Importance

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Abstract

A method and system of drilling multiple radial wells using underbalanced drilling, by first drilling a principal wellbore. There would then be provided a first carrier string having a deflection member on its lowermost end to a certain depth within the principal wellbore. There is then lowered a second drill string, such as coiled tubing, 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 a predetermined direction from the principal wellbore. A second fluid is then pumped into an annular space between the coiled tubing and the carrier string to a position that it co-mingles with the first fluid. The co-mingled fluids and any hydrocarbons are then returned upward to the rig through the annular space between the borehole and the carrier string. There is then provided a volume of fluid to establish an equilibrium within the carrier string. The drill bit at the end of the coil tubing is retrieved from the bore hole. The direction of the deflection member is reoriented to a second depth within the borehole. Finally, the coil tubing and drill bit is lowered to the second depth to drill a second radial well, while the well is alive and producing.

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First Claim