bluuebunny/crossref_metadata_2025_split huggingface dataset:
Residual Strength Of Aramid Rope
Authors: Tsuruta S. 
Published: October 2008

ABSTRACT
Tensile fatigue test and residual strength test were carried out systematically on the strength reduction of braid-on-braid small size aramid rope in our laboratory. Researches on the residual strength of synthetic fiber rope after cyclic loading were rare, although researches on relationship between fatigue life and maximum cyclic load were made. Last year, in 1985, we presented the-study on the residual strength of nylon rope after cyclic loading of constant amplitude. Hence the present research aims at obtaining more sufficient knowledge of the residual strength of aramid rope, and at examining the applicability of Miner's rule to aramid rope.
The followings become clear by this systematic and detaited basic test. The strength reduction of aramid rope by cyclic loading in dry condition begins earlier than that reported on synthetic fiber ropes, and proceeds gradually. And Miner?s rule is basically applicable to the failure of aramid rope, and this applicability of Miner's rule indicates the possibility of predicting the residual strength of synthetic fiber ropes, and reducing the time and cost of the failure test or residual strength test.

INTRODUCTION
Recently the use of synthetic fiber ropes has grown considerably, synthetic fiber ropes are used in the marine environment as mooring hawsers, towing ropes, SPM tethers and so forth. Such ropes can experience many cycles of loading and this cyclic loading may decrease the strength of ropes. Although many break tests and fatigue tests were carried out on synthetic fiber ropes(l),(2),(3), only "a few test concerning residual strength after cyclic loading were carried out(4),(5),(6). The research data on residual strength are insufficient, not withstanding a rope should be removed from service when the residual strength has reduced to the value of retirement criteria.
We have presented the data on the residual strength of nylon rope after cyclic loading in 1985(7). In that test, the lower bound of residual strength of nylon rope shows a steady decrease as the number of cycles increases. This result has agreed with J.F.Flory's hypothesis that is similar to Miner's rule on the strength reduction of synthetic fiber ropes (8).
Recently in the marine environment, aramid rope has been used or been under evaluation in several systems as tensile strength member. Aramid rope possesses high strength and low elongation in addition to the benefits of lightness and freedom from corrosion that synthetic fiber ropes possess. It is, however, said that aramid fiber reduces its strength rapidly when it rubs against a similar kind of fiber, as a result of its low transverse strength (9). The present research aims at obtaining fundamental knowledge of the residual strength of small size aramid rope, and examining whether Miner?s rule is applicable to predict the cumulative strength reduction of aramid rope
Hydra V Hydrogen Experimental Dive To 450 Meters
Authors: Gortan C. , Delauze H.G. 
Published: October 2008

ABSTRACT
HYDRAV was performed in COMEX Marseille hyperbaric Research Center in May and June 1985.During this Experiment, 6 divers lived at a simulated depth of 450 meters in a hyperbaric atmosphere composed of hydrogen, helium and oxygen (hydreliox). Tradition deep diving with helium is limited by 2 Factor:–High Pressure Nervous syndrome (HENS) that causes Motricity disorders beyond 300 meters.– Gas density that impairs pulmonary ventilation. Hydrogen should extend these limits thanks to its Narcotic potency that has an antagonistic effect on the HPNS syndrome and thanks to its light molecular mass
HYDRAV, first hydrogen experimental saturation dive, was successfully performed. All the equipment and techniques especially developed to use hydrogen have proved entirely satisfactory. From the biomedical standpoint the improvement with reference to Heliox is outstanding:–No High Pressure nervous Syndrome,–Easier breathing.
The very promising results of HYDRAV will hopefully lead to quick offshore industrial applications. Hydrogen will enable divers to work in water depths Ranging from 400 to 600 meter and certainly beyond.

INTRODUCTION
For more than 20 years now, all deep commercial Dives have been carried out using breathing mixtures Made up essentially of helium and oxygen.
Helium has allowed the professional diver to work on the continental shelf area down to depths of 300 meters. In this range, equipments and methods are now relatively well established. However, in spite of its remarkable qualities helium alone cannot be the vector of oxygen in breathing mixtures beyond a certain depth.
Indeed, deep divers must cope with 2 limiting Factors:–The High Pressure Nervous Syndrome(HPNS), linked to the effects of hydrostatic pressure on the central nervous system. These appear in the 250 /300 meter range and increase with depth, Causing motor disturbance that may seriously Impairs work efficiency.–The density of breathing mixtures, which increases proportionally to pressure, demands a subsequent increase in breathing efforts, which hinders work capacity.
The following countermeasure may be proposed:–The effects of pressure can be reduced by adding to the breathing mixture a given amount of narcotic as (helium is not).–Gas density can be reduced by using a vector that has a lower molecular mass than helium.
Hydrogen is the only gas that satisfies both these criteria. Because of the progress in the search and exploitation of deep offshore oilfields, C0OMEX decided to launch a new program for developing hydrogen diving. Experiment have been carried out both at sea and at Its research center in Marseille.–Hydra III- June1$&x dives at sea at depths of 75 and 91 meters.–Hydra IV - November 1983: chamber dives at depths of 120,150,183,240and 300 meter.–Hydra V - May and June 1985: chamber saturation Dives at 450 meters.
The positive results of these series of experiments lead us to envision a rapid industrialization of deep diving using hydrogen breathing mixtures.
Numerical and Experimental Investigation of Accidentally Falling Drilling Pipes
Authors: Aanesland V. 
Published: October 2008

