bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Systems Analysis Techniques in Optimizing Gas Lift Installations
Authors: Brown K. E. , Mach J. , Proano E. A.
Published: November 2009

Systems analysis technqiues are applied to several well cases in order to optimize production rate and gas consumption of a continuous flow gas lift system. It is a procedure whereby various components, such as well capability, tubing size, flowline size, and separator pressure are analyzed in conjunction with the entire system in order to optimize the individual well or group of wells in a field. The solution point (node) can be taken anywhere in the system, but normally taken at the bottom or top of the well, and preferably both. Example problems will show the most logical manner to increase the flow rate, reduce the gas consumption, or both. A lowering of separator pressure to increase the flow rate may be a serious mistake. Examples will show that a more logical approach may be to increase the flowline size. In conclusion, all the individual components of a system must be analyzed in conjunction with the entire system for proper final analysis.
Subsidence Associated With Single and Multicavities for Underground Coal Gasification
Authors: Avasthi J. M. , Harloff G. J.
Published: November 2009

The three-dimensional theoretical development of Berry and Sales [1] has been extended to bring the subsidence predictions into agreement with the British National Coal Board comprehensive set of empirical data. New elastic parameters have been determined to fit the amplitude of the ground level subsidence. An empirical correction factor was developed to account for small cavity width-to-depth ratio cases. This correction is believed to account for incomplete closure for half width-to-depth ratios below 0.3. The theory has also been modified to bring the subsidence profiles into agreement with the foregoing referenced data. The development has been used to predict subsidence for an actual U.S. coal mining case with multiple cavities. The theory was also used to predict subsidence level and profile for a recent Gulf/DOE UCG test conducted in a steeply dipping coal seam near Rawlins, Wyoming.
On the Multidimensional Creep Deformation of Ice by Finite Element Analysis
Authors: Liu Y. J. , Hsu T. R.
Published: November 2009

This paper deals with the use of finite element analysis of the creep deformation of ice covers subject to localized loads. An incremental deformation approach was adopted and better computational efficiency and stability were achieved with the selection of proper integration schemes for the constitutive equation. A numerical example is included to illustrate the usefullness of the present method. This case deals with the “sinking” of a heavy pipe into the surface of an ice cover, a situation which is analogous to the stability of heavy structures and equipment resting on frozen foundations in the cold region engineering operations. Close agreement between the analytical and experimental results were obtained.
Dynamic Analysis Models of Tension Leg Platforms
Authors: Jefferys E. R. , Patel M. H.
Published: November 2009

Conventional analysis of tension leg platform structures yields natural frequencies which are well separated from wave excitation frequencies. However, the results presented here show that the tethers can have lateral resonant frequencies in the wave frequency range if the platform is deployed in deep water. Analysis which ignores the lateral tether dynamics gives reasonable estimates of platform motions but can seriously underestimate tether displacements. It is usually assumed that tether tension does not vary with time. However, the vertical waves forces, reacted by the tethers, cause the tension to change with time and this can cause a Mathieu type of instability in the platform sway motion. This phenomenon is investigated using a simple energy balance technique and it is shown that square law fluid damping places an upper bound on oscillation amplitude; it is found that platform sway motions due to Mathieu excitation remain acceptable even in large waves.
Development of an Instrumented Marine Riser Joint
Authors: Evans J. L. , Ganser D. A. , Williams S. J.
Published: November 2009

A marine riser pup joint was instrumented to measure riser tension, bending moment, and mud temperature and pressure. The ground rules for the design, major design decisions, significant details, and calibration and testing are discussed.
Moored Systems Designed to Sense Deep Ocean Earthquakes
Authors: Hartman P. J.
Published: November 2009

The ability to predict earthquakes and tsunamis is becoming increasingly important as world population continues to grow in high-density coastal metropolitan areas. Earthquakes which occur in and near undersea subduction zones where the earth’s crust slides under continental masses generate highly destructive tsunamis. Deep ocean buoy systems and sensor implantation techniques are being developed to obtain seismic data from the earth’s crust in water depths of 6000 m. For the first time, deep-sea drilling, high-resolution seismic sensors, and long-term, deep-ocean mooring technology are being combined to provide systems which continuously monitor earthquake activity in the deep ocean. Such systems provide vital seismic research information to the scientific community.
Some Psychometric Aspects of a Hydraulic Air Compressor (HAC)
Authors: Chen Li-Ting , Rice W.
Published: November 2009

In a hydraulic air compressor the air is surrounded by water during the compression process which is virtually isothermal. Depending on the state of the inlet air, the compressor water temperature, and the compression ratio, the compressed air may have higher or lower absolute humidity than that of the inlet air. Relationships between the two humidities are developed and criteria for “drying” to occur are presented.
Dynamic Analysis of Slender Rods
Authors: Garrett D. L.
Published: November 2009

