bluuebunny/crossref_metadata_2025_split huggingface dataset:
Snorre B Hull: Design, Fabrication, Erection and Transportation.
Authors: Almeland Inge-Bertin , Pettersen Dag Juell 
Published: October 2008

Abstract
This paper gives a summary of the design basis and requirements of the Norwegian Field Development, Snorre B hull. It describes the fabrication of the hull at the Dragados Offshore yard in Spain, and highlights the critical and important features in the design. It describes the method used, the main elements in the hull and the shape of the final product. The paper includes a description of the fabrication sequence, load out, launching and towing to Norway. Experiences gained during fabrication will be discussed and summarised. A full description of the fabricated sections will be performed and this will be visualised with photos and drawings from the yard.

Description of the Floater
The Snorre B platform is a floating drilling and production unit (SSPV) consisting of a steel hull and deck structure. The hull consists of four "square rounded" columns supporting the deck. The columns are connected in the corners at the ring pontoon, which is rectangular in shape.
The deck structure has two main truss-lines in both the transverse and longitudinal directions. In addition to these trusses, there are also two major transverse bulkheads. Each corner of the deck consists of a "rounded square" box. There is a main deck and a cellar deck including a double bottom structure. Fig. 1 shows the floater, hull and deck.
Fig. 1. Snorre B deck and hull

Design
Most of the design work for Snorre B was initiated in 1998. Key factors accounted for in the structural design basis are:Regulatory requirementsEnvironmental CriteriaSafety ConsiderationsFunctional and Operational Requirements

Design criteria
Snorre B is designed for a 100 years storm condition for the location in the North Sea at a water depth of 350 metres. The extreme significant wave height for the area is 15.5 metres ULS, respectively 18 metres PLS. This is combined with a storm wind of 41 m/s. The design has an allowance as shown below:Margins: Mai 1999 August 2001Company: 3,000 tonnes 1,570 tonnesContractor: 1,850 tonnes 1,170 tonnesThe design life is 20 years. Factors are used for the fatigue life calculations.Outside hull below Splash zone: 2Splash zone: 3Above Splash zone: 1Inside hull: 1 and 2Deck general: 1Critical areas not possible to inspect: 10
The deck shall accommodate both drilling (RAM RIG), production equipment and aluminium living quarters.
Snorre B has 16 anchor lines which combine wire and 145 / 137 mm chain. These are connected to suction anchors.

Regulatory Requirements
Based upon experience gained from more recent platform development in the North Sea, design criteria and rules were established for the structural design.
Det Norske Veritas Rules for Mobile Offshore Units (DNV MOU) including supplementary requirements of Norwegian Petroleum Directorate / Norwegian Maritime Directorate and NORSOK, among other, were used as basis for design.
A Practical Procedure for the Evaluation of the Roll Motions of FPSO's Including the Non potential Damping
Authors: Orozco J.M. , Raposo C.V. , Malenica Š. 
Published: October 2008

Abstract
Nowadays, deep-waters are the new frontier of the latest huge oil discovers. The most common technology for oil exploration in deep waters is based on the FPSO concept. Therefore, a key element for a successful exploration of deepwater oil fields is the accurate prediction of the unit motions in order to minimize the stop production due to excessive motions and maximum accelerations to which the process plant equipment and supports are subjected.
The excessive motions of a FPSO can be caused not only due to rough weather but also due to mild weather at beam sea conditions. Beam sea conditions are faced by FPSOs in a spreading mooring configuration or even in single point mooring configuration but moored in regions where the swell sea is important, for instance, in Campos Basin offshore Brazil. In such cases, the accurate evaluation of roll motions is of prime importance. Moreover, in order to reach valuable results, a critical step is the proper evaluation of the different damping effects in particular viscous damping induced by the bilge keel, or those of risers.
The state of the art assumption is that the roll damping is composed of two parts: the linear one and the quadratic one. The former accounts for the potential wave radiation and partly to some frictional effects, while the latter accounts for drag forces, flow separation, and other non-linear effects. In practice, the linear part can usually be neglected and the only remaining damping is the quadratic part. These fact strengths the role played by the non-potential damping in a reliable evaluation of the roll motion amplitude.
In this paper, we will show the implementation of a practical procedure for the evaluation of the roll motions including the non-potential damping of a FPSO moored in a spreading configuration at Campos Basin and its validation through the comparison of the numerical results to the model tests.

