bluuebunny/crossref_metadata_2025 huggingface dataset:
North Sea Offshore Cathodic Protection
Authors: Mackay W.B.
Published: October 2008

1. Abstract:

General principles of cathodic protection are given. Specific design for fixed structures, mobile rigs and sub-sea pipelines in the North Sea are discussed.

The paper compares test results obtained and parameters used in the North Sea with results and design figures obtained and used in other regions and circumstances. It is concluded that North Sea conditions demand specific cathodic protection considerations.

2. Introduction:

In the North Sea the offshore structures are mainly fixed platforms, sub-sea pipelines and mobile rigs with a few mooring buoys and storage tanks. The cathodic protection of structures designed for the North $ea is _ almost totally by sacrificial anodes with impressed current systems playing little part. Impressed current systems, where fitted, have suffered three major defects:Have not been of rugged enough construction to stand up to physical conditions.Have not had sufficient maintenance and supervision given to them in use.Have not been designed to give adequate current distribution and polarization protection.

3. Cathodic Protection by Sacrificial Anodes

3.1 General Requirements :

This requirement is that the anodes will polarize the steel to a point where the steel will not corrode (or corrode only at an acceptable rate) for an acceptable period of time at an acceptable cost.

3.2 Anode Material:

Bare or coated steel structures in sea water may be protected with aluminums or zinc anodes. Sub-sea pipelines which rest in the sea bed should be protected with zinc as at present aluminums alloys have not been developed to the stage where they can be guaranteed to work satisfactorily in a mud environment.

It must be noted that the composition of the aluminum or zinc anode material is critical in order to give a gored capacity and so that physical disintegration or passivity will not occur. Because of the critical nature of the alloying elements and their dispersion within the material rigid quality control is required during manufacture. In order to meet anode specifications high grade primary metal must be used.

It should be remembered that unit weight of aluminums anode alloy gives out approximately three and a half times the ampere hours of the unit weight of zinc anode material. In order for the materials to equate commercially then tile zinc anode needs to be three and a half times as cheap as the aluminum anode on a cost/unit weight basis.

3.3 Anode Potential:

Anode potential is the difference between the potential of the anode and the specified reference or half cell. In marine cathodic protection the half cells used are the silver/ silver chloride half cell, the copper/copper sulphate half cell and the zinc reference electrode.

The significance of anode potential is that the higher the potential the greater the anode output with the associated benefits for this. In addition the higher the potential the quicker the rate of polarization of the steel to which the anode is attached.
Detailed Geotechnical Investigation Around In-Place Mat Foundation Including T-Bar and CPT Comparisons
Authors: Audibert Jean , Neubecker Steve , Stewart William Pratt
Published: October 2008

The Maleo Producer is a converted Bethlehem JU250 mat-supported jack-up unit, which was installed in July 2006, on a soft, normally consolidated clay foundation some 40 km (25 mi) south east of Madura Island and approximately 25 km (16 mi) south of Puteran Island, offshore Indonesia. The unit was connected to a wellhead platform, and gas production began in late 2006. An initial site investigation performed in 2003 indicated that the undisturbed soil conditions consisted of a soft normally consolidated clay profile, with an undrained shear strength of 2 kPa (40 psf) at the mudline, linearly increasing with depth at a rate of 1.22 kPa/m (7.83 psf/ft) down to a depth of around 14 m (46 ft), below which a slightly stronger clay was encountered. The issue of on-bottom stability of the unit and its resistance to overturning were questioned by the classification society (ABS) as part of the reclassification of the rig. The behavior of the foundation under extreme storm loads and seismic events could be more reliably predicted by the designer, and more readily accepted by ABS, if new soil data were available. Two types of soil data were required 1) soil data for foundation design and re-analysis under and around the mat and 2) soil data for seismic analysis of the installation. This paper describes the extensive site characterization undertaken to prove the stability of the Maleo Producer facility during both the design storm and seismic events.

Introduction

The Maleo Field is located in Indonesian waters about 40 km (25 mi) south east of Madura Island and approximately 25 km (16 mi) south of Puteran Island (Figure 1), within the Madura Offshore Production Sharing Contract (PSC) area.

The Maleo Producer is a converted Bethlehem JU250 mat-supported jack-up unit (formerly the CD10) ABS Class Number 7900120. The unit was installed in July 2006, and was connected to a wellhead platform. Gas production began in late 2006 (Figure 2).