A new three-dimensional finite element model of an inextensible elastic rod with equal principal stiffnesses is presented. The model permits large deflections and finite rotations and accounts for tension variation along its length. Its use in static analysis is described and a time integration method for dynamic analysis is developed. Accuracy of the spatial discretization and stability of the time integration method are demonstrated by comparison of numerical results with exact solutions for certain nonlinear problems.
Dynamic Behavior of Submarine Pipelines Under Laying Operation
Authors: Suzuki N. , Jingu N.
Published: November 2009

Theoretical and experimental study on dynamic behavior of submarine pipelines under laying operation with articulated stingers is described in this paper. Wave response tests in regular waves and forced oscillation tests in still water were conducted using the 1/20 scale model of 406.4 mm o.d. (16 in. o.d.) pipeline laid in 150 m (500 ft) water depth. The results show that: 1) the maximum dynamic bending moment of pipeline MDmax occur at a stinger roller, 2) dynamic bending moment of pipelines MD at shorter periods are larger than those at longer periods, 3) the values of MD in an over-bend region depend highly upon stinger motion, 4) those of MD in a sag-bend region are less than MD max in an over-bend region, 5) the values of MD/HMY increase as the stinger volume increases and that 6) stinger motion at shorter periods are different from those at longer periods.
Movements of Submarine Pipelines Close to Platforms
Authors: Palmer A. C. , Ling M. T. S.
Published: November 2009

An analytical model of expansion movements at the ends of pipelines is developed. A comparison with measurements on two North Sea pipelines shows that the analysis is consistent with observed behavior, and can be used to assess the results of corrective action. An alternative mechanism, creep deformation within the corrosion coating, is analyzed briefly.
Hydrodynamic Loads on Flexible Marine Structures due to Vortex Shedding
Authors: Every M. J. , King R. , Griffin O. M.
Published: November 2009

This paper makes a comparison of experimental measurements and a recently developed methodology for the prediction of the increase in the steady drag of a cylinder undergoing vortex-induced vibrations. The experimental results were obtained during the development of a means to reduce the flow-induced vibration of a cable-suspended pile of the COGNAC platform installation and agree well with the predictions made in this paper. Next, a brief consideration is made of some of the authors’ experience of methods used to reduce vortex-induced vibrations, and hence stress levels. Finally, a reduction method which used an air-blowing manifold is described and results presented.
Swivels for Production Risers and Offshore Terminals
Authors: Ortloff J. E.
Published: November 2009

Properly designed and developed swivels represent a reliable and practical means for providing required flowline flexibility in multiline marine production risers. The lack of suitable commercially available swivels caused Exxon Production Research Company, in the early 1970’s, to initiate a research and development program to produce swivels that would meet the requirements for marine riser service. This paper provides some basic information about swivels and describes some promising swivel design concepts. It also discusses potential applications for swivels and the need for continued development effort.
Examination of Commercial Casing Collapse Strength Under Axial Loading
Authors: Tamano T. , Inoue Y. , Mimura H. , Yanagimoto S.
Published: November 2009

Collapse testing of commercial API grade 7-in. casing was conducted under combined external pressure and axial load. The measured collapse pressure was considerably higher than the API minimum value, especially for the large D/t ratio, as expected. For the casings of large D/t ratio, the measured collapse pressure was a little smaller than the theoretical value for ideal pipe and the axial stress had a slight effect on the collapse pressure. In the range of plastic collapse, the measured collapse pressure was not less than the yield pressure for ideal pipe except near the boundary of the elastic and plastic collapse ranges.
Thermo-Elastic Responses Associated With Cavities and Cracks in Infinite Media
Authors: Advani S. H. , Lee J. K. , Wang H. F.
Published: November 2009

The increased adaption of classical thermo-elasticity solutions for rock mechanics applications has been evident in recent years. In this paper, specialized thermo-elastic solutions for a triaxial ellipsoidal cavity with uniform surface temperature are presented and results for several limiting cases are deduced. For completeness and comparison, solutions and results for the related thermally stressed problem of a prolate spheroidal cavity are detailed. In addition, the applicability of the finite element technique and an appropriate failure criteria for in-situ thermo-mechanical problems is indicated.
Analysis of the Horizontal to Vertical Orientation of Deep Water Risers
Authors: Healey A. J. , Flores A.
Published: November 2009

This paper presents an analysis of the problem of reorientation of a riser pipe from an initially horizontal configuration during subsurface tow to the vertical position for installation. Front and rear barges support the pipe through cables. The orientation into a vertical configuration is accomplished by paying out the front cable. The pipe is treated as a Bernoulli-Euler beam with significant tension undergoing large angle deflections. A finite element procedure used state transfer matrices and successive linearization and the results show that the stress critical phase occurs when the pipe is going through the 60-deg angle to the horizontal direction.
Nonlinear Static Analysis of Deep Ocean Mining Pipe—Part I: Modeling and Formulation
Authors: Felippa C. A. , Chung J. S.
Published: November 2009