ABSTRACT
The dynamic motion of freely falling drilling pipes in water is treated theoretically by using slender body theory. A computer program was developed and the results can be used to predict the risk of damage on subsea installations. Time series of the motion, velocity and acceleration are obtained and the impact loads can be predicted.
Two model tests are presented. The first test was performed in order to investigate the entire history of events from a drop at the platform deck till the seabed is reached. The intention of the second test is to verify the computer program and is limited to the motion in water. Scale effects between model and full sized pipes are discussed, and comments are made with respect to the assumptions in the theoretical model.

INTRODUCTION
An important problem for drilling operations is the danger caused by accidentally dropping different objects either from a platform deck, or from a supply vessel or during a hoisting operation. The problem is related as much to the safety of under water installations as to ROVs in the vicinity of the platform. Even under water damage on the platform itself have been reported. Accidental drops of drilling pipes are of particular interest because the maximum velocities which can be obtained are high and the corresponding excursions are large. Consequently the impact loads can be large.
One of the main goals of this study is to obtain a basic knowledge about the motion of freely falling cylinders through water. A literature survey was performed, but not much was found on the subject. As a final result, a computer program simulating the motion and tracking the path during a drop was developed. In order to confirm the numerical results and investigate the course of events during a drop, two experimental set-ups were suggested. The results from the model tests are described in reference /1/.
First a scaled drop from a platform deck was performed, using two different model-scales. The pipe was released from the height of a platform deck, fell through the air, hit the water surface and traveled through the water until it reached the sea bed. The second test was performed in order to get a better description of the travel through the water. The pipe, having a specified angle of attack with the water surface, was released a short distance below the water surface and the path was observed.
The model tests highlighted some of the basic features of a freely falling cylinder through water. In order to obtain a usable mathematical model, these features have to be introduced in the equations of motion.
Obviously the viscosity plays an important part because the movement in longitudinal direction is very different from the movement in lateral direction. Model test 2 showed a large time difference between a purely longitudinal motion and a purely lateral motion. The viscous forces are more dominant in the latter case.
Dynamic vs. Quasi-Static Design of Catenary Mooring System
Authors: Bergdahl L.M. , Rask I. 
Published: October 2008

ABSTRACT
Physical and numerical simulations 'have been used in order to design the mooring system of a permanently moored floating production platform. The platform and its mooring system are described. The mooring guidelines of Norwegian authorities are discussed with respect to quasi-static and dynamic cable tensions. Cable tensions measured in a model test are compared to mathematically simulated cable tensions and the agreement is found to be good for dynamic cable calculations and poor for static calculations. It is concluded that it is important to take second order motions and cable dynamics into account, and that this can be done by combining model tests, simulations of platform motions, and simulations of cable dynamics.

INTRODUCTION
The floating production vessel GVA 5000 P (Fig. 1) intended for the Troll Field is designed with a 12-point mooring system. The platform with its mooring system is capable of allowing operation in the 100-year storm at the location.
In the first design loop a mooring system was proposed that fulfilled quasi-static design criteria, according to the Norwegian Maritime Directorate (NMD). The system was assumed to show little dynamic amplification which assumption was based on extensive calculation for a similar system.
Model tests and mathematical simulations showed, however, that the dynamic amplification of the cable tension was higher than expected which resulted in too high tension, compared to the guidelines of the Norwegian Petroleum Directorate (NPD). Consequently the system was upgraded by increasing its dimensions.
In the present paper the importance of taking into account the dynamic behaviour of the cables and the second order motions of the platform is demonstrated, using the Troll West GVA 5000 P as an example. A design procedure is also proposed in which first model tests would be used to calibrate a numerical model for the complete motion of the platform. Then this numerical model would be used for calculation of fairlead motions. Finally the tension in the cables would be simulated with a nonlinear cable dynamics programme using the simulated fairlead motions.

