Acoustic telemetry stacked-ring wave delay isolator system and method

摘要

A stacked-ring, slow-wave acoustic telemetry isolation system and method for use with tubular assemblies such as drillpipe or production tubing comprising an acoustic wave transmitter, the acoustic isolator behaving such that a “down” wave propagated toward the isolator is reflected back substantially in phase with an “up” wave propagated from the acoustic wave source away from the isolator. The acoustic isolator is similarly effective in reflecting “up” propagating waves originating from below the isolator, hence further protecting the acoustic wave source from possible deleterious interference. It causes substantially all of the emitted wave energy to travel in a chosen direction along the drill pipe, thus aiding the efficiency of acoustic telemetry said pipe.

主权项

1. A method of controlling wave reflections in a drilling apparatus including a series of tubular drillstring members located between an acoustic transmitter and a bottom hole assembly (BHA), the method comprising the steps:
placing the acoustic transmitter in proximity to the drilling apparatus; extending a series of tubular drillstring members between said acoustic transmitter and the BHA; providing a stacked-ring parallel path acoustic isolator comprised of a housing, a stack of first, second and third cylindrical rings with first, second and third lengths, respectively, aligned along a common axis placed within said housing, and upper and lower interfaces for connecting said isolator to the tubular drillstring members; the first length approximately equaling the second length; the third length approximately equaling one-half of said first or second length; placing said acoustic isolator beneath said transmitter and above said BHA along the series of tubular drillstring members; configuring the acoustic transmitter to transmit a split modulated telemetry signal in generally symmetrical uphole and downhole signal paths through the drillstring; configuring the acoustic isolator with slowed and unslowed signal pathways; splitting the downhole telemetry signal into slowed and unslowed downhole signals in the respective slowed and unslowed signal pathways; providing a relative phase shift of approximately 180° in the slowed downhole telemetry signal by controlling the impedance in the slowed pathway; providing a reflection surface below the acoustic isolator and above the BHA; reflecting the slowed and unslowed signals at the reflection surface back upwardly into the acoustic isolator with the slowed and unslowed signals approximately 180° out-of-phase with each other; further slowing the upwardly-traveling, reflected, slowed signal in the acoustic isolator slowed pathway; combining the reflected slowed and unslowed signals in phase with each other below the transmitter; and combining the isolated, reflected, recombined downhole signal with the uphole signal in phase above the transmitter.