Description of the Installation

The installation is in approximately 57-m (187-feet) water depth. The hull is supported on three cylindrical steel legs, 3.66-m (12-ft) in outer diameter. The legs are supported on an "A" shaped mat (Figure 3) that rests on the seafloor. The mat is 64 m (210 ft) long, 52 m (170 ft) wide and 3-m (10-ft) thick. It has 0.6-m (2-ft) deep skirts (extensions of the mat side walls) that extend along all edges of the mat (around the outside mat edges, inside the slot at the aft end and around the inside edges of the 18 m × 33m (59 ft × 108 ft) cut-out within the three legs beneath the hull (Figure 3).

A 14-in (366-mm)-diameter gas export seafloor pipeline connects the installation (from the starboard side of the mat) to the 26-in. (660-mm) East Java seabed pipeline approximately 7 km (4.3 mi) to the south.

Details of the structure's geometry, preload history, and design load conditions were provided by Stewart Technology Associates (2006 a&b), as documented in Ooley and Stewart (2008).
LNG Terminal Expansions; Working Successfully Within a Live Plant
Authors: Tennison Dan
Published: October 2008

This paper is based on the lessons learned during the two recent expansions of the Southern LNG import terminal in Savannah GA. It shows how the Project Management team planned and executed the expansions, and particularly how the team interfaced with Operations.

Possible applications of the information provided in this paper is for LNG terminal owners and operators who seek to perform similar expansions within an operating terminal, or similar mid-stream operating facility (gas processing, etc.).

The paper concludes with 4 major findings that will benefit the reader:Project Management and Operations teams are significantly different in their goals, work practices, structure, culture, and scope, which affect expansion projects. Project engineers may lack operating experience and perspective, which can limit their ability to " Design for Operability??. Operations personnel can have less project management perspective, but are the true authorities on running the plant safely and efficiently. Leveraging both strengths is the key to a successful project.The greatest risk on the expansion project occurs at the Project - Operations interface. This interface is best managed through planned and structured communication systems (meetings, reviews, reports, golf), tailored for a mutual success.Contractor management is challenging when working within a live plant. Tie-ins, notices, permits, interference, slow downs, etc. must be planned for early, and thoroughly addressed in the contract.Commissioning and turnover of the expansion is crucial from the stand point of Operations interface. The phasing in of Operations personnel with Project personnel (training, spares, warranty work, lessons learned, and close out) must be thoroughly planned beforehand.

Three major technical contributions to the knowledge base for the LNG industry are:The Post-Project Lessons-Learned exercise this project confirmed the effectiveness of our communications management approach.The Contracting strategy for the EPC contract included key contractor responsibilities and specified expectations and communications responsibilities that mitigated interface risks.The Project Team acquisition, development and leadership methods used were highly projectized to produce a purpose-built project organization.

1. INTRODUCTION

Southern LNG owns and operates an LNG receiving terminal near Savannah GA. The terminal was built in the late 70s, operated for 3 years and was decommissioned for 18 years until being re-commissioned in 2000-2001. Shortly thereafter, the first expansion was planned. This expansion coincided with the initial years of operations of the newly reactivated plant, and had to be taken into account from a risk and scope standpoint. The project team worked closely with the Operations staff to plan and execute the expansion successfully. Lessons-learned from the first expansion has been applied to the subsequent expansion, now underway at Elba.
Imaging Downed Platforms
Authors: Taylor Michael , Davis Jonathan Peter , Lynch Richard Douglas , Philips Tom , Beck Richard D. , Burhke Mark  K. , Tomaszkiewicz Wojciech , Simpson Richard , Butcher Ron , Openshaw Graham
Published: October 2008

The Downed Platforms project deals with seven platforms containing 59 wells which were toppled during Hurricane Katrina in water depths ranging from 86 to 135 feet. Visibility at these depths is limited at best. A way to visualize the entire platform to aid in planning decommissioning activities was developed. This paper describes the various techniques used to image the platforms, including offshore field work, post processing, and analysis.

The technologies and techniques described in this paper could be applied to imaging of complex subsea structures, seabed surveys and hazard assessment, and processing of complex multibeam datasets.

This project employed new methods for acquiring sonar data which has conventionally been used for mapping the seafloor from a horizontal or near horizontal platform. The results in this paper will highlight the need to consider alternative methods of acquiring data and discuss the reality of deploying these methods in the field. Results from the project will be used to demonstrate the success of these methods.

This project delivered the highest quality datasets possible which removed significant uncertainty and allowed detailed planning to proceed. The paper will showcase a new method for acquiring detailed three-dimensional datasets, the benefits of deploying different imaging devices and highlight the importance of using available technology to minimize uncertainty.

