Solubility of Silica in Alkaline Solutions: Implications for Alkaline Flooding

The expected loss of useful alkalinity caused by the slow dissolution of silica from pure quartz sand is shown for some typical alkaline flooding solutions (about 1 % NaOH or 1.25% sodium orthosilicate) to be only about 10 to 20%. This conclusion is based on the observation that alkaline solutions equilibrate with quartz and on the methodology proposed here for determining the useful alkalinity of a solution. Furthermore, the dissolution of quartz in alkaline flooding can be eliminated by the use of solutions saturated in silica with respect to quartz. Such formulations may be useful in controlling the erosion of the wellbore and gravel pack.