Introduction
Compared to the other modes of motion, the evaluation of the roll motion appears to be much more complicated and the corresponding results more uncertain. The reasons for that are mainly related to the evaluation of the roll damping coefficient, which is usually dominated by the non-potential sources of damping. The usual procedure for calculation of the ship motions is the use of the so-called diffraction-radiation software based on the potential flow theory. The damping calculated by this kind of codes is linear and related to the wave making. As far as the linear theory is concerned the horizontal modes of motion (surge, sway, yaw) are usually out of resonance in the common sea conditions (periods of 5 to 25 seconds). In those cases the role of damping is not very important so that the potential flow theory evaluate correctly the (linear) amplitudes of these motions. The only modes of motion that may enter in the (linear) resonance are vertical modes (heave, pitch and roll) and for these motions the role of the damping is essential.
Laboratory Study of Used HMPE MODU Mooring Lines
Authors: Berryman C.T. , Dupin R.M. , Gerrits N.S. 
Published: October 2008

Abstract
Test results of residual properties of two 12-m HMPE synthetic fibre tether inserts individually used at four and eight deepwater wells respectively in up to 2,049 m water depths are presented against new tether test data and operational loading history. The paper concludes by demonstrating negligible changes in performance from new unused synthetic fibre rope and provides design engineers with new performance data.

Introduction
In May 2000 Unocal Indonesia, Transocean Sedco Forex, Marlow Ropes and DSM High Performance Fibres set an industry first by successfully utilising High Modulus Polyethylene (HMPE) synthetic fibre rope to moor a MODU (Mobile Offshore Drilling Unit) in 2,049 m. The HMPE fibre rope moorings were used at eight well locations in water depths ranging from 1,219 m to 2,049 m.
After completion of the eight-well drilling program two 12-m in-series inserts were recovered for laboratory evaluation. This aimed to assess the residual properties and remaining service life of the HMPE ropes and compare the data to new tether data and prediction tools used in the design of new mooring tethers. The evaluation included residual strength, residual tension-torque fatigue performance of the HMPE tether loaded in line with a conventional 6-strand wire, microscopic analysis, residual creep characteristics and visual inspection. Properties such as elongation, stiffness, rotation, internal condition and the residual strength of both the HMPE tether and the wire after completion of the fatigue test were evaluated.

History of Use
In the spring of 1999 Unocal Indonesia began planning an eight to ten well deepwater exploration drilling program in 1,676 m to 1,981 m water depths offshore East Kalimantan in the Makassar Strait. At that time Unocal's surface stack drilling capability from the Sedco 601 semi-submersible drilling rig was limited to water depths of about 1,524 m with a conventional wire-chain mooring system. To drill in deeper water required introducing a component that reduced the dead weight of the mooring system, yet was easily installed with local anchor handling vessels (AHVs). After evaluating several options, Unocal Indonesia contracted with Marlow Ropes and DSM High Performance Fibres for constructing ten 914-m long Superline Steelite Xtra Dyneema fibre ropes with a 3502 kN minimum spliced breaking load. The fibre ropes were used at eight well locations between November 1999 and June 2000.
Given that the moorings would be non-torque balanced, it was decided to limit the fibre rope use to an eight to ten well drilling program, or not exceeding a period of one year's use. Two 12-m long fibre rope inserts were placed into the mooring systems for testing at the end of the drilling program.
Figure 1 shows a general schematic of a mooring leg and the positions of the HMPE rope and test insert. The HMPE ropes were inserted between the rig's 6-strand wire and a pre-installed (pre-laid) wire-chain mooring system consisting of 6-strand steel wire rope and chain.
Redefining the Static Gel Strength Requirements for Cements Employed in SWF Mitigation
Authors: Mueller Dan T. 
Published: October 2008

Abstract
The decay of hydrostatic pressure due to gel strength development of a static cement results in a pressure underbalanced condition, which can initiate shallow water flow. By determining the static gel strength history verses time relationship of a cement slurry and calculating the annular pressure loss as a function of that static gel strength, the point in time when the pore pressure of the shallow water flow interval exceeds the annular hydrostatic pressure of the gelled cement and sea water can be predicted.