Background

The 2005 hurricane season was the most active on record and hurricanes Katrina and Rita inflicted major damage to Gulf of Mexico (GoM) production facilities on the outer continental shelf (OCS). Seven platforms were completely destroyed in the Grand Isle 41/43/47 field, or " downed??. All platforms located in the Grand Isle (GI) and West Delta (WD) lease areas are in water depths from 86 to 135 feet. The locations were GI 40B, GI 40F, GI 41A, GI 47C, GI 48D, WD 69C, and WD 69K (Figure 1), which are all within 20 to 35 miles west of the centerline track of Hurricane Katrina.
Methodology to Establish the Fitness for Continued Service of a Damaged Export Pipeline in 1000 m of Water
Authors: Raghu Damodaran , Swanson Richard C. , Alexander Christopher Richard
Published: October 2008

Deepwater pipelines are critical arteries that transport gas and oil production from the Gulf of Mexico to onshore transportation hubs. The yearly hurricane season in the GoM has a serious impact on the reliability of this infrastructure, as evidenced by the severe damage experienced, and subsequent difficulty and delay returning to full service. The difficulty arises from the various challenges in damage, inspection and evaluation as well as the delay in analysis and procuring the repair hardware needed. Many of the damaged pipelines need extensive and time-consuming repairs depending on the severity and criticality. However, if sufficiently conservative and prudent analytical methodologies are used, many of the damaged lines can be inspected, analyzed and established to be fit for continued finite service. Employing a combination of repair and fitness for service analysis can effectively manage the risk of damaged deepwater lines, while in some cases, continuing operation.

In this paper, an approach is presented that can be used to analyze and establish the integrity of damaged lines. It reviews the various analysis methods available and integrates one or more of the methods to arrive at a unified approach. The approach is illustrated through an example of a 20" dented pipeline in 1000 m of water, where the fatigue life was estimated using FEA, simple dent fatigue equations and further validated using full scale testing. A decision tree that provides guidelines for deepwater pipeline damage evaluation and fitness for service is provided.

Introduction

The ability to reliably transport hydrocarbon products from the Gulf of Mexico outer continental shelf to refineries in the continental US is very critical to the continued supply of energy to the nation. The total hydrocarbon production, over 300 million STB of oil and 1100 million SCF gas constitute 30% of the US oil consumption and over 25% of the gas consumption1. In the Gulf of Mexico currently there are over 44,000 km of pipelines that transport oil and gas.

Over the last several years hurricanes, such as Rita and Katrina have had devastating effects on this pipeline infrastructure.

In many cases the damage has been severe enough to require extensive replacements. Operators of the pipelines are faced with the increased challenge of inspecting and quickly assessing the damage to establish appropriate repair methods, or in certain cases replacement. Owing to the complexity of deep-water pipeline infrastructure, viz. difficulty to access and inspect and the complex designs required to carry out repairs, operators have to develop relatively elaborate and detailed protocols for inspection, analysis and repair.
Marine Magnetotelluric (MMT) Data Interpretation in the Gulf of Mexico for Subsalt Imaging
Authors: Sandberg Stewart , Roper Tom , Campbell Tracy
Published: October 2008

A marine magnetotelluric (MMT) survey was performed to assist seismic and gravity methods in mapping the base of salt in a complex system in the Gulf of Mexico. For the salt complex investigated, 2D interpretation of MMT data provided an incorrect base of salt, when compared with well-derived data. When 3D inverse modeling was employed, not only the correct base of salt was determined, but additional detail of the subsurface was produced. Resistivity variation within the sedimentary host provides indication of lithologic variation that can be interpreted further. A preliminary correlation between low-resistivity zones and low velocity was also indicated. Separation of data-required subsurface resistivity of the model and resolution effects of the method, was also investigated.

Introduction

WesternGeco has an ongoing project to apply marine magnetotelluric, full-tensor gravity (FTG), and seismic interpretation to refine the base of allochthonous salt bodies in the Gulf of Mexico. The overall goal is to improve the resolution of seismic images of possible hydrocarbon-bearing sedimentary structures beneath the salt.

In this paper, we present some detail of the interpretation of a complex of salt bodies in the Garden Banks region of the Gulf. To map this salt, a total of 171 MMT seafloor stations were occupied in 2006, making it the largest MMT survey collected worldwide at that time.

The Marine Magnetotelluric (MMT) Method

Magnetotellurics (MT) is a natural-source, electromagnetic method of imaging structures in the subsurface. Natural variations in the earth's magnetic field induce electric currents (or telluric currents) under the earth's surface. Measurements of orthogonal components of the electric and magnetic fields at a receiver site constitute the data that are used to image the resistivity structure of the subsurface.

