Distributed Acoustic Sensing Gauge Length Mitigation via Inversion
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Solution Overview
Problem
Current Distributed Acoustic Sensing (DAS) systems face challenges in mitigating gauge length effects, which lead to artifacts and spectral fidelity loss in hydrocarbon reservoir monitoring, requiring complex hardware adjustments and longer measurement times.
Innovation Solution
The method involves generating virtual seismic measurements by subdividing gauge lengths and applying inversion operations to DAS data, allowing for gauge length effect mitigation using a single optical fiber, thereby improving data acquisition speed and interpretation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gauge length is increased to improve signal-to-noise ratio, then measurement reliability is improved, but spectral fidelity is lost due to averaging effects
Solution Approach 1:
The patent segments the gauge length into multiple smaller sub-gauge lengths along the optical fiber. Instead of using a single long gauge length that causes averaging effects, the system divides it into multiple shorter segments that can be individually processed. This segmentation allows the system to maintain the benefits of longer gauge lengths for noise reduction while avoiding the spectral fidelity loss through subsequent deconvolution processing.
Solution Approach 2:
The patent introduces an intermediary processing step involving deconvolution algorithms that act as a mediator between the raw DAS measurements and the final seismic profile. This intermediary process corrects the averaging effects introduced by finite gauge lengths, thereby recovering spectral fidelity while preserving the signal-to-noise ratio benefits of longer gauge lengths.
2Measurement precision
If gauge length is decreased to improve spectral fidelity, then measurement precision is improved, but signal-to-noise ratio deteriorates
Solution Approach 1:
The patent merges multiple measurements from overlapping sub-gauge lengths to reconstruct the seismic profile. By combining information from multiple shorter gauge length measurements that overlap along the fiber, the system achieves both high spectral fidelity (from short gauge lengths) and improved signal-to-noise ratio (from the combined measurements).
3Measurement precision
If multiple measurements at different gauge lengths are used to mitigate gauge length effects, then measurement precision is improved, but device complexity and measurement time increase
Solution Approach 1:
The patent makes the single optical fiber perform multiple functions by using it to acquire measurements at effectively multiple gauge lengths through software processing rather than requiring physically different fibers or hardware configurations. The same optical fiber and DAS system are used universally to collect data that is then processed to simulate multiple gauge length measurements, eliminating the need for complex hardware adjustments.
Solution Approach 2:
The patent changes the measurement parameter from physical gauge length to virtual gauge length through software. Instead of physically adjusting the gauge length by changing hardware configurations, the system maintains a fixed physical gauge length and uses software algorithms to create virtual measurements at different effective gauge lengths, thereby simplifying the device while achieving gauge length effect mitigation.
4Measurement precision
If multiple measurements at different gauge lengths are used to mitigate gauge length effects, then measurement precision is improved, but measurement time increases
Solution Approach 1:
The patent performs preliminary action by acquiring all necessary DAS measurements at a single gauge length in advance, before any processing occurs. The complete dataset is collected first, and then the gauge length effect mitigation is achieved through subsequent software processing that mathematically generates virtual measurements at different effective gauge lengths from this single acquisition pass, eliminating the need for repeated physical measurements.
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 accuracy and clarity of seismic profiles, reducing blurring and noise, and enables more precise geological feature detection, facilitating better drilling and well treatment operations.
Implementation Method 1
Acoustic sensing based on DAS uses backscatter properties of an optical fiber's core
Implementation Method 2
the use of certain gauge lengths which allows the performance of optical interferometric measurements
Data Source
AI summary
A method to generate a vertical seismic profile includes acquiring a set of distributed acoustic sensing measurements from a set of overlapping measurement channels on an optical fiber, wherein each of the set of distributed acoustic sensing measurements are measured at a gauge length. The method also includes generating a set of virtual seismic measurements corresponding with subdivisions in the set of overlapping measurement channels based on the set of distributed acoustic sensing measurements and generating the vertical seismic profile based on the set of virtual seismic measurements.