Qtz-Geotherm: an ActiveX Component for the Quartz Solubility Geothermometer

Abstract

An ActiveX component to calculate temperature and vapour fraction in a geothermal reservoir using the quartz solubility geothermometry was written in Visual Basic. The approach is based on the conservation of mass and energy (enthalpy). Four representative types of regression equations for quartz solubility: (i) a quadratic regression equation of 1/T and pressure P, (ii) a linear equation relating log SiO2 to the inverse of absolute temperature T, (iii) a polynomial of T including logarithmic terms and (iv) temperature as a polynomial of SiO2 including logarithmic terms are programmed. The quadratic regression equation fits well all the experimental solubility data in pure water along the saturation curve and provides better agreement between the calculated and measured down-hole temperatures in the case of Cerro Prieto. The down-hole temperatures in the wells M-50 and M-90 were also calculated through a well simulator, WELLSIM. There is a significant consistency between the estimated temperatures using both the approaches.