Communications System using a 1K22Monoconductor Cable for Down-hole Measurement Tools

Abastract Progressively deeper and hotter oil wells have driven design modification that enhances the performance in sensors and downhole electronic instruments. Oil reservoirs in Mexico are located at mean depths of 6,000 m; as a consequence, the requirements for measuring thermodynamic and geophysical parameters are challenging. This paper describes a bidirectional communication system that exchanges data from a down-hole high pressure and high temperature (HP/HT) measurement tool to the surface installation. The communication medium is a 7 km monoconductor 1K22 logging cable used also as a power supply transmission line. The system consists of a proprietary downhole measurement tool, composed of a HT/HP sensor and a high temperature DSP-based electronic device, and a data acquisition equipment located in the surface installation. The system employs a communication algorithm that automatically switches the modulation technique and changes the carrier frequency to avoid issues derived from noise interference, cable attenuation and thermal drift of the front end passive elements. The laboratory tests results provide a firm basis for testing and evaluating the system in the field.