| 摘要 |
The present invention provides an apparatus and methods to reduce ECD and pressure associated therewith while drilling with casing. In one aspect, the invention provides an energy transfer assembly locatable at a predetermined location in a casing string. The assembly includes an impeller portion in the interior of the casing to be acted upon by the downward moving fluid in the casing and a pump portion disposed outwardly of the impeller portion and arranged in fluid communication with the upward moving fluid in the annulus between the casing and the borehole, adding energy thereto and reducing pressure in the annulus therebelow. In another aspect, the energy transfer assembly is retrievable to the surface of the wellbore prior to cementing. In a further aspect, fluid ports between the interior and exterior of the casing are remotely sealable prior to cementing.
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