bluuebunny/crossref_metadata_2025 huggingface dataset:
The Use and Application of Permanent Downhole Pressure Gauges in the Balmoral Field and Satellite Structures
Authors: Shepherd C.E. , Neve P. , Wilson D.C.
Published: October 2008

Down hole gauges installed in Block 16/21 satellite wells have given invaluable real time data during extended well testing (Sterling and Blair) and have been extremely useful in gaining an understanding of Balmoral and Glamis well and reservoir behavior in the early stages of production.

The long term reliability of these systems has proved disappointing, highlighting the need for further engineering research and development in this area, particularly in sub-sea electrical connectors. It is hoped that experience gained with the reported systems will help others considering their use or those looking at further developments of down hole pressure systems.

INTRODUCTION

The Balmoral Field, located in Block 16/21 and discovered in 1975, received Government development approval in 1984 after extensive appraisal drilling. The field has been developed with 19 sub sea wells, 13 producers and 6 injectors (Figure 1). Ten of the production well s were drilled through a template and the remaining three are tied back to the template via subsea flow lines. All of the six injectors were completed sub sea and tied back to the template by flow lines.

Beneath the Balmoral Field, in fractured Devonian sandstone, lies the Sterling Field. Oil in Devonian sands was observed in a number of appraisal wells in the area and in 1986, well 16/21a-2 was completed and tied back to the Balmoral FPV for an extended well test. At the satisfactory conclusion of the test the well was recompleted as a Balmoral Paleocene producer.

In 1989 two separate satellite fields, Glamis and Blair, were tied back to the Balmoral template. The Glamis Field is in the Jurassic sands to the south west of the Balmoral Field and has been developed with two producers and one injector. The Blair Field is in Paleocene sands partially overlying Glamis and has been appraised from a single production well on extended well test.

The subsea nature of the development in andaround Balmoral and the extensive use of satellite wells makes frequent re-entries for reservoir monitoring purposes both difficult and expensive. The decision was therefore taken at an early stage to install permanent down hole pressure gauges on all satellite wells tied back to the Balmoral template.

This paper covers the details of two different gauge systems which have been installed in the area. The reliability of the systems and how the data obtained from these gauges has been used is addressed. In the light of the operational experience gained, areas for further development in pressure monitoring systems are also discussed.
Transportation, Launch, and Self-Upend Analysis of the Kilauea Jacket Using Proven Analytical Techniques
Authors: Sircar S. , Chandra T.K. , Mills T.R.J. , Roberson W.P.
Published: October 2008

The self-upending, light-weight Kilauea jacket was designed with a minimum amount of flooding and venting equipment. The installation procedure was sensitive to changes in the jacket's weight and buoyancy properties. As a result, this jacket was subjected to extensive installation engineering and careful weight monitoring. This paper describes the methodology and results of the transportation, launch, self-upend, flotation, set-down and on bottom stability analyses of the Kilauea jacket. All hydrodynamic and friction coefficients and weight margins used are based on experience gained from past projects. Controlled ballasting was used to set the jacket down on the seabed and to obtain initial leveling and on-bottom stability.

INSTALLATION PHILOSOPHY

Installation Overview

In the final design stage, it was envisioned that the Kilauea jacket would be installed based on the following general procedures:Load out the jacket from McDermott's fabrication yard on to the launch barge Intermac 650 (I-650) with the barge freely floating at an approximate draft of 30 feet. At this draft, the barge launch ways are level with the fabrication skid ways.After load out, reduce the barge draft to the design Gulf tow draft (24 feet) and install transverse and longitudinal sea fastenings and prepare the jacket and the barge for tow.Reduce the barge draft to 14 feet for river tow and tow the jacket using three river tugs to the Eugene Island sea buoy.Based on good weather forecast, replace the three river tugs with three ocean going tugs and start the Gulf tow while continuing to ballast the barge down to arrive at the Gulf tow draft.Prior to the arrival at the launch site, and on confirmation of good weather forecast for launch, barge ballasting is continued to arrive at the pre-launch configuration.Prepare to launch the jacket against the current and facing the derrick barge. Two tugs and two head lines from the derrick barge are connected to the top four corners of the jacket (see Figure 1).Once all sea fastenings have been cut, and the I-650 is in the pre-launch draft and trim condition, the jacket is jacked until it starts sliding by itself and launch begins. After launch, the jacket self-upends itself and is then pulled in towards the derrick barge using the two headlines.Once the jacket is at the stern of the derrick barge, the derrick barge crane is attached and lifts the jacket about 10 feet to gain more positive control of the jacket. This is followed by lowering of the jacket to the seabed using a combination of hooklC1ad and controlled ballasting of the jacket's compartments. Further ballasting is then used to level the jacket to within acceptable limits and to achieve the desired on-bottom weight.Piles are then launched and self-upended from the side of the derrick barge and stabbed into the pile sleeves using the assistance of Remotely Controlled Vehicles (ROVs). This is followed by pile driving and grouting.
A Comparison of the Erosion Rate of Casing Steels by Sand/Oil Suspensions
Authors: Clark H.M.
Published: October 2008

