Chemical and Mineralogical Characterization of Sulfide Scales in Well 624 from Cerro Prieto Geothermal Field and Its Reactivity in HCl
- Key words
- Sulfide scales; sulfide; Cerro Prieto; geothermal wells; cotunnite; chalcopyrite; cubanite; bornite
- Location
- Cerro Prieto, Mexico
- Conference
- Geothermal Resources Council Transactions
- Year
- 2012
- Session
- Scaling; Petrology/Petrography; Brine chemistry; Sulfides
- Language
- English
Abstract
Chemical and mineralogical characterization of sulfide scales, formed in well 624 from the CP II sector of the Cerro Prieto geothermal field, was carried out by reflected light microscopy, X-ray diffraction and scanning electron microscopy. Samples come from a depth of 551 m, 1765 m, 2155 m and 2355 m. Scale samples consist of chalcopyrite, sphalerite, galena, bornite, cubanite, chalcocite and covellite. Chalcopyrite is the dominant phase in all samples. Electron microscope analyses indicate sphalerite and galena intergrowths in chalcopyrite. The proportions of the minerals assemblages do not show relation to the well temperature. In order to determine the solubility of sulfide scales in an acidic media, samples were treated in 10% hot HCl. As soon as the acid solution contacts the samples, H2S is formed and released. Most of the sulfide minerals are resistant to HCl; galena is the only mineral that partially reacts with the acid forming lead chloride.
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