A static analysis procedure is formulated and implemented for the numerical determination of nonlinear static equilibrium configurations of deep ocean risers or mining pipes. This implementation involves selection of a finite element model, modeling of structure, surface and subsurface environment and external forces, and solution of nonlinear equilibrium equations. The riser is modeled by three-dimensional beam finite elements which include axial, bending, and torsional deformations. These deformations are coupled through geometrically nonlinear effects. The resulting tangent-stiffness matrix includes three contributions identified as linear, geometric (initial-stress) and initial-displacment stiffness matrices. For the solution, a combination of load-parameter incrementation, state updating of fluid properties, and corrective Newton-Raphson iteration is used. The resulting riser configuration reflects the realistic modeling of environments and external forces. The static equilibrium solution can be used as initial condition for vibration or transient analysis. Numerical studies are presented in Part II of this paper.
Finite Element Analysis With the State Variable Transfer Matrix and Geometric Nonlinearity for Marine Pipelines in Subsurface Tow
Authors: Kan W. C. , Healey A. J.
Published: November 2009

An analytical study of subsurface transportation of long marine pipelines has been performed. Systematic models and numerical algorithms are developed to predict the static configuration and stress distributions along the pipeline during transportation phase. A successive linearization technique and the state variable transfer matrix method are utilized to obtain solutions to the nonlinear two-point boundary value system of equations. Discrete buoyancy forces are also included to reduce barge thrust requirement while maintaining safe stress levels along the pipeline.
Dynamic Response of a Double Articulated Offshore Loading Structure to Noncollinear Waves and Current
Authors: Jain R. K. , Kirk C. L.
Published: November 2009

The three-dimensional dynamic response of a double articulated offshore loading structure to noncollinear waves and a steady current is studied for various waves and varying current directions. The governing equations of motion are derived by the Lagrange’s method where the wave and current forces are computed by a modified form of the Morison’s equation which takes account for the relative motion of the water particles with respect to the oscillating structure. The resulting highly nonlinear equations are solved by using a block integration method. The computed results predict complex whirling oscillations of the structure to noncollinear waves and current.
Experimental Study of Two-Phase Normal Slug Flow in a Pipeline-Riser Pipe System
Authors: Schmidt Zˇ. , Brill J. P. , Beggs H. D.
Published: November 2009

Slug flow was studied with air-kerosene flow in a 2-in. pipeline-riser pipe system consisting of a 100-ft pipeline and a 50-ft vertical riser. Pipeline inclinations of ± 5 deg, −2 deg, and horizontal were used. Pressures, flow rates, flow patterns and void fractions were measured. Flow pattern maps were developed and normal slug flow was modeled, permitting prediction of variables necessary to consider when designing a production facility operating under normal slug flow.
Ice Pressure Sensor Inclusion Factors
Authors: Chen A. C. T.
Published: November 2009

The inclusion of a pressure sensor in an ice sheet will disturb the pressure distribution in the ice sheet. The ratio of undisturbed ice pressure to the pressure felt by the sensor, defined herein as the inclusion factor, is required in interpreting the ice pressure measurement data. An approximate equation which expresses the inclusion factor in terms of the geometry of sensor and the sea ice/pressure sensor stiffnesses ratio is proposed in this study. Some results of analytical work and field tests which were performed to evaluate the accuracy of this expression are also presented. These results demonstrate the validity of the proposed inclusion equation.
Design of Discharge Piping for Pressure Relief Systems
Authors: Ross R. H.
Published: November 2009

The ASME Boiler and Pressure Vessel Code and publications by many manufacturers caution the design engineer to consider back pressure in discharge piping when sizing and selecting pressure relief valves. Only general guidelines are given, however, because of widely varying installation requirements. This paper addresses manifolded discharge piping system design. The method of analysis provides a simple technique for determining pressure within a discharge piping system. The method is based on adiabatic flow and uses local Mach number to relate expansion of the gas in the pipes to a mass flow function. The paper illustrates that relief valves discharging into lines and headers should not be sized or selected without careful analysis of the entire relief system.
The Design and Construction of Beaufort Sea Drilling Islands—Sag Delta 7 and 8
Authors: Potter R. E. , Goff R. D.
Published: November 2009

The planning, design and construction of two offshore exploratory drilling islands, constructed in the Alaskan Beaufort Sea during the summer of 1980, is described. Emphasis is given to areas of the work that are either unique to the Alaskan Beaufort Sea or involve modifications to the artificial island technology developed in the Canadian Beaufort Sea. The construction of the islands using a land gravel source, transport and handling of the gravel by highly efficient equipment, and placement of the gravel using the limited marine equipment available at Prudhoe Bay is described. The development of an economical slope protection system, with a design life of 3 yr, in Arctic environment and the monitoring and maintenance program planned to minimize the propagation of anticipated damage and maximize the effectiveness of the slope protection system is described, and knowledge gained to date is also included.
Duluth Co-Disposal Facility
Authors: Huang W. C. , Nelson D. L.
Published: November 2009

