bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measured Dynamic Behavior of North Sea Jacket Platforms
Authors: Langen I. , Spidscbe N. , Bruce R.L. , Heavner J.W. 
Published: October 2008

ABSTRACT
The paper presents results from analyses of full scale measurements of the dynamic response of two steel jacket platforms in the North Sea.
The measurements discussed in the paper were, for both platforms, recorded in extreme environmental conditions.
The main emphasis is on describing the structural system behavior, on the composition of the dynamic response and on the evaluation and characterization of the environmental loading mechanisms.
It is found that the stress response is mainly wave induced and quasi-static. The quasi-static response is non-Gaussian and consistent with theoretical predictions based on Morison-type wave loading. Several other non-linear wave load effects are also apparent. The structural system is close to linear in stiffness and mass. The resonant response is, however, non-Gaussian due to nonlinear damping mechanisms.
The paper discusses also the implications which the observed non-linear wave loading and structural damping may have for potential deep water jackets.

INTRODUCTION
In compliance with the requirements of the Norwegian Petroleum Directorate seven fixed platforms in the Norwegian sector of the North Sea have been instrumented for collection of environmental data and platform performance data (E- and P- data). The main purpose of the collection and analyses of this data is "through a check of the design assumptions and platform behavior, to be able to assess the safety of the load carrying structure and foundation in the production phase". An additional purpose is to gain experience with operative platforms that may be useful when considering new platform concepts
The data collection programmes which lasted for periods of two to three years have created a valuable data base for analysis and research on platform behavior in different environmental conditions.
This paper describes the dynamic behavior of two steel jacket platforms in both moderate and extreme environmental conditions, as evaluated from the full scale measurements. Similar results for gravity structures and an articulated tower have been presented in ref. /1/ and /2/.
The main emphasis of this paper is on the description of the behavior of the structural system including the soil-structure interaction, on the composition and nature of the dynamic response and on characterization of the waves and the hydrodynamic loading.
Furthermore, the nature of the observed behavior is compared with theoretical models of the platform behavior arising from the commonly used design assumptions.

DESCRIPTION OF THE PLATFORMS
The two platforms dealt with are Ekofisk 2/4H and Valhall QP. Sketches of the platforms are given in Figure 1.
Both platforms are four legged quarters platforms situated in approximately 70 metres water depth. Ekofisk 2/4H is K- braced with single corner piles while Valhall QP is X-braced with double corner piles. Both platforms are connected to other platforms with bridges.
A Project Management Approach to Design andConstruction of a New Generation Arctic Drilling System
Authors: Loh J.K.S. 
Published: October 2008

ABSTRACT
A second generation drilling system for the Arctic offshore has been designed and constructed by Gulf Canada Resources Inc. This paper describes the decision process that resulted in the implementation of project management approach to the undertaking. A brief description of the organizational structure and control mechanisms used are presented.

INTRODUCTION
Gulf Canada Resources Inc. formed a new operating division within its Frontier Department in July, 1981, to take on the task of constructing and putting into operation a new generation Arctic drilling system. The decision to invest $674 million Canadian on the new system was driven by the fact that there was not enough equipment in the Canadian Arctic to adequately explore the vast potential of hydrocarbon reserves in the offshore areas; and that a new technology was needed to extend the drilling season in the harsh ice-covered environment.
The dri11ing fleet, commonly known as the Beaufort Sea Drilling System, consists of:Conical Drilling Unit - a near-circular hull semi-submersible drilling unit moored on location with 12 anchors.Mobile Arctic Caisson - an integrated bottom-founded steel caisson structure.Two Ice Class IV Supply Vessels, also used for towing, anchor handling and ice management.Two Ice Class IV Arctic Ice-breakers.Northern operations bases.Logistic and support sys terns 1inking the bases to the drilling sites.
With the exception of Mobile Arctic Caisson, the system went into operation in the Canadian Beaufort Sea in the summer of 1983, on time and under budget. The caisson is scheduled to be delivered in the summer of 1984. When the caisson is delivered, a capital project of main magnitude, managed by a company that departed from traditional approaches will have been successfully executed. The most important factor that resulted in this success was the implementation of project management approach to the undertaking from start to finish.

