bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stress-Concentration Factor Analysis of Large-Diameter Stiffened Nodes
Authors: Krieger W.F. , Mangin D.M. , Gholkar S.S. 
Published: October 2008

ABSTRACT
Stress concentration factor (SCF) determination for large diameter, complex stiffened tubular joints remains a labor and computer intensive effort. This paper describes results obtained from finite element analysis of two such nodes from the Ninian Southern platform in the North Sea. Axial, in-plane moment, and out-of-plane moment SCF's are presented for the five braces of each node. The influence of boundary conditions, weld geometry, and load interaction are considered. SCF's are computed in accordance with U.K. Dept. of, Energy procedures.
Results provide an indication of SCF values for large diameter, stiffened nodes. This, can be of value in comparing cast versus welded nodes for deepwater fixed platforms.

INTRODUCTION
The Ninian Southern structure is a fixed, steel jacket located in 140 meters of water in the 'North Sea. It was towed to location and installed in May 1977.
While conducting a routine inspection in June 1984 it was discovered that a horizontal member at the -43 meter elevation was broken. Investigation by The Welding Institute showed that failure resulted from the propagation of a weld defect at the root of a single-sided weld at a temporary access manway.
While no evidence of cracking was found at, the nodal connections, it was considered prudent to re-evaluate node fatigue lives. Consequently, SCF's were computed for the stiffened and unstiffened nodes on Ninian Southern platform.

NODE DESCRIPTION
This paper describes computational procedures and resulting SCF's for two of the nodes on the large (9.2 meter diameter) flotation legs. These nodes are at elevations -43 m and -12 m, and are representative of the remaining large leg nodes. Figure 1 shows the location of these nodes on the" Ninian Southern platform, as well as the structure's framing pattern.
A cut away view of the -43/F4 node is shown in Figure 2. The node is heavily stiffened with ring stiffeners, horizontal and vertical diaphragms backing the braces, and circular or elliptical back-up tubes behind the "footprint" of all the braces. Except for the horizontal diagonal brace, the chord wall is locally thickened with a 63 mm insert plate. Brace member dimensions are given in Table 1, along with no dimensional joint geometry parameters.
Circular and elliptical back-Up stiffeners are the same thickness as the corresponding brace stubs.
The -12/F4 node is similar, with the following exceptions:Brace and stub sizes differ.Chord wall is generally 25 mm (vs 38 mm for -43/F4).The 63 mm insert plates are at all brace intersections.There is greater eccentricity in the line of action of the braces.The chord is stiffened by longitudinal stiffeners in addition to all previously cited stiffening.
Table 2 contains brace member dimensions and joint geometry parameters for node -12/F4.
API Oilwell Cementing Practices
Authors: Calvert D.J. , Smith D.K. 
Published: October 2008

ABSTRACT
API Cement Standardization Committee 10 has striven through the years to provide the worldwide drilling industry with the latest technology as applied to cement specifications and testing of down hole materials. In addition to publishing 22 editions of these standards and specifications, this group has published over 25 technical papers and bulletins as a mechanism of keeping the industry informed.
Perhaps the most significant achievement of this committee has been the preparation of a new textbook covering worldwide cementing practices. Individual chapters deal with everything from primary cementing to the plugging of wells and were authored by recognized experts of major companies' personnel, most of whom are active in API work. This book also contains a complete bibliography of published literature covering papers and patents to 1989. Noteworthy in the text is a survey of over 200 fields, worldwide, covering casing programs, drilling fluids and cementing practices. Many worthwhile and useful statistics may also be found therein.
The paper and oral presentation will highlight the latest in cementing and findings from these worldwide surveys of drilling and completion practices.

