METHOD FOR BOREHOLE BOTTOM FLUSHING Russian patent published in 2012 - IPC E21B21/00 

FIELD: oil and gas production.

SUBSTANCE: method includes string descending to borehole bottom with wing at the end till it gets into sump contamination, pumping of flushing fluid through the string and its withdrawal through borehole tubular annulus. The wing is used of smaller diameter than the string, the wing is located inside the string with the lower part of the wing projecting from the string, sealing cups are located between the string and the wing. The contact of sealing cups and wing outer surface is lubricated by graphite grease, sealing cups and grease allow performing wing shearing force in relation to the string less than the string weight. String descending and wing stop in sump contamination is performed till the change of string suspension weight with simultaneous partial movement of the wing along the sealing cups. The pumping of flushing fluid is done till recovery of string suspension weight. Operations on string descending till the weight change and flushing till weight recovery are continued till complete movement of the wing into the string and stop of string suspension weight recovery.

EFFECT: improving the cleaning efficiency.

1 dwg