bluuebunny/crossref_metadata_2025_split huggingface dataset:
A New Display Technique for Surveying Sonar Data
Authors: Wood K.E. , O&apos;Farrell J.T. 
Published: October 2008

ABSTRACT
A new display technique has been developed to improve the display capability of 'side-:look sonars used for surveying purposes. The sonar data are displayed in real time as a standard TV pictures which moves across the screen to simulate motion of the sonar over the bottom. The display uses a magnetic video disc in conjunction with digital processing logic to provide a system which is much more rugged and reliable than previous electroniscan converters.
Because seawater is almost opaque to electromagnetic propagation, high-resolution side-look sonar (SLS) has become one of, the primary methods used for undersea searching and for large-area ocean bottom surveying. Sonic energy can penetrate seawater effectively, but its speed of propagation is relatively slow-about 5000 ft/sec. Therefore, the time required for an echo signal from the sonar transmit pulse (about 65 milliseconds for a target 160 feet from the transmitter) dictates a sonar pulse repetition frequency (PRF) much lower than the human eye flicker frequency.
Since scan conversion to a more rapid refresh display for direct viewing adds complexity to the system, the conventional method for imaging slow-scan sonar data has been the paper recorder. Sonar returns (converted to time-varying voltages) are applied to wire helixes that rotate over voltage-sensitive paper. Although that method has been used extensively, the record it provides is generally unsatisfactory - mainly because the image is negative and its dynamic range is limited. Also, when exposed to the high-humidity conditions encountered aboard ship the paper transport often slips and results in image distortion.
Another method for generating a sonar image without scan conversion is the cathode-ray tube (CRT) recorder, similar to the device used in side-look radar imaging. Here, sonar returns are written across the face of a fiber-optic CRT. The light pattern generated is used to expose a dry silver paper that is drawn across the face of the CRT. The image is fixed by heat to provide a high-quality permanent record about 14 seconds after the information is applied to the recorder.
While the CRT recorder does provide an excellent permanent record, there are many applications where it would be desirable to view the ocean bottom directly as it is traversed (as through a "moving window"). For example, it is often useful to make preliminary scans of an area before making permanent records. Or real-time viewing could be used for bottom navigation. But as previously mentioned, direct viewing' requires some form of scan conversion of the slow' sonar PRF to a more rapid refresh rate to permit viewing without annoying flicker. Electronic-tube scan converters have been used for this purpose, and Westinghouse has built several of these systems in the past. They produce a good quality picture, but they are bulky, expensive, and complex to operate.
Investigation of Interference Between Upstream and Downstream Cylinders in a Current for the HRTs and Jumpers With FPSO Application
Authors: Blevins Robert D. , Wu Mason 
Published: October 2008

Abstract
Experiments and analyses have been made to determine the response of a downstream cylinder that is in the wake of a fixed upstream cylinder. This geometry is of great practical importance for risers in deepwater. It arises with jumpers in deepwater hybrid riser towers and in closely spaced risers. The theories of Huse [1], and Blevins [2] are applied to predict the steady response of the down stream cylinder. These predict that within the confines of the wake of the upstream cylinder, the drag on the downstream cylinder is reduced and there is a lift force that acts to draw the downstream cylinder into the wake of the upstream cylinder. There is apparently no simple, direct experimental confirmation of this predicted behavior.
An experiment was made in the flow channel of the Scripps Institution of Oceanography to test these theories up to about 80 000 Reynolds number. The paper describes the methodology and results of these experiments to validate the parameters of the theoretical models.
Preliminary measurements show that as the flow increases the downstream cylinder travels aft and inward towards the centerline of the wake. At small inline spacing the downstream cylinder moves upstream, implies negative lift, and impacts the fixed upstream cylinder.
Dalia Field - System Design and Flow Assurance for Dalia Operations
Authors: Courbot A. , Hanssen R. 
Published: October 2008

Abstract
Evaluating flow assurance risks for the development of Dalia was a key task during system design to safeguard the production over the 20 years design life. A low energy reservoir, heavy, viscous, acidic crude oil sensitive to hydrate formation and one of the world's largest subsea networks in deep water to operate and preserve, led to flow assurance requirements above oil industry experience. Innovative technologies and strategies were required to meet the challenges.
State of the art software tools have been utilised to the edge of their capacity in order to assess the thermal performance of complex subsea structures and the challenging flow conditions associated with relatively large flowline and riser dimensions. Extensive studies have been carried out to help prepare detailed operating procedures, focusing especially on hydrate management and slug handling. Uncertainty in fluid behaviour, naphthenates in particular, has fostered discussions between the project team, partners and expert groups to define best practice management strategies and reduce risk of operational problems.
The paper presents the flow assurance strategies developed to handle the main risks as well as a description of the production system specifics to meet the challenges.