INTRODUCTION
Several thousand wells are drilled and completed annually throughout the world--some productive of oil or gas while some are dry--yet during this drilling and completion process most of these wells are cased, with the casing set in the borehole, surrounded by cement.
Cementing technology in the literature dates from the early 1920's. The major part of this cementing information, however, represents practices used after World War II. In 1937 the American Petroleum Institute established the first committee to study the use of cement down hole. There were already a few cement testing laboratories equipped with strength-measuring apparatus and stirring devices to determine the fluidity or pumpability of cement slurries at down hole temperatures.
Since these early events in our industry, many changes have taken place in cement standardization, in cement testing, and in field practices, particularly in drilling below 10,000 feet. API Cement Standardization Committee 10 and its members have played a significant role in the research and development of all phases of cement technology. In 1989, experts within the industry and from Committee 10 finalized an up-to-date text entitled "Worldwide Cementing Practices." This book attempts to mold all the various cementing technologies used today. It is also significant to note that the processes of "cementing a well" are very similar in most parts of the world. Nomenclature and terminology may vary from one area to another, however, the basic process is about the same worldwide. Highlights of the various chapters and authors' opinions are summarized herein.
The Foundation Stability Analyses of the Ekofisk Protective Barrier for Both the Installation and Operational Conditions
Authors: Broughton P. , den Hertog P.O. 
Published: October 2008

ABSTRACT
This paper describes the results of detailed foundation stability analyses of the Ekofisk protective Barrier for bott the installation and operational phases. Subsidence at the location of the Ekofisk complex has meant that it was necessary to protect the existing concrete Tan structure and the decks and process equipment contained thereon against severe environmental action. The Protective Barrier is a self-supporting concrete gravity base structure, which forms a complete ring around the existing Tank. It was installed initially as two half units and subsequently connected together offshore. The ring-shaped foundation configuration is quite unique for offshore structures. The Protective Barrier if designed to resist external applies. environmental loadings which are in excess of those applied to any other previous marine structure. For both the temporary installation phase (units unconnected), and the operational phase, detailed analyses were performed to determine overall displacements and strain levels within the soil at appropriate design load levels, and also the failure mechanism for each configuration. This data confirmed the required on-bottom weight and hence ballast loads, and quantities in order to satisfy stability requirements.

1. INTRODUCTION
The Ekofisk field is anticipated to reach a final level of subsidence of about 6.0 meters. For this reason, installations within the Ekofisk complex had to be protected against severe environmental action. Figure 1 shows the field layout of the Ekofisk complex. The solution selected for the protection of the existing Ekofisk Tank was to provide an external Protective Barrier. Figure 2 shows a plan and elevation of the existing Tank, including the two main deck levels at +90m and +100 m. Figure 3 provides a plan and elevation of the Protective Barrier. The main dimensions of this structure are provided below:overall height: 106 metersouter diameter of the bottom slab: 140 metersdiameter of the outer wall: 137.5 metersdiameter of the inner wall: 106.5 metersinner diameter of the bottom slab: 104 meterselevation of the top slab: +84 metersbase slab width: 18 meters
Table 1 provides a summary of the main quantities (and weight in air) of the materials used in the construction and installation of the Protective Barrier.
The submerged on-bottom weight of thecomplete Protective Barrier is 500,000 tones.
A brief description of the principles involved in the design of a Protective Barrier for the protection of large bottom-supported marine structures is given elsewhere (1). A more detailed account of the main design and installation aspects of the Protective Barrier to surround the Ekofisk Tank was given previously (2).
Innovative Disconnectible Mooring System for Floating Production System of HZ-21-1 Oil Field at Huizhou, South China Sea
Authors: O&apos;Nion G. , Calo D. , Seguin R. , Huang San Ping 
Published: October 2008

ABSTRACT
To accommodate the harsh environmental condition which can occur in the South China Sea, a disconnect able Buoyant Turret Mooring was designed to moor a tanker floating production system. The disconnect able system (FPSO) is of an innovative design based upon proven components.

