METHOD OF WITHDRAWAL OF FILTER FROM HOLES Russian patent published in 2004 - IPC

FIELD: mining industry, replacement of filter strings of holes. SUBSTANCE: intercoupled filter sections are displaced in sequence. Additional spaces and communication of the latter with internal space of filter string are formed. Density of sand plug between hole wall and filter section is decreased by displacement of the latter. In compliance with invention sand plug between hole wall and filter section is removed to hole surface over tubular annulus by circulation of flushing fluid. Flushing fluid is supplied under pressure into internal space of filter string through holes in rod of telescopic unit of connection elements of filter sections and additional space between filter sections. Prior to removal of sand plug between filter section and hole wall holes in rod of telescopic unit of connection element located above this filter section are shut off beginning from second filter section by displacement of filter sections positioned above. EFFECT: diminished effort required for withdrawal of filters. 2 dwg