bluuebunny/crossref_metadata_2025_split huggingface dataset:
Borehole Mining: Improved Technology Expands Horizons
Authors: Dibble M.F. 
Published: October 2008

ABSTRACT
Borehole mining as a viable concept for mining deep mineral resources has historically been long on promise but short on results. Application of this technology has been of particular interest in the east coast deep middle miocene phosphate deposits. These deposits are potentially enormous in scope and underlie sections of the coastal plain and the near offshore continental shelf.
The landslide portion of these deposits are generally too deep to mine using open pit methods, forcing development of alternative mining methods. A significant proportion of the offshore resources appear to occur at depths below the practical limits of cutter suction dredges and even exceed the limits of bucket ladder dredges. In most cases these deposits are covered by overburden that has to be removed and redeposited before the mineral section can be mined. The depth, thickness, composition of overburden, and environmental sensitivity of a particular location greatly impact mining system selection. It is probable that conditions will exist on portions of the continental shelf that will eliminate dredge mining as a choice for extracting a particular deposit. In these cases new processes such as borehole mining must be developed or the mineral resource will remain undeveloped.
A successful borehole mining test program for extraction of these deep phosphate resources was conducted in northeast Florida in 1984-1985. Based on the results of this test program, plus subsequent laboratory testing, and engineering studies a prototype borehole mining system was designed in 1986. The design contained several innovations that appeared to offer higher productivity and lower power consumption than the test unit actually used. Economic restraints, at that time, prevented the actual construction and testing of this unit.

INTRODUCTION
Extracting mineral values through a borehole is a very old process. Oil wells, brine solution mining, frasch sulphur recovery, etc. are only a few of the borehole recovery systems that have a major economic impact on our society. The extraction of mineral values in slurry form through a borehole has, as yet, not been as successful.
Some of the early work in borehole slurry mining started in the 1920's. Periodically new attempts have been made to develop this technology as specific requirements occured. Unfortunately, no major commercial projects have been developed as a result of this work.
The deep middle miocene phosphate resources generally occur from North Carolina to south Florida. Active test efforts were made to extract these phosphates on shore in North Carolina and Northeast Florida through a borehole during the later part of the 1960's. The cyclic nature of the phosphate industry, unfortunately, always seemed to start a down trend at times most inappropriate for ongoing research programs.
During the 1970's the United states Bureau of Mines (USBM) took an active role in the development of this technology. Test work was conducted on coal, oil sands, uranium bearing sandstone, etc, with varying degrees of success.
Operating Experience With Gas Compression Facilities on North Sea Platforms
Authors: Nilsen N.J. 
Published: October 2008

ABSTRACT
This paper describes the gas compression facilities on Ekofisk Area platforms in the North Sea. It discusses the operator?s experience with several compressors, the problems encountered and the solutions to correct them.
It also describes the improvements that are being made to reduce unscheduled maintenance and improve the reliability of the equipment.

INTRODUCTION
Phillips Petroleum Company Norway (PPCON) has developed and operates seven oil and gas fields in the Norwegian Sector of the North Sea. This operation consists of 25 platforms, with export thru a gas pipeline to Germany and an oil pipeline to England. Oil and gas are partly processed on the outlying platforms, and then transported via subsea pipelines and/or bridges to the Ekofisk Center. This is shown in figure 1.
PPCON has an important role in the transportation of gas from Norwegian fields. The transportation system is used to deliver gas from Elcofisk Area fields and other fields in the Norwegian Sector.
Compressors have a critical role in this operation. They are used in the transportation of gas from the outlying platforms to the center and from the center to Germany. They compress gas and vapor, which has been collected from various parts of the process, before it enters the final stages of processing. Gas above sales quantities is compressed and reinjected into the reservoir.
Operation and maintenance problems developed on some of these compressors after they were installed. These problems had to be solved to operate satisfactory and to keep the maintenance to a reasonable level.
Standby compressor capacity was installed on all critical functions. Increased gas production and gas transport for other fields will require that all installed compressors operate simultaneously in certain functions. Increased reliability and reduced unscheduled maintenance are required to avoid costly installation of additional machines.
Some "key" compressors at Ekofisk Center are discussed below.

