preflush — Oil & Gas Glossary
In chemical flooding, a fluid stage, normally low-salinity water, pumped ahead of the micellar or alkaline chemical solution.One of the purposes of the preflush is to displace reservoirbrine containing potassium, sodium, calcium and magnesium ions from the near-wellbore area, avoiding adverse interactions with the chemical solution. The other purposes are to adjust reservoir salinity to favorable conditions for the surfactant
Detailed Explanation
(chemical solution) and to obtain information about reservoir flow patterns. Sometimes a preflush stage is not necessary, especially when brine-tolerant chemical systems are used.