Practice of Wire-line Coring Drilling in Soft Coal Measure Strata

Abstract:

The drilling construction of 2 deep holes was completed in a mining area of Changchun, which was in soft coal measure strata. The paper introduces the used construction method of wire-line coring with hydraulic percussive-rotary drilling and enlarged annular clearance between borehole wall and drill pipe was selected. The flushing fluid with material compounding of clay, copolymer, plant gum, ammonium salt, potassium humate, sulfonated asphalt and potassium polyacrylate was determined by experiments; daily maintenance management of flushing fluid was strengthened and equipped with centrifugal mud removal machi41ne. The casing thread connection were smeared with rosin (as plastering agent) and welded with thin steel sheet to prevent casing thread releasing. The final hole depth were 1112.45m (ZK6405) and 1359.95m (ZK3201) respectively with 100% core recovery. Coal core samples were not damaged by combustion, the geological requirement was met.