Downhole telemetry and control system using orthogonal frequency division multiplexing

摘要

A power transmission and data communications system for use in a gas or oil well borehole is disclosed. The borehole includes a casing and a piping structure therein and at least one downhole equipment module located therein. The system provides for a power signal to provide power transfer to downhole systems that require power and for data and control signals to be transmitted using orthogonal frequency division multiplexing (OFDM) to the downhole equipment located in the downhole equipment modules. In particular, the system provides for the data signal to be electrically coupled to the case and piping structure for transmission downhole to the downhole systems that are similarly coupled to the casing and piping structure. The downhole equipment includes a power supply that is operative to recover electrical power from the power signal and to provide output power to the other downhole equipment. A downhole modem/receiver is operative to recover the data portion of the power/data signal and to demultiplex the OFDM signal and to demodulate the data provided thereon. The system can further include a downhole data source coupled to a downhole transmitter for impressing the downhole data onto the case and piping structure for transmission uphole. A receiver contained in the surface equipment is operative to receive and recover the transmitted downhole data for analysis and storage by surface equipment. In addition, relaying of signals can be provided for between the surface modem and two or more downhole modems. The relaying function of the middle downhole modem allows downhole modems to be communicated with than other wise possible. The middle downhole modem receives the communications message sent to a downhole modem further down the borehole and after a predetermined period will retransmit the message downhole.