METHOD TO EXTEND CASING STRING IN WELL WITHOUT DIAMETER REDUCTION Russian patent published in 2013 - IPC E21B7/20 

FIELD: oil and gas industry.

SUBSTANCE: method to extend a casing string in a well without diameter reduction, including well deepening to the foot of the string extension zone, expansion of the extension zone with a reamer, lowering of the additional string from profile pipes into the well into the expanded interval, fixation of its upper end in the lower previously expanded part of the casing string, and expansion of profile pipes by development of hydraulic pressure in them with their further expanding as even. Prior to expansion of the well shaft with the reamer, the lower part of the casing string is expanded by the expanding method to form a socket with an expander, the diameter of which is selected such that the inner diameter of the socket during connection of the casing and additional strings provides for their reliable and tight connection between each other without reduction of well diameter.

EFFECT: method makes it possible to extend a casing string without diameter reduction in wells, which have not been previously planned for expansion, for instance, when a string has not been lowered to the bottom during cementing, in case of a complication when drilling from under a string, as a result, to reduce material costs and to speed up the process of well construction.

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