The erosion rates (expressed as g/mm2/min) of three casing steels (P110, N80 and K55) and hot-rolled 1020 steel in quartz sandoil suspensions, GFN 140, solids loading 0.5 - 4 wt%, at speeds from 9.35 - 18.7 m/s have been measured in a slurry pot tester. The velocity exponent was determined as 2.4 and the relationship of erosion rate to solids loading and particle size (for the particle size range 53-180, µm) determined. The erosion rates for all steels were foundto lie within a scatter band of ±m 15%, and could not be related predictively with the measured tensile properties. Results are discussed in terms of the rate of particle impact on the eroding target and the need to control flow conditions through appropriate design to minimize erosion.

INTRODUCTION

This work grew out of the observation of the erosion of oil-well components by fine sand entrained in the petroleum stream in wells off the SE coast of Trinidad (Caribbean). The effect of erosion is progressive, more sand entering the system as damage proceeds, thus engineering parts spend much of their life under conditions of steadystate erosion, component life being determined by the rate of material loss per unit time.

This investigation has focused on the rate of steady-state erosion of three casing steels under flow conditions similar to those found in oilwells and platforms. The flow rate through down-well screens is in the order of 1.5-3 m/s, while across chokes it may be at least an order of magnitude higher. The average sand concentration in a producing well in this field is about 0.5 vol %(1.3 wt%) and may rise to as much as 5 vol.% (13 wt.%).

EXPERIMENTAL

Sand

Sand used in this work was obtained from a sand separator on an off-shore Trinidad oil platform. X-ray analysis showed it to consist almost entirely of ? X-quartz, with traces of feldspar, calcite and clay minerals. The particle size distribution is shown in Fig. 1. The AFS grain fineness number was 140 (106 µm) and the density of particles was 2620 kg/m3. For most tests, the sand was used with the as-received particle size distribution, except as noted. The shape of fresh sand particles is shown in Fig. 2a. One test was conducted with silicone-coated glass beads in the size range 106-150 µm (density 2420 kg/m3). These are shown in Fig. 2c.

Oil

Suspensions were made up using light furnace oil, flash point 67°C, density 850 kg/m3 and viscosity 1.5. 10−3 Ns/m2 at 40°C.

Steels

Three grades of oilwell casing steel were examined, API P110, N80 and K55, having yield stresses in excess of 760, 550 and 380 MPa respectively. The P110 and N80 contained 0.3 °C and 1.9 Mn and were in the quenched and tempered condition. The K55 contained 0.47° C and 1.4 Mn and was hot-rolled. Coupons were cut parallel with the axis of the casing from which tension and erosion test specimens were turned. Tests were also performed on hot-rolled 1020 steel to provide a performance datum.
Diverless Flowline Tie-In Techniques for the DISPS Project
Authors: Bruton A.S. , McKeehan D.S. , Metcalf P.
Published: October 2008

This paper describes the DISPS Project design, development and prototype testing, in the dry, of three diverless tie-in systems for application to flowlines of 4 - 12 inches diameter in water depths of 350 - 750 metres. Full scale simulation of direct pull-in, lateral deflection and vertical stab techniques using two tools for flowline pull-in and connection was undertaken and the design limits established.

INTRODUCTION

Within the DISPS development, diverless flowline tie-in concepts were recognised, as key flowline issues. A study was undertaken and this included the evaluation of possible flowline installation methods, pipeline materials and available connection hardware which would be suitable for diameters of 4 to 12 inches in water depths of 350 to 750 metres.

The main conclusion of this study was that diverless flowline tie-ins play a considerably greater role in dictating field development and installation strategies than flowline tie-ins in conventional diver depths. These diverless tie-in techniques warranted a design philosophy which favoured a highly adaptable system over a case-specific system.

The following engineering targets were established for the DISPS development of diverless flowline tie-ins.The flowline tie-in bays within the template or satellite well structure should be capable of accommodating any of four types of tie-in:Direct Pull-in for Steel Pipe (Figure 1)Lateral Deflection for Steel Pipe (Figure 2)Vertica1 Stab and Hinge-over for Flexible Pipe (Figure 3)Slack Loop Pull-in for Flexible Pipe.The tie-in system should be compatible with flowline installation by laying, reeling or towing.The alignment mechanism should be by structural interaction between a passive guide and pull head without manipulation of the flowline.All pull-ins should be achievable with a single pull wire acting through the pipe centreline.Recoverable tools should be used for pull-in and make-up of the mechanical connector. Both alignment modules should be compatible with these tools.The pull-in and make-up procedure should be performed in discrete steps and allow support vessel demobilisation after docking. This enables a smaller diving support vessel to be used for subsequent connector make-up.The alignment components should be modularised such that finalisation of the template or satellite well configuration can be deferred prior to deployment. This allows field development plans to remain flexible while the seabed structures arebeing fabricated without compromising template/flowline interface areas.The pullhead should allow pigging and hydrostatic testing of the flowline before the connection is made to inboard piping on the subsea structure. This allows the pipe-lay contractor to satisfy contractual obligations even if the final connection is deferred. In keeping with this objective, the flowline remains fixed after docking, with final stroking of the connector by movement of the inboard piping.
India's Programme on Polymetallic Nodules
Authors: Yates J. , Gupta K.R.
Published: October 2008

