DOWNHOLE APPARATUS, DEVICE, ASSEMBLY AND METHOD

摘要

An apparatus for generating a fluid pressure pulse downhole is disclosed which comprises an elongate, generally tubular housing defining an internal fluid passage and having a housing wall. The apparatus also comprises a device for selectively generating a fluid pressure pulse, the device comprising a cartridge which can be releasably mounted entirely within a space provided in the wall of the tubular housing. The internal fluid flow passage defined by the tubular housing is a primary fluid flow passage, and the apparatus comprises a secondary fluid flow passage having an inlet which communicates with the primary fluid flow passage. The cartridge houses a valve comprising a valve element and a valve seat, the valve being actuable to control fluid flow through the secondary fluid flow passage to selectively generate a fluid pressure pulse. Data relating to a measured downhole parameter or parameters can be transmitted to surface via the pressure pulses.