| 摘要 |
<p>A data logging sub is mounted at the downhole end of a drill string, and a receiver, or detector is mounted at the top of the drill string at the well-head. The downhole logging sub includes a digital signal transmitter that is operatively connected to the drill string, such that it can send a series of charge pulses along the drill string. The receiver is mounted to detect changes in electrical charge on the drill string. The drill string leaks charge to the surrounding geological formation, but the time constant of the leakage is large compared to the quantity of charge of the charge pulses, and the low resistance of the drill string as compared to the resistivity of the surrounding formation. The leakage is high enough that the charge leaks off the drill string fast enough to permit a useful baud rate.</p> |
