bluuebunny/crossref_metadata_2025_split huggingface dataset:
Challenges and Experience in ROV-based Deepwater Seabed Mapping
Authors: Rasmussen Gert Juel 
Published: October 2008

Abstract
Detailed seabed mapping by use of multibeam echosounder (MBE), sidescan sonar (SSS) and subbottom profiler (SBP) mounted on ROV's has been common practice for several years in the North Sea region. The details from this type of survey compared to vessel based surveys have added valuable information for planning and detailed engineering for field development. The details revealed by ROV seabed mapping is even more necessary as field development progresses towards deep water (&gt; 1000 metres).
As survey ROV's and survey sensors typically are rated to 1000 metres or less, it requires significant planning and preparation to prepare a spread capable for deep-water operations. Several challenges, known and unexpected, experienced during a mapping campaign off the coast of West Africa in water depths down to 1450 metres are discussed below. The paper describes the pre-studies and analyses carried out prior to mobilisation, problems encountered during mobilisation and survey, and the corresponding problem solving.
The modifications made to the ROV prior to the survey proved to be very profitable as survey speeds in excess of 1.5 knots were obtained in water depths of 1400 metres. The data quality appeared to be good, although some of the survey data partly suffered from background noise.

Background
Even with significant experience in ROV seabed mapping it is a comprehensive task to build a ROV survey spread suitable for deep-water. The task appears simple at first sight. We just want to do in 1500 metres water depth what we have done for years in 300-600 metres water depth.
But after the most obvious thoughts of "what is the depth rating of the ROV" and "how long is the umbilical" more complex questions arose. As the answers turned out to be negative for our standard survey spread for both the above questions, new ideas had to be developed. But first a target objective was established. The work task included more than 800 line km of seabed mapping and therefore survey speed became an important issue. We aimed for a speed of 1.5 knots (0.77 m/s). This was approximately 10 times faster than the only known deep-water ROV MBE survey at that time (but less than the speed we operate with in the North Sea).
In addition to the survey speed, the following main tasks were identified as the key to successful mobilisation and performance:Upgrade of deep rated WorkROV to Survey ROV.Identification and integration of deep rated survey sensors.Fast and reliable data transmission from ROV to surface.

Survey spread
The survey spread should include a vessel with good DP capabilities and high accuracy sub-surface positioning system, e.g. HiPAP (High Precision Acoustic Positioning) from Simrad, and DGPS based heading and attitude sensor (Seapath from Seatex). Low noise environment around the vessel is an advantage for the quality of the acoustic link to the ROV.
Responses of a Tanker-Based FPSO to Hurricanes
Authors: Ward Emmett G. , Irani Mehernosh B. , Johnson Robert P. 
Published: October 2008

Abstract
A series of model tests were completed in the Offshore Technology Research Center wave basin to investigate the responses of a tanker-based FPSO to hurricane environments. Results indicate that transverse responses, particularly roll, are significantly influenced by non-parallel environments and directional seas.

