Angled Borehole Shear Wave Source for Seismic Resolution
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Solution Overview
Problem
The use of shear waves in seismic prospecting is limited due to the unavailability of suitable shear wave energy sources that can efficiently and reproducibly generate high-resolution surveys, as existing sources lack sufficient reproducibility, frequency bandwidth, and power for repeated surveys.
Innovation Solution
The implementation of a shear wave source positioned within angled, cased boreholes, where an explosive charge is detonated in a progressive manner along the borehole axis, utilizing a 'broomstick charge' configuration to generate inclined shear waves, and employing multiple boreholes at different orientations to separate and enhance shear wave signals, allowing for repeatable and broad bandwidth shear wave generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional explosive or mechanical sources are used to generate seismic waves, then compressional waves are readily generated, but shear waves cannot be efficiently generated with sufficient power and reproducibility
Solution Approach 1:
The explosive charge is segmented into multiple discrete charges positioned at different depths and orientations within the borehole. Each charge segment is detonated in sequence to generate controlled shear wave components that combine to form the desired horizontally polarized shear wave field, achieving reliable and reproducible generation
Solution Approach 2:
Different segments of the borehole contain explosive charges with specific orientations and timing designed to generate shear waves with particular polarization characteristics at different locations. This local customization of charge properties enables the complex shear wave field to be constructed from simpler local sources
2Measurement precision
If shear wave sources are designed to generate high-resolution data, then frequency bandwidth must be increased, but existing sources lack sufficient frequency band width
Solution Approach 1:
The explosive charges are detonated in periodic sequences with controlled time intervals between detonations. This periodic activation of multiple charge segments generates a broad frequency spectrum shear wave signal that maintains high resolution while achieving the required frequency bandwidth for versatile seismic surveys
3Productivity
If shear wave energy sources are developed for repeated surveys, then power must be sufficient for high resolution surveys, but existing sources lack sufficient power
Solution Approach 1:
Multiple explosive charge segments within the same borehole are combined to function as a single high-power shear wave source. The cumulative energy from all charge segments, detonated in sequence, generates sufficiently powerful shear waves that can be used for repeated high-resolution surveys while maintaining the infrastructure in place
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 the generation of repeatable and high-resolution shear wave data, allowing for improved subsurface imaging and monitoring of reservoirs, hydraulic fracturing, and other geological applications by enhancing the detection of subterranean anomalies and fluid-filled fractures.
Implementation Method 1
an explosive charge is detonated in a progressive manner along the borehole axis
Implementation Method 2
generate inclined shear waves
Data Source
AI summary
Seismic shear-wave survey systems and methods that employ inclined borehole pairs with directional detonations. If the boreholes have substantially equal inclinations in opposite azimuthal directions, the resulting signal traces can be combined to isolate shear wave energy contributions, thereby offering potentially enhanced resolution and reduced-complexity interpretation. The boreholes may be cased to ensure repeatability for, e.g., monitoring of reservoir fracturing, treatments, and/or drainage. The directional charges may be immersed to improve coupling of seismic energy into the formation.