The world’s first full-scale fluidized bed reactor co-disposal facility located at the Western Lake Superior Sanitary District’s (WLSSD) central waste-water treatment complex in Duluth, Minnesota, began its shakedown operation in the fall of 1979. The authors present herein basic design criteria, a system description, November 1979 system status, and areas of operational concern.
Modeling Capabilities for the Devonian Gas Shales
Authors: Kucuk F. , Sawyer W. K. , Alam J.
Published: November 2009

Mathematical models for predicting gas performance of Devonian gas shale reservoirs can be divided into two groups: single and dual porosity models. Further, two dual porosity models have been developed. Although the shale matrix is known to contain a large quantity of gas, it is not known what fraction can be produced economically. No conclusive evidence in support of the various model concepts is given, but the information in this paper will facilitate comparison of existing models. Area requiring further study in order to advance current modeling technology are discussed.
Field Results From a Linked Vertical Well UCG Test in Deep, Thin-Seam Bituminous Coal
Authors: Martin J. W. , McClung J. D. , Liberatore A. J. , Strickland L. D. , Zielinski R. E. , Seabaugh P. W. , Agarwal A. K.
Published: November 2009

For a first in the United States, a 900-ft (275-m) deep, 6-ft (2-m) thick, swelling, eastern bituminous coal has been gasified successfully in situ. Under the direction of Morgantown Energy Technology Center, the relatively small-scale field test, Pricetown I, affected the equivalent of approximately 735 tons (665 t) of a high-sulfur, high-ash section of the Pittsburgh coal seam near Pricetown, Wetzel County, West Virginia, during the 4-mo burn. A methane rich gas with an average heating value greater than 200 Btu/cf (7450 KJ/m3) was produced at low flow rates during operations to enhance the coal seam permeability by reverse combustion. During the high-flow gasification phase, a gas with an average heating value of 124 Btu/cf (4260 KJ/m3) was produced resulting in an average energy production of 510.9 MMBtu/day (539.1 GJ/d). Initial test results and plans for continued development of this alternative energy source are discussed.
Heat Transfer to Oil Shale in a Closely Spaced Bundle as an Approximation to a Packed Bed
Authors: Udell K. S. , Jacobs H. R.
Published: November 2009

The heat transfer to a single cylindrical sample of oil shale in a staggered tube bundle was studied both numerically and experimentally in order to evaluate the thermal and chemical processes associated with the retorting of oil shale in packed beds particular to in-situ processing. The cylinders were subjected to constant gas temperatures and to gas temperature histories experienced in an actual combustion retort. The results of the numerical modeling were compared with the experimental data in order to evaluate the model’s performance. It was found that the model satisfactorily described the thermal processes experienced during the combustion retorting of oil shale within the limits of the accuracy of published data on oil shale thermal properties and chemical kinetics. Net heat transfer to cylindrical oil shale samples in a staggered bundle configuration was also calculated and was shown to nearly duplicate published data related to gas-solid heat transfer in a packed bed combustion retort.
Jet Piercing of Oil Sands
Authors: Gilpin R. R. , Gates E. M.
Published: November 2009

This paper describes the results of an experimental investigation of the penetration of oil sands by continuous and pulsed high-pressure water jets. Both laboratory and field tests were carried out to determine the influence of the jet dynamic pressure, nozzle diameter, pulse frequency, and total jetting time upon the depth of penetration.
Packer-Induced Stresses During Hydraulic Well Fracturing
Authors: Warren W. E.
Published: November 2009

Well bore stresses induced by inflatable packers during hydraulic fracturing operations are investigated. The geologic formation is modeled as an unbounded homogeneous isotropic linear elastic solid containing an infinitely long circular cavity, while the packer is modeled as a semi-infinite thin-walled circular cylindrical shell. For given packer properties, these induced stresses are shown to depend on the difference between packer pressure and fracturing pressure and can become significant. Typical numerical results are obtained and presented graphically. Analytical approximations for the maximum values of these stresses are also presented. While these effects are of no importance in the usual application of hydraulic fracturing to enhance oil and gas recovery, they are crucial in attempts to estimate in-situ stresses from hydraulic fracturing pressure data.
Ice Force Prediction Using a Limited Driving Force Approach
Authors: Kreider J. R. , Vivatrat V.
Published: November 2009

This paper discusses the importance of environmental driving forces in determining ice loads on Arctic offshore structures. Limits to the environmental driving force in a first-year ice field are analyzed by considering models of ridge formation, wind and current driving forces, and irregularities such as leads and tidal cracks. Average driving forces are estimated to be approximately 10–50 kips/ft for far-field, with some local concentration near fixed structures. These order of magnitude estimates are sufficiently less than failure loads for many ice features to indicate that limited driving force approach may reduce estimated ice loads on Arctic structures.
On the Efficiency of Some Recently Developed Integration Algorithms for Offshore Problems
Authors: Datta T. K. , Sood A. M.
Published: November 2009

