METHOD OF INCREMENT FLUID OVERFLOW INITIATION BY PRINCIPLE OF COMMUNICATING VESSELS TO RAISE DRILL STRING BOTTOM LAYOUT DURING DRILLING IN CASING STRING Russian patent published in 2013 - IPC E21B23/08 

FIELD: mining.

SUBSTANCE: drill string bottom layout is raised through casing string by reducing drilling mud density in casing string above drill string bottom layout to a value below drilling mud density in annular space behind the casing string. Drill string bottom layout moves up the casing string under effect of force generated by fluid density difference. During upward movement, less dense fluid displaced by raising drill string bottom layout exits casing string. When drill string bottom layout stops rising wedge, slips suspend the layout in middle point in casing string. Then operator reduces drilling mud density in casing string below drill string bottom layout once more creating upward force affecting drill string bottom layout by raising it upwards in casing string.

EFFECT: force required to release and raise drill string bottom layout is created.

20 cl, 14 dwg