| 摘要 |
The invention concerns a method for casing a borehole which consists of successively lowering an unlimited plurality of strings of casing having a common diameter, the next one through the preceding one, to be installed one beneath the other and being sealingly connected. Thus a next casing ( 6 ) is lowered folded through the preceding casing ( 5 ) and the expansion process consists either in injecting pressurized fluid through the drillstring ( 54 ) towards the next casing ( 6 ) so as to re-inflate it, or the next casing ( 6 ) is a cylindrical pipe having a diameter smaller than the internal diameter of the preceding casing ( 5 ) and the expansion process consists in forcing a cylindrical gauge ( 52 ) from the top end ( 26 ) to the bottom bell ( 28 ) of the next casing ( 6 ) so as to increase its diameter to make it equal to the diameter of the preceding casing ( 5 ). The method can use a cementing shoe ( 34 ) and a metal-to-metal seal ( 29 ) between the casing string.
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