Electromagnetic Coupling-based Downhole Remote Telemetry in Well Testing

摘要

To implement accurate and timely measurements of continuous pressure and temperature parameters in oil and gas well testing, a downhole data transmission method for electromagnetic (EM) coupling-based telemetry relating to full bore drill stem testing apparatus was developed. The method analyses coupling characteristics of coils and designs structure parameters with the mathematical model of EM coupling between input and output presented. Besides, it designs downhole coreless inductive coupling with oscillator circuit of three-point capacitance based on intermittent oscillation mode. Then the telemetry system is integrated with a time-sharing transmission method based on a 'A-B-' mode and software pulse number coding/decoding technology for downhole remote transmission. The telemetry system diagram is presented. The experiments show that coreless inductive coupling can function reliably under the shielding of cylindrical tube. The proposed downhole telemetry system can work well for about 240h in the temperature up to 125°C and pressure up to 70MPa, and has access to surface readout and reduce surface operational time and costs. It has been successfully applied to onshore well testing.