Communications System for Down-Hole Measurements

Abstract

Progressively deeper and hotter oil wells have driven design modification that enhances the performance in sensorsand downhole electronic instruments. Oil reservoirs in Mexico are located at mean depths of 6,000 m; as aconsequence, the requirements for measuring thermodynamic and geophysical parameters are challenging. Thispaper describes a bidirectional communication system that exchanges data from a down-hole high pressure and hightemperature (HP/HT) measurement tool to the surface installation. The communication medium is a 7 km monoconductor1K22 logging cable used also as a power supply transmission line. The system consists of a proprietarydownhole measurement tool, composed of a HT/HP sensor and a high temperature DSP-based electronic device, anda data acquisition equipment located in the surface installation. The system employs a communication algorithm thatautomatically changes the carrier frequency of the modulation technique employed, to avoid issues derived from noiseinterference, cable attenuation and thermal drift of the front end passive elements. The laboratory tests results providea firm basis for testing and evaluating the system in the field.