This article is a review of India's programme aimed at developing deep sea manganese nodules on a commercial basis. A brief history of the programme is followed by an outline of current work in the areas of survey and exploration, deep-sea mining technologies, extractive metallurgy and environmental studies. There then follows an analysis of the resources available to the project both fiscal and in terms of available manpower. The programme is viewed in the wider context of Indian science and technology policy in general and the ocean sciences in particular, emphasising major factors which have led to its implementation. The article concludes by detailing some current trends within the programme and likely future options for its development.

Introduction

Since Independence in 1947, successive indian governments have placed great emphasis on the development of indigenous science and technology, viewing this as a means of narrowing the technological gap between India and the more industrialised western nations, and thereby improving the average standard of living within the country. This strategy has led to the development of a range of ambitious programme; space, nuclear, electronics, Antarctic, and the subject of this article deep-sea mining. Although India has had a long sea-faring tradition, it is only after Independence that priority has been given to the R&D programme related to the tapping of living and non-living marine resources. Oceanographic research and development has been given extra impetus during the last 25 years with the establishment of the Institute of Oceanography, the marine work of the Oil and Natural Gas Commission, and the establishment of the Marine Geology Division in the Geological Survey of India. Studies by naval research groups and participation in major international programmes like IIOE, GRAP and MONEX have also played an important role 1 As a result of this activity, major advances have been made in indian oceanography in recent years.

In order to plan, coordinate and develop an indigenous capability in Oceanographic research, the Government of India set up an Ocean Science and Technology Agency (OSTA) in the Department of Science and Technology in 1976. A separate Marine Research and Development Fund was set up under OSTA to support R&D in this area. Subsequently, a Department of Ocean Development (DOD) was created in July 1981, charged with matters regarding coordination, security, regulation and development of the ocean including 2,3promotion of R&D in the marine sector.surveys to locate and map the availability of living and non-living resources of the Exclusive Economic Zone and of the continental shelf (excluding hydrocarbons).development of skills and manpower.protection of the marine environment in the high sea areas.survey, exploration and development of deep sea bed mining.promotion and coordination of Antarctic Research. The basic policy underlying this ocean development has been defined in the Ocean Policy statement adopted by the Parliament in November 1982.
Veslefrikk Field Development Concept
Authors: Solberg L.
Published: October 2008

VESLEFRIKK FIELD DEVELOPMENT CONCEPT

This paper gives a brief description of the Veslefrikk Field development concept, from the start of the conceptual phase to the construction and start-up phases. The different main contracts are described as well as some challenges and experiences gained duringthe execution of the Project.

FIELD HISTORY AND RESERVOIR

The decision to develop the field was taken in 1986, just as the oil price had suffered a dramatic drop. As a consequence of this, the field had to be developed to meet a low oil price.

Veslefrikk is located in block 30/3 situated 145 km west of Bergen in WestNorway, and close to the Oseberg Field.

Statoil was appointed as operator in 1979, and the first oil was found in 1981. The field was declared commercial by Statoil in the autumn of 1986.

The owners of the field are:(Available In Full Paper)

The reservoir is estimated to contain 36.4 million m3 oil and 4 billion m3 gas.

The detailed engineering started in October 1987; the production start-up was 26 December 1989, that is to say 27 months later.

The daily production is estimated to be 10.000 m3 oil (65000 bbl/day) and 1.5 million m3 gas.

The field will reach peak production in 1990. After 3 to 5 years the output will decrease and the production will come to an end after 20 years. Thewater depth at the field is 174m.

The reservoirs are located at the depths of 2800 m and 3050 m. The total number of wells is 18 of which 11 are producers and 7 are injectors.

PROJECT PLANNING

Studies for development of the Ves1efrikk Field were started in the autumn of 1985.

Because of a water depth of 174m a whole range of field installations were studied. During the spring of 1986 theoil prices fell drastically presenting a new challenge in the development i.e. tomeet an oil price down to 12 USD/bb1.

The following 3 main concepts were evaluated in detail:Integrated process, drilling and quarters platform like Statfjord and Gullfaks, but downscaled.Floating production platform connected to a fixed drilling platform of steel or concrete.Subsea wells linked to a floating production platform. During technical and financial evaluations the integrated process, drilling and quarters platform turned out to be more expensive for this field compared to the selected alternative.