The efficiency of some recently developed integration schemes, namely, Hilber’s ∝-method, collocation schemes and large time step integration schemes developed by Argyris, is evaluated by applying them to the response analysis of an idealized offshore tower. The tower is fixed at the base, having an additional mass at the top. For the analysis the tower has been modeled as an assemblage of 2-D beam elements. The dynamic degrees of freedom at each node are taken as those corresponding to the rotational and sway degrees of freedom. Using the normal mode theory the equations of motion have been decoupled except for the generalized loading vector which appear nonlinearly coupled, thus requiring iterative solution at every time step. The results of the study show that the large time step integration schemes developed by Argyris are more efficient than other integration methods considered here.
Determination of In-Situ Stresses From Hydraulically Fractured Spherical Cavities
Authors: Warren W. E.
Published: November 2009

Several problems in analysis can arise in estimating in-situ stresses from standard hydraulic fracturing operations if the borehole is not aligned with one of the principal stress directions. In these nonaligned situations, the possibility of fracturing a spherical cavity for estimating the in-situ stresses is investigated. The theory utilizes all the advantages of direct stress measurements associated with hydraulic fracturing and eliminates the geometrical problems associated with the analysis of hydraulic fractures in cylindrical boreholes.
Fracture Analysis of Ceramic Proppants
Authors: Swanson S. R. , Cutler R. A.
Published: November 2009

Small particles (traditionally sand) are mixed with fluid in hydraulic fracturing treatments of petroleum wells to stimulate production. The solid particles, called proppants, are used to prop open the fracture as hydraulic pressure is reduced. Deep wells can demand higher strength than provided by sand, while low specific gravity is desired to improve proppant transport. This paper considers the stress and strength analysis of proppants, and considers the use of high-strength ceramics as possible proppants. The stresses produced by interparticle contact are analyzed, which along with a failure criterion based on a critically stressed volume lead to a fracture prediction. The results show that ceramics can give adequate strength, even when used in low-density forms such as with high porosity or as hollow spheres. Laboratory tests of the effect of closure pressure on fluid permeability are seen to be in good agreement with the fracture predictions.
Axial Stretching Oscillation of an 18,000-Ft Vertical Pipe in the Ocean
Authors: Chung J. S. , Whitney A. K.
Published: November 2009

For a long pipe in deep ocean with the equipment attached to its free bottom end, the bottom end oscillation can be amplified near resonance several times the top end oscillation amplitude. This can become a unique design and operation problem of the deepsea mining or drilling system equipment. Accounting for the added mass and damping of the bottom end equipment, the solution is obtained through numerical iteration for an 18,000-ft long vertical pipe with the bottom equipment, which is handled from a 300,000-t mining ship. It shows significantly large oscillatory pipe stretching near the resonance. The same trend of stretching is measured by the at-sea test with the Glomar Explorer test-mining operation. Near resonance, the bottom end motion is out of phase with the top end motion, thus increasing the net pipe stretching. The pipe response characteristics can be significantly altered by the pipe weight distribution, wall thickness, and length. These transfer functions, spectral analysis results and parametric analyses are presented. The stretching oscillation can impose stringent requirements on the design and operation of the equipment hardware at the bottom end. The analysis method also applies to the OTEC cold water pipe, to the re-entry operation of deepsea drilling, and to the submarine pipelines/laying.
An Analysis of the Thermal Fixation of Pilings
Authors: Callinan J. P.
Published: November 2009

Pilings, fixed in place with frozen sand-water fill, are used as foundations in regions of the world where the ground is permanently frozen. The heat transfer processes in the piling-fill-ground-ambient air system have been studied using a finite difference formulation of the heat conduction equation. A composite ground with a time-varying snow layer and time-varying meteorological conditions, typical of the North Slope of Alaska, are considered. The method of analysis is verified by comparing the computed thermal history of the natural ground with temperature measurements in the ground. This study indicates that when a piling is first set in the ground (in the late winter) the fill freezes completely in two days, that the system reaches a condition of periodic steady state within two weeks, that seasonal thawing of the sand-water fill will extend no more than 0.3m deeper than the seasonal thawing of the natural ground, and that the temperature of the ground adjacent to the fill is within 1°C of the temperature of the unaffected ground.
Time Effects on the Lateral Soil Resistance to Pipeline Movement
Authors: Karal K.
Published: November 2009

Resistance to pipeline motions in cohesive soils is shown to change with time. The following time effects are distinguished: aging of disturbed soil, duration of constant loading on the pipeline (consolidation time) and rate of external loading. Theoretical treatment of the two latter of these effects is compared with experimental results available in the literature. These experiments confirm the increase of the soil resistance with increasing consolidation time as shown by the theory. They are, however, insufficient to demonstrate the effect of loading rate set forth by the theoretical considerations herein.
ARMA Algorithms for Ocean Wave Modeling
Authors: Spanos P-T. D.
Published: November 2009

