Polygonal Core Ultrasonic Velocity Testing
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Solution Overview
Problem
Current stress-dependent acoustic anisotropy tests face limitations in measuring wave velocities in anisotropic materials like shale, as they require multiple plug specimens from the same spot, which is impractical due to tight spacing of horizontal laminations, and assume equivalent measurements in opposite directions, which is not true for natural rocks with discontinuities.
Innovation Solution
A method and system for measuring wave velocities using a polygonal-shaped core specimen with at least ten faces, where stress is applied to each face using hydraulic rams and ultrasonic waves are introduced and detected across opposing faces, allowing for three-dimensional stress-dependent ultrasonic wave velocity testing without assuming symmetry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple plug specimens are taken from the same spot to measure acoustic anisotropy, then measurement precision is improved, but it becomes impractical due to tight spacing of horizontal laminations in shale
Solution Approach 1:
The cylindrical core specimen is segmented into multiple polygonal-shaped specimens by cutting at different orientations (vertical, 45°, horizontal) relative to the bedding plane. Each polygonal specimen can be tested independently for acoustic anisotropy, allowing multiple measurements from a single core without requiring separate plug specimens from the same spot.
Solution Approach 2:
The invention transitions from traditional three-dimensional plug specimens to two-dimensional polygonal cross-sections obtained by cutting the core at specific angles. This dimensional transformation allows multiple measurement directions to be captured in a single planar specimen, eliminating the need to extract multiple separate plugs from the same location.
2Device complexity
If the assumption of equivalent measurements in opposite directions is made, then device complexity is reduced, but measurement precision deteriorates for natural rocks with discontinuities
Solution Approach 1:
The invention explicitly accounts for asymmetry in natural rocks by measuring wave velocities in multiple directions (vertical, 45°, horizontal) relative to the bedding plane. The polygonal specimen geometry and multi-directional testing setup allow detection of directional variations in wave velocity, eliminating the need to assume equivalent measurements in opposite directions while maintaining manageable system complexity through systematic measurement protocols.
3Measurement precision
If eight plug specimens are taken from whole core to study anisotropy, then measurement precision is improved, but productivity deteriorates due to discarding remaining core material
Solution Approach 1:
The core specimen is pre-cut into multiple polygonal-shaped specimens at different orientations before testing begins. This preliminary segmentation allows all required measurement directions to be obtained from a single core sample without requiring extraction of multiple separate plugs, thereby maximizing core material utilization and improving productivity while maintaining measurement precision.
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
Enables accurate measurement of wave velocities and elastic properties in unconventional formations like shale with a single specimen, overcoming the limitations of prior methods by applying different stress orientations and conditions, and providing a more accurate description of material properties without symmetry assumptions.
Implementation Method 1
an ultrasonic wave velocity is introduced to at least one face of the polygonal-shaped specimen, and the ultrasonic wave is detected on the associated opposing face
Implementation Method 2
The acoustic assembly is associated with the set of opposing faces and configured to send an acoustic signal into one of the opposing faces and receive a signal from the other opposing face
Implementation Method 3
stress is applied to each face of the polygonal-shaped specimen. The stress is applied by a plurality of rams with each ram being associated with one of the faces
Implementation Method 4
stress is applied to each face of the polygonal-shaped specimen such that the same or different stress can be applied to each set of opposing faces
Implementation Method 5
The stress applied to each face is monitored, such as by a load cell
Data Source
AI summary
A system for and a method of measuring ultrasonic wave velocities in a subterranean core specimen is provided. Ultrasonic wave velocities are measured from the side surfaces (faces) of a polygonal-shaped core specimen having at least ten sides or faces. Stress is introduced to the core specimen by hydraulic rams associated with each set of opposing sides. As stress is applied, ultrasonic waves are introduced to at least one side of the set of opposing sides and the wave transmitted through the core specimen is measured. Subsequently, the wave velocity for the ultrasonic wave can be calculated based on the measurements taken. Also, elastic properties associated with the core specimen can be calculated.