PROJECT IDENTIFICATION
In the initial stages of the project identification, management must first set precise objectives, and, then rigorously assess the company's internal capabi1ities to determine whether or not the objectives can be .met. At the same time, external environment, such as government regulations and market demand, must also be evaluated.
In the industrial sector, project objectives are generally to either add new income generating assets, or to offer improved products at competitive prices. It is a complex process to match available internal resources to such objectives. Common sense must prevail, so that the objective can be accomplished without negative impact on other company interests.
In the case of Beau fort Sea Dri11ing Sys tern, Gulf Canada Resources began by assessing dri11ing systems then available on the world-wide market to determine whether or not equipment existed that would satisfy our specific requirements in the Arctic offshore.
The Iwaki Platform in Japan: The Influence of Severe Earthquakes
Authors: Wardell J.B. , Fry R.K. 
Published: October 2008

ABSTRACT
The Iwaki platform-was recently installed in 154 meters of water for developing the Iwaki Gas Field in Japan. The platform is located 40 kilometers off the east coast of northern Honshu, about 250 kilometers northeast of Tokyo, in an area known for severe earthquakes. The design and construction of the platform were dominated by earthquake motion considerations.

INTRODUCTION
The Iwaki platform is the major-component of the Iwaki Gas Development Project. Field operator for the project is Offshore Iwaki Petroleum Co., an affiliate of Teikoku Oil Co. Its partners are East Japan Oil Development 'Co. and Esso Production Japan (EPJ), an Exxon Corporation-affiliate. EPJ is the acting field operator for the planning, engineering, and construction phases of the project.
Planning and engineering design of the platform began in 1978 by Exxon Production Research Co. (EPR). A conventional design concept was developed (Figure 1). The 15000 mt launched jacket is secured to the seafloor with eight 1829 mm (72 in.) main piles and sixteen 2134 mm (84 in.) skirt piles. The module support frame (MSF), which weighs about 1100 mt, is positioned on top of the main piles and supports the modularized deck. The deck consists of nine major module units plus a unique drilling rig, two platform cranes, and various smaller packages.
Topside facilities of the platform are designed for drilling and producing from up to 24 wells. The facilities were designed to handle a production rate of about 2.1 million cubic meters of gas per day. The gas will be dehydrated on the platform and then transported to shore through a 305 mm diameter pipeline. Following processing at an onshore plant, the gas will be delivered to Tokyo Electric Co. 's Hirono power plant.
Platform fabrication was initiated in mid-1981, and offshore installation was completed by year-end 1983. Virtually all construction engineering and land-based fabrication activities were contracted to various Japanese companies, and the offshore installation was contracted to Heerema Marine Contractors (HMC). Numerous aspects of the project were influenced by the consideration of severe earthquake motions.

EARTHQUAKE ENVIRONMENT
Iwaki is the first offshore platform located off the Pacific coast of Japan. It is in an area known for extremely severe earthquakes. Extensive site-specific studies were conducted to develop two distinct design criteria for the platform-strength level and ductility level criteria. The strength level event has a recurrence interval of approximately 200 years, and the recurrence interval of the ductility level event is several thousand years. The ductility level event is generally representative of an earthquake of Richter magnitude 8.0 that occurs at a distance of 42 kilometers from the platform. The shaking associated with the ductility level earthquake may possibly cause liquefaction of the upper portion of the soil hence soil liquefaction was accounted for in the design.
Ore Assays of Massive Sulfides From Three Spreading Centers
Authors: Morgan C.L. , Selk Bruce W. 
Published: October 2008

