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Interlaboratory test for chemical analysis of geothermal fluids: A new approach to determine deep geothermal reservoir fluid composition with uncertainty propagation

Verma MP, Izquiedo G, Barth J, Rayes-Delgado L, Chandrasekhar T, Algabre JE, Caballero MAC, Godoy JM, Sanchez M, Brusca L, Malimo S, Monvoisin G, Kretzschmar T, Villanueva-Estrada RE, Armienta MA, De Silva N (2022)

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Publication Type: Journal article

Publication year: 2022

Journal

Book Volume: 147

Article Number: 105477

DOI: 10.1016/j.apgeochem.2022.105477

Abstract

A representative fluid sampling of surface geothermal manifestations and its analytical data quality assurance and quality control (QA/QC) are challenging aspects of understanding the geothermal reservoir processes. To achieve these goals, an interlaboratory test for the chemical analyses of ten water samples: one synthetic water, two lake waters (i.e., duplicated), one stream water, and six water samples from two geothermal wells of Los Azufres Geothermal field (LAGF), Michoacan, Mexico, was conducted. The geothermal wells were sampled at four points: (1) total discharge of condensed fluid at the wellhead, (2) separate liquid condensed in the well separator, (3) flushed liquid at the weir box, and (4) separated vapor condensed at the well-separator (data taken from Verma et al., 2022). Sixteen laboratories from ten countries reported their results. The pH, electrical conductivity, Ca²⁺, Li⁺, SO4²⁻, B, and Si-total measurements were 8.35 ± 0.04, 12.25 ± 0.53 mS/cm, 25 ± 1 mg/l, 18 ± 1 mg/l, 569 ± 33 mg/l, 320 ± 21 mg/l, and 20.5 ± 0.7 mg/l, which are close to the conventional true values, 8.40, 12.31 mS/cm, 23 mg/l, 19 mg/l, 647 mg/l, 330 mg/l, and 20.0 mg/l, respectively. Analytical errors for major ions, Na⁺, Cl⁻ and CO2-Total are 17, 21, and 42 percent, respectively; however, the analytical uncertainties are relatively lower, except for CO2-Total (19%). Similarly, the analytical uncertainty for CO2-Total measurements of the lake water sample is 18%. Thus, the analytical method of individual laboratories for CO2-Total measurements needs revision. The NIST Uncertainty Machine web app was used for the stepwise geothermal reservoir fluid composition calculation with uncertainty propagation from the samples collected at different points of a geothermal well. The wellhead fluid sample does not represent the geothermal reservoir fluid, including the sample collected by connecting a portable separator at the wellhead. The samples collected at points 2 and 3 represent equally well for non-volatile species; however, the sample collected at point 2 is a better representative of geothermal reservoir fluid in analyzing the pH and alkalinity values. It is associated with considering the effect of non-condensable gases (CO2, H2S, etc.) liberated at the silencer of the weir box. The geothermal reservoir fluid pH uncertainty, an essential parameter for geochemical modeling, is three to four times the measured fluid pH uncertainty due to the propagation process. Thus, the alkalinity measurement and its calculation procedure of geothermal fluid need revision to understand its correction for the boric, silicic, and other alkalinities.

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How to cite

APA:

Verma, M.P., Izquiedo, G., Barth, J., Rayes-Delgado, L., Chandrasekhar, T., Algabre, J.E.,... De Silva, N. (2022). Interlaboratory test for chemical analysis of geothermal fluids: A new approach to determine deep geothermal reservoir fluid composition with uncertainty propagation. Applied Geochemistry, 147. https://dx.doi.org/10.1016/j.apgeochem.2022.105477

MLA:

Verma, Mahendra P., et al. "Interlaboratory test for chemical analysis of geothermal fluids: A new approach to determine deep geothermal reservoir fluid composition with uncertainty propagation." Applied Geochemistry 147 (2022).

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