Open AccessOn modeling of chemical stimulation of an enhanced geothermal system using a high pH solution with chelating agent
Author(s) -
XU T.,
ROSE P.,
FAYER S.,
PRUESS K.
Publication year - 2009
Publication title -
geofluids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.44
H-Index - 56
eISSN - 1468-8123
pISSN - 1468-8115
DOI - 10.1111/j.1468-8123.2009.00246.x
Subject(s) - dissolution , calcite , quartz , porosity , geothermal gradient , injection well , silicate , plagioclase , permeability (electromagnetism) , chemical engineering , mineralogy , chemistry , materials science , geology , petroleum engineering , metallurgy , composite material , membrane , organic chemistry , geophysics , biochemistry , engineering
Dissolution of silica and calcite in the presence of a chelating agent (NTA) at a high pH was successfully demonstrated in laboratory experiments using a high‐temperature flow reactor. (Note that the term ‘silica’ used here includes amorphous silica, quartz, and silicate glass bead.) The mineral dissolution and associated porosity enhancement in the experiments were reproduced by reactive transport modeling using TOUGHREACT. The chemical stimulation method was applied by numerical modeling to a field geothermal injection well system to investigate its effectiveness. Parameters applicable to the quartz monzodiorite unit at the Enhanced Geothermal Systems site at Desert Peak (Nevada) were used. Results indicate that the injection of a high pH chelating solution results in dissolution of both calcite and plagioclase, while avoiding precipitation of calcite at high temperature conditions. Consequently, reservoir porosity and permeability can be enhanced especially near the injection well. Injection at a lower temperature of 120°C (temperature is over 160°C in the base‐case) results in a porosity increase that is smaller close to the injection point, but extends to a larger radial distance. A slower kinetic rate results in less aggressive mineral dissolution close to the injection point and larger extent along the flow path, which is favorable for chemical stimulation.