Neutralization of Acid Fluids from Well H-43 (Superheated Steam), Los Humeros Geothermal Field in Mexico

Abstract

Well H-43 was drilled northeast of the geothermal field of Los Humeros in the state of Puebla, Mexico, from October 21, 2007 to January 18, 2008. In this area were built at least 7 wells during the eighties with similar chemical conditions to the H-43, these wells were cemented and abandoned definitively because their fluids were highly corrosive for their operation. Those wells showed low pH values in the extracted fluid which was attributed to the presence of hydrogen chloride (gaseous HCl) which in the presence of humidity ionizes to form hydrochloric acid. In the case of this geothermal well the pH values are around 3 and the laboratory analysis confirmed HCl gas content. The H-43 is a well that provides approximately 35 tons per hour of superheated steam (30 °C of superheat), the pressure and temperature at wellhead conditions are 40 barg (580 psig) and 285 °C respectively, this thermodynamic characteristic was used to commercially integrate the well to the power stations because the superheating condition ensures that the HCl remains in the gas phase, thereby preventing corrosion in the well casing. The well has been supplying steam to the power generation electric system since May 2013, working in a superheated way until connection with the gathering system, in which an acid inhibitor is injected as explained in this paper. The importance of this achievement is that it opens the possibility of exploiting wells of similar acidity characteristics, representing approximately 200 MWe of power electric generation in this part of the reservoir.