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EDITORIAL

J. Energy Resour. Technol. 1980;102(1):1. doi:10.1115/1.3227843.
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Abstract
Commentary by Dr. Valentin Fuster

RESEARCH PAPERS

J. Energy Resour. Technol. 1980;102(1):2-11. doi:10.1115/1.3227845.

An empirical method is presented for calculating temperature profiles in flowing oil wells. The method is applicable to wells in which two-phase flow is occurring and in which the inlet fluid temperature is known. It was developed from field data and can be used in design problems which require accurate subsurface temperatures, such as flowing pressure traverse calculation and gas-lift design.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1980;102(1):12-17. doi:10.1115/1.3227841.

The effects of surfactant solution aluminum chloride on cutting granite rock with a diamond were investigated experimentally. Tests were conducted by cutting on the cylindrical surface of a granite cylinder in a lathe with a single spherically shaped diamond cutting tool. The cutting fluid consisted of various concentrations of aluminum chloride in deionized distilled water. The cutting force components were determined by means of a tool post dynamometer and were recorded continuously during the tests. Diamond wear was determined by periodically photographing the wear flat through an optical miscroscope. Results indicate that cutting forces and diamond wear rate are influenced by the additive. The normal cutting force is maximum at a concentration of 7 × 10−6 molar, and the tangential cutting force is maximum at 3 × 10−6 while the diamond wear rate is minimum at 3 × 10−6 molar. It is also found that there is an effect of concentration on relative tool life for constant depth cutting, but that maximum life occurs at higher levels of concentration.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1980;102(1):18-23. doi:10.1115/1.3227842.

The expanding use of prestressed concrete in offshore structures, both fixed and floating, in ever more hostile environments has generated intense interest in its fatigue endurance capabilities, even though, as far as it is known, no fatigue problems have arisen in actual structures. Although concrete does suffer progressive loss of strength with increasing number of cycles, a comparison of the Wöhler curves developed on the basis of laboratory tests with the probable distribution of compressive stresses during a service life in an environment such as the North Sea shows extremely low cumulative usage at the high-cycle end of the spectrum. However, significant damage can occur at the low-cycle, high-amplitude end of the spectrum under a relative small number of cycles of very high magnitude. This damage is displayed by a reduction in stiffness and by rapidly increasing axial and lateral strains that lead to cracking and spalling. Repeated cycling into high compressive ranges causes a substantial increase in creep, reducing the effective prestress. Confining reinforcement resists lateral deformation and delays compressive fatigue failure. Cycling into the tensile range a large number of times can produce cracking due to tensile fatigue at about half the static tensile strength. Cracking also can occur due to overload, accident, construction procedures, and thermal strains. Repeated excursions of submerged concrete into the crack opening range leads to pumping of water in and out of the crack and hydraulic wedging, leading to splitting of the concrete. Cracking subjects the reinforcing and prestressing steel to cyclic tension. Loss of bond ensues and may lead to eventual fatigue failure. Adequate endurance can be ensured by prestressing, so as to avoid a large number of cycles extending into the crack opening range, and by the provision of adequate percentages of steel across the section plus transverse and confining steel. Cyclic membrane shear may produce diagonal tension cracking at about half the static strength. Conventional reinforcing in an orthogonal grid pattern is very inefficient in resisting such cracking. Crack widths grow rapidly. Repeated loading may lead to abrasion of concrete surfaces and failure of the steel due to combined axial force and bending. Vertical prestress is an efficient and practical method of resisting high-amplitude cyclic shear. For the typical concrete sea structure, high-cycle, low-amplitude, cumulative fatigue is not a significant problem. However low-cycle, high-amplitude fatigue requires consideration, expecially when there are numerous cycles into the tensile cracking range. In this latter case, fatigue of the steel and/or concrete may occur unless adequate amounts of steel are provided to ensure that crack widths and steel stresses are kept within allowable values.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1980;102(1):24-29. doi:10.1115/1.3227844.

Individual tubulars attached to marine risers are modelled as continuous axially loaded multiple-spanned beams. Traditional methods for solving continuous beam-column problems require the solution to many simultaneous equations. The calculation procedure in this paper requires that only two equations be solved simultaneously; intermediate support reaction loads are obtained by using recursion formulas.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1980;102(1):30-34. doi:10.1115/1.3227846.

