| 摘要 |
A method of installing a casing section in a well, by means of first and second connection devices arranged on a tubular lowering device, the first connection device being connected at an upper end of the casing section and the second connection device being connected at a lower end of the casing section, the tubular lowering device extending through the casing section. First and second flow paths are provided to enable fluids from the well to pass through the inside of the casing, as the casing is lowered into the well. A hollow is provided through the second connection device connecting the inside of the tubular lowering device to the outside of the casing. A lockable nonreturn valve is provided in the hollow which permits the well fluids to flow form inside the internal bore of the tubular lowering device to the well outside the section being installed, and also permitting fluids to flow form the well to the inside of the tubular lowering device and thus back to surface. When the casing to be fitted has been lowered to its installed position, the lockable return valve is unlocked, thus operating as a conventional nonreturn valve and preventing the unwanted flow of fluids up the internal bore of the section being installed.
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