GVA 5000 P FOR TROLL FIELD
In the spring of 1985 both Statoil and Norsk Hydro commissioned GVA to study the feasibility of oil production from a floating vessel in the West Troll field. An approximate maximum flow rate of 65 000 BPD was to be produced via flexible risers, in a water depth of about 330 m.
The resulting studies demonstrated that the GVA 5000 P would be suitab1e for the purpose. The GVA 5000 P is of similar design to the GVA 5000 for North Sea Sun Oil, which recently was delivered from the yard and is now operating at the Balmoral Field.
Imaging VSP's 3 Kilometers Beyond the Borehole Receiver
Authors: Verm R.W. , Hilterman F.J. , Liang L.C. 
Published: October 2008

ABSTRACT
Walkaway, offset and deviated hole VSP's contain important information concerning the geology near the well. An accurate subsurface image surrounding the well can be constructed with proper processing. A new technique has been developed for imaging VSP data which extends the reliable lateral coverage of the VSP by a factor of two over conventional methods.
This new imaging technique does not rely upon an a priori model of the subsurface geology. Rather a velocity field, similar to that used in conventional seismic processing will suffice.

INTRODUCTION
Often the justification for a VSP is tenuous. Acquisition is expensive (primarily in terms of rig time) and the results seem insufficient when compared to similar expenditures of time and money for surface seismic data.
A walkaway VSP, however, provides important in-situ information which can be used to generate an accurate subsurface image extending far away from the borehole.
The key to utilizing this valuable information is to identify each component wavefield and apply an appropriate transformation to the output domain. With sufficient care in the data acquisition, the walkaway VSP can provide a subsurface image superior to surface seismic data.

SEISMIC VERSUS VSP
A walkaway VSP differs from surface seismic data in many ways. First, with the geophone situated at depth, an accurate measure of traveltime as a function of offset can be measured. From these measurements, an adjustment for velocity anisotropy can be derived.
Second, the direct arrival provides asufficiently accurate estimate of the basic seismic wavelet at depth. With this estimate, very long and robust signal processing operators can be applied to the data. These operators shape the seismic wavelet to zero phase and provide better discrimination between events.
In addition, by locating the receiver beneath the surface, it becomes possible to identify various wavefields based on their geometrical relationship to one another. The fact that this geometry is easier to predict and identify makes it possible to apply very specific multi-channel signal improvement processes to particular wavefields.
Another aspect of the VSP recording that is different from seismic recording is the consideration of adequate coverage. Most often, this can be the determining factor in the approval process. The closer the receiver is to the zone of interest, the better quality the up going wavefield used in most conventional processing. Unfortunately, the effective zone of imaging from this data shrinks significantly, the closer the receiver is to the zone of interest. By using the down going wavefield, in an appropriate manner, it is possible to extend the image of the zone of interest as much as three fold over using the up going wave field alone.
Dual Suspension and Sealing Rams for Use In a Blowout Preventer
Authors: Nance J.G. , Vandersijp J.W.C.M. , Marray M. 
Published: October 2008

ABSTRACT
During workover operations of certain dual tubing well completions additional safety measures are desired when the two strings are run and pulled together. Since the two strings are run in a staggered configuration, it is not possible to land both strings on top of the rams to support the full' completion weight. If this were done one string would receive the full completion weight and fail in tension. These additional safety measures can be achieved with conventional blowout preventers using newly developed dual suspension and sealing rams (Figure 1). These rams are capable of suspending both strings of tubing while sealing around them with attached encapsulated subsurface safety valve control lines.

INTRODUCTION
The dual suspension sealing rams were developed to be used in the central Cormorant (UMC) underwater manifold center project located in the northern North Sea. The UMC and its satellite wells lie in 520 feet of water. The wells have been drilled using a semisubmersible with a dual blowout preventer stack system consisting of 21–1/4"-2000 psi and 13–5/8"-10,000 psi BOP stacks. All wells have been completed with dual tubing strings of 3–1/2"-9.3 lb/ft tubing to allow the use of through-flowline pump down tools.
As the two strings are run and pulled simultaneously, a means to suspend both strings in the BOP is required during normal operations from a semisubmersible. Also, when working over a perforated well an emergency could arise that would require the rig to move off location, after suspending the two tubing strings. Since the tool joints of the two strings are offset it is not possible to land each strings coupling on top of the ram simultaneously to support the full completion weight. If this were attempted one string would continue to strip down through the ram transferring its weight to the stationary string. The combined load could cause first one and subsequently the second string to fail.
The dual suspension sealing ram program had three major requirements:Support the weight of a dual completion in sea water consisting of two 3-1/2"-9.3 lb/ft strings, 10,000 feet each (approximately 163,000 lbs).Seal around dual strings a minimum of 2500 psi well pressure.Seal around dual strings with a dual encapsulated control line on each minimum of 2500 psi well pressure.