Three different algorithms are presented for simulating a time series which is compatible with a given power spectrum of ocean waves. The first algorithm generates the current value of the time series as the sum of a linear combination of its past values and a white noise deviate. The second algorithm produces the values of the time series as a linear combination of white noise deviates. The third algorithm is a combination of the first and second algorithms. These algorithms are applied to the Pierson-Moskowitz (P-M) spectrum, exclusively. The third algorithm is associated with simple analog filter approximations of the P-M spectrum. The advantages and disadvantages of each of the three algorithms are discussed in context with their applicability to offshore engineerng problems.
An Analysis of Chain Forces of a SBS Under Regular Wave Action
Authors: Yu Yu-Xiu
Published: November 2009

Since the first Single Buoy Storage System (SBS) installed in Aquitaine-Tunisia in 1974 [1, 2], many similar systems have been installed. To facilitate oil production in Gulf Bohai, China, a model test of a SBS to investigate its motion and the forces under the action of regular waves has been carried out. Consulting the test results, this SBS “OFFSHORE 621” has been designed and launched. In this paper, the methods for determining the static characteristics of the multichain anchoring buoy system (MABS) and the measure for decreasing the chain force are given.
Stresses in Multilayered Cables
Authors: Costello G. A.
Published: November 2009

A theory is presented which will predict the stresses in a multilayered cable, subjected to axial, bending and torsional loads. In the axial case, the axial force and axial twisting moment are represented as linear combinations of the axial strain and the rotational strain. An analyisis is also made of a cable subjected to axial loads and wrapped around a drum. The analysis involves a superposition of the stresses caused by the axial loads and the bending loads.
Frictional Pressure Losses for Single-Phase and Two-Phase Flow of Drilling Muds
Authors: Elfaghi F. A. , Langlinais J. P. , Bourgoyne A. T. , Holden W. R.
Published: November 2009

The vertical flow of mud and gas-mud mixtures in long pipes is of interest in the design and operation of subsea well control equipment where long choke lines are required. Heretofore, the question of two-phase flow of non-Newtonian drilling muds has not been investigated experimentally in full-scale well systems. Frictional-pressure losses were measured in a 2 3/8-in., 3000-ft long, vertical tubing when flowing drilling mud alone, and flowing mud-gas mixtures. The single-phase data was compared to values predicted by both the Bingham plastic and power law rheological models, which are commonly used to describe non-Newtonian fluids. The multiphase pressure loss data were used to evaluate various published correlation techniques.
Design and Operation of a Versatile Pollution Control/Liquid Waste Thermal Destruction System With Maximum Energy Recovery
Authors: Hasselriis F.
Published: November 2009

This paper describes an innovative fume incinerator which supplies all the steam needs of an industrial plant by burning waste liquid fuels, yet is flexible enough to match the instantaneous, hourly, weekly and seasonal variations in steam usage of the plant. Even though fume input is nearly constant, the load can be followed by adjusting the fuel input while furnace temperatures vary in a range above that needed to destroy the selected wastes. A steam accumulator reduces peak steam demand on the boilers. Ash from the waste oils accumulates on the furnace refractory, and boiler and air preheater tubes, requiring periodic cleaning. By maintaining sufficient minimum temperatures, effective atomization and mixing, these systems can destroy liquid wastes containing difficult chemicals such as chlorinated phenol and benzene compounds. The required temperatures can be determined by plug-flow thermal destruction in the laboratory, and confirmed by testing typical materials in the full-scale oxidizer.
Direct Coburning of Unprepared Municipal Solid Waste and Sludge
Authors: Dvirka M.
Published: November 2009

The paper describes derivation of data and guidelines for coburning of municipal sludges and unprepared solid waste, giving approximate limits of applicability using direct coburning model with minimum sludge preparation. No attempt is made to evaluate or compare direct coburning with alternate codisposal concepts such as flash drying, indirect drying, coburning with refuse-derived fuel, etc.
Model for Heave and Settlement Predictions in Discontinuous Permafrost
Authors: Coulter D. M.
Published: November 2009

Heave and settlement of soils in discontinuous permafrost regions may be predicted using a model based on capillary stress theory. A one-dimensional numerical method has been developed which couples temperature and ground water migration to or from a freeze/thaw front and predicts the resultant ground heave/settlement. This model is among the first to predict both heave and settlement based on seasonal natural ground surface thermal disturbances. The results of the model are presented as graphs of time-dependent temperatures, excess pore water pressures, water contents, heave and settlement, and frost and thaw penetrations versus depth. The heave/settlement predictions follow closely experimental results presented elsewhere and indicate that an accurate model has been constructed within the limitations of the chosen data and the numerical technique.
Implementation of Phase Change in Numerical Models of Heat Transfer
Authors: Hayes L. J. , Diller K. R.
Published: November 2009