Introduction
While FPSO.s have successfully used in many other areas worldwide, none have been used to date in the Gulf of Mexico. With increasing interest in their use in the Gulf, model tests were conducted at the Offshore Technology Research Center wave basin to examine the behavior of FPSO.s in wave, wind, and current conditions typical of the passage of a severe hurricane. FPSO.s for the Gulf of Mexico will likely be passively moored through a turret system so that the tanker can weathervane or rotate in response to the changing wave, wind, and current directions in a hurricane.
In many areas where FPSOs have been used, the wind, wave and current conditions are relatively parallel or collinear. In such an environment, the FPSO is generally subjected to head seas. The typical design practice for such FPSOs assumes that the design wave, wind, and currents are parallel. The waves are assumed to be unidirectional or long-crested.
However waves, winds, and currents in a hurricane can be quite non-parallel [1], and subject the vessel to quartering or beam seas that can significantly influence the response of a ship-shaped vessel. For example, conditions that result in quartering or beam seas can cause larger roll amplitudes than that would result from head seas. The extreme responses of a moored FPSO can be sensitive to non-parallel waves, winds, and currents. The extreme or design responses of an FPSO is recognized to be sensitive to non-parallel waves, wind, and currents [1,2], but few studies have addressed this issue.
A recent study investigated response based design criteria for FPSOs in the Gulf of Mexico [3]. A frequency domain analytical model was used to predict the responses of an FPSO from hindcast hurricane waves, winds, and currents that were generally non-parallel. The effect of directional waves was approximated in the model. Results showed larger than anticipated roll that was due in part to quartering to beam seas that can result from non-parallel waves, winds, and currents, and in part to directional seas.
Larger than anticipated roll has also been observed on operating FPSOs[4].
The model tests described here were designed and conducted to examine the responses of an FPSO in nonparallel wave, wind, and current conditions and wave directionality (i.e., short-crested waves) typical in the passage of a severe Gulf of Mexico hurricane. Results from these tests can be used to assess the importance of realistic descriptions of hurricane wave, wind, and current conditions on the simplifying assumptions often used in design practice.
Field Test Results of a Rotary Separator Turbine on the Ram/Powell TLP
Authors: Rawlins C.H. , Ross G.D. 
Published: October 2008

Abstract
This paper will present the design of the Rotary Separator Turbine and skid package used in the first offshore field trial of this technology on the Ram/Powell tension leg platform (TLP) located in the Gulf of Mexico. The RST is a compact gas-liquid separation and power generation device designed to operate on process fluid pressure. This technology offers a potential 50% weight and space savings over conventional vessel separators, and is under development for use on minimum footprint facilities. The purpose of the test was to verify the separation and mechanical characteristics in actual production conditions. An integrated test package installed on the Ram/Powell TLP in June 2000 tested the RST on actual well production.

Rotary Separator Turbine
The Rotary Separator Turbine (RST) enables compact and efficient gas-liquid separation while recovering pressure drop energy. The energy provides liquid pressurization, shaft power, or a combination of the two. Separation efficiency of the gas and liquid meets or exceeds the performance of a conventional vessel separator, with substantial weight and volume reduction. Additional benefits of the RST stemming from the centrifugal separation include foam reduction and improvement in operability due to motion insensitivity.
The RST is a product of high velocity two-phase flow research at the Jet Propulsion Laboratory1. During the 1970's and 1980's several prototype turbines were tested in geothermal power applications. A 30" full-scale unit installed in August 1998 at Cerro Prieto, Mexico operates at a power output of 0.5-1 MW.
The first oil and gas application employed the RST as a centrifugal foam breaker for an offshore application. A reaction design RST tested in an onshore gas facility on natural gas/crude mixture provided complete foam breakdown with a liquid carryover of 30 PPM. Further test work in 1996 used a RST for separation of inert gases and crude oil during offshore loading. A pilot plant unit tested on a North Sea shuttle tanker exhibited good separation and performance unaffected by ship motion. A 1997 Joint Industry Programtested a second RST at a major oil and gas flow facility2.

Operating Principle
Figure 1 shows the basic principles of operation with the liquid and gas flow paths. The four main components identified in the diffuser type RST are the two-phase nozzles, rotor drum, gas path blading, and diffuser scoop3.