INTRODUCTION
During early 1988 ACT OPERATOR GROUP (ACT-OG) called for tender for a tanker based floating production system to be installed in the Huizhou 21-1 field in the South China Sea, located approx. 100 miles SW of Hong Kong and lying in 116 m of water, see Figure 1. ACT-OG opted for a disconnect able mooring system as the site is frequently Subjected to typhoons and severe tropical storms. The advantage of a disconnect able system compared to a permanent system is that the mooring system does not have to be designed to accommodate the economically penalizing severe loadings associated with typhoon conditions. However, the possibility of typhoons occurring during winter months dictated a relatively high reconnection sea state in order to minimize production down time while waiting a reconnection. To fulfill the above requirements, Single Buoy Moorings proposed a innovative disconnect able mooring system which utilized components and experience gained from the disconnect able riser turret mooring system previously installed and successfully operating on the Jabirus field in the Timor Sea.
The proposed disconnect able system, Buoyant Turret Mooring, is an internal turret located in the forepeak structure of the tanker floating production system, see Figure 2. The mooring of the tanker is achieved by an array of eight equally spaced catenary anchorlegs connected to the turret by means of a Submerged mooring buoy. The mooring buoy is connected to the turret structure by a cullet type structural connector. To reconnect the tanker the mooring buoy is lifted up under the tanker using a reconnection wire rope hauled in on a drum winch.
By optimizing the size and location of the mooring buoy in relation to the tanker, the specified reconnection sea states could be achieved.

CONCEPT
The disconnect able Buoyant Turret Mooring was developed for the tanker FPSO to be installed in the Huizhou Field in South China Sea in a water depth of 116 m of water. The field lies 100 miles SE of Hong Kong, and is subjected to typhoons and severe tropical storms, on average 3 to 4 times a year. A call for tender was issued in early 1988 for proposals for both a permanent and a disconnect able mooring system. During the bid evaluation stage the permanent solutions were soon dismissed as being uneconomical in respect to the field size in favor of the cheaper disconnect able option. The permanent system is also considered to be susceptible to damage in the event of a typhoon with green water breaking over the deck.
Development and Testing of an Active Motion Compensation System for Production System Support
Authors: Maxwell J. Patrick , Hughes E.W. 
Published: October 2008

ABSTRACT
An active motion compensation system has been successfully tested which will allow hardware such as control pods and choke modules to be lowered and mounted to seabed installed hardware from a DP monohull multi-service vessel. The compensation system attenuates vessel vertical heave effects on the liftline and sub sea equipment in up to sea state five. This system enables an MSV to provide cost effective support to deepwater production facilities by allowing shock and vibration sensitive sub sea equipment to be run, set and recovered from the MSV. Testing instruments monitored the vessel, liftline, a subsea test package and the compensator control. Offshore testing is essential to determine the system's capabilities and suitability for intended purpose.

INTRODUCTION
Production systems are being installed sub sea at greater depths and in more severe climates. At depths greater then 1,000 FSW, dynamically positioned (DP) monohull multipurpose service vessels (MSV) can provide cost-effective support, work overs and maintenance to control and maintain sub sea systems. A monohull MSV equipped with a motion compensation system can provide a cost-effective alternative to drill ships and semi submersibles.
The motion compensator pre-engineeringspecified the operating parameters, including a testing program to coincide and guide system development, and confirm that operating parameters were met. The design and operating parameters are as follows:Working depth of 4,000 FSWHandle loads from 2,000 to 40,000 poundsNot sensitive to load variationsVessel heave periods of 6 to 13 secondsDouble heave amplitude of 15 feetMaintain sub sea package +/- six inches from a fixed referenceMaximum velocity of sub sea package is 1 foot/second (ft/sec)Interface with existing winch systemFit in deck space allotted
Due to the wide load range specified, the requirement to set down and recover equipment, and the level of compensation required, an active motion compensation system was selected rather than a passive unit. The handling system layout, including the winch, sheaves, and motion compensator is shown on Figure 1. Figure 2 shows the details of the motion compensator hydraulic skid.
The active motion compensator's hydrauliccylinder drives a traveling sheave assembly that interfaces with the liftline. In the compensating mode as the vessel heaves down the cylinder rod retracts, shortening the liftline. As the vessel heaves up the cylinder rod extends paying out cable. An accelerometer package mounted by the over boarding sheave measures vessel vertical motion. The compensator control for processing accelerometer outputs 'is located on the bridge. outputs are double integrated to determine vessel heave displacement. This signal regulates cylinder hydraulics so the traveling sheave mirrors vessel heave. The motion compensator control process is illustrated in Figure 3.
Integrity Testing of Three Drilled and Grouted Piles
Authors: Briaud J-L. , Dupin A.M. 
Published: October 2008

