| 摘要 |
<p>Pulses generated, in response to parameters sensed down a borehole, by rapidly opening and shutting a valve in a comparatively wide bore passage which by passes the drill head or hydraulic motor which restricts mud flow in the borehole arrive a receiver in the high pressure side of the mud flow path positioned at the earth's surface and equipped with means to eliminate from the received signal the "noise" which is due to pressure variations arising from pulses due to the drilling mud pump. The valve used to open or close the bypass is almost balanced by opposed pressure faces but is biassed by pressure bistably to its open or closed position such that only a very small driving force from a driver is required to drive it. Hence a downhole driving power source may be provided to have a life at least equal to that of the drill head itself. The power source may include a molten salt battery or an electrolyte battery specially adapted for operations under high pressure temperature conditions by being held in a container in which there is also enclosed a source of balancing pressure.</p> |
