Wellhead and downhole water samples were collected and analyzed from a 114.3-m well at Coso Hot Springs (Coso No. 1) and a 1477-m well (CGEH No. 1) 3.2 km to the west. The same chloride concentration is present in hot waters entering both wells (about 2350 mg/kg), indicating that a hot-water-dominated geothermal system is present. The maximum measured temperatures are 142øC in the Coso No. 1 well and 195øC in the CGEH No. 1 well. Cation and surfate isotope geothermometers indicate that the reservoir feeding water to the Coso Hot Spring well has a temperature of about 240ø-250øC, and the reservoir feeding the CGEH well has a temperature of about 205øC. The variation in the chemical composition of water from the two wells suggests a model in which water-rock chemical equilibrium is maintained as a convecting solution cools from about 245øC to 205øC by conductive heat loss. of the geologic relations) on land included in the U.S. Naval Weapons Center, China Lake. In the evaluation of a geothermal energy prospect such as that at Coso the reservoir temperature and nature of the reservoir fluid are important parameters to consider when calculating the economics of extracting the energy and when interpreting the geophysical data used to estimate the size of the resource. The surface expression of hydrothermal activity at Coso is hot ground, fumaroles, and acid-sulfate springs with low rates of discharge. No chloriderich springs are present. This type of surface expression is typical of vapor-dominated systems [White et al., 1971] but is not diagnostic. Unfortunately, the chemical compositions of waters from acid-sulfate springs are not weB-suited for chemical geothermometry. The object of this report is to use the geochemical character of waters from presently available wells to predict reservoir temperatures and fluid characteristics in still unexplored parts of the system. Waters from two wells drilled for geothermal energy exploration have been sampled and analyzed. The first well was drilled in 1967 in altered alluvium and granitic rock to a depth of 114.3 m at Coso Hot Springs by the China Lake Naval Weapons Center in cooperation with the California Division of Mines. That well (Coso No. 1) is described by/lustin and Pringle [1970]. The second well (Coso Geothermal Exploration Hole (CGEH) No. 1) is located approximately 3.2 km west of Coso Hot Springs and 1.9 km north of Devil's Kitchen. It was drilled in 1977 to a total depth of 1477 m in granitic and metamorphic rocks using funds provided by the U.S. Department of Energy. Static downhole characteristics of the CGEH No. I well are described by Goranson and Schroeder [ 1978]. The hydrothermal system at Coso appears to be controlled by fractures in Mesozoic granitic plutons and older metamorphic rocks that form the basement under scattered Pliocene and Pleistocene volcanic and sedimentary rocks [Duffield et al. This paper is not subject to U.S. copyright. Published in 1980 by the American Geophysical Union. 1980; Hulen, 1978]. The metamorphics in approximate decreasi...
The transmission and decay of stress waves have been studied in bars of igneous rocks, including a coarse‐grained leucogranite, a fine‐grained spessartite, and a fine‐grained to aphanitic basalt. Ballistically suspended Hopkinson bars of these materials, 2.146 cm in diameter and approximately 46 cm long, were impacted longitudinally by 1.27‐cm‐diameter hardened steel spheres at a initial velocity of 8255 cm/sec ±1.5%. The shape and velocity of propagation of the resultant wave in the rock rod were measured with strain gages. Similar experiments with an aluminum alloy bar of identical size determined the dispersion resulting from the three‐dimensional geometry of the rod and permitted an assessment of of the validity of various models proposed for geologic materials. Static tests performed on fresh and shocked rods agreed with predicted effects of stress wave passage on the rock structure, including the formation of oriented fractures and a general lowering of the static Young's modulus.
The U. S. Naval Ordnance Test Station has a continuing program of applied research in rock and earth dynamics. One aspect of this program has been the investigation of rock masses subjected to jet attack from lined-cavity shaped charges. The detailed testing of rock response has been carried out in air using dry bulk targets of sufficient size to preclude gross target fracturing during penetration. Overcoring methods have then been used to remove the penetration area to permit section in g and studying the hole walls. During these tests two distinct modes of penetration wall response were observed. One mode is well illustrated by coarse-grained silicate rocks which yield penetrations with severe adjacent grain damage plus significant compaction and stored energy, which is slowly released by failure of the hole walls. The second mode is illustrated by limestone, which gives virtually no megascopic damage adjacent to the hole and which is stable following penetration. Under proper conditions, however, the limestone samples consistently yield liner-metal and liner-metal-oxide filled fractures adjacent to the penetration. Tests were also performed which permitted evaluation of the effect of gross target fracturing during penetration, and evaluation of the concept of rock density as a criterion of penetration depth. Introduction The mechanisms of jet formation by various configurations of lined-cavity shaped charges and of penetration in metallic targets have been extensively reported in the technical literature. Jet penetration into rock and earth materials has been investigated in conjunction with mining uses and a considerable body of technical literature established on the petroleum industry applications of shaped-charge phenomena. Examination of these many publications reveals that the details of the response of rock targets to the jet penetration process are not well known. The studies reported in this paper were performed to establish the detailed response of rock targets in air to jets from lined-cavity shaped charges and, as such, do not necessarily represent down-hole, well phenomena. The rocks selected for testing are representative of broad groupings of geologic materials that occur in bulk on the earth's surface, but only the general materials applicable to the petroleum industry are discussed. Although the igneous rocks, per se, are of minor interest to petroleum engineers, these rocks are occasionally important reservoir rocks. Furthermore, the igneous rocks, despite their limited occurrence as reservoir rocks, offer a wealth of pertinent data on general rock behavior. The behavior of igneous rocks is also believed to be representative of the behavior of dense, hard, low porosity silicate rocks in general. Quartzites, strong sandstones and many metasediments are believed to belong in this grouping of materials.A set of standard definitions of penetration effects must be established in order to permit a useful discussion of jet penetration phenomena. JPT P. 41^
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