bluuebunny/crossref_metadata_2025_split huggingface dataset:
Main Pass 299 Sulphur Mine: Offshore Design in a Soil Subsidence Bowl
Authors: Camp J.J. , Langley W.E. 
Published: October 2008

ABSTRACT
The structural configuration and design of the Main Pass Block 299 sulphur mine structures is described. These structures are subjected to significant settlement and severe soil movements caused by the extraction of the sulphur ore. The mine structures consist of 14 platforms connected by bridges and one "stand alone" platform.
All sulphur mine platforms are steel jacket structures similar to typical oil and gas structures in the Gulf of Mexico. However, two basic factors related to the sulphur mine operations make these structures different from oil and gas structures: gradual subsidence of the seafloor and a design service life of 40 years. The predicted soil movement induced stresses are so severe at several of the platform sites that 100 ksi yield strength steel has been specified for use in the piles and nonlinear analysis of the piles has been performed.
In addition to incorporating the predicted soil-induced movements of the piles in the design of the structures, platform decks and appurtenances such as boat landings and barge bumpers are designed to be elevated to compensate for the platforms' downward movement.
Bridges are designed to accommodate significant horizontal movements and differential support settlements created by the motion of interconnected platforms.

INTRODUCTION
The Main Pass Block 299 sulphur mine initial development consists of 15 platforms and 13 bridges located in water depths ranging from 208 ft. to214 ft. about 15 miles east of the Mississippi River Delta. Figure 1 is an artist's rendition of the mine development. A salt dome underlies most of the block, which is surrounded by oil and gas platforms. Within the caprock lies a layer of limestone which contains the sulphur ore. The sulphur lies approximately 1500 ft. below the seafloor and the deposit is about 150 ft. thick at its deepest point.
Nine of the 15 platforms will serve as bridge supports (three of which will also support helidecks). The other platforms include a Loading & Storage, Power Plant, Living Quarters & Warehouse, and two Production platforms. The stand-alone platform is the Facilities platform. Plans call for the present Production platforms to be relocated, as well as new ones installed in other areas of the mine, once the sulphur is exhausted in the initial mining regions. Several of the bridge support platforms and bridges are also designed to be relocated.
The Frasch mining process will be utilized to extract the sulphur. Water produced at the Power Plant platform and from brine wells located on Bridge Support 2 will be pumped to the Power Plant Module to be chemically treated and heated. Water will then be piped to the two Production platforms where it will be injected into the sulphur formation. Molten sulphur will be recovered at the Production platforms and pumped to the Storage platform. The sulphur is to be stored in two 90 ft. diameter by 40 ft. high tanks. The sulphur will finally be loaded into specially built double-hulled barges and taken to an onshore terminal near Port Sulphur, La.
TOGI Pull-In and Connection Systems
Authors: Bakken C. 
Published: October 2008

ABSTRACT
A unique and prototype pull-in and connection system were developed for the TOGI project. The offshore pull-in of the 20" pipeline and service lines and cable were performed without any problems. The mechanical and electrical connections became more problematic than envisaged. Supplementary methods and equipment had to be developed during the offshore phase for some of the operations. The paper will present design characteristics and experiences during testing and operations.

INTRODUCTION
For pull-in and connections on the TOGI template the following tools were developed:Pull-in tool for 20" pipeline and service lines and cableConnection tool for horizontal hub connections of20" pipelineService lines to manifoldX-mas tree to manifoldPig module to manifoldElectrical bridge connection tool for connection of inductive connectors between cable termination and manifold.Control pod running tool for electrical connections between control pod and manifold. Fig 1 shows the pull-in and connection areas on the template.
The tools developed during the offshore phase for rectification work were:Honing tool for repair of 20" outboard hub.ROV operated brushing tool for 20" and 11" hubs.ROV operated brushing tool for electrical female receptacles.ROV operated inspection tool. The main parameters for the design and operation of the pull-in and connection systems have beenfirst end tie-in of pipeline and service lines and cableall modules on the Template to be independent retrievableall metal to metal seals to be replaceabledual electrical connections for each welldesign life of 18 yearsdiverless operations This paper is one in a series of six which are presented at the OTC 1991.