ABSTRACT
Ocean Minerals Company (OMCO), a deep seabed mining consortium has, through its general contractor, Lockheed Advanced Marine Systems, analyzed massive marine sulfide samples from three sites on the Juan de Fuca Ridge, one site on the East Pacific Rise (near 2PN), and one site on the Galapagos Rift, for the concentrations of Ca, Mn, Fe, Co, Ni, Cu, Zn, Ag, Cd and Pb. The samples were collected with dredges and submersibles, and were generously provided to OMCO by government and academic investigators. It is possible that marine sulfides may be a future commercial source of Cu, Ag, Zn and other metals and those studies of these young, relatively unaltered deposits will also provide useful guidelines for the location of unexplored and commercially viable land deposits of marine origin. OMCO has supported this comparative study of the major and minor element composition of sulfides from these three medium-rate spreading centers to obtain a preliminary estimate of ore grade variability and to identify likely sites for future exploration.
From the samples analyzed to date, it appears that there are significant differences among the sulfide compositions characteristic of each spreading center. The samples from the Juan de Fuca Ridge are all Zn-rich (maximum concentration greater than 50%) with significant concentrations of Ag (6–12.5 Tr. oz/metric ton). The 21°N East Pacific Rise samples are either Zn-rich or Cu-rich, but have lower Ag concentrations than the Juan de Fuca Ridge samples. Samples from the Galapagos Rift are Cu-rich and Fe-rich. Silver concentrations in these samples appear to be inversely correlated with water depth. Though the high metal values obtained are encouraging and clearly justify the continued support of the several U.S. projects which are presently investigating such deposits worldwide, much additional information is needed to justify serious commercial interest. The distinct compositional differences noted between spreading centers may well be regional in character, and may imply basic differences in the source rock, the development of the hydrothermal fluid, or the deposition process.

INTRODUCTION
Sixteen samples of marine massive sulfide deposits were recently provided to Ocean Minerals Company (OMCO) by academic and U.S. Government researchers for preliminary ore assay analysis. These samples have been subsampled and analyzed by Lockheed for Ca, Mn, Fe, Co, Ni, Cu, Zn, Ag, Cd and Pb using atomic absorption techniques. The samples were collected from very young hydrothermal deposits at five sites; three on the Juan de Fuca Ridge (the Endeavor segment, the Axial seamount, and the southern Juan de Fuca Ridge), one from the East Pacific Rise at 21°N and one from the Galapagos Rift at 86°W. The samples were collected by both dredges and manned submersibles. The purpose of this paper is to report the results of these preliminary analyses. Since identical methods were used in the analysis of all samples, the data set provides a good means of comparison of deposits from different locations.
Articulated Riser for Subsea Production System (SPS)
Authors: Nakamura S. , Sasaki M. , Kuwabara K.I. 
Published: October 2008

ABSTRACT
An articulated riser having three universal joints to give high flexibility for a floating storage and production platform has been developed. All pipes in the riser including those for the through flow line (TFL) services, are not flexible pipe but are made of steel. Pipe swivels are applied to accommodate the articulation of the universal joints.
This riser can be disconnected at the upper and lower ends and retrieved for periodic maintenance. The installation method for the riser, the underwater positioning system for installation, and the guiding mechanism to mate with the riser base have also been developed and verified at sea tests. Finally, during the offshore pilot test of SPS, the riser functioned effectively with no leakage at any part of the pipe lines.