THE PROJECT
The work described in this article was done to evaluate the ability of oil field grout logging technology to determ1ne the integrity of drilled and grouted piles.
Three drilled and grouted piles were constructed at one of the two Texas A&M University sites for geotechnical experimentation. At the site the soil is a stiff to very stiff clay. One boring with Shelby tube sampling and pressure meter testing was drilled. Three cone electrometer soundings were also performed. Unconsolidated Untrained Tests and some Drained Direct Shear Tests were performed. Figure 1 gives a summary of the soil data.
The drilled and grouted pile designed for logging purposes was 110 ft (33.5 m) long, and had an average diameter equal to 30 in. (0.76 m). The steel casing was 20 in. O.D. (0.51 m) and had a wall thickness equal to 0.75 in. (19 mm). The hole was drilled dry, the grout was placed at the bottom of the hole and the closed end steel casing was lowered to the bottom squeezing the grout up in the annulus. From 0 to 20 ft (0 to 6.1 m) the annulus was made of loose cuttings of clay, from 20 to 40 ft (6.1 to 12.2 m) the annulus was left unfilled by creating a 360° chamber void, from 40 to 60 ft (12.2 to 183 m) a 45° vertical channel void was created in the grout curtain, from 60 ft to 85 ft (18.3 to 26 m) the pile was fully grouted with a 5 in. (127 mm) thick grout curtain and from 85 to 110 ft (26 to 33.5 m) the pile was fully grouted with a 2 in. (5 mm) thick grout curtain. Figure 2 shows the pile.
The two drilled and grouted piles designed for capacity determination were 40 ft (12.2 m) long and 8 in. (203 mm) in diameter. The steel casings were 5 in. (127 mm) in diameter. The holes were drilled with betonies drilling mud, the grout was tremied to the bottom of the hole and the closed end casings were slowly lowered in place. The grout filled the annulus from 40 ft (12.2 m) depth to 5 ft (1.52 m) depth. The no defect pile had no purposely designed defects, while the defective pile had a 45° defect from 5 ft (1.52 m) to 25 ft (7.6 m) depth and a 45° defect from 15 ft (4.57 m) to 35 ft (10.7 m) depth at 180° from the other defect. Figure 3 shows the defective pile.
The logging pile and to a lesser extent the two load test piles were logged by Schlumberger with a series of sonic, ultrasonic, gamma-gamma, and neutron logging tools. A well head was placed on the three piles so that the logging could be done at various pressure levels.
The two load test piles were subjected to various tension load tests after the logging. This article gives the details of the logging part of the work.
Dual Sensors for Improved Resolution in Marine Seismic Data
Authors: Barr F.J. , Sanders J.I. 
Published: October 2008

Summary
The use of both pressure and velocity detectors at each station in a water-bottom cable has been theoretically investigated and field tested. As a result of this study, we present a method for combining the two signals recorded at each station in such a manner that receiver-station, water column reverberations associated with each reflection wavelet are essentially eliminated from the data.
In addition to being less operationally complicated than using pressure detectors at two depths, we've found the dual-sensor method to be less sensitive to noise sources in the water column.