The MMT method generally refers to an MT survey in which the receiver sites are located at the seafloor beneath the seawater. The overlying seawater significantly changes the available signal strength at higher frequencies, and creates a current flow path above the receiver positions.

Approach and Previous Work

Electromagnetic investigations of the earth beneath the seafloor have a long history (Bannister, 1968 [active source]; Wannamaker et al., 1989; Heinson et al., 1993). Recently seafloor MT instruments have evolved to be capable of reliably measuring higher frequencies associated with structures shallower than the oceanic mantle and crust (Key and Constable, 2002).

Applying the MT method to mapping salt bodies for hydrocarbon exploration has been discussed in the literature. For example, Watts, et al. (2003) described an onshore example of how MT could be applied where the seismic method had difficulty because of velocity inversion associated with both salt and carbonate structures.
Onshore Commissioning of Greater Plutonilo focused on Offshore Start Up
Authors: Forster Matthew W.
Published: October 2008

Multi-billion dollar projects are becoming increasingly common for the integrated oil majors, requiring a complex series of multiple activities to be coordinated globally to reach a successful outcome. Delivery of performance is brought about by rigorous application of best practices and the building of strong relationships with all the involved parties to allow program flexibility to work around unexpected events. Additionally, clear, aligned overall objectives defining desired project outcomes are paramount.

This paper addresses the scope of the Greater Plutonio commissioning team, and its success in meeting construction & commissioning completion requirements for the FPSO prior to departure of the vessel from the Korean shipyard to offshore Angola. It makes the case to set overall project objectives on desired offshore start up targets. It covers the activities undertaken to complete an extensive program of work to provide assurance of maximizing build completion onshore, thus providing confidence of avoiding traditional offshore scope growth, and minimizing offshore work. This assurance provided confidence on aggressive start up, ramp up, and first year production targets, with corresponding reduced carbon footprints. This requires common technical processes and systems to be introduced into the project from an early stage to ensure alignment between the parties. The successful application of a common certification system across the Greater Plutonio project provided the means of tracking the hundreds of thousands of quality checks throughout the construction and commissioning process, the execution of which resulted in high confidence of systems integrity, which will, ultimately, sustain the revenue stream.
Deepwater Gas Fields Development Offshore Egypt, Concept Selection and Installation Aspects
Authors: Ellaithy Wael F. , Gaber Mohamed
Published: October 2008

The simian / sapphire fields are located 114 km and 74 km respectively from shore ranging from 500m up to 1100m water depth in the west delta deep marine concession offshore Egypt in the eastern Mediterranean.

These fields lie in the vicinity of the existing scarab / saffron fields and produce via manifolds and infield pipelines into existing offshore pipelines (24-inch and 36-inch) which bring the gas to a terminal onshore.

The development concept is a long distance subsea tieback of the wells direct to the control platform and shore with control by umbilicals. This paper describes the different way to develop simian / sapphire two fields as a stand alone through controls platform.

One of the keys to a successful simian / sapphire subsea development is the control philosophy and umbilical design. A long distance tieback is an issue due to the location of fields from the shore and the number of wells needs to be accommodated within both two fields.

This paper will explain the advantage, disadvantage and lessons learned form having a shallow water control platform to control both two fields. And accommodate future expansion.

Introduction

Simian / Sapphire fields development comprise fourteen (14) wells, four subsea manifolds, two tie-in manifolds, four subsea distribution assembly, two main hydraulic and electric umbilicals connect the subsea distribution assembly to the control platform and power communications cable umbilical connect the platform with the onshore facilities.

This paper is concerned with the following:Having controls platform to monitor and communicate between Simian Sapphire subsea wells and onshore terminals.controls platform case studyadvantage, disadvantage and lessons learned from using the controls platformConclusion

Fields layout

Simian, Sapphire and Scarab/ Saffron general locations are shown in figure 1.

Starting in the deepwater area, the Scarab/Saffron, Simian and Sapphire fields comprise 8, 6 and 8 wells respectively.

Wells at each field are connected to subsea distribution assembly (SDA) for control and susbsea manifolds for gas flow collection. Each field export lines pass the gas production to the subsea pipe line end manifold (PLEM) located at 95 m water depth. From the PLEM, two main export lines 36-inch and 24-inch carry the production gas to the onshore terminal. Main export lines are designed to accommodate the flow from Scarab/Saffron, Sapphire and Simian fields, future field's development.
CO2 Sequestration in the Offshore Environment: Challenges, Opportunities and Solutions
Authors: Reilly Joseph M.
Published: October 2008

CO2 sequestration is an extremely important global issue facing both the energy industry and the public at large. Research in this area is in its early phases, with significant challenges in geoscience, engineering and policy.

