Importance

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Abstract

A method and system of drilling multiple radial wells using underbalanced drilling, by first drilling a principal wellbore; then providing a first carrier string having a deflection member on its lowermost end to a certain depth within the principal wellbore; orienting the deflection member into a predetermined direction; lowering a second drill string, such as coiled tubing or segmented drill pipe, down the bore of the carrier string, so that the drill bit on the end of the second string is deflected by the deflection member in the predetermined direction from the principal wellbore and a first multilateral well is drilled. When coiled tubing is used, fluid is pumped downhole through the annulus of the coiled tubing, and into an annular space between the coiled tubing and the carrier string so that it co-mingles with produced hydrocarbons; and the co-mingled fluids and any hydrocarbons are returned to the rig through the annular space between the borehole and the carrier string. When segmented drill pipe is used, fluid is pumped down the bore of the drill pipe and down the annular space between the carrier string and the borehole, and fluid and any hydrocarbons are returned up the annular space between the drill pipe and the carrier string; in either method, maintaining an underbalanced borehole, so that addtional multilateral wells may be completed while the well is alive and producing.

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First Claim