Two-Phase Nozzles
The inlet nozzles convert the pressure energy of the two-phase flow mixture into kinetic energy. Due to the density difference, the gas phase accelerates more rapidly than the liquid. Shear forces, exerted by the high velocity gas, break up the liquid into small droplets. In turn, the small liquid droplets have a large surface area to mass ratio. This facilitates efficient momentum transfer between the liquid and the gas during the pressure decline, resulting in an even distribution of fine liquid droplets suspended in a continuous gas phase of the exit jet.
Norne-Heidrun: Closing "The Loop" With Diverless Flanged Connections
Authors: Jansen J.O. , Corbetta G. , D&apos;Aloisio G. 
Published: October 2008

Abstract
Subsea completions in deep waters are becoming more and more frequent around the world. This entails the use of innovative technology, remote interventions but, of course, also a constant attention to cost effectiveness to make any possible development a viable one.
As a result of these continuous efforts towards new solutions, Statoil decided in 1999 to focus their attention on the possibility of using flanges as remote connection system. The idea originated from two basic concepts:Flanges have been widely used in the past within the offshore industry, therefore they have got a large track record and are standardized equipment (e.g. ANSI or API);Procurement cost for flanges is low when compared to other type of connectors.
Sonsub proposed to Statoil the use of their newly developed Brutus system as part of the new development in the Norne-Heidrun area. Brutus is a tie-in system capable to tie-in rigid pipeline up to 16" and with minor modification could reach up to 24"; larger sizes are strictly dependent upon specific scenario requirements.
It was Statoil's intention to connect the Norne FPSO to Heidrun TLP and to the 42" Åsgard Transport system through a 16" piggable pipeline system called "The Loop".
With this respect Sonsub were awarded an EPCI contract for the design, fabrication and installation of two subsea manifolds, tie-in spools and relevant protection covers, two In-Line tee protection covers and the installation of the flexible riser to Norne FPSO. The offshore campaign took place in the last quarter of 2000.
This paper presents the project, briefly describe the Brutus system capabilities and give all information on how the operations for "closing" the Norne-Heidrun U-Loop were completed.

Introduction
The objective of the project is to connect two production facilities operated by Statoil on the North Sea (Norne FPSO and Heidrun TLP) with a 16" piggable pipeline system (called "The Loop") in order to export the produced gas towards the 42" Åsgard Transport System. Norne Heidrun Subsea Structure and Tie-in is the name of the project that in September 1999 Statoil decided to award to Sonsub. Statoil specifically decided to trust the use of flanges and gave Sonsub the go ahead on the basis of a competitive economical proposal, which showed that the avoidance of mechanical connectors is in itself a major saving.
This is an EPCI contract which has seen Sonsub for the first time as main contractor for such kind of work, and it has been carried out in co-operation with Saipem and Sasp Offshore Engineering involved in the installation analysis and engineering respectively.
The scope of work includes the Engineering, Fabrication, Testing and Installation of the following subsea structures:Norne Export Riser Base;U-Loop Manifold;Norne and Heidrun In-Line Tees Protection Covers;Norne Expansion Spool, Heidrun Expansion Spool and Åsgard Crossover Spool;GRP Protection covers for the three spools;Subsea Pig Launcher;Blind Flange Removal Tool.
Mooring Analysis of a Truss Spar
Authors: Kristoffersen Guro , Weaver Tim 
Published: October 2008

Abstract
A time domain analysis procedure is used to calculate maximum design tensions for the mooring system of a truss spar. Fairlead motions are used as input to calculate time histories of dynamic mooring line tensions. Several random simulations are used to derive design values of maximum tension. The variability from simulation to simulation in maximum tension and in the dynamic portion of the response is summarized. Alternative methods for estimating the maximum value are compared and the effect of the number of simulations on the uncertainty in the maximum is demonstrated. The dynamic characteristics of the mooring line tensions are examined by looking at the high frequency and low-frequency portions of the response. A comparison of mooring line tensions for a truss spar and a classic spar is also provided. In addition, maximum tensions from the time domain analysis are compared with results from a frequency domain analysis.