The floating production platform was evaluated with two options, one as a purpose-built platform, and the selected alternative with conversion of an excisting rig. The selected alternative showed a cost saving and also a schedule saving of one year.

As a result of these evaluations the optimal solution appeared to be drilling facilities supported by a steel structure in combination with a floating production and quarters unit see figure.
Design and Installation of the Veslefrikk Jacket
Authors: Baerheim M. , Fossan T.I. , Eriksen K.
Published: October 2008

The Veslefrikk A jacket, standing in 174 meter water depth in the North Sea, was lift installed in May 1989. The jacket is the heaviest lift installed offshore structure in the world.

The jacket is relatively tall and slender, and the lift weight was close to the capacity of the available heavy lift crane vessels. Structural design and weight optimisation were thereforeimportant.

This paper gives a general description of the jacket and highlights some of the special features and lessons learnt in the design and installation of the structure.

INTRODUCTION

The Veslefrikk field is developed with a two platform concept. The drilling equipment is placed on the Veslefrikk A jacket, while processing equipment and quarters are located on the semisubmersible platform Veslefrikk.

The field development is further described in reference 1.

Being 184 metres long and with a lift weight of 9086 tonnes, the jacket was lifted and installed by the world's largest dual crane semi-submersible lift vessel. The lift took place inshore at the mouth of Sognefjorden. The jacket was then towed in a partly submerged position to the field for the upending, mating and piling operations.

Various special design methods and features were introduced in the jacket design. Most of these were introduced since the weight of the structure during lift was critical, others because thejacket is slender and dynamically sensitive.

JACKET DESCRIPTION

The Veslefrikk jacket is a four legged structure, as shown in fig 2. Both the faces and the horizontal levels are X-braced. The jacket extends from the sea bed up to elevation +9.8 metre.

The top and bottom dimensions of the jacket are 18.3 by 18.3 and 54.9 by 54.9 metres respectively. These dimensions were largely determined by lift clearance requirements. A separately installed deck support frame extends up to elevation +25.5 metres.

The legs have an outer diameter of 1.3 metres between elevation +25 and -60 metres. The legs in this area are reinforced by 1.1 metre diameter internal tubes grouted to the outer legs. Below -60 the leg diameter increases from 2.2 to 3.5 metres.

The face bracing varies from 0.8 to 1.6 metres diameter at the top and bottom of the structure respectively. The plan level bracings are 1.1 metre in diameter. The jacket is supported by four piles at each leg.

The jacket was installed over a template having six pre-drilled wells.

The following criteria were used in the design :(Available In Full Paper)

SPECIAL CHALLENGES IN DESIGN

The decision to design a liftable jacket was taken after feasibility studies of both lifted and launched structures. The lift operation determined the geometry of the jacket and put emphasis on weight optimisation.

The jacket is slender and light and founded on relatively weak soils. This also put special emphasis on design for temporary and permanent foundation strength and dynamic behaviour of the jacket.
A Unified Design Procedure for Tubular Members
Authors: Loh J.T.
Published: October 2008

A new unified procedure for designing tubular members under combined axial load (compression or tension), bending, and hydrostatic pressure on offshore structures, fixed or compliant, is presented. The equations are applicable to members at all water depths, but are limited to members with outside diameter to wall thickness ratios less than 80. In addition to a pure hydrostatic check against hoop collapse, the procedure recommends only one check each for the axial compression and tension cases. The new design equations have been calibrated to test data from several recently completed test programs, and are thus more reliable than currently available technology. The new equations are also simpler to use. The procedure can replace several subsections in the 18th edition of API RP 2A-ASD and the draft RP 2A-LRFD (yellow copy).

The recommended procedure provides unambiguous guidance for determining the member axial, bending, and hoop stresses from a frame analysis in order to check the design adequacy or determine the unity check (member utilization) of the member. The recommended procedure includes a reduced safety factor for hoop compression, but other safety factors in RP 2A-ASD are unchanged. Further examination of the reliability question may be warranted, but it is not envisioned that such an evaluation would alter the proposed procedure so as to become more conservative.

A comparative design study using the new equations on a 2500-foot compliant pile tower resulted in about 5% tower steel-weight saving (2300 tons) compared to the approach proposed by Chen, Bubonic, and Sohal. Even larger weight savings can be expected for TLP tendons although a comparative design example is not yet available.

The new equations are currently being reviewed as part of an ongoing API PRAC 89-56 study on analysis of the cylindrical shell database and validation of design formulations.

INTRODUCTION

Both API RP 2A-ASD1 and RP 2A-LRFD2 provide incomplete guidance for the design of tubular members under combined axial compression, bending, and external hydrostatic pressure loads, as shown in Fig. 1. The guidance in both documents is limited to checking local cross-sectional buckling. (Shear forces are not shown in Fig. 1. These forces have negligible impact on the strength of beam-columns.) In addition, there is an inconsistency in both documents relating to the allowable bending capacity term. However, this inconsistency generally results in a conservative design.

