Coreless Electromagnetic Coupling-Based Drillstem Telemetry Using Dual Electronic Gauges

Abstract

Summary A coreless electromagnetic coupling-based telemetry system for well-test data involving a full-bore drillstem test apparatus has been developed. This system allows the retrieval of formation pressures and temperatures above and below a tester valve by means of a wireline-conveyed electronic gauge and a permanently installed gauge. A wireline-deployed coreless electromagnetic proximity sonde is put into the well to transfer the data using time-division frequency transmission technology in the "Synchronization-Pressure-Low-Temperature-Low" mode on a single-core wired-armored cable. The coded pulse data are modulated on DC power signals. The surface processor uses a double-counter synchronization method to measure signal frequencies to eliminate ±1 most significant bit (MSB) error. Then a simplified algorithm is proposed, based on least-squares curve fitting and dimensionreduction methods, for computing actual temperatures and pressures for analysis of well-testing data. The proposed system is calibrated for temperatures up to 125°C and pressures up to 70 MPa with a pressure accuracy of 0.1% full scale (FS) and temperature accuracy of ±0.5°C. This approach combines the advantages of drillstem testing and wireline formation testing and has been successfully applied to onshore well testing.