Definition - What does Completion Fluid mean?
A completion fluid is a liquid used by the oil and gas industry during completion of an oil or gas well. It is a low solid mud or salt solution (brine) used for well testing and upon a well's completion. It is intended to minimize formation damage and to control formation pressure. Brine is preferred over mud due to salt's ability to go into the solution rather than having suspended solids that may settle after a prolonged time.
Corrosionpedia explains Completion Fluid
Completion fluids are used by drilling operators when they are about to complete the production of an oil or gas well and while performing well testing. Completion fluid is placed inside the well to facilitate the final operations prior to starting hydrocarbon production. The fluid reduces the friction in the wellbore's equipment when the well goes live. Also, this fluid helps setting down the screen production liners, downhole valves, packers and other equipment in the producing zone.
Completion fluids are brines (i.e., mixture of water with chlorides, bromides and formats) and have the proper density and flow characteristics. These fluids have a high pH content and ionic composition and are chemically compatible with the reservoir formation.
Completion fluids, if used for general purposes, are very corrosive and expensive.