| 摘要 |
<p num="1"><br/><br/><br/><br/>The invention relates to apparatus for generating a fluid pressure pulse <br/>downhole. The invention also relates to a <br/>downhole assembly comprising a first apparatus for generating a fluid pressure <br/>pulse downhole and at least one further such apparatus, <br/>to a device for selectively generating a fluid pressure pulse downhole, and to <br/>a method of generating a fluid pressure pulse <br/>downhole. In one embodiment, an apparatus (12) for generating a fluid pressure <br/>pulse downhole is disclosed which comprises an <br/>elongate, generally tubular housing (28) defining an internal fluid flow <br/>passage (30) and having a housing wall (32). The apparatus <br/>also comprises a device (34) for selectively generating a fluid pressure <br/>pulse, the device comprising a cartridge which can be <br/>releasably mounted entirely within a space (36) provided in the wall of the <br/>tubular housing. The internal fluid flow passage defined <br/>by the tubular housing is a primary fluid flow passage, and the apparatus <br/>comprises a secondary fluid flow passage (72) having <br/>an inlet (74) which communicates with the primary fluid flow passage. The <br/>cartridge houses a valve comprising a valve element <br/>(46) and a valve seat (48), the valve being actuable to control fluid flow <br/>through the secondary fluid flow passage to selectively <br/>generate a fluid pressure pulse. Data relating to a measured downhole <br/>parameter or parameters can be transmitted to surface <br/>via the pressure pulses.<br/>
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