Introduction
Shallow water flow (SWF) is the most feared of the geohazards associated with deepwater drilling. Normally encountered in the upper 2,500 ft of a deepwater well, SWF occurs when over-pressured, low-shear strength sands are drilled while the wellbore is in an underbalanced state. SWF is a slurry of water and sand, which if sufficiently pressured, flows up the wellbore to the sea floor. Once initiated, SWF's are capable of impacting well construction in any number of ways including:The deposition of large amounts of sediment around the wellhead to a point at which re-entering the wellbore becomes problematic;The abrasive force of the SWF eroding the sediment at the formation-cement sheath interface to produce a flow conduit back to the mudline, even at considerable depths below mudline;The SWF removing a sufficient volume of formation to produce a near-wellbore subsidence which can shear the casing;The SWF producing an annular washout which induces buckling of the casing due to lack of lateral support.
The tophole section of a deepwater well may contain several individual sand bodies each with its own flow potential. Above the individual sand body is usually a low-permeability, clay-rich section. The clay interval serves as an impermeable boundary, which prohibits the pressure within the sand body from equilibrating with its surroundings. A typical SWF sand is 10 to 50 ft in thickness, has a permeability in the range of 1 ? 10 Darcies and a porosity in excess of 40%. Shallow water flow has been experienced in the North Sea, Trinidad, Norwegian Sea, Caspian Sea, the Gulf of Mexico1 and West Africa.
It is important to note that SWF sands differ markedly in physical properties from the more familiar reservoir rocks. The sands are considered to be in transition between unconsolidated sediment and rock.2 The semi-solid nature of the sediments encountered in the tophole section is demonstrated during the drilling process: a rate of penetration (ROP) of 150 to 300 ft/hr is common. In fact, the biggest drilling challenge in the tophole section is not ROP, but solids/gumbo removal.

Flow Mechanism
The metastable nature of the sands found in the tophole section is the key to understanding why the sands flow. Huffman and Castagna propose two possible mechanisms:3 First, is that the sands are already in an initial stage of failure, and the dynamic load imparted by drilling is sufficient to initiate flow.
Bonga: Oil Off-loading System using Flexible Pipe
Authors: Lebon L. , Remery J. 
Published: October 2008

Abstract
A number of large deep water oil fields offshore West Africa are developed on the basis of a large spread moored FPSO with a CALM buoy located at a safe distance to allow tankers to moor alongside for oil off-loading operations. For the transport of the stabilized oil from the FPSO to the CALM buoy, the proposed base case for a number of fields has been to use large diameter steel pipe hung between the two floaters. Design experience has however shown that the fatigue life of such an off-loading line is extremely critical and as such negatively influences the reliability of the system.
By adapting the configuration and/or using flexible pipe instead of rigid steel pipe, the fatigue life can be significantly increased. A different configuration can reduce the loads in the pipe and a flexible pipe, by its inherent compliance, is significantly less sensitive to curvature variations and will thus have a longer fatigue life than a rigid steel pipe.
After a general overview of the impact of different design choices on the total solution and the feasibility of flexible pipe oil off-loading systems, this paper presents in details the flexible pipe system that has been chosen for Shell's Bonga field offshore Nigeria. It addresses the main phases of design: namely, the flow aspects that dictate the number of lines and the operating pressures, the mechanical and hydrodynamic aspects that determine the structural integrity and the fatigue life and also the installation operations.

1 INTRODUCTION
For a number of Ultra Deep Water fields West of Africa the export of oil is performed by tanker. However as the FPSO is spread moored it is not practical for the tanker to unload directly from the FPSO barge. Therefore a separate offloading buoy situated approximately 1 nautical mile from the FPSO is used for this purpose. The export of the stabilised oil is typically achieved through a subsurface partially buoyant line. The line is given buoyancy in it's middle section to obtain a wave shape and as such provide a certain amount of flexibility to accommodate relative motions of the off-loading buoy and the FPSO.
Design experience in the industry has shown that fatigue is a real problem for rigid steel pipe oil off-loading systems and that to achieve the specified fatigue life special mitigating measures are often required (double flex-joints, thick steel forgings for offshore welds and VIV suppression strakes) (ref. 1 and 3). These specific items are not required when flexible pipe is used, which is therefore considered a good alternative as is illustrated in this paper.

2 INFLUENCE OF THE MAIN DESIGN PHASES OF AN OIL OFF-LOADING SYSTEM

2.1 Flow Aspects.
To optimise the design of an oil offloading system, thus to maximise the flowrate, the following parameters need to be considered :Pressure drop allowable along the lines (inlet pressure and requested outlet pressure)Diameter and type of line (internal roughness) of the linesNumber of lines
This section describes how these parameters influence the design and show how optimisation is possible.
Reelability of Steel Bulkheads for Pipe-in-Pipe
Authors: Giacomelli Yvan , Bell Mike 
Published: October 2008

Abstract
Technip-Coflexip has recently developed a technical solution to allow the reeling of a pipe-in-pipe bulkhead. The reeling of bulkheads compared to welding bulkheads into the pipe-inpipe offshore will save a significant amount of offshore time. The design is presented, fabrication procedures are discussed and the results of optimization work by Finite Element analysis utilizing ABAQUS£ are included. Results from fullscale reeling trials of bulkheads on the CSO Apache reelship are also presented, proving the feasibility of this design reelable steel bulkhead design.

