Tubing Clean-Out Studies with an Environmentally Safe Pickling Fluid

A slightly, acidic (pH of 5.8-6.3) Tubing Clean-Out Fluid has been evaluated in the laboratory and in the field for use as a pickling fluid to replace the traditional acids. This fluid's capability to remove iron scales on coiled tubing, prevent or delay rust from reforming, clean up commercial pipe dopes and reduce corrosion rates, was compared to traditional hydrochloric acid in laboratory studies. This fluid performed as efficiently as 15 wt% hydrochloric acid at 140_F in removing rust/iron scale as well as pipe dope from the workstring with lower corrosion rates at typical bottom hole temperatures. Furthermore, a work string treated with this fluid retained a protective coating that resisted re-oxidization for up to 30 days. Also, several case histories detailing the product's field use for pickling completion workstring are discussed.