Abstract
A brief report is given of studies of brine chemistry on both high- and low-salinity geothermal fields in support of a field corrosion testing program being conducted by the USBM in the Imperial Valley, CA. Specific results are reported for four geothermal wells: Mesa 6–1, Mesa 6–2, Magmamax No. 1, and Woolsey No. 1. These results demonstrate the necessity for careful reporting of the specific well operating conditions and brine sampling techniques under which the brine analyses were obtained. In particular, information related to recent well shut-in particular, information related to recent well shut-in periods, total stabilization time, recent production periods, total stabilization time, recent production engineering, brine flow rate from the well, and identification of nonturbulent-structure brine-flow configurations must be documented carefully with any reported analyses.
Introduction
For the past several years, the USBM has been involved in the nation's geothermal program, with primary responsibility for developing technology for primary responsibility for developing technology for recovering important metals and minerals from geothermal brines. Because the most accessible U.S. geothermal mineral resources occur in extremely corrosive hydrothermal fluids, the bureau also has conducted research to identify construction materials for process plants designed to recover these resources.The largest identified geothermal resource area in the U.S. containing substantial quantities of potentially recoverable metals and minerals is in the potentially recoverable metals and minerals is in the Imperial Valley. Of six known geothermal resource areas (KGRA's) there, the Salton Sea KGRA contains brines with the highest mineral content - 25 to 32% total dissolved solids (TDS). The brines from the Salton Sea KGRA, however, are among the most singularly corrosive natural fluids to be found, and during any type of brine processing a wide range of scaling phenomena occurs that can create havoc within a geothermal resource recovery plant. Early attempts to recover these geothermal resources were abandoned, partly due to the failure to overcome these corrosion and scaling problems.This paper presents on-site brine chemical analyses for the early stages of production for four geothermal wells and discusses how these analyses can be influenced by operational conditions. In addition to specifying the analytical and sampling procedures used for geothermal brine analyses, a procedures used for geothermal brine analyses, a number of important conditions concerning the geothermal well in question must be specified for meaningful interpretation of the analytical data. Much of the data reported in the literature does not include this type of information, thus limiting its value. These conditions, defined here as the "reportable conditions for geothermal brine chemistry data," are (1) sampling procedure (to include temperature, pressure, date, type of sampling port, and either suspected or known phase of the port, and either suspected or known phase of the preextracted sample - i.e., brine, steam, or mixed preextracted sample - i.e., brine, steam, or mixed phases), (2) total flow rate from the well (in volume phases), (2) total flow rate from the well (in volume per time interval), (3) shut-in time (if well is being per time interval), (3) shut-in time (if well is being restarted after a period of nonflow), (4) total operating time (of actual brine-flowing operations), (5) production engineering (including any recent perforation, recasing, or bottomhole extension), and perforation, recasing, or bottomhole extension), and (6) variations in baseline chemistry (to distinguish between average operating values and unique well conditions or to specify unusual brine flow patterns).These six points are essential for meaningful comparisons of the brine compositions of different wells, the variations in brine chemistry with time for a single well, and the sampling and analytical results for brines from the same well obtained by different organizations.
SPEJ
P. 105
Models of Geothermal Brine Chemistry