In addition to hoop stress, external hydrostatic pressure will impose a capped-end axial compression force in a member if the ends are capped, as shown in Fig. 2. On the other hand, external radial pressure only imposes hoop compression in a tubular member and no capped-end compression. Since the hoop and capped-end axial stresses from external pressure are always in compression, they are assumed to have a positive sign.
In-Situ Pile Segment Model Experiments at Harvey, Louisiana
Authors: Bogard J.D. , Matlock H.
Published: October 2008

Three field experiments have been conducted in normally consolidated soft clay at Harvey, La. using instrumented 3inch diameter probes to simulate pile behavior under a variety of static and cyclic axial loadings. Lateral total pressure and pore pressure were observed and shear transfer versus pile displacement were recorded. The results represent the first phase of a comprehensive program to develop an improved basis for pile design.

Introduction

As a part of a comprehensive program of research into the behavior of friction piles in clay, in situ pile segment models, or probes, have been developed to measure total radial pressure, pore pressure, shear transfer, and relative pile-soil displacement during installation, consolidation, and static and cyclic axial loading.

The experiments reported herein were the first of 47 experiments performed with the probes, which have included tests at the onshore sites of two large-diameter instrumented pile load tests, the offshore site of load tests on instrumented large-diameter driven and drilled-and-grouted piles, and three onshore sites where parallel large-diameter pile load tests are not available.

Four of the six sites contain soft-to-stiff normally consolidated clays. At the four sites, a total of 42 experiments were performed, with load testing at times ranging from minutes to three months after installation. The data are believed to represent a sound basis for developing a fundamental understanding of pile-soil interaction and for developing reliable design procedures for the design of pile foundations subjected to static and cyclic axial loading.

Methods

The pile segment models were developed at The Earth Technology Corporation (Refs 1 and 2). Two sizes, 3.00 and 1.72 inches in diameter, have been built and utilized in field tests at various locations. The 3-inch size permits investigation of various cutting shoes or end conditions and is the type employed for the tests reported in this paper.

The features of the 3-inch probe and the three stages of installation are shown in Fig 1. The tool is impact-driven or jacked into the soil beyond the end of a drilled hole. The leading section is a tube which is long enough to simulate the effects of an open-end pile in the zone where the instrumented section comes to rest. Various wall thicknesses or a fully plugged condition can be utilized. At the slip joint shown at the left, the leading section is free to move one inch with respect to the instrumented section and the relative movement is indicated with an internal displacement transducer. After installation, the leading section serves as an anchor for accurate measurement of pile-sail displacement. Soil shear transfer is measured as the differential reaction between the two load cells. The pressure measurements aid in interpreting soil consolidation and set-up processes, plus pore water and structural changes during shear.
Commercial Potential for Titanium Off the Coast of Virginia
Authors: Hennigar H.F. , Siapno W.D.
Published: October 2008

The continental shelf of Virginia may have the potential for commercial quantities of titanium-bearing heavy minerals, however, data which have thus far been collected by various government entities are not sufficient to calculate in-situ resources. Government efforts should be focused on gathering additional data to delineate the extent of these deposits rather than on developing policies to regulate a nonexistent offshore mining industry.

INTRODUCTION

Production and consumption of titanium dioxide TiOZ) pigments reached record-high levels for the sixth consecutive year in 1988 (Lynd, 1989). Titanium is one of the few base metals that has consistently increased in value over the last decade. In the US, imports have risen continually and in recent years constitute three-quarters of TiOZ concentrates consumption. Major US producers include Associated Minerals Ltd., Inc. at Green Cove Springs, Florida. and E.I. DuPont de Nemours & Co. at Starke and Highland, Florida. Kerr-McGee, located in Mobile, Alabama, is the sole producer of synthetic rutile. P.W. Gill1brand Company separates and stockpiles heavy-mineral concentrates containing limonite in Soledad Canyon near Los Angeles. Subsidiaries of several of these companies also operate overseas. Major titanium companies around the world are planning to upgrade their facilities to meet increasing demand. Figure I, from the March 1989 Engineering & Mining Journal, summarizes titanium activity during 1987 and 1988.

These data show total concentrates grew at a rate of 5.18% between 1987-88. Demand growth is conservatively projected by the US Bureau of Mines at about 5% for the next few years. Increases in demand will be driven by hi-tech programs coupled with expansion in the chemical-processing industries. The market for titanium metal is closely tied to aircraft, spacecraft and jet and rocket engine developments where strength to weight ratio and resilience at high temperatures are important characteristics. The worldwide fleet of commercial airliners is suffering the effects of age and overuse, and many aircraft are long overdue for replacement. Construction of new aircraft will sustain demand for titanium at high levels for the near future.

