The design, calibration and application o/ a clamp-on type strain transducer for the simultaneous monitoring of axial and transverse strain under both uniaxial and triaxial test conditions is described The transducer attaches directly to the test specimen and utilizes a number of linear variable differential transiormers to provide average strain data. Tests have been carried out on specimens of a number of metallic (steel, brass and aluminum) and geologic materials (granite, limestone and sandstone) at confining pressures oi up to 5,000 psi. No difficulties are contemplated in using the transducer at confining pressures of 10,000 psi and higher.
Introduction In spite of the increased research on the behavior of geologic materials which has been undertaken in recent years, many of the most important mechanical properties have not been investigated in detail. In particular the effect of time has received very little attention from the experimental point of view, although its importance has been suggested by many workers. Many workers have reported that test results appeared to be influenced by the rate and duration of loading, although few have been willing to accept the fact that such behavior is indicative of an inelastic material. A general study of the Mechanical properties of geologic materials was initiated in 1951 in The Mining Research Section of the Fuels and Mining Practice Division, Mines Branch, Canadian Dept. of Energy, Mines and Resources, as part of a fundamental study of ground stress in Canadian Coal Mines. initial work was restricted to short-period tests on typical mine rock under uniaxial compressive stress, but as the importance of the "time factor" became more obvious, studies were undertaken to investigate time-dependent behavior. These studies, which were initiated in 1957, consisted mainly of a comprehensive literature search on the subject, and the initial development of experimental facilities. This research project was inactive during the period 1959–1961 due in part to the relocation of laboratory facilities. In the fall of 1961 the project was reactivated with the proposed research program being broadly outlined as follows: "To study experimentally the mechanical behavior of selected geologic materials and to analyze these experimental data using the concept of Technical models and the analytical methods of viscoelasticity. In particular to develop governing equations for these materials based on suitable laboratory experiments and valid at least within a range of stress, confining pressure, duration of loading, and temperature consistent with practical applications." The first phase of this research program included the experimental investigation of the inelastic behavior of a number of "simple" geologic materials using incremental creep experiments, and the associated development of the necessary experimental facilities and analytical methods. This paper outlines briefly the experimental and analytical techniques developed, and presents experimental results for the initial deformation studies carried out on Wombeyan marble. THEORY Papers dealing with the behavior of geologic materials are found to be widely dispersed throughout the literature. However, extensive bibliographies dealing with the general mechanical properties of these materials have been published recently by Griggs and Handin and Mitra and Willson. In the more specific field of time-dependent behavior of geologic materials extensive bibliographies have been given in papers by Hardy, Murrell and Misra, and Robertson. P. 105^
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This paper was prepared for the Northern Plains Section Regional Meeting of the Society of Petroleum Engineers of AIME, to be held in Omaha, Neb., May 18–19, 1972. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers Office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract Research presently underway at the Pennsylvania State U. is concerned with the Pennsylvania State U. is concerned with the study of the mechanical stability of underground gas storage reservoirs. This research involves a number of phases including a laboratory model study which will be outlined in the present paper. paper. In these studies small scale models containing reservoir cavities of simple geometry were first loaded under typical in-situ stresses then pressurized internally until failure occurred. Microseismic techniques were utilized to detect reservoir failure. A description of the experimental facilities and the model fabrication techniques are included along with a review of results obtained from tests on a number of differently shaped reservoir cavities. A discussion, relative to the effect of reservoir geometry and depth below surface, on the optimum storage pressure is included. In general, the results of the model study indicate that optimum storage pressures may be considerably higher than those based on the discovery pressure or the average hydrostatic gradient. Introduction General The natural gas industry today is faced with the problem of locating and developing sufficient underground storage reservoir capacity to meet peak seasonal demands. Since it is economically desirable to store the gas at the mammon possible pressure, an accurate value for the optimum pressure, namely the maximum pressure to which a reservoir could be pressure to which a reservoir could be pressurized and still remain mechanically stable, is pressurized and still remain mechanically stable, is of great importance. Natural gas is stored underground in former gas and oil reservoirs, aquifers and man-made cavities. As the demand for natural gas increases the necessity for storing larger and larger volumes of gas underground during periods of low demand has increased markedly. In 19701 a total of 325 storage reservoirs were reported in the U. S. The majority of underground storage was located in former gas and oil reservoirs with a lesser number in aquifers and relatively few in man-made cavities.
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