Development of Two-way Electromagnetic Underground Communication System for Drilling

Abstract

In the field of oil well drilling, the underground communication system applying mud pulse method or electromagnetic wave method is put to practical use. However these communication systems are only one-way telemetry systems allowing communication from the underground to the earth surface for data transmission. In this paper the authors describe a construction of a two-way communication system and the performance experiments of it. The modulation and demodulation techniques are obtained by combining with Barker code and the differential shift keying method. By this technique, the bit rate of data transmission is decreased and the communication in the low signal to noise ratio becomes possible. According to the experimentally proved result, signal to noise ratio of the received signal could recover to-4 dB, and agreed with simulation results. Moreover, in the communication experiment with a transmission depth of 4000m, the rate of recognition of the transmitted bit information became 100%. The carrier frequency in this experiment is 1Hz. The possible limit case of transmission is estimated as the bit rate of (the receive signals in the underground) is 0.03bit/sec, and one in the surface is 0.04bit/sec.