Use of nanoemulsion for effective removal of both oil-based drilling fluid and filter cake

In order to remove the oil-based drilling fluid adhering to borehole and casing walls efficiently and achieve excellent bonding strength of the casing-cement-formation interface, we develop a novel kind of oil-in-water nanoemulsion flushing fluid. The nanoemulsion flushing fluid possesses the characteristics of low interracial tension, nanoscale particle size, excellent wettability reversal ability, high stability and excellent penetrability. Lab tests are conducted to measure the flushing efficiency and the interface bonding strength. Results show that the nanoemulsion flushing fluid can remove the oil-based drilling fluid and filter cake effectively, which ensures the normal hydration of the cement slurry. As such, a large amount of the fiber-shape calcium silicate hydrate can be formed and interwoven together to form a tight network, which improves the bonding strength of the casing-cement-formation interface. (C) 2016 Elsevier B.V. All rights reserved.