DESIGN OF PULL-IN AND CONNECTION TOOLS

Pull-in Tool
The pull-in tool system consists of:Pull-in Tool (PLT)Alignment Funnel/Lock Down structures being part of the TemplatePipeline/Service Line Termination
A common pull-in tool was developed for both 20" pipeline and the service lines and cable. Fig. 2 shows the main features of the tool.
The functional requirements of the tool are:Direct pull-in from lay barge for both 20" pipeline and service lines and cable.All tool operations shall be fully reversible at any point in the operation.The tool shall be able to lock itself down to the template.In case of hydraulic failure, the PLT shall be retrievable by means of ROV override.Pull-in angle of the pipeline shall be within +/- 4 degrees. Final alignment to achieve the connecting tolerances of +/- 0.25 degrees shall be performed by the Pull-in Tool.The hub shall feature a removable hydrostatic pressure cap which prevents flooding during pipeline laying.Flooding of the pipeline shall be from the laydown head at Oseberg prior to connection. The pressure shall be equalised over a pressure cap which shall remain fitted until making the 20" connection.To remove the pull-in head.The tool shall be deployed by the use of drill string and guidewire techniques.The pull-in force for pipeline is estimated to be 60 tonnes.
TOGI Service Lines and Cable Installation: Concept Selection and Field Experience
Authors: Meling J. , Sunde L.A. 
Published: October 2008

ABSTRACT
This paper presents the concept for the TOGI service lines and cable bundle used to provide hydraulic and electric power and chemical injection fluid for the TOGI Subsea Station. The paper also presents the fabrication and installation methods used and some of the technical challenges experienced during the fabrication and installation phases. The paper includes descriptions of MSV "Regalia" used as the laying vessel and the water jetting system CAPJET 500 used for trenching.

INTRODUCTION
The TOGI service lines and cable bundle consists of three 34 mm ID duplex steel service, and one 75 mm OD electrical cable. The length of the service lines and cable bundle is 48km equal to the distance between the Subsea Station at Troll and the Oseberg Field Center. The waterdepth at the end points is 303m and llOm, respectively. See Fig. 1.
The four bundle elements were all prefabricated onshore in their full lengths and stored on three service line installation reels, and one carousel type basket for the cable.
During the summer of 1990 the TOGI service lines and cable bundle were successfully installed between the TOGI Subsea Station and the Oseberg Field Centre. The laying and later trenching of the three duplex service lines and the electrical cable marked the completion of four years period of engineering, fabrication and installation efforts, starting with the conceptual engineering in mid 1986 and ending up with the fabrication and installation contract which in spring 1989 were awarded to Ugland Coflexip A/S (UCAS), a joint venture between Ugland Offshore and Coflexip Norge. The work included new installation methods and equipment not earlier used in the offshore pipeline industry.
This paper is one in a series of six, which are presented at the OTC 1991.

TOGI CONTROL BUNDLE CONCEPT
The TOGI subsea wells are controled and monitored via a multiplexed electro-hydraulic system operated from the Oseberg A platform some 48 km away. The hydraulic supply and communication lines are gathered into a service line and cable bundle, consisting of three separate 34 mm ID duplex steel service lines and one 75 mm OD electrical cable, as shown in Fiq. 2. One of the service lines is used for chemical injection, and the other two for hydraulic pressure supply. The electrical power and signal cable consists of 12 pairs of conductor elements, where the control signals and power supply are transferred through common elements.
The bundle concept was established in the basic engineering phase of the project, and the following principles were adopted for the specification of service lines:One dedicated high pressure line (345 bar) for the surface controlled subsurface safety valves (SCSSV's) and one separate medium pressure line (207 bar) for the X-mas tree valve functions.One chemical injection feeder line with distribution chokes to each tree.No hydraulic fluid return lines.No spare lines, neither for the chemical injection nor the hydraulic system.
Transpacific Tow Oceanographic Criteria
Authors: Vermersch J.A. 
Published: October 2008

ABSTRACT
Planning the Harmony and Heritage jacket tows from Korea to the Santa Barbara Channel required assessment of meteorological and oceanographic conditions. This paper describes the data bases and methodology used to determine the probabilities of exceeding specified wind speeds and seastates along various tow routes and at different times of year. The method considers the effects of both extratropical storms and tropical cyclones.