This manuscript is intended as an introduction to the OTC.08 panel discussion scheduled for Tuesday 6th May 2:30pm-4:00pm. The OTC.08 program also includes a complimentary technical session entitled " CO2 Challenge: Monitoring, Minimization, Removal Technology and Detection?? which is scheduled for Tuesday 6th May 9:00am - noon.

The members of the OTC.08 panel session represent a selection of the premier research efforts in this area from the United States, Australia and Europe:Dr. Sally Benson, Stanford GCEPDr. Kevin Dodds, CSIRO, CO2CRCDr. Heleen Groenenberg, ECN Policy Studies, CO2ReMoVeDr. Daniel Schrag, Harvard University Center for the EnvironmentM. Nafi Toksöz, MIT

The discussion will focus on CO2 sequestration activities which will impact the offshore environment; including geotechnical research, storage options, monitoring, verification, utilization for enhanced recovery and regulatory framework.

Following are the detailed biographies and introductory comments from our distinguished panel.

Sally M. Benson

Sally M. Benson was appointed GCEP Executive Director in March 2007. An internationally-recognized scientist with extensive management experience, Benson is responsible for guiding the development of GCEP's diverse research portfolio. A Professor (Research) in the Department of Energy Resources Engineering in the School of Earth Sciences, Benson has been a member of Stanford's faculty since 2007.

Prior to joining GCEP, Benson was a staff scientist in the Earth Sciences Division at Lawrence Berkeley National Laboratory (LBNL). In 2004, she completed a four-year term as Deputy Director of Operations at the lab. Benson also served as Division Director for Earth Sciences and Associate Laboratory Director for Energy Sciences at LBNL.

A ground water hydrologist and reservoir engineer, Benson has conducted research to address a range of issues related to energy and the environment. Her research interests include geologic storage of CO2 in deep underground formations, technologies and energy systems for a low-carbon future, influence of climate change on critical habitats, biogeochemistry of selenium, and geotechnical instrumentation for subsurface characterization and monitoring. She is an internationally recognized expert on geological storage of carbon dioxide storage in geological formations and was a coordinating lead author for the IPCC Special Report on Carbon Dioxide Capture and Storage.
High Resolution Seismology A Marine Digital System for Engineering Applications and Direct Hydrocarbon Detection
Authors: Neidell Norman S. , Moore Neil A.
Published: October 2008

Digital marine high resolution seismology offers advantages in many applications ranging from engineering studies to geological investigations for exploration purposes. Advantages take both the form of economies in the acquisition of necessary data and also in the securing of more reliable measurements. Processing techniques subsequently make such data suitable also for estimating velocities and litho logy, and even for suggesting the presence of hydrocarbons.

INTRODUCTION

High resolution marine seismic data has recently assumed a new importance in view of its relevance to the direct detection of hydrocarbons (see Albright (1973) and Tinkle, Antoine, and Kuzela (1973)). Nevertheless, the two traditional roles of such surveys, the study of near s ea- bottom geology and the engineering or load competence investigations, have in themselves assumed a new stature with the introduction of digital techniques. Application of the digital methods has stimulated on integrated view toward the survey encompassing all its essential elements.

Naturally, these must begin with the appropriate economics and objectives and end with considerations of the resolution and reliability inherent in the final processed section.

Typically, the benefits of an integrated or systems approach prove to be mutually enhancing making their whole of more value than their parts. While the system we describe here is neither totally ideal nor even complete, tests of its performance tend to support this premise Tangible advantages take both the form of savings in usually required follow on studies as well as in the basic value of more reliable, better resolved, relevant measurements about the upper sea floor. For example, if data is sufficiently reliable, a number of the costly comings might be eliminated with confidence that no information is being lost. Also, the final processing step makes such data suitable for estimating velocities, litho logical character and even charting the presence and migration routes of hydrocarbons.

The most novel element of this system is a streamer cable of unique design with provision for a variable geometry. Thousands of survey miles have since demonstrated the streamer cable's practicability and standard of performance. Comparative tests with conventional systems also confirm the validity of the design premises. Six active channels of data are acquired at all times and only 32 double crystal hydrophones in array and sub array patterns contribute to each group or channel.

Sot engineering and resources exploration have benefited substantially from the information acquired by the system. Design and operation of the system will be outlined in some detail. The companion data processing sequence will be treated only briefly and in passing since it is essentially a standard procedure. A few examples will be examined which illustrate both the engineering worth of the data as well as its exploration significance.
Digital Quality Seismic Streamer System
Authors: Luehrmann W.H.
Published: October 2008

The marine seismic streamer is an integral part of the complex signal detection system used in offshore oil exploration.

