Published March 2015

Release of stuck drill string

D.S. Akhundov

Among complications and failures the sticking of drill string is more difficult case. For its liquidation more than 50 % of whole time of failures is spent. The sticking of drill string occurs due to the various reasons, the main of which are overpressure in well-layer system, the adhesion of drill string surface to the clay mud crast and electromagnetic power in clay rocks. The most common method of stuck tool release method is installation of an oil bath. However, in most cases the oil bath does not always give positive results. That is why when releasing the stuck drill string for installation of oil bath the oil with addition of 10 % caustic soda solution in the water with density of 1350 kg/m3 is applied. In the area of stuck during the contact of soda with clay particles, the dispersion of clay particles, surrounded by oil film, occurs and in the consequence of this the firm connection of heterogeneous surfaces formed in the boundary of double electric layer, decreases. With application of oil-alkali mixture in installation of bathes for stuck drill string release, its total release is achieved in minimum time.