PROCESS
The process is the separation of oil and gas. The liquid goes to England and the gas is processed and piped to Germany.
At Ekofisk Center the oil and gas are routed to different separators depending on the pressure. The separators and the pressures at which they operate are:
(Available in full paper)
A simplified diagram of this process is shown in figure 2.
Machines recompressing the different gas streams are the Flash Gas Compressors, Booster Compressors, and the Pipeline Compressors.
Steam-Powered Offshore Oil Producing Platforms
Authors: Tronstad I.M. 
Published: October 2008

1. ABSTRACT
This paper will briefly describe the parallel development of an oil production platform topsides with a conventional gas turbine driver system. This will include waste heat recovery and a topside with steam turbine drivers for large rotating equipment and steam heating system.
The base process configuration is outlined and key elements in the steam system design philosophy are described by diagrams, along with brief system explanations.
Principles regarding the layout of major steam system equipment are also described.
Comparative conclusions are drawn regarding weight and space requirements, as well as operation, maintenance and safety aspects.
Generally, the conclusions are promising and indicate potential for topside simplification by utilizing steam for heating and powering purposes.

2. INTRODUCTION
The conventional method of producing electric power on a large oil production platform is by gas turbine driven generators. Additionally diesels may be used for auxiliary purposes. Heating for processing or other purposes is accomplished by a heating medium or directly by fired heaters.
A heating medium heat source may be gas turbine exhaust.
Thermal efficiency has seldom been a major consideration since the local price of gaseous fuel is low.
Looking at the landbased pendant, you will often see a different picture, with back-pressure steam turbine driven power generators and the exhaust steam utilized directly as the heating medium.
There are many arguments for rechecking the validity of old conclusions, such as fluctuating oil prices, changing on-board value of associated gas, possibility for reduction of operation and maintenance cost, or better tools for production availability analyses, etc.
This paper describes the key elements in the development of a topside concept based on both a conventional system, as outlined above, and a topside based on steam turbine drivers for large rotating equipment and the use of steam as the heating medium. None of these concepts are optimized, and since the steam option is new, it will most likely have a greater potential for further savings than the conventional topside.
The development is done for the Heidrun field outside mid-Norway where Conoco Norway Inc. is operator.

3. SYSTEM DEFINITIONS
1. Heidrun field.
The Heidrun field is planned to be developed with a single concrete TLP platform with a concrete subsea crude storage. The platform will produce approximately 1450 m3/hr of stabilized crude, exported via offshore loading system. Gas will initially be reinjected. No decision has been made regarding later gas disposal. Gas-oil ratio will initially be approximately 100 Sm3/m3. Water depth is approximately 350 m.
2. Steam system basics.
The main elements in a steam system will be a high pressure steam boiler, steam turbines as drivers for rotating equipment, and steam operated heaters for various purposes. A simplified flow diagram is shown in fig. 1. In this case, the steam turbine is working against a low pressure (vacuum) condenser, cooled by seawater.
On-Bottom Stability of Jackups
Authors: Stewart W.P. , White R.M. , Rapoport V. , Devoy S.D. 
Published: October 2008

ABSTRACT
A new approach to assessing the on-bottom stability of jack-up rigs during preloading is presented. A leaning Instability IS described, which may appear similar to a punch through, but is associated with soil stiffness and rig flexure. Suggestions for avoiding this instability are given.