Introduction
There are three production spars presently operating in the Gulf of Mexico. Those spars are deep draft, vertical steel cylinders and are referred to as "classic" spars. An alternative configuration is the truss spar, where the ring-stiffened shell of the midsection is replaced by a tubular steel truss (Figure 1). The improved structural efficiency of the truss reduces the weight of the hull, which reduces the cost and fabrication time. In many cases, the drag load on the open truss section is less than for the classic spar. This reduces the mooring line tensions in high current conditions. There are three truss spars presently under construction.
From a global motions perspective, one disadvantage of the truss spar is that there is no longer the large mass of water (both enclosed mass and added mass) associated with the midsection of the classic spar. The added mass and damping of the truss heave plates produces a heave response that is nearly the same as a classic spar. However, the reduction in lateral mass of the truss spar increases the surge/sway highfrequency response. This is because the lateral wave load on the truss spar is essentially the same as it is on a classic spar. Since the mass is less, the high-frequency response in surge/sway will be greater for a truss spar than for a classic spar.
Due to the increased high-frequency motion, it is important to accurately account for line dynamics in designing the mooring system of a truss spar. When using time domain simulations to evaluate maximum response, it is also important to understand the variability in the response and the uncertainty in the estimate of the maximum response.
The results presented herein are for a typical truss spar hull configuration and mooring system. The mooring tensions are also compared with those of a classic spar whose topside capacity and maximum pitch response matches those of the truss spar.
Dynamic Mooring and Fendering System
Authors: Tam W.A. 
Published: October 2008

Abstract
This paper describes a new approach to the problem of docking and mooring ships. This system utilizes momentum transfer-between relatively high pressure stream of water and the sea to draw the tanker to the docking facility and hold it there during the loading operation. The system can either partially or wholly eliminate the requirement for tugs and mooring line depending upon the design basis.
Experimental results are presented for a full size one foot wide section of the dynamic docking device. Predicated upon experimental work done to date a preliminary operational procedure is presented illustrating the techniques used in docking and undocking a ship.

Introduction
An increasingly higher percentage of exploration and development funds are being expended for offshore work. This trend is expected to continue or perhaps accelerate during the next decade. In those cases where the field under development is distant from shore or located in an area where there are no immediate port facilities adequate to handle large tankers, the ability to load out a tanker offshore becomes increasingly attractive from an economic standpoint.
The economics of tanker operations has resulted in a trend toward the mammoth super tanker. Feasibility studies have been completed for a one million DWT-tanker. In many areas a requirement to handle a tanker of 75 to 100'; draft makes the conventional harbor berthing system economically unattractive. Furthermore, while the tanker size has increased, the turnaround time has not increased correspondingly. Consequently the load out rates are truly impressive 100,000 bbl. per hour is not an unusual figure.
When berthing and mooring tankers offshore, the loading and mooring system are exposed to more severe environmental conditions than those normally experienced in sheltered waters. Wind, waves and currents loads are the three principle factors which affect the berthing and mooring operation. All three may have different directions or may act in the same direction. The conditions vary widely from one geographical location to another and must be thoroughly investigated before attempting to design any type of mooring system.
Motion Compensation On Drilling Vessels
Authors: Butler Bryan , Larralde Edward 
Published: October 2008

Ten years ago the problem of attenuation of ship heave motion was receiving only scattered attention from the drilling industry, mostly because the offshore oil industry was mainly operating from jack-up rigs in 200 feet of water or less. However, the last five years have seen a rising interest in deep water drilling from floating vessels and the problems associated with heave motion have prompted a number of ideas to be patented for various types of motion compensators. These ideas can be generally divided into three approaches. One approach places the compensating device between the hook and the block. In another, the device is attached to either the fast line or dead line, alternately paying out or taking up line. The third approach moves the crown block. However, because simplified analytical models of such systems indicated difficulties would be encountered; or because of other reasons, most of these ideas remained unused in the patent files. However, a few small units that hung between the block and the hook were built for wire line work in 1965, and later a larger unit operating on the dead line was built by Rucker for the STAFLO. In February, 1970, a motion compensator designed for general drilling operations was invented by E. Larraldel and a small prototype was built by Vetco Offshore Industries. It was tested in June, 1970, in the Santa Barbara Channel. The initial success of the test led the company to make a detailed investigation of the dynamics of the machine. Additional tests were also conducted which led to the design of a larger machine capable of drilling to 20,000 feet. The results of this effort are the substance of this report.

