The Rise and Fall of Chloride in Larderello Steam

Abstract

Significant amounts of C1 appeared in steam from upflow zones of Larderello in the early 1960s. The general pattern of C1 concentrat i o n includes: a rapid rise, a more or less constant plateau (coincident with a low, stabilized flow rate ), and rapid decrease generally after 1980. The rim correlates with a general decrease in pressure throughout the field presumably due to the disappearance of liquid in the two-phase, vapor-dominated reservoir. The plateau may be related to the distance from centers of upflow and inhomogen e i t i e s in the temperature and chemistry of deep brine. The decrease is correlated with the start of liquid introduction from reinject i o n and drilling losses and particularly with the time of breakthrough of steam formed from injected water. This history suggests that when liquid was exhausted in some areas and pressure dropped, other areas suffered accelerated boiling and dried o u t as well, allowing high-Cl steam formed from boiling of deep brine to move upward to reach the wells. introduction of liquid after 1980 reversed the process. A similar situation may be occurring now at The Geysers, California.