The "Century" DSS-V digital seismic streamer system was designed to meet today's expanded requirements in seismic techniques. It incorporates up to 120 data channels, a maximum active length of 4800 meters, Multidyne? acceleration cancelling hydrophones for low noise towing, and an electronic shipboard interface which eliminates signal distortion due to salt water leakage in the streamer and provides various array configurations to meet both high resolution and high penetration geophysical needs.

INTRODUCTION

Developments in marine seismic techniques have come rapidly and with increasing complexity during the past few years. While many, perhaps the majority, of these have been in data processing, it is also true that a significant impetus for processing improvements has been the tremendous volume of marine geophysical data acquired at modest cost per mile.

Hardware developments coupled with associated operational techniques have, over this time frame, contributed greatly in this effort to reduce the cost of marine seismic data without sacrificing data quality. Significant hardware developments include fast cycling non-dynamite acoustic sources, and towed detector arrays (seismic streamers) with extremely low self noise and with detector configurations specifically designed to minimize both mechanical and radiated noise signals. It is to the latter of these developments, towed arrays, that this paper is addressed.

W. A. Schneider in a paper on developments in seismic data processing, published in the December, 1971 issue of Geophysics5, said the following, "Of equal significance, and in support of these processing and analysis trends, are data acquisition developments which, deserve special mention. In particular, the continuing trend toward the use of longer spread and higher stacking multiplicity has resulted in more accurate velocity and statics estimates, improved record-section SiN ratios, and generally better deep data."

He continued, lithe bulk of marine data currently collected is 24-fold and is collected with 8,000 foot streamers 48-fold will likely become the future standard with streamers approaching 10,000 feet. Some argue that both operational and physical constraints limit present streamer design philosophy beyond 10,000 feet. Stacking fold, however, can and will increase beyond present levels until the incremental gains in product improvement no longer offset the added expense."

Also pointed out by Schneider, the expected benefits associated with longer spreads and higher fold coverage and processing may be further enhanced by synergism in the several steps involved in processing and interpretation. Figure 1 indicates how parameters in the processing cycle are affected by increased fold and spread length. How important these may be individually is obviously a function of physical and geologic conditions, as well as the exploration objectives of the geophysicist working the area.
Development of a Supply Vessel for Arctic Oil Operations
Authors: Rpsandhaug Kare
Published: October 2008

This paper presents a concept of an icebreaking supply vessel specifically designed to meet the needs of both onshore and offshore Arctic drilling operations. The ship has been developed for use in the Norwegian Arctic, i.e., Svalbard and the Continental Shelf of the Barents Sea. It is designed to be able to operate in the area on a year"' :round basis.

The design considerations are reviewed bearing in mind the operating, icebreaking, and classification requirements. A description of the ship is given and its operating modes as well as expected capabilities are discussed.

INTRODUCTION

The first exploration drilling on Svalbard started in 1965, when Caltex put up the first rig. Since then, most of the oil potential areas have been claimed by Norwegian and foreign oil companies.

Drilling so far has only been taking place during the summer. Equipment and supplies are being brought in from Norway by ice-strengthened cargo ships. Unloading is carried out by landing crafts and helicopters. The shipping season usually lasts from May to October, but this depends very much on the ice conditions.

So far a dozen wells have been drilled, but no commercial fields have yet been discovered. There have, however, been interesting traces of oil and gas. The future development will probably be that, as soon as commercial discoveries are made, the drilling season will be extended and year-round operations will commence. As more advanced offshore drilling technology becomes available, exploration of the ice-covered waters around the Svalbard islands will probably also begin. These waters are very promising with large sedimentary basins, and them may well turn out to contain major oil fields.

In anticipation of such a development, the shipyard Kaarbp's Mek. Versed and the supply organization Nor service, both of Hardstand, Norway, have decided to analyze some of the problems involved in the transportation of equipment and supplies needed for these activities. Part of these studies have been carried out in cooperation with The Ship Research Institute of "Norway, and as one of the results of this cooperation, a concept of an Arctic supply vessel has been developed. The ship is intended to serve both onshore and offshore oil drilling and will, in addition to carrying supplies and passengers, be able to do towing and anchor-handling, as well as act as an icebreaker.

