Application of a Detailed and Comprehensive Computational Chemical Geothermometer to Low Enthalpy Geothermal Waters in Northern Greece

Abstract

Various chemical geothermometers are used to estimate deep geothermal reservoir temperature based on the chemical composition of hot waters as a function of the concentration of specific elements and constituents (Na, K, Ca, Mg, Li and SiO2). Large deviations in the estimated reservoir temperature are observed by the use of different geothermometers. A detailed and Comprehensive Computational Chemical Geothermometry (CCG) method is proposed in this paper. This novel methodology has been based on the consideration of the equilibrium between geothermal water and specific minerals at a given temperature within deeper reservoir. It consists of two steps: (a) At first, specific minerals are assumed to in equilibrium with the fluid in the reservoir based on a detailed chemical analysis of the geothermal fluid (selection of minerals). (b) In the second stage, a technique is applied to estimate the optimal temperature for the water in the reservoir by minimizing the deviation from equilibrium (optimization technique). In this paper, the Comprehensive Computational Chemical Geothermometer (CCG) has been applied to geothermal waters from significant low enthalpy geothermal fields in Northern Greece (e.g. Nigrita, Akropotamos, Eratino-Chrysoupolis, Neo Erasmio, Aristino). These fields are of high interest for further development and investments. The obtained results are compared with the ones from other classic geothermometers and the validity and reliability of the proposed CCG methodology are evaluated.