Sub-bottom Sonar Imaging for High-Resolution 3D Geotechnical Assessment
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Solution Overview
Problem
Current methods for imaging shallow formations and discrete seismic anomalies below the bottom of a body of water lack the resolution and reliability needed for accurate offshore geotechnical assessments, as they fail to capture the true nature of sub-bottom stratigraphy and often misinterpret diffuse reflections as noise, leading to incomplete and inaccurate data sets.
Innovation Solution
A sub-bottom sonar imaging apparatus with a carriage assembly equipped with acoustic transmitters and receivers, utilizing a line array of receivers transverse to the carriage's motion, and position determining transponders to coherently stack and beam steer signals, enabling high-resolution imaging by moving the carriage in a controlled manner to generate detailed images of the sub-bottom formations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional sonar techniques are used for sub-bottom imaging, then data acquisition is simpler, but measurement precision and imaging resolution deteriorate due to sparse coverage and inability to capture diffuse reflections
Solution Approach 1:
The imaging volume is divided into discrete volumetric elements (voxels) that are individually interrogated and characterized. This segmentation allows each voxel to be independently analyzed for its acoustic properties, enabling high-resolution 3D imaging of sub-bottom formations without requiring complex continuous scanning systems.
Solution Approach 2:
The system transitions from traditional 2D seismic profiling to 3D volumetric imaging by adding the lateral dimension to depth imaging. Multiple acoustic sources and receivers are positioned at different locations to illuminate and detect reflections from all directions, creating a three-dimensional representation of sub-bottom structures.
2Reliability
If physical core sampling is used for sub-bottom assessment, then direct samples are obtained, but reliability deteriorates due to sample alteration, compression, and inability to capture lateral discontinuities
Solution Approach 1:
Acoustic waves serve as an intermediary to probe and characterize sub-bottom formations without physical contact or sample retrieval. The acoustic signals interact with the formations and return information about their acoustic properties, providing a non-intrusive method to assess formations that avoids the distortion and loss inherent in physical sampling.
Solution Approach 2:
The mechanical core sampling system is replaced with an acoustic field-based interrogation system. Instead of physically extracting and transporting core samples, the system uses acoustic wave propagation and reflection to remotely sense and characterize sub-bottom formations, eliminating mechanical disturbance and sample alteration.
3Measurement precision
If diffuse reflections are filtered out as noise, then signal-to-noise ratio improves, but measurement precision deteriorates due to loss of textural information
Solution Approach 1:
The system converts what was traditionally considered harmful noise (diffuse reflections from sub-bottom heterogeneities) into beneficial information about formation texture and composition. By specifically targeting and analyzing these diffuse reflections, the system transforms a previously problematic signal component into the primary source of detailed formation characterization.
Solution Approach 2:
The system changes the approach to signal processing by not filtering out diffuse reflections but instead selectively enhancing and analyzing them. The processing parameters are adjusted to preserve and emphasize the scattered, diffuse signal components that contain information about sub-bottom textural properties, rather than removing them as noise.
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 provides high-resolution, three-dimensional imaging of sub-bottom features, improving the accuracy of geotechnical assessments by capturing diffuse reflections and reducing noise, thereby enhancing the reliability of data sets and enabling better correlations between different data sets.
Implementation Method 1
imparting acoustic energy into the formations along a predetermined length swath at a selected geodetic position
Implementation Method 2
Acoustic energy reflected from the formations is detected along a line parallel to the length of the swath
Implementation Method 3
position determining transponders to coherently stack and beam steer signals
Data Source
AI summary
A method for imaging formations below the bottom of a body of water includes imparting acoustic energy into the formations along a predetermined length swath at a selected geodetic position. Acoustic energy reflected from the formations is detected along a line parallel to the length of the swath. The selected geodetic position is moved a selected distance transverse to the length of the swath. The imparting acoustic energy, detecting acoustic energy and moving the geodetic position are repeated until a selected distance transverse to the length of the swath is traversed. The detected acoustic energy from all the selected geodetic positions is coherently stacked. The detected acoustic energy is beam steered to each of a plurality of depths and positions along the length of the swath to generate an image for each such depth and position.