Fracture Barrier Identification via Strength Contrast Profiling
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Solution Overview
Problem
Traditional stress-based methods for modeling stimulated rock volume in hydraulic fracturing are limited, especially in complex formations, as they fail to accurately identify fracture barriers due to their reliance on elastic properties and stress contrast profiles that do not account for geological and structural variations.
Innovation Solution
A strength-based method using rebound hardness values and mineralogy to generate a strength contrast profile, converting rebound hardness values to unconfined compressive strength (UCS) values, and applying micro-X-ray fluorescence analysis to identify fracture barriers through relative and absolute strength contour plots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If stress-based methods are used to model stimulated rock volume, then the modeling process is simpler, but the accuracy of fracture barrier identification deteriorates in complex formations
Solution Approach 1:
The patent changes the fundamental parameter used for modeling from stress contrast to strength contrast. Instead of using elastic properties and stress contrast profiles, the invention uses rebound hardness values converted to UCS strength values to create strength contrast profiles. This parameter change enables accurate identification of fracture barriers in complex formations while maintaining practical applicability through the use of standard core measurement techniques.
2Ease of operation
If stress contrast profiles are generated using elastic properties, then the method is easier to implement, but the ability to account for geological and structural variations deteriorates
Solution Approach 1:
The invention replaces stress contrast parameters with strength contrast parameters derived from rebound hardness measurements. Strength properties captured by rebound hardness are less sensitive to stress state variations and more directly reflect the inherent mechanical properties of different rock types and mineral compositions. This allows the method to adapt to various geological and structural conditions while remaining operationally straightforward.
Solution Approach 2:
The patent substitutes the stress-based mechanical modeling approach with a strength-based approach. Instead of calculating stress contrasts from elastic properties, the invention uses rebound hardness measurements that directly quantify rock strength. This substitution provides a more direct measure of fracture propagation resistance that is applicable across diverse geological settings.
3Ease of manufacture
If rebound hardness values are converted to UCS values using empirical equations, then the measurement process remains simple, but the conversion accuracy may vary between different core types
Solution Approach 1:
The patent applies different empirical conversion equations tailored to specific core types (1/3 slab section cores versus 2/3 butt section cores). By recognizing that measurement geometry affects the rebound hardness-UCS relationship, the invention uses locally optimized conversion equations for each core type, thereby maximizing conversion accuracy for each specific measurement configuration while keeping the overall process simple.
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 more accurate identification of fracture barriers, improving hydraulic fracturing operations by relating core-scale measurements to reservoir-scale analysis, enhancing engineering decisions and business performance in unconventional reservoirs.
Implementation Method 1
a rebound hardness tester to determine rebound hardness values of the rock specimen
Implementation Method 2
a micro-X-ray fluorescence analyzer to determine the mineralogy of the rock specimen
Data Source
AI summary
Methods, systems, and computer-readable medium to perform operations for identifying fracture barriers in a well. The operations include converting rebound hardness values of a rock specimen from the well to unconfined compressive strength (UCS) values, where each of the rebound hardness values corresponds to a respective coordinate of a measurement grid imposed on the specimen. The operations further include, for each column of the grid, plotting the UCS values versus depth. Further, the operations include mapping, based on a maximum UCS value and a minimum UCS value, a relative strength contour plot for the specimen. Yet further, the operations include mapping, based on a fixed strength range, an absolute strength contour plot for the specimen. In addition, the operations include determining, based on the relative strength contour, the absolute strength contour, and mineralogy of the rock specimen, that the rock specimen is indicative of a fracture barrier in the well.