Key Parameters and Flow Assurance Risks
The subsea production network for Dalia is located at a water depth of 1,200 to 1,450 metres. The Dalia field is part of the Angolan Block 17 (Figure 1) and consists of four main reservoirs formed at the Miocene period (Figure 2). They are situated 800 to 1,000 metres below the mudline and are characterised as unconsolidated and highly heterogeneous. They cover an area of 230 km2 and the subsea production system covers an area of 100 km2. Dalia oil is acidic and heavy with an API gravity of 21-23, a viscosity of 4-7 cP at down-hole conditions and the gas oil ratio (GOR) is in the order of 70 Sm3/Sm3. These characteristics combined with the low reservoir temperature (46 to 55oC) and an initial pressure of 215 to 235 bars present one of the greatest technical challenges for operations. The main characteristics are shown in Figure 3 with a comparison with Girassol, which was the first field developed in Block 17. The figure illustrates important differences between the two fields, leading to different system design requirements and flow assurance challenges.
Figure 1 - Dalia Field Location (available in full paper)
Figure 2 - Dalia Reservoirs (available in full paper)
Figure 3 - Reservoir and Fluid Characteristics compared with Girassol
These key parameters emphasise the main flow assurance risks for Dalia:
- Hydrate formation due to low reservoir temperature, water depth and flowline length
- Unstable flow conditions associated with seabed elevation profiles, low GOR and flowline and riser dimension
- The heavy and acidic oil can create strong emulsions and the risk of naphthenates deposition
- The oil viscosity in combination with surface active agents provides the risk of foaming in the surface facilities
Dalia Development-The FPSO Story and Package Challenges
Authors: Mouillerat G. , Regnault G. , Leroux J. 
Published: October 2008

Abstract
This paper will review the hull design together with topsides process modules and functions. It will also focus on the schedule challenges during construction in Korea, the steel crisis and the yards workloads. The global supply chain and management of the contractors and main subcontractors will also be addressed.
Designed and built by Dalia Mar Profundo (DMP), a consortium of Technip / Saipem / Stolt in the TSS joint venture together with Samsung Heavy Industries (SHI) and Daewoo Shipbuilding & Marine Engineering (DSME) in Korea, the FPSO is 300 metres long and 60 metres wide capable of 2 millions barrels oil storage at an average production capacity of 240,000 barrels per day. It has a "total liquid" handling capacity of 405,000 barrels per day and a gas compressing capacity of 8 million sm3 per day. A special seawater treatment for sulphate removal module is incorporated. SHI undertook the task of building the 55,000 tonnes double skinned hull and "about half" of the topside modules. DSME completed the remaining modules and undertook the installation and integration of all the topsides modules before sail away. TSS had the responsibility for onshore pre and final commissioning.
The FPSO is moored with a 12 point chain spread linked to 17 metre high, 106 tonnes suction anchors and attached to the vessel by 120 mm diameter, sheated cables 1,800 metres long, with 100 metre chain segments at either end. Weight control was very effective maintaining the weight within the original targets.

Dalia Field Overview
For more details refer to Dalia paper OTC 18538.
Refer to Figure 1 for the general field layout with the FPSO and its mooring lines, above the subsea production facilities.
Figure 1 - Dalia Development Layout (available in full paper)

General Introduction to the FPSO
The 300 metre by 60 metre new build FPSO, weighs over 85,000 tonnes dry and with a surface area of more than four football pitches, was designed and built by the DMP consortium. With storage for up to eight days at the average plateau production of 240,000 barrels per day, the twin train process system has two stages for oil separation. Each train is designed for 55% of the total capacity, to give better reliability of the separation system. After dehydration and desalting, also undertaken in two phases, the oil is cooled down to 50°C before storage.
Produced water is treated and re-injected into the reservoir for pressure maintenance. Seawater is treated to complement the total injection capacity of 405,000 barrels of water per day. Produced gas is used as fuel and the balance is re-injected in the reservoir until export to the future Angola LNG plant. Three 24 MW Gas turbines generate the power on the FPSO. These gas turbines are dual fuel and run on high quality diesel at start-up and during periods when gas is not available. Anchored in the Dalia field in September 2006 by the 12 mooring lines spread, the FPSO is built to remain in place for the design life of 20 years.
The Development of an FPSO for the Deepwater Gulf of Mexico
Authors: Wodehouse J. , George B. , Luo Y. 
Published: October 2008