This paper investigates some of the numerical problems involved in simulating heat transfer in porous media in the presence of phase change. Applications of this type of simulation include modeling of certain metal forming processes, of biological tissues and organs during cryosurgery or cyropreservation, and of heat transfer in frozen soils subjected to transient environmental conditions. A two-dimensional finite element model was used in which the latent heat is treated directly as an energy source in the problem formulation. Several parameters addressed in this work are crucial to the successful implementation of numerical methods for nonlinear heat transport with phase change, including: the effect of nodal point spacing on the occurrence and magnitude of numerical oscillations in the temperature solution and the use of grid point spacing to control these oscillations; the limiting element size which should be used in order to insure stable temperature fields; and the effect which the range of temperatures over which latent heat is liberated has on the solution. The results indicate that numerical stability is achieved for combinations of the foregoing parameters which yield small values of the Stefan number.
The Coaxial Pipe Electric Heating System for Pipelines
Authors: Koyanagi M. , Hojo H. , Nagamune A. , Ogata J.
Published: November 2009

To transport highly viscous crude oil efficiently through pipelines, some electric heating systems have been conventionally used. But they include heating cables or tubes, which are troublesome in submarine pipeline construction. A new electric heating system without a cable has been developed and is applicable to long-distance submarine pipelines. This system has a coaxial steel pipe structure, using the pipes as a heater by applying AC current to this coaxial circuit. In this paper, electromagnetic analysis on this system, experimental study using a 30-m length test pipeline, and mechanical tests on the electric insulating structure of the system are described.
Computer-Controlled System for Nondestructive Thickness Measurement of Corroded Steel Structures
Authors: Singh A. , McClintock R.
Published: November 2009

Over a period of time, corrosion attacks the surface of offshore and waterfront steel structures and can cause catastrophic failures. To date, thickness measurement to determine loss from corrosion has been performed visually; however, this method provides only limited assessment [1], A computer-controlled ultrasonic system to more accurately measure corroded steel structure thickness is described. The system is based on an innovative concept using an ultrasonic focused transducer aligned directly over the center of corrosion pits. At each of these positions, a corrosion pit acts as an acoustic lens, collimating the beam inside the steel specimen. Using this approach, the reflection from the back surface of the steel specimen is strong. The time difference between the back surface and front-surface reflections is used to calculate the thickness of the plate. The prototype system developed for implementing this concept is capable of automatically locating the pit centers, acquiring waveforms, and determining the thickness. During this process, the system rejects waveforms with spurious signals using simple pattern recognition approaches. Results have shown that the thickness of corroded plates can be measured with an average error of 4 percent. The system not only is accurate for thickness measurement, but also is easy to operate. Commercially available equipment used for the system makes it simple to build and less expensive than a fully integrated custom system.
Analysis of Tubular Connections Using a Thin Cylinder Approximation—Part II
Authors: Pattillo P. D.
Published: November 2009

The results from Part I of this two-part study are used to predict the performance of threaded connections, in particular API round thread connections. The effects of inelastic deformation, taper tolerance, and thread lubricant on makeup and on the stress state of such connections are examined. Important insights gained from the analysis include the variation of makeup torque and ensuing bearing pressure and leak integrity with variations in tubular material properties and geometry.
Investigation of API 8 Round Casing Connection Performance—Part II: Stresses and Criteria
Authors: Asbill W. T. , Pattillo P. D. , Rogers W. M.
Published: November 2009

Comparison of stresses in Part I showed that the APILT&C 8 Round threaded casing connection could be accurately analyzed with finite element methods, with models that both included and excluded the threads. Part II further investigates the effects of thread tapers and external loads on connection stresses. It also assumes a criteria for determining maximum assembly interference using the finite element models. Tension loading is shown to affect pin hoop stresses, while being insignificant to coupling hoop stresses. Hand-calculated stresses are shown to give reasonable hoop stress values.
Damage Detection in Offshore Structures by the Random Decrement Technique
Authors: Yang J. C. S. , Chen J. , Dagalakis N. G.
Published: November 2009

The Random Decrement Technique has shown promise as an inspection technique for offshore structures. The major advantage of this technique is that it requires only measurements of the dynamic response of the structure and not the input excitation causing the response. On offshore platforms, such random input forces occur from wind, waves, and currents. The Random Decrement Technique was evaluated together with a number of other NDE techniques under the NDE round robin testing program sponsored by the United States Geological Survey and the Office of Naval Research. A series of tests, damage scenarios, were conducted on a model of an offshore structure in a blind-mode by an independent neutral agent. Test data were given to the corresponding advocates to be analyzed and interpreted to predict the damages. Initial results indicated that the Random Decrement Technique was able to identify all the damage and non-damage situations with the usage of only four accelerometers mounted on each of the legs of the structure.
The Influence of Tension, Pressure and Weight on Pipe and Riser Deformations and Stresses
Authors: Sparks C. P.
Published: November 2009

