Study and application of flushing fluid for oil wells with lined tubing

To thermally clear the wax attached in oil wells with conventional lined tubing, different surface active agents, the modified inorganic nano silicon dioxide or alumina or titanium dioxide, a very small amount of fluorocarbon surfactant, and vitamin A are combined to obtain the flushing fluid with strong wetting and foaming performance and strong surface energy, and it can be used at 50 ℃. The laboratory evaluation and field test prove that the flushing fluid can remove the crude on the rod and tubing, and enhance cleaning ability for wax, resin and asphaltenes. The generated small bubbles can improve the carrying capacity of the flushing fluid, and change the wettability of the inner surface of tubing and the outer surface of rod into neutral wetting, which could extend the clean out period. Field tests on more than 50 wells show that the average upgoing load of rod decrease by 10.32% after the clean out operation, and the average oil production recovery period has a reduction of 54.12%, The annual oil rate growth is more than 760 tons. The technique provides a technical support for the use of lined tubing.