Abstract
This paper presents the issues specific to the engineering and operation of FPSOs in the US Gulf of Mexico, and discusses the design of one FPSO currently under development and how it addresses those issues.
The areas of the FPSO design which are discussed in this paper include:Regulatory and environmental requirementsVessel selection and refurbishment for design life extensionRiser and station keeping/mooring design for hurricane and loop current conditions in deepwaterTopsides design including associated gas disposalOil import and export facilitiesShuttle tanker requirements
The design basis of this FPSO has been developed with the intent of enabling the unit to be easily redeployable in different locations, either as an Early Production System (EPS) for large fields, or a Full Field Development on marginal or medium size fields (30- 80,000 bopd). Different technologies are compared and their design and operational limitations identified, for riser design (flexible risers, hybrid riser towers, top tensioned risers, single well riser towers, permanent and disconnectable) and station keeping design, (permanent or disconnectable, dynamic positioning or anchor leg moorings, polyester or wire rope mooring systems). Those aspects of the design which require technology new to the Gulf of Mexico, will be highlighted and comparable applications of the technology elsewhere in the world, if applicable, identified.
There has been an increased interest recently in the application of FPSOs for the development of deepwater fields in the Gulf of Mexico. Damage to offshore facilities and the pipeline infrastructure during recent hurricane seasons, has made the benefits of the FPSO concept more apparent, with its large onboard oil storage capacity and capability to offload via shuttle tankers or pipelines, and its ability to disconnect from risers/moorings and avoid the hurricane conditions design case. Understanding the issues relative to the use of FPSOs in the Gulf of Mexico and developing a design, which utilizes the proven technology of FPSOs elsewhere in the world, is key to applying this concept successfully in this region.

Introduction
So far there have been no FPSOs installed in the US portion of the Gulf of Mexico (GoM) even though the concept has been increasingly selected for field developments elsewhere in the world. What are the key issues when reviewing the suitability of an FPSO for this region, and what has changed recently to affect the selection process? The damage caused to the offshore units and pipelines system by hurricanes Ivan, Katrina, and Rita, plus the continuing exploration success in the ultra deepwater beyond the continental shelf, are two of the main drivers towards the current interest in FPSOs in the Gulf of Mexico.
The ability of the FPSO to be designed to disconnect and sail away prior to the arrival of a hurricane, and the fact it is not dependent on the pipeline network to transport oil, makes it an inherently more robust and safe design concept.
The Effectiveness Of Offshore Motion Compensators
Authors: Pomonik George , Butler Bryan 
Published: October 2008

ABSTRACT
Heave motion compensators are rapidly becoming standard equipment aboard offshore drilling vessels. The effectiveness of these devices are dependent on a large number of variables; not all of which are a function of the compensator 'design. This paper reviews the basic principles for sizing compensators, and uses a computer analytical model to graphically show the changes in dynamic load that result from varying the significant parameters in the compensator system. The variables studied include: piston size, operating pressure" accumulator size, pipe Size, static load, compensator internal damping, depth of operation, vessel heave period, external damping and external added mass.
The'theoretical graphs presented can be used as a design guide for selecting and improving actual systems. The material includes dynamic loads during drilling, as well as for hoisting and lowering a blow-out preventer.

INTRODUCTION
Motion compensators provide numerous advantages during offshore drilling operations. However, the effectiveness of a compensator system is dependent on more than just the theoretical spring rate of' the compensator. The following material reviews the principles and advantages of motion compensators, discusses the parameters of importance, outlines preliminary methods for sizing a compensator, and finally, presents and discusses analytical material which shows the effects of varying the parameters in the compensator systems.

COMPENSATOR DESCRIPTION

Purpose
The purpose of heave motion compensation is to hold a load suspended from an offshore vessel while simultaneously reducing the oscillating force on that load due to vessel motion. At this time the major application of heave motion compensators is for offshore exploratory drilling operations. The advantages provided by a heave compensator system in this application are as follows:Reduction in bit load variationReduction in pipe load variationControl of bit load and drilling feed RateAccurate positioning during setting of casing hanger sealsControl during setting of packersSafety during pulling stuck pipeControl during setting off jarsThe ability to avoid stripping of tool joints through blow-out preventer ramAccuracy during logging and wire line servicesReduction of blow-out preventer stack oscillation during installation (thereby avoiding guide post wear and impact)Safety and control during testing.

Principle of Operation
Primary components of a motion compensator consist of a piston (or pistons) in a cylinder connected to a gas accumulator. As shown in the conceptual schematic in Figure l the pressure in the cylinder supports the load on the pistons and the accumulator provides an air spring for the load on the piston. The compensator pressure is adjusted in order to balance load on the piston.