OPERATING FEATURES
The Vetco Motion Compensator is basically a hydraulic-pneumatic device which follows the heaving ship while transmitting very little of this motion to the hook. Basic models of the machine have either a 200 or 300 ton operating capacity and are offered with either a 15 foot or 20 foot stroke capability. Static load capacity is equal to the rated capacity of the derrick and blocks. The basic parts of the motion compensator are shown in Figure 1. Two cylinders are mounted in a frame connected to the traveling block and move up and down with heave motion. Within the cylinders are pistons connected by rods to a framework supporting the hook. The pistons remain relatively stationary with respect to the earth so that as the cylinders move upward with the ship, fluid is driven out, and as they move downward; fluid returns. This active fluid volume from the cylinders is received by piston type accumulators which have fluid on one side and pressurized gas on the other. Incoming fluid drives the accumulator piston against the gas, thus decreasing the gas volume and creating a pressure rise. Likewise, the outgoing fluid will create a pressure drop. The magnitude of the pressure changes is reduced by connecting the accumulators to additional gas vessels known as accumulator back up bottles.
Lift And Drag Forces On A Submerged Circular Cylinder
Authors: Beattie J.F. , Brown L.P. , Webb B.F. 
Published: October 2008

ABSTRACT
Correlations for drag coefficients of circular cylinders in a symmetrical flow field have been available in the technical literature for a number of years. However, correlations for drag coefficients on a circular cylinder adjacent to a plane wall are not available in the literature. In addition to the drag forces, the aforementioned geometry of a cylinder adjacent to a plane results in a lift force on the cylinder due to the induced flow. The correlations for this resultant lift coefficient are also unavailable in literature.
Investigation of the relationships between the various flow and geometric parameters for the case of a full-size (diameters ranging in size from 6 to 30 in.) circular cylinder submerged in a semi-infinite induced flow stream was undertaken in the U. of Tulsa low speed wind tunnel and the U. of Tulsa-Williams Brothers water tunnel. This was accomplished by placing full-size test cylinders adjacent to a flat plate. Data was recorded for the test cylinders in both the vertical and horizontal position. The depth of the semi-infinite flow field was varied depending on the size of the test cylinder to eliminate the hydraulic jump effects.
An empirical correlation of lift coefficients vs Reynolds number and drag coefficients vs Reynolds number were obtained for smooth and rough pipe.

INTRODUCTION
In the design of'; pipelines which traverse the bed of a flowing stream, hydrodynamic lift and drag forces must be considered. Insufficient strength can result in pipeline rupture due to drag. Insufficient weighting can lead to oscillation and fatigue due to lift forces.
Accordingly, an experimental study was undertaken to measure and correlate lift and drag forces. The study was conducted in a water tunnel using pipes ranging in diameter from 6 to 30 in. Pipes were tested in an "as received'; condition and in an artificially roughened condition intended to simulate a concrete jacket.

LABORATORY EQUIPMENT
Equipment utilized during this investigation included the U. of Tulsa water tunnel. The tunnel circulates water through a test section. In order for flow in deep channels to be simulated and to avoid the difficulties involved in constructing and operating a water tunnel with a very deep test section, a vane is provided in the test section simulating a fluid streamline in very deep flow. The effect of the vane, or solid streamline, is to eliminate free surface effects resultant from the placement of the test object in the shallow test section. The tunnel test section with vane is pictured schematically in Fig. 1.
Circulation in the water tunnel is accomplished by means of a stationary propeller driven by an automobile engine.
Tunnel velocities are measured by a pitot tube coupled to a mercury inclined manometer. Test object pressures are measured on a water manometer board.