| Popis: |
Down-hole oil and gas industries are important users of high temperature electronics. In these applications the operating temperature is function of the underground depth of the wells. Oil reservoirs in Mexico are located at mean depths of 6,000 m and the typical geothermal gradient is 25°C/km, however in some areas it is greater. Consequently, the requirements for measuring thermodynamic and geophysical parameters, for instance pressure, temperature, vibration and multiphase flow, are a challenging task. Accomplishing these necessities requires a complete signal communications chain of high-performance components and effective communication techniques to provide system reliability. Nevertheless, noise interference, cable attenuation and thermal drift of the front-end passive electronic elements can lead to poor signal-to-noise ratio (SNR) and possibly loss of the communication link. 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 channel is a multi-conductor coaxial logging cable used also as a power supply transmission line. The system consists of a proprietary down-hole measurement tool, composed of a HP/HT sensor and a high temperature DSP-based electronic device; and located in the surface installation, a data acquisition equipment. The system employs a communication algorithm, based on the SNR characterization of the whole communication chain, which determines in real-time the optimal carrier frequency that is automatically implemented in the selected modulation/demodulation technique. The obtained laboratory tests results of the down-hole tool, using changes in temperature from 25 °C – 185 °C, provide a firm basis for testing and evaluating the system in the field. |