RESOURCES

Titani um is the ninth moss t abundant element, following oxygen, silicon, aluminum, iron, calcium, magnesium, sodium, and potassium, which make up more than 98 percent of the earth's crust. Though widely disseminated, commercially valuable concentrations occur infrequently. Significant industrial demand began only within the last 100 years and titanium is consumed principally by advanced economies. The principal raw materials for titanium products are the minerals limonite (FeTi03), its alteration product 1eucoxene, and rutile (TiOZ)' Rutile is the preferred ore, however, limonite and leucoxene are more common. In 1986, DuPont ceased to use leucoxene of 71-90% Ti02 from ASARCO's New Jersey deposit. Limonite with 44-70% TiOZ is far more abundant and can be used to produces TiO concentrates as well as synthetic rutile.
A Bothnian Bay Manganese Nodule Deposit: A Case for Inference of Seabed Variability by Multimode Data Processing
Authors: Vikgren K.J.
Published: October 2008

Field data from a manganese nodule deposit in the Bothnian Bay were used in this Case study for the application of image processing to sea floor imagery. A digital data-base was acquired from box core samples, bathymetric records, side-scan sonar records, and in-situ camera inspection. Multimode processing of the data-base in overlapping data planes was used with various analytical tools including texture-analysis. As a result of the study it was found feasible to infer knowledge about the seabed variability from this data-base.

Introduction

Underwater ferromanganese concretions were historically collected in shallow lakes in the southern part of Sweden - particularly in Small and. This ore was scraped together with hand-operated long rakes before it was moved over to a shallow sieve bucket in Which it was washed and lifted on to a raft or through holes in the ice. Investigations of slag mounds in this Province indicate that this form of mining went on for about 1000 years.

Present Swedish work related to manganese nodules is related to geological studies, underwater exploration, and development of hydrometallurgical leaching methods.

The manganese nodule deposits in the Gulf of Bothnia were described already in 1934. The first extensive study was made in 1962 and treated geological, mineralogical and genetically aspects of the nodules. This work has been confirmed to a great extent by Subsequent geochemical and mineralogical mapping of the sediments and nodule occurrences. The nodules lie either on the surface or in the top 1-5 cm layer of oxidized surface sediment which lies over the reduced sediments. various nodule constituents are remobilized when nodules are surrounded by reducing sediments. These remobilized elements have been precipitated to form the nodules. Some of the released manganese, barium and nickel also enter into suspended phases which eventually leave the Baltic Sea.

Present work on these deposits has been related to a target area (fig. 1) near Bjur6klubb in the Bay of Bothnia. 9 Field data from a cruise to the area was used in this case.

The Data-base

The data-base from the R/V ARGOS cruise to the Bjur6klubb field in June 1986 comprises the following items:Results of geological and chemical analyses of 134 seabed samples collected by a light (30x30x50 cm) box corer in a grid with a mesh-size of one nautical mile, plus a further 21 samples in a one nautical square mile area.855 topographical points which were digitized from bathymetry measurements made during the cruise with narrow beam echo sounders.
Current Offshore Hard Minerals Projects and Activities of the Minerals Management Service
Authors: Drucker B.S.
Published: October 2008

The Minerals Management Service' s (MMS) Office of Strategic and International Minerals (OSIM) provides policy and program direction for development of all minerals other than oil, gas, and sulphur on the U.S. Outer Continental Shelf (OCS). In order to develop the potential of the OCS as a domestic supply source for solid minerals and to encourage development of a viable ocean mining industry, OSIM has joined with several coastal States to form Federal/State task forces to assess potential economic mineral commodities off their respective coasts and to assure that environmental and other issues are identified and fully addressed. This paper describes and summarizes the projects and activities in which OSIM is currently involved relating to the development of an environmentally sound offshore hard minerals program.

INTRODUCTION

The OSIM was established by MMS in 1983 to focus Federal efforts in developing a no energy minerals program on the nation's outer continental shelf. Goals of the program are to develop the potential of the OCS as a source for solid no energy minerals and to encourage development of those minerals in a sound and environmentally safe manner. A'key objective of OSIM has been to provide a regulatory climate conducive to industry initiative while protective of the environment. Accordingly, final regulations governing prospecting for OCS hard minerals were published in July 1988, and rules governing leasing and operating activities were published in January 1989.

OSIM has focused attention on areas and resources where there is industry interest and where the coastal States would like to take part in coordinated efforts to identify and evaluate deposits of economically recoverable minerals and work together to resolve environmental concerns. This has resulted in the formation of several Federal/State task forces and cooperative agreements to address and resolve issues and potential controversies in an orderly and timely manner, and to involve the coastal States in discussions of programmatic concern. Currently, the MMS supports six Federal/State Task Forces (Fig. 1), the status of which is discussed in detail in the following section.

