METHOD FOR REAGENT CLAY CAKE REMOVAL FROM WELL Russian patent published in 2013 - IPC E21B43/27 E21B43/22 

FIELD: oil and gas industry.

SUBSTANCE: method for reagent clay cake removal from a well involves preliminary lowering of the tubing to lower perforation holes, formation in the zone of perforation holes of the first bath by pumping to the well via the tubing of a clay cake removing solution, its exposure, removal, further formation in the same zone of the second bath of water solution of acid with its being forced through the perforation zone to the formation and removal of the second bath by flushing; development of the well. As the clay cake removing solution, water solution of caustic soda with addition of surface active substance (SAS) is used. When the tubing is being lowered to the ell, it is equipped with a packer. Then, at open casing valve there performed is formation of the first bath by pumping of the above water solution of caustic soda via the tubing string, and the specified water solution of caustic soda is delivered to the formation by its being forced with process liquid via the tubing. Them the packer is set at the depth of not less than 50 metres above the treated formation, and forcing of water solution of caustic soda is performed with process liquid to the formation without exceeding allowable pressure on the formation; then, the well is kept for 10 hours for reaction under pressure not exceeding allowable pressure on the formation. Then, the packer is unpacked, and the working face is flushed by reverse flushing with process water by additional lowering of the tubing to the distance of 1-1.5 metres till the working face. Then, the packer is lifted so that it can be located at the depth of not less than 50 metres above the formation. Then, in the same zone there formed is the second bath by pumping of clay-acid solution with addition of Katapin KI-1 reagent on the basis of the fact that volume of clay-acid solution shall be 0.5-1 m³ per metre of the formation. The above clay-acid solution is forced with process fluid via the tubing to the formation; then, the packer is set and forcing of clay-acid solution is performed with process fluid to the formation without exceeding allowable pressure on the formation. Reaction exposure is performed during 1-2 hours. Then, well swabbing is performed via the tubing in the volume of 1.5-2 of the well volume. Then, the well injection capacity is determined at the pressure not exceeding maximum allowable pressure on the formation. When the required well injection capacity is not achieved, the above operations are repeated maximum for three times till the required well injection capacity is achieved.

EFFECT: simplifying the method and reducing costs for its implementation without loss of well clay cake removal efficiency, protection of the production string against action of high pressures occurring at forcing-through of the reagent to the formation considering maximum allowable pressure on the formation during implementation of process operations, and by development of the well via the tubing with a packer.