INTRODUCTION
A Japanese National R&D project to develop "Subsea Production System (SPS)" was started by the Agency of Industrial Science and Technology, under the Ministry of International Trade and Industry (MITI), in September 1978 and was completed at the end of 1984.
The overview of the project is reported in another Paper, OTC 4963.
This project proceeded separately as a total system and four subsystems, Le. wellheads, pipelines, manifold and riser-storage systems.
Finally, the equipment manufactured based on the results of the development in each subsystem were installed on the seabed and connected to each other. After that, type offshore pilot test was carried out using a simulation well in 1983.
Production conditions for the riser-storage A Japanese National R&D project to develop "Subsea Production System (SPS)" was started by the Agency of Industrial Science and Technology, under the Ministry of International Trade and Industry (MITI), in September 1978 and was completed at the end of 1984.
The environmental and the basic requirements Finally, the equipment manufactured based on the results of the development in each subsystem were installed on the seabed and connected to each other. After that, type offshore pilot test was carried system were Requirements installation tools. provided by the total system group. included guide lineless, driverless and maintenance and work over by TFL tools.
The riser-storage system is roughly divided in two parts lone is the floating storage tank which carries the production treatment plant and the offloading equipment to the shuttle tankers.
The other is the riser connecting the storage tank and the equipment on the seabed.
A monocolumn, cylindrical, semi-submersible storage tank moored by multiple catenary anchor lines was selected. The produced crude is stored in the tank compartments replacing sea water and is offloaded by being replaced with sea water. On the deck above the storage tank, the treatment plant and the other necessary equipment are installed. The shuttle tankers are moored directly to the storage tank to offload the crude.
Wave and Motion Measurements on Board the Semisubmersible Pipelaying Barge LB-200
Authors: Weyers L.J. , Vlaming M. , Verdonck J. 
Published: October 2008

ABSTRACT
For a barge laying pipe under rough weather conditions at sea, pitch, roll, heave, surge, sway and yaw are important phenomena to be known and monitored. It is of vital importance that the static and dynamic stresses in the pipe are kept within prescribed limits. The static bending stress in the pipe at the upper bend, on the stinger, and at the lower bend, near the sea bottom touch point, are highly dependent on the deformation of the pipe. The horizontal tension of the barge mooring lines will effect the static pipe deflection. However pipe deflection does not depend only upon static forces. Dynamic forces caused by dynamic barge motions add an important part to the stresses in upper and lower pipe bends. Too much stress will cause pipe buckling in the bends and results in much delay time and costs as the pipe, already at the sea bottom, will have to be replaced. Usually extensive calculations and model studies are performed in an early stage of the pipe lay project.
This paper gives a general description of the barge motion measuring system used on board of the pipelaying barge LB-200 owned by HcDermott International Inc., North Sea Division. In the Norwegian sector of the North Sea the LB-ZOO was contracted for the Statpipe Development Project requiring more than 300 miles of pipelines, which will bring gas from offshore fields to Norway. One of these rich sources is the Statfjord field, where oil as well as gas has been found. In 1983 the LB-ZOO layed the pipeline to shore at Karmoy Island and went on to lay 125 miles of 28-inch-diameter line to block 16/11, crossing the Norwegian Trench in water 300 m deep. Lay rates of 2.3 miles a day were made in the western slope of the trench toward Karmoy.
All motions of the barge i.e. pitch, roll, heave, surge, sway and yaw had to be monitored continuously. The pipe had to be disconnected once those movements reached a certain magnitude due to weather circumstances. Another condition was that an historical record of all movements mentioned had to be kept on file.
This paper describes the realization of the motion monitoring system. The following demands had to be fulfilled:automatic computer controlthe least possible maintenanceonline continuous monitoringcontinuous filing

INTRODUCTION
The lay barge LB-200 is roughly 160 m long and it has a width of 60 m. The deck is supported by six columns placed on two pontoons. Fig. 1 gives an overall view. A twelve mooring line system keeps the barge in position. Pitch motions are important for pipe laying because of the danger of pipe buckling. Plus or minus two degrees of pitch motion was set as the limit during operations. Beyond this limit operations were stopped.
Ice Forces Exerted on a Conical Structure in the Gulf of Bothnia
Authors: Maattanen M.P. , Mustamaki E.O. 
Published: October 2008

ABSTRACT
A joint Finnish consortium of industry and state research organizations has designed, constructed and instrumented a conical test structure for full-scale measurements of ice forces against a conical fixed off-shore structure. The structure and its instrumentation are described. The test cone was installed around the existing Kemi-I lighthouse in the Gulf of Bothnia.
Field measurements have started. The intention is to measure the action of all typical first-year ice features, including pressure ridges, with an average sheet ice thickness of 0.8 m. Model tests with a scale ratio of 1:15 have been conducted and the results are described. Theoretical models of ice forces against a cone will be calibrated using both the model and full-scale test data. This will provide a reliable basis for extending ice force predictions to arctic conditions, where the ice is about 2 to 3 times as thick as in the Gulf of Bothnia.

