Importance

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Abstract

An apparatus for selectively activating a downhole Measurement While Drilling (MWD) tool, so as to prolong the life of the MWD battery and improve function of the MWD flow restrictor pilot valve assembly, includes a switch actuator responsive to pressure differential disposed incorporated within a fluid sealed pressure chamber which also incorporates a pilot valve assembly for activating the flow restrictor for causing mud pulse signals. The switch actuator comprises upstream and downstream bellows sealing a fluid filled reservoir, with a push-action switch within the upstream bellows, isolated from the drilling fluid. Ports expose the upstream and downstream bellows to longitudinally spaced points in the flowstream, the upstream ports providing flow-through cleaning of the upstream bellows. During drilling fluid flow, a friction pressure loss occurs between the ports, and with flow within desired rates, the resulting pressure differential on the upstream bellows actuates the switch and activates the MWD tool. The flow restrictor pilot valve assembly is partly within the reservoir and comprises a dual dashpot, controlling valve stem movement, with a volume compensating means that permits stem movement within the reservoir without affecting switch actuator function. The actuator integrates the pilot valve length and internal volume so as to minimize the overall length of the actuator and more fully utilize tool length formerly used for a single purpose.

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First Claim