INTRODUCTION
Planning long, open-ocean tows requires knowledge of the expected ocean environment over the towing route. Transoceanic tows of jackets (or any structure) require knowledge of wind and wave conditions to specify an optimum tow route, tug requirements, allowable towing season, tiedown configuration, and any special structural modifications. Additionally, some rare, extreme target wind event must be chosen in order to determine barge stability requirements. Exxon recently towed two of the world's largest steel jackets, Harmony and Heritage, from Ulsan, Korea to the Santa Barbara Channel, California. This paper describes the development of tow wind and wave criteria for tows over various transpacific routes and during all seasons.
A common approach in the design of permanent, fixed structures is to specify the condition which has 0.01 probability of occurrence in a random year, the so-called "100-year return period" event. In a 20 year lifetime, the risk of the structure encountering this event is 1-(1-.01)20 - 0.18. Note that this is not the risk of structural failure, merely the risk of exceeding a given environment. Factors of safety are used in design to reduce the risk of failure by several orders of magnitude below 0.18. Shorter term operations such as exploration drilling, offshore construction or oceanic towing also require specification of some design environment, but here the frequency of occurrence of the selected design event varies considerably. Some operators choose to specify the 10 year return period storm, others prefer the 0.1 percent exceedence condition, and some specify a total risk of encounter over the duration of the operation. For long open-ocean tows, Exxon has historically selected the 5% tow risk seastate and the 1% tow risk wind speed as the tow criteria. It is not the intent of this paper to propose a risk management philosophy, but rather to present the methods by which these criteria were established for the Harmony and Heritage transpacific tows. This paper will first discuss the methods and results describing the extratropical environment, then the tropical cyclones, and finally present the combined, year-round wave and wind criteria.

TOW ROUTES
Initially, three routes were considered from Ulsan, Korea to the Santa Barbara Channel (Figure 1). The northernmost route is a great circle passing near the Aleutian Islands. The middle route is a rhumbline at about 34.5 degrees north, and the southernmost route, designated "southern", passes near Hawaii. The initial towing strategy was to avoid the peak typhoon season, approximately July-November, necessitating a winter tow.
Site Location Survey for the Heritage Platform
Authors: Siciliano R.J. , Nordin J.K. , Irick J.T. , Grundmeier B.L. , Taylor S.L. 
Published: October 2008

ABSTRACT
This paper describes a geophysical and geotechnical site survey for the Heritage Platform to assess jacket levelness and water depth. Data were obtained from deep-tow seismic and cone penetrometer equipment which were positioned within the survey area through the use of an on-bottom network of medium frequency acoustic transponders. This allowed the high degree of seafloor mapping accuracy to be carried through to jacket placement. Upon set-down, the jacket was found to be well within the required levelness tolerance and in a water depth within one foot of the design specifications. This application demonstrates the accuracy with which the methods described in the paper can characterize the seafloor for engineering applications.

INTRODUCTION
The Heritage Platform was one of two jackets installed in 1989 as part of the Santa Ynez Unit Expansion Project. Harmony was installed in the Summer of that year in approximately 1200 feet of water. Heritage was installed in the Fall in about 1075 feet of water. The near surface soils in the vicinity of the Heritage location consist of a thin clay layer at the surface with thickness varying between 0 and 20 feet. This clay layer is commonly characterized as being seismically transparent since it is faintly recorded on high resolution sub-bottom profiler records. Immediately below the clay is a stratum of dense sand. This uppermost sand stratum extends to a depth of about 90 feet. Below that penetration, layers of stiff clay and silty clay, ten to twenty feet thick, alternate with other sand strata several tens of feet thick (1).
The top surface of the uppermost sand layer is cut by numerous channels formed by ancient turbidity flows. The thickness of the surficial clay varies with the presence or absence of these channels; being thin over high areas such as channel levees or interchannel highs and thicker where channels are present. The seafloor and the top surface of the sand slope to the southwest with a gradient of about 1 to 2 percent.
The bottom framing of the Heritage jacket was designed to match the slope of the seafloor as determined from regional bathymetry and sub-bottom profiler data obtained in the early 1980's. The mudmats were sized to penetrate through the soft surficial clay and bear on top of the dense sand just below. These early surveys indicated that the thickness of the clay and the seafloor slope were fairly constant over the area selected for jacket placement.
However, a detailed review of data from soil borings performed in 1984 and drop cores from a pipeline survey in 1988 indicated that the clay thickness was considerably more variable than originally thought. More variability in the clay layer thickness implied a more irregular bearing sand surface. This suggested the possibility that the jacket could exceed the levelness tolerance by as much as 1.4 degrees upon set-down on the seafloor. Correcting levelness after set-down would have been difficult because of the size of the jacket and stiffness of the sand layer.
Newest Experiences on Shielded Metal Arc Welding of Grade X-80 Pipes
Authors: Dittrich S. 
Published: October 2008

Abstract
A significant part of the future gas pipelines in Alaska and Canada will probably be constructed by using the new ultra high tensile steel X 80. This will be the first time that pipe materials of such high strength have to be welded under field conditions in a major project. The Arctic environment conditions will additionally be another challenge. This paper deals first with the weldability of the pipe material in conjunction with the use of cellulose and low hydrogen electrodes. Furthermore, all relevant welding procedures and combinations are discussed including vertical-up and vertical-down welding. The electrodes designed for these purposes are ready for use and proved by various test procedures. The actual results will be reported in this paper. The field welding experiences with low hydrogen downhill electrodes refer to a 2 mile demonstration line which has been constructed in South Germany in 1985.

