Brine Chemistry Research Articles

Scaling and Corrosion in an Experimental Geothermal Power Plant

JPT Forum articles are limited to 1,500 words including 250 words for each table and figure, or a maximum of two pages in JPT. A Forum article may present preliminary results or conclusions of an investigation that the present preliminary results or conclusions of an investigation that the author wishes to publish before completing a full study; it may impart general technical information that does not warrant publication as a full-length paper. All Forum articles are subject to approval by an editorial committee. Letters to the editor are published under Dialogue, and may cover technical or nontechnical topics, SPE-AIME reserves the right to edit letters for style and content. Introduction The San Diego Gas and Electric Co./U.S. DOE Geothermal Loop Experiment Facility (GLEF) located near Niland in the Imperial Valley, CA, has operated on a high-salinity (about 200,000 mg/L) geothermal fluid from the Salton Sea Field since May 1976. The conversion process being tested is a four-stage binary system (Fig. 1). The geothermal fluid is flashed at successively lower pressures in open drum-type separators. Generated steam pressures in open drum-type separators. Generated steam passes through a scrubber and into a tube and shell heat passes through a scrubber and into a tube and shell heat exchanger, where the heat is transferred to a secondary, working fluid. Steam condensate can be cascaded and mixed with the brine in the next stage, collected and combined with the cooled brine and reinjected, or used for cooling water make-up. The working fluid is condensed after expansion across a throttling valve that simulates a turbine. Waste heat is removed with a conventional spray pond, With a turbine generator (to be installed later) this facility will become a 10-Mw power plant. Water was used as the working (binary) fluid plant. Water was used as the working (binary) fluid during start-up and initial operation. Isobutane, which is the expected preferred working fluid for a binary power plant, will replace water. plant, will replace water. The GLEF operated for about 3,000 hours with frequent interruptions for inspection and facility modification. During this period, the facility operated on one production well (either Magmamax 1 or Woolsey 1). production well (either Magmamax 1 or Woolsey 1). Flow rates were 400,000 lb/hr, about one-half the GLEF design capacity. The temperature and pressure of the fluid entering the first stage is 370 deg. F and 165 psia. Exit temperature of the brine is 200 deg. F. All unflashed brine is reinjected in the reservoir. Brine Chemistry The geothermal fluid available from this reservoir is a hypersaline brine containing about 200,000 mg/L total dissolved solids (TDS), mostly chlorides (Table 1). These chlorides remain in solution during the heat extraction process and subsequently are injected back in the reservoir. Certain minor species, however, such as silica, lead, and iron have limited solubility and, as the brine is cooled during the heat extraction process, they precipitate from solution and deposit on pipe and vessel precipitate from solution and deposit on pipe and vessel surfaces. The principal noncondensable specie is carbon dioxide. Small amounts (up to 6 mg/L) of hydrogen sulfide also are found in this geothermal brine. Ammonia is also present in the geothermal brine and has a significant present in the geothermal brine and has a significant effect on brine chemistry. The pH of the brine (5.6 to 5.8) is such that a carbonate type of precipitate normally is not observed in spite of the high carbon dioxide level (up to 0.3 wt %). In this process, the available energy in the geothermal brine is extracted as steam. Drum separators and scrubbers can produce high-quality steam with a TDS content of less than 10 mg/L. However, noncondensable gases (carbon dioxide and hydrogen sulfide) also accompany this steam. Part of the ammonia in the geothermal brine also is driven off with the steam. When these noncondensable gases are removed, the pH of the brine increases to about 6.0. JPT P. 1240

A chloride complex model for Kuroko mineralization

A chloride complex model for Kuroko mineralization at the Uchinotai-nishi deposit of the Kosaka mine is constructed. Possible chemical composition of the ore solution and possible physicochemical properties of the ore-forming environments calculated on the basis of the thermochemical data of HELGESON (1969) can be limited to narrow ranges, if more than 1 ppm Cu is assumed to be dissolved in the ascending Kuroko-forming solution. The model ore-forming environments derived here are consistent with the data of temperature and sulfur fugacity estimated from studies of fluid inclusions, mineral equilibria and sulfur isotopes of the Kuroko deposits. The characteristic mineral zoning of the deposits are explicable by differential precipitation of ore-constituent minerals from the model solutions moving along the gradients of the model ore-forming environments. In order to explain the distribution of sulfate minerals in the deposits, it is necessary to assume mixing of the ascending solution and the coeval seawater. In comparison with the chemistry of the natural metal-rich brines, the model solutions are low in Na/K ratio, while high in Na/Ca and reduced sulfur to metal ratios. It is suggested that these features might be characteristic of volcanogenic ore-forming solutions, which are likely to retain equilibrium conditions at higher temperatures as a result of their rapid ascent from the source reservoir.

Chemical composition of selected Kansas brines as an aid to interpreting change in water chemistry with depth

Chemical analyses of approximately 1,881 samples of water from selected Kansas brines define the variations of water chemistry with depth and aquifer age. The most concentrated brines are found in the Permian rocks which occupy the intermediate section of the geologic column of this area. Salinity decreases below the Permian until the Ordovician (Arbuckle) horizon is reached and then increases until the Precambrian basement rocks are reached. Chemically, the petroleum brines studied in this small area fit the generally accepted pattern of an increase in calcium, sodium and chloride content with increasing salinity. They do not fit the often-predicted trend of increases in the calcium to chloride ratio, calcium content and salinity with depth and geologic age. The calcium to chloride ratio tends to be asymptotic to about 0.2 with increasing chloride content. Sulfate tends to decrease with increasing calcium content. Bicarbonate content is relatively constant with depth. If many of the hypotheses concerning the chemistry of petroleum brines are valid, then the brines studied are anomolous. An alternative lies in accepting the thesis that exceptions to these hypotheses are rapidly becoming the rule and that indeed we still do not have a valid and general hypothesis to explain the origin and chemistry of petroleum brines.

Contributions to the chemistry of brines

Contributions to the chemistry of brines