A Microwave Liquid Level Determination Method for Oil and Gas Pipelines

The modeling and design of a complete wireless liquid level determination system within a metallic pipeline is examined. Applications include the oil and gas industry, and propagation within other enclosed environments like tunnels, mines, and airplanes. For the oil and gas well scenario, the liquid level determination is achieved by measuring the delay between the original and the reflected signal by a liquid that could be positioned at the bottom of an oil well. In the design of the proposed system, the propagating mode was selected to be a superposition of the TE₂₁ and the TE₃₁ modes of the overmoded guide as standard pipeline dimensions from the oil and gas industry were employed. The wave velocity for the adopted signal within the guide was also defined and verified by theory, full wave simulations, and measurements. In particular, the excited signals were Gaussian and rectangular pulses. A specific link budget equation was also developed for the 2.4 GHz microwave system and measured successfully using a 2 meter carbon steel pipeline. Based on this link budget equation, which was supported by lab measurements, the maximum depth that can be achieved with the proposed system is 250 meters, and when the stimulated power is 1 kW; this range is mainly defined by the attenuation due to metal along the length of the pipe. Regardless of these factors and to the best knowledge of the authors, no similar microwave liquid level determination system has been developed previously with supporting theory, full-wave simulations, and measurements for propagation within industry standard oil and gas wells.