Integrated Drilling Services Limited

Dailey International, Inc.

Shell Internationale Research Maatschappij, B.v.

Paul Anthony McClure

Edward J Beshoory

William David Murray

Jan-Jette BlangÉ

Apparatus for sensing the resistivity of geological formations surrounding a borehole includes a tubular body member (1) which is adapted to form a portion of a length of drill string. An antenna (10) is mounted within the body member (1) and the body member (1) has apertures (2) adjacent to the antenna (10) to permit an electro-magnetic signal to pass through the body member (1) after transmission from, or for reception by, the antenna (10).

Well logging apparatus having a separate mounting member on which a

A well data telemetry system for transmitting data along at least a part of a well bore containing tubing of magnetically permeable material comprises a transmitting coil located to transmit a magnetic flux signal along the tubing and/or the surrounding geological formations, modulation circuitry connected to the coil for modulating the magnetic flux signal in response to a data signal, and an a.c. magnetometer located to detect and respond to the magnetic flux signal at a position spaced from the transmitting coil. By using an a.c. magnetometer instead of a conventional receiver coil to detect and respond to the magnetic flux signal, the system is capable of responding to the low levels of signal which are likely to be received in practice. Furthermore, the response of the a.c. magnetometer is independent of frequency so that the system may be used at low frequencies as well as high frequencies and demodulation of the transmitted signal can be effected without difficulty.

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Aberdeen, United Kingdom

Paul Anthony McClure