METHOD FOR DRILLING WELL ON PRESSURE DRAWDOWN Russian patent published in 2006 - IPC E21B21/14 

FIELD: oil industry, possible use when drilling well on pressure drawdown.

SUBSTANCE: method includes assembling drilling column, organizing circulation along drilling column and behind-pipe space with use of gas, drilling project interval with buildup of drilling column. In accordance to invention drilling column includes serially positioned check valves. Drilling of project interval is performed in one slotting without extraction of drilling column. Before each growth of drilling column, well is washed by forcing nitrogen gas into it and periodical reciprocation of drilling column for maximally possible height from condition of removal of mudding elements from well. Gas is fed into pipe space. Oil is added to pipe space. Behind-pipe space is pressurized for period of growth of drilling column or interruptions in work. Drilling column is grown. Behind-pipe space is depressurized and well drilling is continued until new growth of drilling column. During whole drilling cycle pressure in bed is kept below bed pressure.

EFFECT: increased quality of opening of productive bed when drilling on pressure drawdown.

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