INTRODUCTION
Jack-up foundation failures during preloading are generally associated with a so-called "punch through". When a strong soil layer overlies a weak layer punch through may occur. The typical example is a sand layer, or sand lens, above a weak clay. If spud can load exceeds the bearing capacity of the sand layer, the spud can will penetrate into the weaker layer. This may happen suddenly and penetration into the weaker layer may be deep. Buoyancy support on the hull may eventually prevent further spud can penetration.
In soft uniform soils, where bearing capacity increases continuously With depth, punch through failures are not expected. However, there have been foundation failures in such conditions, which appear to be punch through, but cannot be explained geotechnical by the normal punch through model. Ingram & Dutt (Reference 1) describe such an event in the Gulf of Mexico in 1982.
This paper describes a new method for calculating elevated stability of jack-ups during preload where spud can loads are steadily increased. It shows how unstable leaning, leading to rapid leg penetration, can occur in soft soils where punch through cannot be the failure mechanism. For the purposes of this paper, the term rapid leg penetration is used to describe leg penetration rates which are faster than the rig's jacking rate. This typically means 1.5 feet per minute. As will become evident in the paper, the speed at which events take place is a critical factor.

STABILITY REQUIREMENTS
Stability requirements (Operations Elevated) for Mobile Offshore. Drilling units are normally addressed by classification societies along with governmental regulatory bodies.
These requirements vary from being quite extensive as pertains to Environmental Forces, Soil Particulars, Overturning moments, Air Gaps and various Safety Factors, to being Just a general statement in regards to these variables.
The U.S. Coast Guard (USCG) and the American Bureau of Shipping (ABS) make a general statement in regards to operations. Elevated/Stability On Bottom. The ABS, in their publication Rules for Building and Classing Mobile Offshore Drilling Units, Section 3' Part 3.13 state :

Units Resting on the Sea Bed
"Units which are to rest on the sea bed are to have sufficient positive downward gravity loadings on the support footings or mat to withstand the overturning moment of the combined environmental forces from any direction. Realistic variable loads are to be considered."
Underwriter-approved Marine Surveyors can provide Location Approvals for Mobile Offshore Drilling Units Operations Elevated. '
It is standard in the industry that these location approvals be based on compliance with the approved Rig Operations Manual.
Advanced Composite Tubular Tendons for Deepwater TLP's
Authors: Odru P. , Sparks C.C. , Metivaud G. , Bono H. 
Published: October 2008

ABSTRACT
This paper presents an original concept of composite tubular tether for TLPs, made from carbon fibers and resin. The technica1 advantages of the concept are compared with those of alternative tether solutions by considering their application to an example TLP in 1200 m of water. Economic aspects are presented.

INTRODUCTION
Tension leg platforms (TLPs) are promising concepts that are considered for future deepwater developments by many oil companies. The principal feature of such platforms is that they are anchored vertically by axially stiff tethers, which are maintained in tension by the excess buoyancy of the platform itse1f. Heave, pitch and roll movements are virtually suppressed and the platform behaves like an inverse pendulum. One of the major advantages of a TLP (over a straight semisubmersible) is that it allows the wells to be continued up to deck level, by means of individual production risers, with the wellheads insta11ed on the platform itself.
As many authors have pointed out, TLPs are weight sensitive structures (ref. 6). Successful applications in deep water will depend greatlyon the abi1ity to contro1 and limit weight. Savings can plainly be made in the structure, deck and production equipment, but it is particularly important for deepwater TLPs that they shou1d not be penalized by the weight of their tether (and riser) system.