Types
A number of different types of heave motion compensators are presently in existences including traveling block and crown block units.
J-Lay and Steep S-Lay: Complementary Tools for Ultradeep Water
Authors: Perinet Dominique , Frazer Ian 
Published: October 2008

Abstract
The pipelines are major components of the oil and gas production. With Ultra deep water development, the increasing of assisted recovery and zero-flare policy, pipelines specifications are much more elaborate: fatigue resistance due to cyclical operational loads and frequent shutdowns, thermal insulation for flow assurance purpose. They are often short and associated with many singularities, termination or inline structures. The design of pipelines must take into account walking and buckling, lay out in congested areas, sometimes with geohazards issues. The paper will expose the design of the different pipelines and associated components and describe how the contractors have met these challenges, improved the laying efficiency with using the J- lay method or the steep Slay, which is adapted from conventional laying method continuously improved since the seventies with a deep water application resulting from the revisited strain criteria on the laying ramp.
The S-lay methods are much more appropriate from the pipeline fabrication point of view, and appear as a better option for the laying of relative long lines such as gas trunk line or long tie back. The J lay method appears as a natural configuration from the catenary point of view and is much more appropriate to the installation of in line structures. The paper will illustrate with practical applications that these two methods are not opposed but are complementary tools and have each their own domain of excellence in the production and recovery of the hydrocarbon resources.

Introduction
The driving phenomena for deep water pipelines have drastically evolved over the last ten years with the development of deep water fields. The key driver for the design of the field layout and the flowlines is undoubtedly the flow assurance of multiphase fluids. This has led to a significant increase of insulated flowlines, which has had a great impact on the overall behavior of pipelines on the sea bed. The use of wet insulation materials such as polypropylene and polyurethane has resulted in a general reduction in the submerged weight of production flowlines, this in combination with the very soft soil conditions found in deep water locations has led to the significant increase in pipeline movements induced by pressure and temperature of the internal fluids. These movements known as pipe walking and lateral buckling have been the subject of much discussion within the offshore pipeline industry in recent years /1/, /2/, /3/, /4/. The details of these phenomena are not discussed in this paper, however the influence they have on the installation methods used for deep water pipelines will be addressed. The field layout selected for a particular offshore development has a significant influence on the pipelines and in particularly the installation techniques. In deep water fields, which are dominated by subsea wells, the field layout tends to be very different from those selected for more conventional water depths.
Float-Over High Air Gap: New Solution
Authors: Cholley J.M. , Cahay M. 
Published: October 2008

Abstract
Technip has previously developed, and has widely used, the jacking assisted float-over deck installation concept, called "UNIDECK®", for decks requiring a relatively low air gap. This has demonstrated the advantages of the float-over method which minimizes the overall cost of transport, installation and hook-up by having a deck that can be installed on a jacket as a fully completed and tested single unit without using a conventional crane barge. That concept has been successfully used for relatively benign areas of the world where a low air gap is acceptable but installation is problematic due to the impact of long period swells on the dynamic behavior of the installation vessel.
To allow the float-over method to be extended to harsher environmental areas of the world, a methodology is required to allow deck transportation at low level, but then enable the deck to be installed with a high air gap.
This paper describes a new float-over solution, which is applicable to platforms requiring air gaps of 20m (66 ft) or more, and deck weights up to 20,000 t (22,000 short tons) and extendable to higher weights. It is called "float-over high air gap" - FOHAG.

Introduction
With the discovery of oil & gas fields located in remote harsh environment areas of the world, a cost effective alternative is required to relying on crane vessels for installation, the availability of such vessels becoming limited as demand for their services increases around the world. The FOHAG concept greatly extends the geographical range for deck installation using the float-over method as an alternative to using a crane vessel.
If only using ballasting for float-over deck installation, the stability criteria during transportation restricts the height of the deck above the transportation vessel and hence limits the maximum finally achieved air gap. To achieve a higher final air gap, the use of jacks allows the deck to be raised up once at site and under suitable weather window conditions.
Technip has developed a jacking assisted float-over installation system, called "UNIDECK®", which has been successfully used for decks up to 18,000 t (Ref 1).. This technology uses hydraulic jacking to provide a safe and quick transfer of the deck weight onto the pre-installed jacket. However, the height to which jacks can lift the deck is constrained by the sensitivity of the jacks to lateral forces (at high elevation) and their limited stroke.
The newly developed FOHAG solution consists of replacing the limited stroke jacks by a rack and pinion system that has no stroke limitations within all conceivable air gap requirements.
The main characteristics of the system are that, during transportation, the deck is at a minimum elevation from the vessel in order to maximize the floating stability and reduce horizontal acceleration applied on the deck. Once arrived at the installation site, the deck is elevated to a sufficient height using a rack and pinion system for the vessel to enter above the preinstalled substructure (see Fig 1).