Nedihulls-motor og fremgangsmåte for operasjon

摘要

A down hole motor assembly includes a hydraulic drive portion, a drill bit operatively connected to the drive portion and a disengage mechanism (11) arranged to disengage drive to the drill bit. The disengage mechanism (11) is arranged to be actuated by supplying drilling fluid to the drive portion at a flow rate which is greater than the flow rate at which fluid is supplied to run the drive portion during normal drilling. The disengage mechanism is arranged to be re-set so that drive is reconnected to the drill bit when the fluid supply to the drive portion is shut off.