Telluric Referencing for EM Telemetry Noise Subtraction
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Solution Overview
Problem
Conventional electromagnetic (EM) telemetry systems face challenges in maintaining a high signal-to-noise ratio (SNR) due to telluric noise, which degrades the accuracy and reliability of data transmission during drilling and logging operations.
Innovation Solution
The implementation of telluric referencing, where a reference signal is measured at a distance from the transmitter and receiver, allowing for the subtraction of telluric noise from the received encoded signal, thereby improving the SNR and facilitating accurate demodulation and decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional EM telemetry systems operate at frequencies between 1 and 50 Hz, then data transmission can be achieved, but the signal-to-noise ratio is degraded due to telluric noise
Solution Approach 1:
The patent introduces a reference receiver as an intermediary component that measures telluric noise at a remote location. This reference receiver acts as a mediator between the telluric noise source and the main receiver, allowing the noise to be characterized and subsequently subtracted from the received signal, thereby improving the signal-to-noise ratio without affecting the primary communication function
2Measurement precision
If telluric noise is present in the received signal, then data transmission occurs, but the accuracy and reliability of data transmission is degraded
Solution Approach 1:
The patent extracts the telluric noise component from the received signal by measuring it separately through a reference receiver and then subtracting it. This extraction process separates the harmful noise from the useful signal, allowing for more accurate measurement and data transmission without the degrading effect of telluric noise
3Reliability
If a reference receiver is added to measure telluric noise, then the signal-to-noise ratio is improved, but the system complexity increases
Solution Approach 1:
The patent segments the noise measurement function from the main communication system by placing a separate reference receiver at a remote location. This segmentation allows the telluric noise measurement to be performed independently, and the resulting data to be used for signal correction without requiring complex integration into the primary communication architecture
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the SNR of EM telemetry systems, leading to higher reliability and faster data rates, enabling more accurate and efficient communication in the presence of telluric noise.
Implementation Method 1
geomagnetic pulsations induce telluric currents within the earth from the mHz to Hz frequency bands, and that atmospheric sources (e.g., lightning and/or sferics) induce telluric currents above the Hz band
Implementation Method 2
Telluric currents induce electromagnetic fields that are measured as a noise by the receiver of EM telemetry systems
Data Source
AI summary
An electromagnetic (EM) telemetry system with telluric referencing for use with downhole equipment is described. Embodiments of an EM telemetry system with telluric referencing include a downhole transceiver comprising an encoded signal transmitter, a downhole sensor disposed to monitor the downhole equipment, the downhole sensor coupled to the transceiver, an encoded signal receiver, a reference receiver spaced apart from the encoded signal receiver and communicatively coupled to the encoded signal receiver, and a telluric voltage module coupled to one of the encoded signal receiver and the reference receiver. The telluric voltage module is communicatively coupled to the encoded signal receiver and the reference receiver to receive an encoded signal and a reference signal, respectively, which may include telluric noise. The telluric voltage module synchronizes the encoded signal and the reference signal, subtracts the reference signal from the encoded signal, and outputs a signal free from telluric noise.