Managing Chemistry Underground: Is Co-Sequestration an Option in Selected Formations?

Geochemical simulations indicate that co-injection of CO2 and SO2 results in mineral sequestration of SO2. The amounts sequestered are greater and more persistent in dolomite and basalt than in glauconitic sandstone. In a predominantly dolomite formation, dissolution of calcite, and to a lesser extent, dolomite, will provide Ca in solution to promote the precipitation of anhydrite, thus removing the SO2 from solution. In basalt, dissolution of basaltic glass under acidic conditions provides Ca and Fe in solution, which promotes the sequestration of SO2 as anhydrite and, eventually, pyrite. As magnetite in the formation is consumed, pyrite redissolves. In the basalt, 86% to 47% of the SO2 remains sequestered after 5000 years. In glauconitic sandstone, SO2 precipitates as alunite, but it eventually redissolves. After 5000 years, 87% to 0% of the SO2 remains sequestered in the glauconitic sandstone. In all cases, co-injection of 1% SO2 with CO2 did not appreciably reduce the amount of CO2 sequestered, and did not induce a measureable change in porosity versus injection of CO2 alone. (C) 2010 Published by Elsevier Ltd.