CURRENT STATUS OF ACTIVE FEDERAL/STATE TASK FORCES AND COOPERATIVE AGREEMENTS

Hawaii Cobalt-Rich Manganese Crusts The Federal/State of Hawaii Task Force was established in 1984 to evaluate the possible development of cobalt-rich manganese crust deposits located adjacent to Hawaii and Johnston Island, in water depths from 800 to 2,400 meters. A final environmental impact statement (EIS), prepared with the oversight of the task force, was completed earlier this year The final EIS evaluates an area of 26,910 km2 (approximately 6.65 million acres).
Upheaval Buckling: A Practical Solution Using Hot Water Flushing Technique
Authors: Craig I.G. , Nash N.W. , Oldfield G.A.
Published: October 2008

In the development of the Glamis Field, a sub sea satellite to Balmoral, measures were required to avoid the expected problem of upheaval buckling of the long hot insulated flow lines.

Following review of various solutions, Sun opted for the novel technique of boosting the temperature of the Balmora 1 produced water and pumping it through the Glamis flow lines as a means of inducing a tensile pre stress.

The technique proved successful and could be considered to have a wider application in other satellite developments where similar water supplies are readily available.

INTRODUCTION

Sun are operators of the Glamis Field in UK North Sea Block 16/21a which has been developed as a Sub sea step out 8km South West of the Balmoral Field (Ref 1).

Glamis comprises three satellite wells - 2 production and 1 water injection - tied back to the Balmoral template by individual flow lines. The two production flow lines are insulated to maintain separator inlet temperatures above 25°C. Preliminary analysis indicated that upheaval buckling could occur.

Several methods of preventing or stabilizing buckling movements were considered before a decision was made to use the hot water flushing technique which is the subject of this paper.

The sequence of events from the evaluation of theupheaval buckling movements, through selection of the hot water flushing technique to the offshore operation are described in detail. The effectiveness of the method is assessed from the results of the post hot water flushing, post trenching and post first oil pipe movement surveys.

BACKGROUND

Flow lines buckle when the net compressive load in the pipe exceeds the bending stiffness and the frictional restraining force. Vertical movements occur if the pipe's preferential lateral mode of movement is restrained and the compressive load is able to overcome the weight of the pipe and cover weight/resistance. The compressive load is a combination of the internal pressure effects and the temperature induced expansion forces.

Experience with an existing Balmoral (l6/21b-12) flow line revealed upheaval buckling movements. The limited extent of the observed movements was at variance with theoretical analysis which indicated that the buckling should be much more widespread on this and other flow lines where no buckling has been observed.

The conclusion was that first order analytical techniques were too conservative. The Balmoral experience did however make it clear that some means of preventing or mitigating the effects of upheaval buckling was necessary for Glamis to avoid exposing the flow lines to the risk of trawl gear impacts, over stressing and, in the extreme, pipe crimping.
Efficient Wave-Theoretical Imaging Through Complex Water-Bottom Topography
Authors: Lynn W.S. , MacKay S.W. , Beasley C.J.
Published: October 2008

An efficient means for imaging structure beneath complex water-bottom topography can be obtained using conventional time-migration algorithms and a simple modification to the migration-velocity field. The process consists of two migration steps: one with the migration velocity set to zero below the water bottom and the other with the migration velocity set to zero above the water bottom. Between the two steps the data are time-shifted to account for the so called "thin-lens" term used in depth-migration algorithms. Efficiency is obtained by applying the thin-lens term only once and by using existing computationally optimized time migration algorithms. Results obtained from this technique are nearly identical to more costly layer-replacement and depth-migration techniques.

Introduction

Structures targeted for imaging by seismic surveys are often quite simple; yet their seismic response can be significantly distorted by more complex overlying water-bottom topography. This problem is well-recognized and several solutions have been proposed, such as wave-equation layer replacement (Berryhill, 1979, 1986; Yilmaz and Lucas, 1986) and depth migration (Judson et al., 1980). Although accurate, these solutions are usually impractical to use because of their large computational requirements-especially when applied to prestack data. A more common approach is to adjust the migration-velocity field to compensate for image mispositioning caused by water-bottom topography. This rather ad-hoc approach, however, can leave considerable uncertainty as to the actual target structure. In this paper, we propose an accurate and cost-effective wave equation technique that uses conventional time-migration algorithms and a simple well-defined modification to the velocity field.

Background

To review the problem and lay the groundwork for our solution, consider the model in Figure 1. This model has a deep water-bottom canyon (with relief of 750 m) underlain by flat horizons. The shallowest of these horizons has a normal fault positioned under the right flank of the water bottom canyon. For simplicity, the model has only two velocities, 1500 mls in the water layer and 2200 mls below the water bottom.

The zero-offset seismic response of the model recorded at the surface (Figure 2) shows a time sag in the flat horizons. This time distortion, caused by the change in water bottom depth, has made the fault in the shallow horizon less obvious; and, in fact, one might interpret both of the sub water-bottom horizons as continuous, or as faulted. Ordinary time migration, even with the exact velocity field, does not remove the uncertainty as to the true structure of these horizons. As the time-migrated section (converted to depth) in Figure 3 shows, the deep horizon has not been imaged properly and could easily be interpreted as being faulted. The reason, of course, for the improper imaging is that time migration is not appropriate when strong lateral velocity variations are present.
Use of an Electronic Imaging System on a Major Offshore Project
Authors: Liddell R.E. , H.B. Stone G.C.H.B.
Published: October 2008

1. ABSTRACT

This paper highlights the experiences of introducing Electronic Imaging to a major offshore project in Norway, to store and distribute all drawing documentation. The paper describes the objectives and features of the system and ultimately practical experiences with the system. The paper concludes by recommending it as a powerful tool for future major projects.