TETHER DESIGN CONSIDERATIONS
It is normal practice to design a TLP so that, even in extreme conditions, the tethers remain subjected to positive (effective tension at all times. This implies that the minimum tether tension at keel level must always exceed the apparent weight of the tether itself.
Heavy TLP tethers would, of course, require increased buoyancy to provide increased pretension. This would imply a larger platform, which would tend to be subjected to increased environmental loads, 1eading to 1arger fluctuating forces in the tethers, requiring increased pretension. The prime motivation for reducing tether weight is to avoid this vicious circle.
Heavy tethers are subjected to sag, when the platform is offset under the influence of horizontal loads. As a result, platform offset and set down are increased. Vertical re1ative movements, between the platform and we11 heads, are also increased. Conversely, buoyant tethers (with positive upward sag) would give rise to reduced offset, set down and relative movement between platform and we 11 heads. There" is of course no difference between the pretension requirements of neutrally buoyant tethers and positively buoyant ones, since tethers cannot be allowed to go into compression at the upper end (anymore than at the lower end).
In the case of steel tethers, the apparent weight can be reduced by making the tethers from large diameter tubes, left air filled to give them buoyancy. This solution has been adopted for most TLP projects since HUTTON, which had virtually solid steel tethers (in 150 m of water, the tether weight prob1em does not arise).
The Behaviour of Flexible Risers in Waves
Authors: van Elsacker A.W. 
Published: October 2008

ABSTRACT
In this paper results of flexible riser model tests will be discussed and compared with results of time domain simulations for regular and irregular wave conditions with current.
The model tests were performed at the Maritime Research Institute Netherlands (MARIN) with a large scale riser model instrumented to determine bending moments at a number of point along the riser. Motions of the riser were measured by means of underwater optical tracking systems. The riser top was attached to a mechanical oscillator programmed to carry out the motions of the attachment point of a tanker in irregular waves. Special attention was given to the correct phasing between riser motions and irregular waves. The calculations were performed with the MARIN riser analysis program DYNAFA.
Results of tests and calculations are compared for the riser top area. Correlation is obtained for both regular and irregular wave conditions. It is concluded that computations for irregular wave conditions provide valuable information in early design stage and can be used to extend the model test results.

INTRODUCTION
During the last years it has been recognized that permanent floating production units can be a viable solution for marginal field development in hostile environments like the North Sea. Due to the crucial role of flexible risers as link between oil well and floater, stringent demands are put on the safety and reliability of flexible riser schemes designed for these extreme conditions.
Current riser design procedures are mostly based on theoretical prediction methods for maximum internal load levels and bending radii, using numerical methods to simulate the riser behavior. Design procedures generally include static geometry analyses in near and far position to determine the required pipe length. In addition to this, deterministic regular design wave analyses are performed for several wave height/period combinations and corresponding harmonic top displacements [1].
In recent years a variety of numerical tools has been developed generally based on finite element or finite difference solution schemes offering different options for analysis, see refs. [2] to [6]. An indication of the computing efficiency of several of these methods is presented in [7]. Although most of the programs have been verified against simple analytical and/or model test cases, very little data is available on correlation between computational results and realistic test data for extreme design conditions.
To assess the overall behavior of specific flexible riser systems and to provide measured data to enhance theoretical prediction methods BP International, London, commissioned the Maritime Research Institute Netherlands (MARIN), Wageningen, to carry out representative scale model tests on several flexible riser configurations exposed to extreme environmental conditions and large top displacements.

MODEL TESTS
As part of a BP design study on permanently moored floating production system MARIN was requested to perform model tests for a tanker-based system, see Figure 1.
Foundation Problems in Coral Soils: A Case History-the Oil Terminal of Matanzas, Cuba
Authors: Puech A. , Bustamante M. , Auperin L. 
Published: October 2008

ABSTRACT
This paper presents the case history of the MATANZAS oil terminal constructed on metallic piles driven into coral formations. Particular emphasis is laid on the difficulties encountered to characterize the coral formations, the results of the static and dynamic pile test program implemented and the installation procedures developed.

