Chemical Modeling of Geothermal Systems

Abstract

A computer modeling study is described which simulates individual chemical reactions in geothermal brines at high temperatures. It has been found that many such chemical changes in flowing process systems can be predicted by relatively simple equilibrium calculations. The procedure makes use of effective activity coefficients for ions which take into account the effects of extensive chloride complexing. The results are illustrated by several examples of chemical processes in fluid from the Magmamax #1 well. These include sulfide species distribution, PbS precipitation, pH changes, and buffering effects due to the carbonate content. Such estimations have been found to be consistent with the actual observed behavior. The method is also generally applicable to geothermal fluids, wherever chemical composition and temperature are known.