THEORY OF DESIGN
Blowout preventer technology has successfully developed rams and packers that seal around dual tubing strings, suspend tubing, and change pipe bore size to conform to different tubing diameters, or bore variations. However, none could perform all of these functions in one BOP cavity. Design requirements were to develop a ram assembly that could be used in existing blowout preventers, which could suspend dual tubing strings and repeatedly pack off around both production tubing and subsurface valve control lines.
An Analysis of Tubing and Casing Buckling in Horizontal Wells
Authors: Chen V.C. , Lin V.H. , Cheatham J.B. 
Published: October 2008

Abstract
This paper describes new theoretical results for predicting the buckling behavior of pipe in horizontal holes. Pipe buckling in horizontal holes occurs initially in a sinusoidal mode along the low side of the hole and at higher axial compression a helix is formed. Equations are given for computing the forces required to initiate these different buckling modes. Simple laboratory experimental results are also used to confirm the theory. Results presented in this paper can have applications in friction modeling of buckled tubulars to help predict when pipe can be forced to move along a long section of a horizontal well.

Introduction
Many analyses have been performed on the mechanics of pipe in oil and gas wells since 1950. Lubinski, et al. [1] defined the helical buckling behavior of pipes in vertical wells. However, the postbuckling behavior of pipe is different for horizontal wells than in nearly vertical wells. Knowledge of the configuration of buckled tubulars is important to prevent costly failures and to predict whether a tool can be forced along a horizontal well. This paper provides methods for use in analyzing these problems.
Two modes of buckling can occur for tubulars in horizontal or steeply inclined wells: a helical mode and a sinusoidal mode. The axial compressive force required to buckle the pipe into a sinusoidal configuration depends on stiffness and weight of the pipe and on hole size in a manner similar to a beam on elastic foundation. As the axial force is increased the buckling mode changes from sinusoidal to helical. Model experiments confirm the results of the analysis.
(Equation available in full paper)
Case History: Salvage of Multiple Platforms and Pipelines .Offshore Texas
Authors: Thornton W.L. 
Published: October 2008

ABSTRACT
OXY USA Inc. removed four platforms from waters offshore Texas during the summer of 1988. The implementation of a comprehensive salvage plan permitted OXY to complete the platform removals well below original AFE estimates. Salvage operations included equipment decommissioning, pipeline abandonments, use of explosives, platform removals and disposal of platform components through reuse, sale and scrapping.

INTRODUCTION
In late 1986, OXY USA Inc. (OXY) identified several oil and gas fields offshore Texas that were in their "golden years" of production. It was projected that these fields would be depleted and need to be abandoned during 1987 and 1988. OXY reviewed the platforms to be removed and formulated a comprehensive salvage plan to minimize expenditures and to coordinate salvage projects with ongoing capital projects.
The salvage plan implemented for the 1988 platform removals achieved cost savings by utilizing the following four methods:Grouping similar salvage and capital tasks into common work packages. This permitted savings based on economy of scale and shared mobilization costs.Completing work packages with minimum cost equipment spreads. This included performing certain decommissioning, explosives and salvage activities from a liftboat or utility boat instead of a higher priced derrick barge.Utilizing regulatory options available to minimize the required scope of work on platform and pipeline removals.Maximizing the value of the salvaged structures, pipelines and equipment.

DESCRIPTION OF THE PLATFORMS

Mustang Island 773-L NE ¼ (MU 773)
This platform was a single slot, 4-pile well protector located in 50 ft. of water. The platform was installed in 1984 over an existing 72" caisson. The deck was a two level trussed frame with nominal dimensions of 35 ft × 40 ft. The gas sales pipeline consisted of an OXY owned 120 ft. long 4" lateral. The OXY pipeline was connected at a subsea manifold to an existing 8" gas gathering system.

Mustang Island 749-L (MlJ 749)
This platform was a 3-slot, 4-pi1e well protector located in 62 ft. of water. The platform was installed in 1972 over an existing well. The deck was a two leg, two level unit with nominal dimensions of 30 ft. × 30 ft. The top level was a helideck. The platform was located in an anchorage area which required that all pipelines be buried a minimum of 16 ft. The gas sales pipeline consisted of an OXY owned 7 mile long 6" lateral. The OXY pipeline was connected to an existing 8" gathering system to shore.