DRILLING METHOD OF OIL WELL OFFSHOOT IN RESERVOIRS WITH HIGH CONDUCTIVITY Russian patent published in 2015 - IPC E21B7/08 E21B33/10 

FIELD: oil and gas industry.

SUBSTANCE: method includes cut out of the string interval at sidetracking depth, isolation of expansion interval, installation of temporary cement bridge below the sidetracking point and offshoot drilling from the main borehole. Production string 1 and cylindrical cement stone are cut out completely from the top and below of truncated cone, expansion interval is isolated by installation of cylindrical easily drillable insert 2 with length more than cutting length interval by spring-supported locks 3 mounted in the lower part of the insert. In the upper part of the insert there is a channel 4 connecting inner cavity of the casing string faced to day surface with annular space formed by the insert and wall of the expanded interval. Then hardening sealing compound 5 is injected into the expansion interval, upon polymerisation of the above compound the insert is drilled out, a temporary cement bridge 6 and whipstock 7 is installed and offshoot 10 is drilled through hardened sealing compound, thereafter the main borehole is opened by drilling the whipstock 9 and temporary cement bridge. Easily drillable insert is made of soft metal.

EFFECT: improved reliability and efficiency due to hermetic isolation made within expansion interval of the main borehole and at sidetracking.

2 cl, 1 dwg