Physico-chemical sampling of high temperature wells in connection with their encrustation by calcium carbonate

Abstract

The most important practical problems of physical-chemical studies of high-thermal underground waters are connected with investigating the conditions of well encrustation due to calcium carbonate. We have worked out a set of methods of high-thermal well sampling to determine the state characteristics of carbonate equilibrium in water, the temperature and the rate of forming calcium carbonate precipitate and have used these methods in the high-thermal water-fields of Bolshebanny and Pauzhetsky in Kamchatka and Goryachy Plazh (Hot Beach) on Kunashir island. For water sampling of operating wells, a probe, a tube made of stainless steel, was used and inserted in the well through a gasket below the vaporisation level. To measure pH in deep-seated water samples the probe was connected to a high-temperature cell with a glass and reference electrodes mounted in autoclave where natural pressure and temperature conditions were created. A probe with thermistor was applied for the continuous temperature measurement at different depth and for determining the position of vaporization zone in operating wells. The checking of the well encrustation process was done by means of measuring their internal diameter and the thickness of calcium carbonate layer encrused on the probe lowered in the well. The data obtained allow us to determine the character of the process of well encrustating due to calcium carbonate and ascertain the difference in the composition of waters of encrusting and non-encrusting wells.