AREA OF OPERATION

Even if an Arctic supply vessel should be able to operate in ice-filled waters worldwide, it appears that the wide range or ice and - -weather conditions that egoist in the Arctic. itself will necessitate different types of vessels. It was therefore decided to construct the vessel for one particular area, the Norwegian Arctic.
Wave Forces on Submerged Model By Structures
Authors: Versowsky Paul E. , Herbich John  B.
Published: October 2008

The results of a model study of the forces caused by oscillatory waves on large rectangular tank-like submerged objects are presented. Three phases of the problem were examined:description of the forces in terms of dimensionless parameters,description of the effect of large wave heights which are of importance to the designer, andthe presentation of a format to be used in model studies on submerged structures.

Theoretical studies of the problem have assumed wave heights to be small and the forces to be entirely inertial. However, of interest to the engineer are the forces caused by the larger waves generated by severe storms. In the model study the forces caused by the larger waves were determined and the effect of the water particle velocity in producing a drag force was examined.

The relationships between the fluid particle displacement and the coefficients of mass and drag were evaluated. Previous studies indicate that particle displacement is related to he values of empirical coefficients assumed by previous investigation.

The experimental results are given in a dimensionless form. Provided the laws of modeling are followed, and there are no scale effects, these results may be used to determine the forces on prototype structures in the ocean.

INTRODUCTION

The extremely large energy requirements in developed countries has prompted the oil and gas industry to explore remote offshore areas and deep water regions in search for oil and natural gas. The problems encountered in extracting the oil and gas found in these areas have produced new innovations in the petroleum recovery industry.

The problem of crude oil storage at offshore fields distant from adequate shore and port facilities was solved by the Dubai Petroleum Company and Chicago Bridge and Iron Company with the construction and placement of three large submerged tanks at their field in the Arabian Gulf. With processing equipment located on platforms atop two of the tanks, the facility represents the world's largest self contained offshore production complex with capabilities for storage and tanker loading (1).

The need to extend the oil recovery capabilities of the petroleum industry to deeper water has led to the development of plans for an entire oil field underwater. Phase One of such a project was completed in August of 1972 when Lockheed Petroleum Services Ltd. and Shell Oil Company completed the installation of the world's first dry underwater oil well in 375 ft. of water in the Gulf of Mexico (2). The actual well head structure is thirty ft. high and ten ft. in diameter. Future plans call for additional underwater well heads with a submerged manifold center to commingle production, and a submerged production station where oil and gas are separated and then pumped to the appropriate facilities.

Of primary concern to the designer working in an ocean environment (where water depths range from intermediate to shallow) are the forces due to gravity waves which are usually of considerably greater magnitudes than the forces due to currents.
Effect of Ice Thickness on Ice Forces
Authors: Schwarz Joachim , Hirayama Ken-ichi , Wu Han  Chin
Published: October 2008

Ice forces are the main concern in designing offshore structures such as drilling platforms, translating points, or bridge piers in arctic regions. Even though some results have been obtained by field measurements in recent years, there are still significant gaps in the knowledge of ice forces on structures. In order to fill some of these gaps, the Iowa Institute of Hydraulic Research has undertaken model studies on the investigation of ice forces on vertical piles. Model techniques for the study of ice-breaking phenomena have been developed, and the similarity between the model indications and prototype conditions has been shown. Tests have been completed on the _ relationship of ice forces (ice strength) vs pile diameter, ice thickness, and the relative velocity (strain rate) between ice and structures. The results suggest a formula considering these parameters, which agrees with field measurements and also in part with model investigations in Russia. The suggested formula will be used as a basis for considering other parameters such as temperature, shape of the structure, contact between ice and structure, and scale effects. The model investigations of these additional influences are nearly completed. Simultaneously, studies on the fracture criteria for ice are progressing, which hopefully will lead to analytical investigations of ice-force problems.

INTRODUCTION

The effect of ice forces on structures has been investigated with steadily increasing interest and activity over the last decade. The driving force for these studies has been the discovery of oil and other mineral resources in arctic regions. Parts of these resources are located offshore, and engineering structures, such as drilling platforms and translating points, are affected by the forces of drifting ice fields. These forces are limited by the strength of the ice, which is a function of several parameters such as temperature and salinity of the ice cover, width, inclination, and shape of the structure, the velocity of the ice floe relative to the structure, and the thickness of the ice cover.