Introduction
The transportation of gas over very long distances is the more efficient, the more of the original gas pressure can be maintained. This requires, at least for the first part of such lines, pipe materials with a higher yield and tensile strength than given by the present conventional API steel grades X 65 or X 70. The necessary steel development was taken up in the early eightees by several manufacturers in the world and can in the meantime be regarded as completed. The result of this development was the new line pipe steel X 80 with a minimum yield strength of 80 KSI and a minimum tensile strength of 90 KSI.
The first major use of X 80 is intended for the construction of the Yukon Pacific gas Line in Alaska as well as for the new Transit Gas Lines from the Yamal Peninsula in North Siberia to East and Central Europe. Besides these, several shorter X 80 lines are in planning to connect West and East Germany.

Weldability of X 80 Pipes
The question of weldability is mainly relevant for the optional use of cellulose electrodes which are generally characterized by a very high hydrogen input. From all field welding experiences gained so far it is wellknown that the most important objective is to guarantee a crackfree heat effected zone in the root pass area. This area is the most sensitive one because of the additional notch effect from inside of the pipe and the effect of pipe movements before the hot pass is fully completed. These two effects can result in the formation of root cracks, if the Carbon equivalent of the pipe material is too high or the preheating temperature too low.
Since the increased yield and tensile strength of the new steel X 80 is achieved only by a subsequent accelerated cooling after the thermo-mechanically controlled rolling process and not by a correspondingly increased Carbon equivalent, the weldability of this steel is on the same level as the thermo-mechanically treated steel X 70 which has in the meantime successfully been welded for more than 20 years.
The Brage Platform: A New Generation of Gravity-Base Structures
Authors: Helland K. , Kvalstad T.J. , Karlsen V. , Fjeld S. , Hermstad J.M. 
Published: October 2008

ABSTRACT
This paper describes the main features of the concrete gravity base platform designed for the Brage field in the Northern North Sea. This design concept encompasses several new design features. The traditional caisson is not used and the necessary strength and stiffness is provided by the base slab and skirts. The well conductors are guided outside the towers which are slimmer than previous concrete platforms. The global wave forces are thus reduced and the foundation can be simplified.
The platform can be installed over predrilled wells. Necessary skirt penetration is achieved and the soil strength improved by the application of suction under the skirts.
The paper describes the platform and the investigations conducted to substantiate its feasibility. It is shown that the large caisson, normally a prime element of gravity base structures, can be deleted for multishaft platforms and soft soil. Buoyancy in floating phases during construction is achieved by compressed air under the skirts. Main dimensions of the platform are governed by requirements of floatability during offshore tow and dynamic behaviour in operation rather than strength in operation. Thus a reduction in material quantities and construction time of about 40% is achieved. Towout without a heavy topside load is necessary to take full advantage of the platform concept.

INTRODUCTION
The majority of offshore concrete gravity structures has been of the so called caisson and tower type. This concept is composed of a deck supported by a number of towers projecting from a voluminous caisson. The caisson is a closed box with an upper and a lower level slab or assembly of domes. It is subdivided in cells by straight (Sea Tank, Andoc) or circular (Condeep) partition walls.
The caisson is used to serve three or four purposes:Act as structural element of adequate strength and stiffness to absorb the tower bending moments with acceptable deformations. The top and bottom slabs act as beam flanges and the partition walls as webs.Act as a foundation which transfers the functional and environmental forces on the platform to the subsoil with adequate safety. On soft soils the caisson will be fitted with skirts which penetrate down to soil layers of adequate bearing capacity.Act as a buoyancy volume in the temporary phases of floating construction, transportation and installation. Towout with the topsides installed is thereby possible.In many cases the caisson is used for temporary crude storage. Recent platforms in very soft soil e.g. Gullfaks C, have been fitted with very deep skirts, i.e. more than 20 m. Other platforms have been designed to obtain the necessary buoyancy from the volume of the towers alone, independent of the caisson. New offshore cranes of huge capacity can now be used to install the topsides and inshore deck mating is not a major asset.
For Norsk Hydro's 136 m deep Brage field in the Northern North Sea, several platform designs of traditional tower and caisson type were conceived.