Microwave Reflectometry for Real Time Intervention-less Well Data Acquisition
Authors: Littleford Sydney J. , Gardiner Kim 
Published: November 2023

The paper will outline a novel microwave (MW) sub-surface monitoring technology and detail the sensor types, their applications and deployment in Queensland, Australia. The sensor technology development program was to investigate the potential of retrieving real time, liquid level measurements and extrapolated bottom hole pressure data from wells.

Currently, the acquisition of subsurface data including, bottom hole pressure (BHP), fluid levels depths (FLD) and liquid/ gas ratios (LGR) are obtained using traditional methods incorporating, wireline, BHP gauges (BHPG), acoustics, and fiber optics. These conventional techniques carry significant well entry risks and high mobilization and intervention costs. Additional variables, including well location, availability of support services and installation costs impact the operator's methodology decision together with challenging technical, operational and financial factors. Therefore, well data retrieval methods that minimize risk exposure and provide accurate, repeatable, static and dynamic well data while addressing operational and environmental concerns are desirable. The subsurface data acquisition and monitoring systems have been developed using Frequency Domain Reflectometry (FDR) and Frequency Modulated Continuous Wave (FMCW) Radar with integrated signal processing software. The intervention-less well technology obtains gas/fluid interface measurements, retrieving in-well data from static and producing wells. The sensor transceiver is typically positioned within the wellhead structure and emits MW scans of various frequencies and bandwidths into the well via a wellhead feedthrough and signal transmissions are guided through each well section that act as waveguides. Using MW transmission theory, the reflected signals are translated into a measured depth. The in-situ gas or oil/water interfaces and other artifacts within the well create impedance mismatches, causing the transmitted microwave pulses to send reflections back to the surface. The reflected signals are collected by a surface receiver for real-time data processing and analysis. Analysis and interpretation of the return signal allows interface identification to be obtained instantaneously. Scanning operations also provide measurements to include tubing connection locations that can be correlated to a historical tubing or casing tally. Both measurement accuracy and repeatability performance meet or exceed current industry norms. MW sensing has been developed and deployed to identify well artifacts such as liquid levels and scale deposition and to monitor gas permittivity changes caused by liquid loading. MW sensing provides a cost-effective and time-efficient precision measurement method that can be implemented regardless of subsurface pressure, temperature, and corrosive environment. All physical well activity is surface located, eliminating well entry risk and using contactless in-well measurement techniques. Permanent and temporary (drive-by) installed MW sensors allow measurements to be obtained from remote wells without requiring a work-over or well intervention. The real time continuous monitoring of remote subsurface structures can be implemented by employing minimal well servicing requirements.