The offshore pilot test of Exxon’s Submerged Production System (SPS) has reached a successful conclusion. This pilot test encompassed the entire spectrum of SPS equipment, spanning from the well completion intervals to, but not including, common surface processing and storage facilities. Since the SPS is designed to meet all the life cycle needs of a subsea field, one of the objectives of the pilot test was to evaluate both the techniques and the equipment used to install, operate, and maintain a prototype version of the SPS. The equipment under test was designed for use in water depths up to 2000 ft, but with minor modifications it is capable of operating in significantly greater depths. Evaluation of pilot test results has shown that the deep water installation techniques are practicable and that the deep water maintenance machinery is competent to repair any failures likely to occur in an operating system. One of the most significant problems in conducting the pilot test was achieving adequate quality control during equipment manufacture. The test results have demonstrated that, with relatively minor modifications, the SPS is suitable for commercial application.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1980;102(1):35-48. doi:10.1115/1.3227847.

The occurrence and properties of subsea permafrost near Prudhoe Bay, Alaska, were investigated by drilling and probing. Nine holes were drilled and 27 sites were probed with a cone penetrometer. The deepest drill hole was 65.1 m below the seabed, while a depth of 14.1 m was reached with the cone penetrometer. Engineering and chemical properties were determined from core samples and point penetration resistance data were obtained with the penetrometer. Thermal profiles were acquired at both the drill and probe sites. Temperatures below 0° C were observed in all the drill and penetrometer holes logged, although frozen sediments were encountered only occasionally. Seasonally frozen sediments were observed near the seabed at each site. The degree of ice bonding, or strength, could be related to seabed temperature and was greatest in shallow water (<2 m). The penetrometer resistance and thermal data indicated that deeper ice-bonded sediments occur, for example approximately 12.7 m below the seabed in 2 m of water off the Sagavanirktok delta. Of eight holes drilled offshore, it appeared that four encountered bonded permafrost. In general, the position of the ice-bonded permafrost interface was extremely irregular. The depth below the seabed to this interface at various distances from shore along the line studied was 28.8 m at 1 km, 65.1 m at 3.5 km, 44.1 m at 6.8 km, and 29.5 m at 17.2 km. Shallow, over-consolidated marine sediments were found in the upper fine-grained section at all of the drill sites investigated; the degree of over-consolidation varied considerably among the sites. This fine-grained section was up to 10 m thick and covered sands and coarse gravels.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1980;102(1):49-54. doi:10.1115/1.3227848.

The search for oil and gas has already extended to the Arctic areas of the world. To date conventional sand islands have been used for exploration drilling purposes in water depths of up to 43 ft. In deeper water exploration has only been possible using floating drilling equipment which can only operate during the short summer season of open water. This paper briefly outlines the geotechnical principles and development to date of hydrostatically supported sand islands. This construction technique, which utilizes hydrostatic water pressure to stabilize dredged sand at near vertical underwater slopes, would allow sand islands to be quickly and economically built in water depths of up to 200 ft. The hydrostatically supported sand island is a gravity structure and, therefore, is only suitable for use on competent seabed soils. This paper presents two different designs which are currently proposed for use as drilling structures in such areas as the Beaufort Sea. One design is intended for use as a movable exploration structure and the second for a permanent production island that would remain on location for 30 to 50 yr. The near vertical side slopes of the hydrostatically supported sand islands reduce the amount of sand required to manageable amounts, and allow the construction on location to be safely completed during the short Arctic summers. The sand provides sufficient mass to resist ice pressures.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1980;102(1):55-60. doi:10.1115/1.3227849.

At the Union Electric Meramec power plant in St. Louis, tests in which refuse-derived fuel was co-fired with pulverized coal in a tangential suspension-fired coal boiler have been conducted. Data obtained were used to calculate the megawatt-hours of electrical energy produced by refuse-derived fuel. The experimental method used, the results obtained, and a discussion of these results are presented in this report.

Commentary by Dr. Valentin Fuster

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