overflush — Oil & Gas Glossary
A specially prepared fluid used to displace matrix acid treatments away from the wellbore at the conclusion of a stimulation treatment. The overflush is typically formulated from a weak acid solution or brine to maintain a low pH environment in the near-wellbore formation that prevents the precipitation of reaction products as the treatment fluids are flowed back.The overflush is normally
Detailed Explanation
a weak acid or brine pumped behind the main treating fluid (mixture of hydrofluoric [HF] and hydrochloric [HCl] or organic acids).The overflush has several purposes:· displacement of the nonreacted mud acid into the formation.· displacement of mud-acid reaction by-products such as amorphous silica. The minimum overflush volume should have at least 3 ft [1 m] of radial penetration inside the formation to displace potential problems away from the critical matrix.· removal of potential oil-wet
relative-permeability problems caused by some corrosion inhibitors.