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Downhole logging tools

Enhanced Digital Telemetry Cartridge (EDTC-B*)


The Enhanced Digital Telemetry Cartridge (EDTC-B*) is a downhole tool that combines two commonly run sensors with a high-speed telemetry downhole modem that can be used in high-pressure and high-temperature environments. The primary function is to provide high-speed (over 1 Mbps) communications between the wireline tools downhole and the acquisition system at surface. In addition, it includes a scintillation gamma ray detector that provides a simple total GR count in API units that provides basic gamma ray measurements for correlation between logging runs without the need for an additional tool, thus reducing the length of the string. Finally, the EDTC-B includes a single-axis accelerometer to provide the "z-axis" (i.e., along the longitudinal axis of the tool string) acceleration. This measurement can be used to observe downhole tool motion and apply speed corrections during the post-logging data processing, if desired. On the JOIDES Resolution, the vertical (z-axis) acceleration data can be fed into the DAQ computer, developed previously be LDEO, in real-time via a serial link for the purpose of evaluating heave compensator performance. The auxiliary measurements (GR and Az) provided by the EDTC cannot be used unless the EDTC is the downhole modem (telemetry module) for the entire string, so it cannot be run strictly for those measurements in combination with a different telemetry tool. On the other hand, if the EDTC is deployed as the telemetry cartridge, it is still quite possible to use alternate sensors such as the HNGS and GPIT to provide the GR and Az measurements without any conflict. By combining telemetry, basic gamma ray, and a vertical accelerometer, the EDTC provides the greatest telemetry bandwidth currently available in a shorter package than would otherwise be necessary to acquire the same basic measurements.


    • High speed telemetry communication
    • Simple gamma ray measurements

Major Outputs

ECGR: Environmentally Corrected Gamma Ray
EHGR: High Resolution Corrected Gamma Ray
GR: Gamma Ray
HGR: High Resolution Gamma Ray
MTEM: Mud temperature

Deployment Notes

The EDTC-B is typically run on each tool string. Depending on the environment, the HNGS may be run as well.

* ®trademark of Schlumberger