INTRODUCTION
An oil terminal for 250 000 Dwr supertankers has been built in the bay of MATANZAS (Cuba). The structures were founded on driven 32" and 48" D.D. steel pipe piles. The soil is composed of materials of coralline origin exhibiting a strong spatial heterogeneity and very low resistances to driving.
This paper is devoted to the foundation problems encountered during the construction works. Substantial design modifications were required. They were based on a comprehensive program of static and dynamic pile tests. The aim of the paper is to identify the difficulties associated with the specific soil conditions prevailing on the site, to present the results obtained from the pile tests and to describe the remedial procedures implemented.
The case of the MATANZAS terminal may be considered as a reference-project for the construction of structures founded on metallic piles driven into coral formations. Guidelines and recommendations are proposed; they may be useful for further similar applications.

THE MATANZAS OIL TERMINAL
The oil terminal is located in the bay of MATANZAS. The marine facilities. installed on a shallow submarine terrace, include (fig. 1):two unloading platforms PTl and PC2 installed near the -20m isobaths on top of a natural steep slope. These platforms are supported by twelve 48" O.D. steel pipe piles with 19mm-thick walls;breasting and mooring dolphins, respectively 70" and 86" in diameter:a 600m-long trestle for pipeline support and truck access connecting the platforms to the shore. The bridge is composed of sixteen 36m-long spans and supported by forty-seven 32" O.D. steel pipe piles with 16mm-thick walls. The average water-depth under the bridge structure is about 5m.
Typical sections Of the terminal facilities are shown on figures 2 and 3.

PRELIMINARY SOIL INVESTIGATIONS
At the terminal location, the first submarine terrace is sub-horizontal, 200m-wide with a depth increasing from 2 to 5m.
Monotonic Testing of a Model Pile Driven in a Calcareous Sandy Silt
Authors: Tan C.P. , Parkin A.K. , Yee Y.W. 
Published: October 2008

ABSTRACT
A monotonic pull test was performed on a driven model pile in a large calibration chamber fried with incremented calcareous sandy silt, prepared as an analogue of material obtained in the vicinity of a new platform in Australia's Bass Strait. A cone electrometer test was performed prior to the installation of the pile. Strain gauges mounted along the pile enabled the evaluation of pile axial loads developed during the pile driving and pull test.

INTRODUCTION
Calcareous soils are found in many parts of the world where offshore platforms are built, for example Bass Strait and the North West Shelf of Australia, Arabian Gulf, Gulf of Mexico, Mediterranean Sea and the Brazilian Campos Basin. The carbonate formations occur in varying states of cementation, with classification ranging from well-graded sand to silty sand and sandy silt. There is, however, a lack of detailed information on pile behavior during driving and pull testing in the finer materials, and also on the geotechnical characteristics of such materials.
As part of an investigation of the behavior of axially loaded driven piles and grouted piles in calcareous soils, a monotonic pull test was performed on an instrumented pile driven into a large calibration chamber filled with calcareous sandy silt. ?Ile soil, designated Soil B, is an analogue of material found in the vicinity of a new platform in Australia's Bass Strait, and was produced by grinding a medium calcareous sand, designated Soil A, dredged from another site in Bass Strait [1].
Descriptions of the cone electrometer, pile driving equipment, model pile, chamber and other associated equipment are given in [1]. This paper describes the characteristics of the test soils, the procedures that were developed to prepare the test sample, and the results of the cone penetration and model pile test that were performed in this soil

PROTOTYPE AND ANALOGUE SOIL CHARACTERISTICS
The in situ soil to be modeled in this investigation has a particle size distribution of a sandy silt. It is cemented, with typical in situ void ratios of 0.95 ± 0.05.
Due to the unavailability of prototype soil to carry out model pile testing, an analogue material (Soil B) was produced by passing Soil A through a variable gap disc mill. Platey shells and elongated and coral fragments were broken down during the milling process. Grain size distribution curves for samples of the product were obtained during the process, and the gap between the discs was adjusted to compensate for disc wear when required.
The particle size distribution curve of Soil B is shown in Fig. 1 and the specific gravity was found to be 2.73. It should be noted that the material is extremely fine and to the authors' knowledge, no other model pile tests have been conducted in such fine cohesion less material.