The goal of engineers is to find the functional relationship among these quantities. So far, theoretical analysis has not solved this problem, because the fracture mechanism and the failure criterion of ice, as a viscous elastic, anisotropic material, has not been fully established yet. Several investigators, including Peyton, Croasdale,5 Nevel,13 and Schwarz15,16 have measured ice forces on structures directly in the field. The results of these field tests are limited to the data for specific ice conditions and structural dimensions prevailing for the individual tests. The data indicate trends, but do not allow for the development of complete ice-force equations.
Electrical Equipment to Meet North gea Drilling Requirements
Authors: Stephen D.D.
Published: October 2008

Introduction

The severe environmental conditions which any oil drilling or production unit has to meet in the North Sea has resulted in a new generation of designs, and the high capital cost and value of fixed platforms together with their remoteness intensifies the requirements of high reliability and safety of both plant and personnel. Increased involvement in such details by governmental bodies and classification societies is also leading towards a more precise and onerous set of requirements applying to plant intended for use in problem areas such as the North Sea.

The power requirements for a large platform to be used for drilling and production is such that a review of the basic logic of plant capabilities is necessary to obtain the most economic overall solution while complying with all envisaged and stipulated conditions. As a result of such a study the new North Sea Platforms will incorporate many unique features applied to conventional equipment together with some items of a completely new design.

The functions of the electrical generating and distribution system is merely to provide adequate power for drilling and production and the other services required by the platform operators, and the system has been designed to ensure maximum integrity of supply with minimum requirement of supervision and control. Some of the main system design features are as follows.

Power Generation

To allow adequate flexibility of capacity requirements as the field is developed a minimum of three sets with space and facilities for five were allowed for. In addition units were installed with a capacity for updating at a later date if required. As an adequate supply of gas will be available at the production stage gas turbine prime-movers were selected suitable for fully automatic, remote, starting. The loading capacity of gas turbines is a function of ambient air temperature and a total load comparator system is provided to indicate what margin exists between kW load on the platform and kw capability of the connect generator sets, and this is related to an alarm system with an adjustable setting which can be used for personnel warning or to take remedial action if required.

Generators are normally auto-synchronized with a main and back-up synchronizer and isochronous governors ensure satisfactory set load sharing as well as keeping the platform frequency constant with all the associated advantages on production plant.

Emergency diesel generator sets which can be used for peak loading as well as "Black Start" are provided with governor droop control to enable them to operate on base load when paralleled with the main G.T. sets.

Because of the possible connected capacity it was economic to generate at 11 kV 50 Hz, this being a standard industrial rating, and to increase integrity double busbar, with two sections in each was used for the 11 kV switchgear. Normally the complete system is solidly connected but any section can be isolated if faulty, or alternatively the system can be operated as independent subsystems.
Pressure Grouting: An Improved Method of Offshore Structure Grouting
Authors: Tragesser Arthur F. , Dalton Charles F. , Kay Franklin J.
Published: October 2008

A new method of grouting the legs of offshore oil platforms has been evaluated with respect to resultant grout quality, economics and reliability. The experience gained from more than 40 actual grouting operations in the Gulf of Mexico was considered. A scale model of a typical jacket-piling assembly was constructed. The model was constructed from clear plastic material that would allow visualization of the process. A series of tests was conducted by displacing water in the annulus with compressed air and introducing a Class A cement slurry into the annular space. These tests were observed and recorded on color movie film.

The results from the scale model tests and from field operations show that a high quality grout column can be obtained by the new method and that the process is feasible from an economic and operational standpoint.

INTRODUCTION

The methods of grouting the legs of offshore oil structures that are commonly used today inject the grouting material into the bottom section of the legs near the ocean floor. This procedure requires that grouting lines extend from the surface to the bottom of each leg. The bottom of the leg must also be sealed. Generally, inflatable subsurface packers or grout seals are used. As the grouting material is pumped into the bottom of the leg, the water inside the leg is displaced through a surface vent. The injection is continued until grouting material of the desired specification is noted at the surface vent. In some situations, divers are used to remove the grout lines and packer inflation lines.

Satisfactory results are not always achieved with these conventional methods because:The sealing system could sustain damage during the installation of the platform that would not allow it to support the full column of grout. This would result in incomplete filling of the leg with grout.The injected grouting mixture could overrun static water in the leg and leave water pockets or water channels. This overrun water would signify cantle reduce the strength of the grout in those local areas.The platform jacket might have sustained unknown damage that would allow the grouting material to leak out after placement.

A new method of grouting has been developed that will overcome these potential problems, that will offer substantial economic savings in most cases and that promises improved reliability. This paper discusses the results of a scale model study of this method, describes the field experience gained to date and briefly describes the operational procedure.

This method is called the "pressure method". The details of the method have been previously disclosed in U. S. Patent No. 3,601,999. The authors believe this to be the first published report concerning the laboratory and field performance of the method.

PURPOSE" OF MODEL

Since the inside of a platform leg could not be observed during the grouting operation, it was necessary to build a transparent scale model to demonstrate the viability of the pressure grouting method.