Cross-Correlation Filtering for Noisy Wellbore DAS Signals
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Solution Overview
Problem
Wellbore operations face challenges with excessive noise in distributed acoustic sensing (DAS) systems, which hinders effective control and decision-making in wellbore operations such as fracturing operations.
Innovation Solution
A cross-correlation filter is applied to the DAS system, utilizing an initial pulse reflection or a synthetic initial pulse to enhance the signal-to-noise ratio (SNR) of DAS signals, thereby improving the accuracy of measurements and control in wellbore operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DAS system is used to monitor wellbore operations, then measurement capability is provided, but excessive noise renders controlling wellbore operations difficult
Solution Approach 1:
The patent applies preliminary action by using cross-correlation filtering with an initial pulse template before final signal analysis. The system pre-processes the raw DAS signals by correlating them with a known initial pulse template, which enhances the signal components while suppressing noise. This preliminary filtering operation improves the signal-to-noise ratio before the signals are used for wellbore operation control decisions.
2Measurement precision
If cross-correlation filter is applied to enhance SNR, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent applies the copying principle by using a stored template copy of the initial pulse for cross-correlation filtering. Instead of complex real-time signal processing, the system creates a digital copy of the known initial pulse template and correlates it with the received signals. This approach simplifies the processing complexity while effectively enhancing the signal-to-noise ratio, as the template copying and correlation operations are computationally efficient compared to other filtering methods.
Data Source
AI summary
A system can include a distributed acoustic sensing (DAS) system and a computing device coupled with the DAS system. The DAS system can include a pulse generator and a sensing fiber that can be positioned in a wellbore. The system can generate a light pulse to be transmitted into the sensing fiber to make one or more measurements relating to a wellbore operation involving the wellbore. The system can receive an initial pulse that includes a reflection of the light pulse prior to the light pulse entering the sensing fiber. The system can apply a cross-correlation filter to one or more subsequently received pulse reflections originating from the sensing fiber. The cross-correlation filter can include the initial pulse reflection or synthetic initial pulse. The system can generate, based on applying the cross-correlation filter, an output signal that can be used to control the wellbore operation.