Conventional matrix acidizing treatments rely on hydrochloric acid to stimulate carbonate formations. However, the success of these treatments is often limited because of rapid acid spending at low injection rates and asphaltic sludge precipitation. This study investigated ethylenediamine-tetraacetic acid (EDTA) as an alternative stimulation fluid. Results show that EDTA can effectively wormhole in limestone, even when injected at moderate or non-acidic pH values (4 to 13) and at low flow rates where only face dissolution would occur with HC1. Stimulation with EDTA at low injection rates is consistent with the dependence of the wormhole structure on the Damköhler number for flow and reaction. Sludge tests show that EDTA does not induce the precipitation of asphaltic sludge from crude oil, even in the presence of 3000 ppm of ferric iron. This result is attributed to EDTA being able to form stable chelates with ferric and ferrous iron.

Keywords:
wax remediation, wormhole, hydrate remediation, remediation of hydrates, limestone, acidizing, asphaltene remediation, asphaltene inhibition, da 0, paraffin remediation
Subjects:
Production Chemistry, Metallurgy and Biology, Unconventional and Complex Reservoirs, Acidizing, Inhibition and remediation of hydrates, scale, paraffin / wax and asphaltene, Carbonate reservoirs, Well Operations, Optimization and Stimulation
Copyright 1996, Society of Petroleum Engineers
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