Core Holder CT Imaging for Grain-Scale Rock Property Analysis
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Solution Overview
Problem
Conventional methods for determining rock mechanical properties of formations, such as downhole sonic logs and load frame measurements, fail to provide accurate mechanical properties at the grain scale, leading to errors in fracture models and completion designs in unconventional reservoirs, and are expensive and subject to calibration and interpretation errors.
Innovation Solution
A core analysis system that applies axial, radial, and pore fluid pressures to a core sample while rotating it to obtain CT images, using a radon transform to generate three-dimensional representations, allowing for the determination of properties like confined compressive strength, permeability, and mineralogy, thereby simulating in-situ conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If downhole sonic logs are used to determine rock mechanical properties, then the properties can be obtained, but the measurement precision and reliability are insufficient due to calibration and interpretation errors
Solution Approach 1:
The patent replaces conventional mechanical measurement systems (load frames with displacement sensors) and acoustic methods (sonic logs) with an optical imaging system. CT scanning uses X-ray attenuation to directly visualize and measure grain-scale mechanical properties, eliminating the need for mechanical loading apparatus and acoustic wave interpretation, thereby improving both precision and reliability
Solution Approach 2:
The patent creates detailed three-dimensional digital copies of the core sample's internal structure through CT scanning. These virtual models allow for repeated analysis and measurement without physical manipulation, eliminating calibration errors associated with physical measurement devices while maintaining high measurement precision
2Measurement precision
If load frame measurements are used to determine rock mechanical properties, then the properties can be obtained, but the measurement precision is insufficient at grain scale and the cost and time requirements are high
Solution Approach 1:
The patent transitions from conventional one-dimensional or two-dimensional mechanical measurements to three-dimensional volumetric imaging. CT scanning captures the entire core sample volume in 3D, enabling grain-scale resolution of mechanical properties throughout the entire sample simultaneously, achieving high precision without the time-consuming sequential measurements required by load frames
Solution Approach 2:
The patent performs the measurement action in advance by capturing the complete three-dimensional structure in a single scanning operation. The entire core sample is imaged at grain scale resolution before any analysis is performed, eliminating the need for time-consuming sequential mechanical testing while providing comprehensive grain-scale data
3Measurement precision
If conventional methods are used to determine rock mechanical properties, then the properties can be obtained, but the device complexity and cost are high
Solution Approach 1:
The patent employs a CT scanner that serves multiple functions: it images the core sample's internal structure, measures grain-scale mechanical properties, determines mineral composition, and creates three-dimensional models. This single multi-functional device replaces the need for separate sonic log equipment, load frames with multiple sensors, and other specialized measurement apparatus, reducing overall system complexity while maintaining high 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
Provides accurate rock mechanical properties at the grain scale, improving fracture model accuracy and completion designs, while being cost-effective and avoiding calibration and interpretation errors, with faster turnaround times.
Implementation Method 1
obtaining a series of computed tomography images of the core sample, the series of computed tomography images including an image of the core sample for at least every degree of rotation of the sample holder assembly
Implementation Method 2
obtaining at least one computed tomography image of the core sample
Data Source
Figure 1A
Figure 1B
Figure 1C~1D
AI summary
Embodiments include systems and methods for determining properties of a formation including disposing a core sample of the formation within a core holder assembly, applying pressures to the core sample, rotating the core sample about a center longitudinal axis of the core holder assembly, obtaining a series of computed tomography images of the core sample at different rotation increments of the core sample, generating, based at least partially on the obtained series of computed tomography images of the core sample, a 3D representation of the core sample utilizing a radon transform, measuring a displacement of at least one characteristic of the core sample due to the applied pressures, and based at least partially on the measured displacement, determining at least one property of the formation as a function of the applied pressures.