INTRODUCTION
The advantage of a conical shape at the waterline of an off-shore structure is that the failure mode of level ice is flexural, which greatly reduces ice loads compared to crushing against a vertical structure. Both horizontal and vertical ice force components develop and the latter has a stabilizing effect, which is important in deep water applications. The underwater part of the structure can then be narrower, which also results in reduction of loads from pressure ridges. At water depths greater than 30 m the cone is regarded as the most economical choice for a fixed bottom-founded structure.
The concept of the cone has been well known for more than 20 years. There are many theoretical models /1, 4, 5/ for predicting ice forces against a cone and model test results as well /3, 5, 6/. However, no full-scale field ice force data are available to evaluate theoretical models. Only tentative results have been published for a cone with a 1.5-m'waterline diameter in the St. Lawrence Seaway /2/.
Theoretical models of the ice forces exerted against a cone take account of the formation of radial and circumferential cracks in the oncoming ice sheet, friction between the ice and the structure, the work required to raise broken ice floes up along the cone and for them to be pushed aside. Some models have been evaluated in model tests but due to the large scale ratios, there are many uncertainties in the prediction of ice forces for full-scale arctic off-shore structures.
The objectives of this research are to acquire data for evaluating theoretical models of ice forces against a cone. The test cone around Kemi-I lighthouse in the Gulf of Bothnia will provide full-scale measurements of the ice forces against a conical structure with level ice up to 1 m thick and with first-year pressure ridges and rafted ice.
Dip Moveout And Prestack Imaging
Authors: Gerlad H.F. , Wang S.Y. , Pan N.D. , Zhang Z. 
Published: October 2008

ABSTRACT
Dip moveout is presented as a data conditioning process in which a diffraction surface in midpoint-offset-time space is transformed into a surface of revolution. Pre-stack imaging operates on constant-time slices of the data, after dip moveout has been applied, in which diffractions appear as circles, adds data along these circles, and plots the sum at the largest offset point of each circle. After both operations, a standard velocity analysis and stacking algorithm produces a migrated section. Both operations are independent of velocity.

INTRODUCTION
Two problems commonly associated with CDP stacking are (1) a loss of resolution because the reflection point moves updip as the offset increases and (2) the stacking velocity depends on the dip angle of the reflector. The first problem is particularly severe if the reflection point moves across a fault as it moves updip, as indicated in Figure 1. The second problem means that stacking velocities are not appropriate for migration after stack.
Dip moveout (DMO) helps with both problems, as first explained by Judson et al. (1976). There is less loss of resolution because the gathers, after DMO, have events with common reflection points. Also, the stacking velocity is not so dependent on the angle of dip and is more useful for selecting velocities to migrate the data after stack. However, the stacking velocity is estimated at the slant travel time T2 and not at the vertical travel time To, as one would wish.
DMO can be followed by another processing step called pre-stack imaging (PSI). After PSI, the data are migrated but not yet stacked. In other words, gathers formed after DMO and PSI have been applied can be stacked using a standard velocity analysis and stack program. In this case, there is no loss of resolution, the stacking velocity gives the root-mean-square velocity at time To, and the stacked traces are fully migrated.
Both DMO and PSI are independent of velocity. The processes do not have to be repeated if the velocity is changed. The selection of velocity is made at the last step when the migrated traces are being stacked. Thus the velocity analysis may be more robust because the traces used in the analysis have a better signal to noise ratio.
This paper gives an overview of both processes and illustrates the algorithms by showing how a diffraction in multi-fold data is summed and plotted at a point.

THREE-STEP PRE-STACK MIGRATION
The first step is DMO. Viewing a 2D multi-fold line as a three-dimensional space with axes m (the midpoint coordinate), h (half the offset), and t (time), as shown in Figure 2, we can see that DMO operates on vertical sections with constant h. The original data cube is transformed into a new cube by processing the constant-offset sections one by one.