The influence of tension, pressure, and weight on different aspects of pipe and riser behavior has already been the subject of many articles (see references). In spite of this it has frequently been misunderstood, sometimes with serious consequences. The object of this paper is to explain the subject clearly and the approach is therefore deliberately very elementary. The principal problems of bending, buckling, yielding and strains, usually treated in separated papers, are here treated homogeneously. The widely used concepts of “effective tension” and “effective stress” are given interpretations, easy to visualise, which are related to analogous concepts in other engineering fields. Finally, eight diverse particular examples of the influence of tension, pressure and weight on pipe and riser behavior, are discussed.
Solutions for Small Slope Pipeline Lifting Problems
Authors: Hobbs R. E.
Published: November 2009

Two classes of submarine pipeline handling problems are considered, namely the lifting of a pipe with a free end for tie-in purposes, and the raising of part of a continuous line for hot-tapping or repair. If pipeline slopes are small (as is usual in seabed work), engineers’ beam theory may be used in combination with a Newton-Raphson solution to locate the separation points between pipe and seabed. Key results are presented.
A Reconnaissance Study of the Hydrothermal Characteristics of Pilgrim Springs, Alaska
Authors: Osterkamp T. E. , Gosink J. P.
Published: November 2009

A reconnaissance level study of the Pilgrim Springs geothermal system was conducted to determine the near-surface thermal regime and to obtain information on the ground water flow regime within the thawed ground area. Measurements included soil temperatures, apparent electrical conductivity of the soil, electrical conductivity and temperature in the Pilgrim River, saturated hydraulic conductivity of the soil and ground water flow characteristics (direction and velocity). In addition the size, number and characteristics (geometry, direction of flow) of near-surface convective plumes were investigated. Measured temperature profiles were used to estimate ground water flow velocities. There are approximately 2–3 km2 of thawed ground surrounded by permafrost on the order of 100 m in thickness. The highest temperatures were found in the southwest quadrant of the thawed area where a pool of ground water at ≈ 92°C exists at 14–32 m below the ground surface. Temperature measurements suggest that water in the pool is flowing laterally and vertically. Temperature and electrical conductivity measurements suggest that this pool of water underlies most of the thawed ground area although the possibility of several, unconnected sources of hot water and multiple pools has not been ruled out. Conductivity measurements suggest that hot and/or saline water rises in convective plumes from the pool at about 40–60 sites. The Pilgrim River appears to be heated by heat transfer from the geothermal area. Saline ground water enters the Pilgrim River, probably through its bed, increasing the conductivity of the river water.
Summer Ice Floe Impacts Against Caisson-Type Exploratory and Production Platforms
Authors: Croteau P. , Rojansky M. , Gerwick B. C.
Published: November 2009

Summer impacts of large ice floes against arctic offshore platforms are likely to be a governing condition for the global foundation stability in medium and deep-water offshore platforms in the Alaskan Beaufort Sea. Some features of the impact phenomenon are illustrated by analyzing two vertically faced caisson-type gravity platforms. The two structures differ in their function, size and environmental exposure: the first is a smaller exploratory drilling caisson while the other is for production of oil and gas. Both structures are assumed to be in 30 m of water. A description of the analysis techniques is given: it is based on a dynamic modeling which considers the effects of inertia, damping, foundation compliance and slippage at the base in addition to a crushing failure mechanism in the ice at the contact area. Comparisons are made between the structural response computed for both the exploratory and production platform and for typical “soft” and “firm” site conditions. A discussion as to the relative importance of various design and modeling parameters is presented. The comparison of response characteristics of the assumed structures provides some insight for the purpose of formulating rational design criteria with regard to ice floe impact.
Vortex-Induced Vibrations of a Flexible Cylinder Near a Plane Boundary Exposed to Steady and Wave-Induced Currents
Authors: Tsahalis D. T.
Published: November 2009

Model tests were carried out in a wave tank to determine the effect of combined steady and wave-induced currents and/or the proximity of a plane boundary (seabottom) on the vortex-induced vibrations of a flexible pipe. The response of the center of the pipe span was measured using a biaxial accelerometer. The results show that the proximity of the plane boundary and/or superposition of waves on the steady flow have a pronounced effect on the amplitude and frequency response in both the transverse and in-line directions.
Nonlinear Inertia Forces on Slender Cylindrical Members
Authors: Williams A. N.
Published: November 2009

An expression for the nonlinear wave force on a vertical, circular cylindrical member whose diameter is small compared to the incident wavelength is derived from an exact solution to the second-order diffraction problem. A comparison is then made with the inertial force estimates obtained using Stokes’ second and fifth-order wave theories in Morison’s equation with a mass coefficient derived from linear potential theory, as is currently recommended in the offshore design codes. Results indicate that in water depths of the order of 1/16 of a wavelength, nonlinear free-surface effects contribute significantly to the total inertia force on a slender cylindrical member.
Wavelength and Celerity for Interacting Waves and Currents
Authors: Li Y.-C. , Herbich J. B.
Published: November 2009

The main objective of this paper is to present a simple nomogram for a quick evaluation of changes in wavelength and celerity when waves interact with currents.