METHOD FOR BOREHOLE BOTTOM FLUSHING Russian patent published in 2014 - IPC E21B21/00 

FIELD: oil and gas industry.

SUBSTANCE: method includes flow string running to the borehole bottom with a wing at the end till it gets into sump contamination, pumping of flushing fluid through the string and its withdrawal through borehole tubular annulus. A ripper is made at the lower end wind. Inside the wing there is a partition with openings of smaller diameter made off-centre over the ripper. Opposite the openings of smaller diameter in the partition there is an opening of a bigger diameter and a return valve with a valve cage is installed over the partition, at that the valve passes fluid bottom upwards. The flow string is run in to the well; rotation of the flow string is made simultaneously with injection of flushing liquid through openings of smaller diameter and liquid lifting through tubular annulus. The return valve is closed. Rotation of the flow string with injection of flushing liquid is continued till the tubing hanger is unloaded in place per 10 kN. Then rotation and injection are stopped. Flushing direction is changed and flushing liquid is injected through tubular annulus under pressure that does not exceed the permitted value. Ripped and eroded sludge is lifted through the flow string till weight of the tubing hanger is recovered. Working operations are repeated.

EFFECT: improved efficiency and reliability of flushing.

2 dwg