Introduction
Steel bulkheads can be included within pipe-in-pipe systems primarily to allow load transfers between the outer and inner pipes during installation and in-service. In addition, the use of pipe-in-pipe in deepwater necessitates an effective repair strategy in the event of a wet or propagating buckle. As bulkheads combine the functions of a buckle arrestor and a waterstop, their installation at regular intervals along the pipeline would allow the replacement of any defective section between bulkheads (Reference 1).
Reel-lay provides clients with a cost effective installation method and high quality installed pipeline. The inclusion of bulkheads during the onshore fabrication procedure of a pipein-pipe system requires a conventional bulkhead design to be further developed in order to achieve a fast assembly and remove the need for half shells. The design, construction and testing of a pipe-in-pipe including an innovative modular bulkhead based on a combination of threaded parts is therefore described. The assessment of the bulkhead behavior during the reeling process and under various loading conditions was carried out by Finite Element Analysis. This theoretical work was validated by a full-scale prototype test performed on the CSO Apache reel-lay vessel and the results are presented hereinafter.

Innovative Design
For the reel lay method individual stalks of pipe-in-pipe up to approximately 5000ft in length are prefabricated on the designated spoolbase prior to vessel arrival. The flowline and carrier pipes are fabricated separately before the flowline systematically inserted into the carrier while spacers and insulation are applied (Reference 2). On arrival of the pipelay vessel the first stalk is spooled onto the reel preceded by a lead string. Each subsequent stalk is connected to the previous by two tie-in welds. First the flowline ends are brought together and welded. Then the carrier pipe of the trailing stalk is slid over the flowline to close the gap for the second weld.
Bulkhead spacing will be dependent on the project requirements. Stalk lengths can be modified to allow the insertion of bulkheads in the pipe-in-pipe assembly during tie in operations. The inclusion of a classical one piece forged mid-line bulkhead in such a fabrication procedure will require the use of half shells. Figure 3 describes a step-by-step assembly of a forged bulkhead at the tie-in station.
Performance Comparisons Of Scuba Divers Vs Submersible Manipulator Controllers In Undersea Work
Authors: Pesch Alan J. , Hill Robert G. , Klepser William F. 
Published: October 2008

ABSTRACT
The basic problem to which this research program is devoted is the current inability of ocean engineering personnel to design undersea hardware systems which complement the capabilities of the human operator. This problem Stems largely from a lack of quantitative research data on the relative shortcomings and strong points of divers and a similar lack of data describing the capabilities of various underseamanipulator work systems. The research has been oriented toward quantitative data collection which describes how rapidly, how proficiently, and under what circumstances an operator can or cannot perform tasks of what difficulty, both as a diver and as a manipulator operator aboard a submersible. The results are presented in the form of a ratio of performance time for the diver versus a manipulator. The conclusions of this research are based on data collected in a wet simulation facility. The tasks range from simple tasks such as sample gathering, valve turning and hooking to tasks of increasing difficulty such as cable rigging, unbolting, Hansen connect/disconnect functions, hole drilling, hole tapping, and pipe threading. The overall ratio for all tasks studied was 1/4; e.g., a diver was four times faster than a rate-controlled manipulator. More importantly, depending on the task, this ratio changed drastically. For example, the tapping of holes in 1/2inch aluminum plate was performed equally fast by the diver and the manipulator (1/1); however, the diver frequently broke taps. Another task required the connecting and disconnecting of a 1/2-inch Hansen quick-disconnect fitting which the diver performed 31 times faster than the manipulator.
The diver also-always ensured that the connection was securely made. Conclusions are presented in this article in terms of which tasks and task aspects contributed most to the observed positive or negative performance of divers and manipulator operators.(This work was sponsored by the Office of Naval Research under Contract NOOO14-69-C-0 I 68, NR196090/11-27-68 (455).)

INTRODUCTION
A major consideration in the development, operation, and maintenance of subsurface installations is the type of implementation methodology selected to perform the work. Examples include surface-controlled rigging, a direct diver deployed in any of serveral configurations, and submersibles equipped with manipulators.
Experience with the performance capacities of these methodologies varies from a great deal of experience in surface-controlled rigging to somewhat less experience in the diver area, to marginal experience with submersible manipulator systems. A selection from among these approaches would consider many variables, including depth, environment, cost, and personnel. The objective of our research is to improve the level of experience and, therefore, to increase the information available for decision making on one of these variables - performance ability of the operator.