Acoustic Telemetry Sub-band Modulation for Drill String Data
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Solution Overview
Problem
Acoustic telemetry through drill strings faces challenges due to frequency-selective channels with stop-bands and pass-bands, limiting communication from the downhole to the uphole location, especially when the precise frequency-domain locations of pass-bands are unknown, hindering dynamic adaptation of data transmission.
Innovation Solution
The method involves parsing data into sub-channels and modulating them into sub-bands with spaced apart center frequencies for concurrent transmission across multiple pass-bands, allowing data to be received even when the precise frequency-domain locations of pass-bands are not known, using techniques like Frequency Division Multiplexing (FDM) and orthogonal frequency division multiplexing (OFDM).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If acoustic telemetry is used through the drill string, then data communication from downhole to uphole is enabled, but transmission is limited by frequency-selective stop-bands and pass-bands in the acoustic channel
Solution Approach 1:
The acoustic spectrum is segmented into multiple sub-bands, each occupying a different frequency range. Data is divided and transmitted across these sub-bands concurrently, allowing the system to bypass stop-bands and utilize multiple pass-bands simultaneously, thereby overcoming the limitations of frequency-selective fading in the drill string acoustic channel
Solution Approach 2:
The system transitions from single-frequency transmission to multi-frequency parallel transmission by utilizing the frequency dimension. Multiple sub-channels operate at different center frequencies spaced apart to avoid interference, enabling data to be transmitted through multiple pass-bands concurrently and improving overall communication reliability
2Reliability
If single-frequency acoustic transmission is used, then system complexity is low, but reliable data transmission cannot be achieved when precise frequency-domain locations of pass-bands are unknown
Solution Approach 1:
The system dynamically adapts to unknown channel conditions by using multiple sub-channels with different center frequencies. When the precise frequency-domain locations of pass-bands are unknown, the system can still achieve reliable transmission by distributing data across multiple sub-bands, ensuring that at least some sub-channels will pass through pass-bands effectively
Solution Approach 2:
The system changes the frequency parameter by utilizing multiple center frequencies for different sub-channels. This allows the transmission system to adapt to varying acoustic properties of the drill string and unknown pass-band locations, improving reliability without requiring precise frequency domain knowledge
3Productivity
If multiple sub-bands are transmitted concurrently, then broadband acoustic transmission is achieved, but modulation and multiplexing complexity increases
Solution Approach 1:
Multiple sub-channels carrying different data streams are merged into a single composite acoustic signal for transmission through the drill string. The receiver separates and processes these sub-channels, achieving high-speed data transmission by combining multiple parallel communication paths while managing complexity through systematic multiplexing
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 enables effective broadband acoustic transmission across multiple pass-bands, ensuring reliable data communication from the downhole to the uphole location, even with changing acoustic properties of the drill string, and allows for dynamic adjustment of transmission parameters.
Implementation Method 1
acoustic telemetry through the drill string... acoustic signal travels... the channel or transmission medium comprises the drill string itself
Data Source
AI summary
A method for transmitting data in a frequency selective communication channel in provided. The method comprises: parsing data to be transmitted into a plurality of data fields; assigning the data from each data field into a corresponding one of a plurality of sub-channels; modulating the data from each of the plurality of sub-channels into a corresponding one of a plurality of sub-bands, the plurality of sub-bands having spaced apart center frequencies; and concurrently transmitting the data from the plurality of sub-bands onto the channel.