| 摘要 |
The invention relates to a downhole tool for generating a fluid pressure pulse, and to a method of generating a fluid pressure pulse downhole. In one embodiment of the invention, an improved downhole tool (10) and method for transmitting data signals from a downhole environment to surface is disclosed, the downhole tool (10) comprising a fluid actuated flow restrictor (22); a first fluid flow path (23) for flow of actuating fluid to actuate the flow restrictor (22); a second fluid flow path (25) for flow of actuating fluid to actuate the flow restrictor (22); and a control member (12) movable between a first closed position where the first fluid flow path (23) is closed and the second fluid flow path (25) is open, and a discrete second closed position where the first fluid flow path (23) is open and the second fluid flow path (25) is closed, for controlling actuation of the flow restrictor (22) to generate a fluid pressure pulse.
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