METHOD AND DEVICE FOR FORMATION PENETRATION Russian patent published in 2006 - IPC E21B21/00 E21B10/18 

FIELD: drilling technology and all-purpose well construction, particularly to expose formations characterized by different formation pressures, including abnormally low formation pressure.

SUBSTANCE: method involves performing rotation and axial supply of drilling assembly provided with bit during formation exposure; supplying flushing fluid via inner drilling assembly cavity to well bottom; lowering and cementing casing pipe with wedge-type seating ring in bottom section thereof; uncovering formation characterized by partial or full flushing liquid loss along with supplying flushing liquid via inner drilling assembly cavity to well bottom, wherein during above formation uncovering hole annuity is isolated over formation characterized by partial or full flushing liquid loss. All flushing liquid flow is fed via inner drilling assembly cavity into hole annuity zone located over isolation point simultaneously with pressure reduction in hole annuity zone located below isolation point and along with differential pressure drawdown and sludge-containing liquid injection from bottom to hole annuity zone over isolation point via inner drilling assembly cavity so that sludge-containing liquid is mixed with flushing liquid in direction towards well head. Device for above method realization comprises bit, bit sub, ejection pump and well pipes. Polished pipe with isolation packing unit is installed between bit sub and ejection pump. Wedge-type seating ring is installed at casing pipe bottom. Vacuum chamber of ejection pump communicates with interior spaces of bit, bit sub and polished pipe. Liquid discharge zone of injection pump communicates with hole annuity and is arranged above isolation packing unit.

EFFECT: increased reliability and efficiency of well drilling for loss formation exposure.

1 dwg, 1 ex