INTRODUCTION
The performance of 3D surveys using pressure detectors in water-bottom cables is well established (Rigsby et al., 1987). The method has proven itself effective for obtaining full 3D coverage in areas too congested with obstacles for normal towed streamer operations.
But the ghost reflection from the air-water interface which accompanies each reflection wavelet is a problem inherent in the method. Of course it shares this problem with the towed-streamer method, but the time delay between reflection wavelet and ghost is greater because the detectors are farther removed from the air-water interface. And as water depths increase to hundreds of feet, concern grows regarding the effectiveness of disconsolation techniques in removing the ghost reflection and other water-column reverberations.
Two basic approaches have been proposed in the literature for eliminating the ghost reflection. The first involves recording signals from detectors at different depths and performing a wave field separation (Bell and Cox, 1987; Brink and Swenson, 1987).
The second, and operationally more straightforward method utilizes paired pressure and velocity detectors at identical locations (Haggerty, 1956; Gal' Erin, 1974; Loewenthal et al., 1985). This method takes advantage of the fact that the two types of detectors generate signals of the same polarity for upward traveling waves, but of opposite polarity for downward- traveling waves (the ghost reflection).

ACOUSTICS AT THE WATER-BOTTOM
To determine how to most effectively combine the signals from the pressure and velocity detectors, it is necessary to solve the elastic wave equation subject to appropriate boundary conditions for the model shown in Figure 1 (White, 1965). In this figure, A's represent compression waves and B's represent shear waves.
Converting the solutions for pressure and vertical particle velocity at the water-bottom from the spatial and temporal frequency-domain to the time-domain, one obtains the pressure and velocity detector signals shown in Figure 2 (assuming detector transduction constants of unity and infinite bandwidth).
Fatigue Design and Overall Safety of Grouted Pile Sleeve Connections
Authors: Ingebrigtsen T. , Loset Ø. , Nielsen S.G. 
Published: October 2008

ABSTRACT
This paper covers two main subjects. Firstly the main results obtained in a joint industry research project on the strength of grouted pile sleeve connections in fixed offshore steel structures are presented. The testing and the specimens are described and guidance is given for both static and fatigue design. Secondly the main elements and results of a safety calibration study on the ultimate strength of such connections are presented.

INTRODUCTION
The purpose of the research project was to provide new and improved design formula for the capacity calculation of axially loaded, grouted pile sleeve connections. This was obtained through new and already established test results on reduced scale specimens. Both plain pipe and shear key connections were tested. The project 1 produced61 test results on the static strength of grouted pile sleeve connections. Together with other available data these have formed the basis of the development work. The total data base comprises202 test results.
In the first half of the 1980's Department ofEnergy (DEn), UK', and American Petroleum Institute(API)6 issued revised design regulations for grouted pile sleeve connections. DEn used an overall safety factor of 6.0 (4.5) for the grouted pile to sleeve connection. API, which uses the allowable stress method, does not express the overall safety factor explicitly. It is implicit in the allowable stresses specified. An overall safety level of about 4.5 is aimed at7. This is significantly greater than that used for other types of structural members and connections. A level of 1.5-2.0 on characteristic values is generally used in the offshore design codes.
In the studies the level of the material factor was calibrated within in safety format of the Norwegian Petroleum Directorate(NPD)8. The DEn and API design equations were used. The 202 test results were valuable support for the study together with records from offshore installation work concerning obtained grout strength and frequency of packer failure.
The NPD-regulations differentiate between uncertainties connected to the loads and those to the material. This is appropriate for a safety calibration study

STRHNGTHINVESTIGATION

GEOMETRY OF SPECIMENS
The cross sectionalize of piles and sleeves used are mainly 1/5 to 1/3 compared to offshore size. A few specimens of full scale diameter and thickness have been tested. The principal geometry of the grouted pile-sleeve connections tested is shown in Figure 1.
All specimens were fabricated from standard size seamless pipes satisfying the requirements of ASTM - A106 grade B.
To eliminate the effects of variations in surface condition the outer surface of inner pipe (i.e. that in contact with grout) was sandblasted, with a preparation grade BSa 2% in accordance with Swedish StandardS1S 05-5900 - 1967. Then the surface was allowed to corrode slightly in humid air, but not directly subjected to water.