2. INTRODUCTION

Gyda is a $1.3 billion project to develop an integrated oil platform in the Norwegian sector of the North Sea. It has a production capacity of 60,000 BPSD and delivers oil to Teesside in the UK and gas to Emden in West Germany.

The purchase of an Electronic Imaging System arose as a result of a requirement for CAD facilities during the fabrication, installation and commissioning phases of the project. After a thorough investigation of possible alternatives it was considered that Electronic Imaging was the only method of accommodating all the dissimilar drawing media inherited from the Norwegian design contractor (Figure 1 shows a breakdown of the media received from the contractor).

Prior to "close-out" of the detailed design Contractor, 16,500 design and supplier drawings were scanned over a period of 4 weeks. As a temporary measure all scanned data was stored on magnetic tape prior to delivery of the system in April 1989.

One of the major justifications for making all drawings electronic on the project was the fast transmission of drawing documentation to the widely dispersed remote sites on the project (Figure 2 shows the geographical locations of the remote sites accessing the Electronic Imaging System).

There are two alternative methods of storing drawing data on an Imaging System known as "Raster" and "Vector". Raster data is received directly from a document scanner and is rather like an electronic version of a high resolution tealeaf image. The drawing, once scanned, is represented as a series of non-intelligent dots at a density of 200 Dots/inch. Vector data is more intelligent and is made up of geometric entities such as lines, arcs, circles, etc., the entities can be manipulated as self contained objects. CAD systems exclusively use Vector data, but Imaging Systems can use a combination of both to fit the purpose.

They also have the capability to convert Raster data into Vector known as "factorizations".

Raster drawing data requires a lot of storage space, therefore it is necessary to use data compression techniques to reduce storage demands. On Gyda all drawing data is held as highly compressed Raster data and no attempt has been made to convert this into Vector data. Since timescales were short and the compressed image file sizes were slightly less than Vector, it was decided to edit and store drawings solely in Raster.
Submerged Wellhead Platform System
Authors: Thory G.G. , Vora M.R. , Stockard D.M.
Published: October 2008

Many hydrocarbon fields exist in water depths between 800 - 2000 ft which are not commercially viable using existing methods of production. It is clear that various types of Floating Production Systems (FPS) are viable alternatives to fixed platforms in deeper water depths, as shown by the Green Canyon Block 29 development.

The Submerged Wellhead Platform System (SWPS) concept (Figure 1) is based on the requirement to produce deep water fields at the lowest cost using proven technology.

This paper discusses the design of the submerged jacket, vessel selection, mooring systems, flexible riser configurations, installation, semi-submersible downtime criteria and overall concept economics.

Estimates indicate that significant cost savings can be realized using this concept, when compared to existing project developments. It is especially important in this era of fluctuating oil prices to provide a sufficient profit margin against possible market downturns in the future. This reduces the financial risk of developing and producing a discovery, especially one located in deeper water.

Due to the excessive motions of the production vessel, it has not been possible for rigid risers, with surface wellheads, to be incorporated in the floating production systems which have been installed to date. Instead, it has been necessary to rely on more complicated seabed wellheads which are connected to the production vessel via flexible risers. As deep water fields are evaluated it has been found that a combination of high seabed wellhead maintenance costs and inexperience with very long flexible risers (greater than 1500 ft) has resulted in uneconomic or unfeasible field developments.

To overcome these problems, the Submerged Wellhead Platform System (SWPS) has been developed as an economic solution. This system focuses on utilizing simpler diver accessible wellheads and shorter flexible risers, together with a cheaper converted drilling/production semi-submersible vessel and lightweight jacket.

Evaluation of wave forces on the submerged jacket indicate that the amount steel required is substantially less than for a conventional surface piercing jacket. If the wellheads are located at a relatively shallow water depth, saturation diving becomes unnecessary and diving costs are minimized. However, increasing the jacket submergence allows drilling operations, which are limited by the drilling riser ball joint angle to continue with a greater vessel offset. Locating the jacket top between 200 and 290 feet below the surface accomplishes both objectives by allowing diver access at minimal costs and also permitting a sufficiently large vessel excursion, and hence drilling weather window.

Currently, the jacket has been optimized to a uniform cross-section rectangular configuration, with 24 producing well slots and 4 reserve slots in case problems are encountered in the drilling operations. A minimum production rate of 25,000 BOPD has been assumed, with an increase possible depending on the reservoir and FPS capabilities.