Dissolution Rate Change of Dissolving Magnesium in a Deoxygenated Environment

The corrosion rate of dissolvable magnesium for frac plugs must maintain integrity for the duration of the operation and dissolve fully thereafter. This study compared water bath corrosion testing to testing in an autoclave with and without a nitrogen purge with the same temperature (95 °C) and salinity (1 wt% KCl). The water bath test dissolution rate fell within the range of the unpurged autoclave. There was a substantial decrease in the dissolution rate of the autoclave where the nitrogen was used for purging entrapped air. The delayed dissolution rate of the material in the purged autoclave appears to be more representative of the deoxygenated downhole environment. The possible reasons for the dissolution rate reduction of magnesium in the deoxygenated environment will be explained in the paper.