has caused the seabed to move horizontally inward towards the Ekofisk Center, this is termed Subsidence Related Horizontal Movement (N-M). The Phillips Group has decided to partly redevelop the Ekofisk complex to reduce the future operating cost and compensate for the vertical subsidence of the field. One new drilling platform (2/4X) will be installed in 1996 and one new process and transportation (2/4J) will be installed in 1997. Both platforms will be designed for 20 m total field subsidence.
Qualification of Large Diameter Duplex Stainless Steel Girth WeIds Intended for Low Temperature Service
Authors: Presser K. , Robinson A.G. , Rogers P.F.
Published: October 2008

British Gas recently had a requirement to fabricate some UNS3 1803 duplex stainless steel pipe work for an offshore opsides process plant. The pipe work had a maximum diameter of 600mm, with a corresponding wall thickness of 18mm, and it was designed to operate at a minimum temperature of - 40°C. There is a lack of published toughness data for girth welds in duplex stainless steel at this thickness and minimum design temperature. Additionally, toughness requirements for girth welds in current pipe work and pressure vessel codes are based on experience with carbon steels. As a result, a programme of work has been carried out to study the Charpy, CTOD and wide plate toughness of girth welds in 22%Cr duplex stainless steel pipe work. The welds were produced using a typical gas tungsten arc/gas metal arc pipe work fabrication procedure. In addition, non destructive evaluation trials have been carried out on a deliberately defective weld using radiography and ultrasonics. It was demonstrated that double wall single image y-radiography. single wall single image and panoramic X-radiography, and conventional shear wave ultrasonics were all able to detect planar root defects varying from 3 to 7mm in depth. There was good agreement between the sizes recorded by ultrasonics and those measured from macro sections. Small scale mechanical tests demonstrated that welds with overmatching tensile properties, and low temperature toughness properties whichwere acceptable to specification, could be produced. Wide plate tests demonstrated that defect size calculations from BS PD6493 were conservative.

Introduction

The process plant for a British Gas North Sea offshore platform topsides facility required the use of 22%Cr (UNS3 1803) duplex stainless steel pipe work. The pipe work varied in diameter from 26 to 600mm, with a corresponding wall thickness of 3 to 18mm. The work described in this paper had the objective of confirming that the material properties of this welded UNS3 1803 pipe work were such that the selected non destructive evaluation (NDE) procedures, would allow detection of the allowable defect sizes determined by fracture mechanics with reasonable confidence,

The design of the pipe work was generally to ANS1/ASME B3 1.3', and the material toughness requirements were derived from EEMUA 153*. This specification gives the appropriate Charpy test temperature, known as the materials reference temperature (MRT), for the particular design reference temperature (DRT) of the pipe work and the pipe wall thickness involved. The DRT at full design pressure was -40°C. although in the blow down condition, the temperature could fall to -50°C (in this case the stress would be less than the full design pressure). The EEMUA requirements for service in the as-welded condition are shown in Figure 1. It can be seen that, for the maximum pipe work thickness of 18mm the MRT is -40°C for a DRT of -40°C.