| 摘要 |
A drill collar primarily for use with measurement-while-drilling and logging-while-drilling sensors, the drill collar composed of a non-magnetic nickel alloy, and having three or four elongate nitral elastomer ribs parallel the longitudinal axis and mounted on the inner surface of the drill collar, defining a central aperture for receiving the down-hole sensor and inter-rib apertures for receiving drilling fluid. This novel drill collar is especially useful in rough or underbalanced drilling applications, protecting the sensor and enhancing measurement accuracy by dampening flow-based harmonic vibrations, absorbing vibration from lateral tool movement, and stabilizing/centralizing the sensor within the central aperture. Also, the novel drill collar allows the operator to run lower fluid rates while drilling, minimizing formation damage from fluid invasion.
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