Digital Core Relative Permeability Calculation via MicroCT Fractal Analysis
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Solution Overview
Problem
Current methods for calculating relative permeability in tight reservoirs are time-consuming and lack accuracy due to low permeability and neglect rock morphological characteristics, leading to discrepancies between calculated and measured permeability curves.
Innovation Solution
A digital imaging technology-based method involving MicroCT scanning, 3D image fractal analysis, and simulations to calculate relative permeability, considering threshold pressure gradient and capillary forces, and rock pore structure characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If displacement experiment is used to obtain permeability curve, then measurement accuracy can be improved, but measurement time increases significantly and requires high accuracy measuring instruments
Solution Approach 1:
The patent creates a digital core model that copies the actual rock pore structure through CT scanning and fractal analysis. This digital model allows for virtual displacement experiments and theoretical calculations without requiring physical core samples, thereby eliminating the time-consuming nature of physical displacement experiments while maintaining measurement accuracy through the detailed digital representation of pore structures.
Solution Approach 2:
The patent transforms the physical measurement problem into a digital simulation problem by changing parameters from physical core properties to digital model parameters. The fractal dimensions (DT, Df) and pore structure parameters extracted from digital imaging allow the system to calculate relative permeability through mathematical models rather than physical experiments, significantly reducing measurement time while preserving accuracy.
2Productivity
If theoretical calculation method is used, then calculation speed is improved, but accuracy deteriorates because rock morphological characteristics are not considered
Solution Approach 1:
The patent performs preliminary digital imaging and fractal analysis to extract accurate pore structure characteristics (fractal dimensions DT, Df, and pore distribution parameters) before conducting theoretical calculations. This preliminary action ensures that the subsequent theoretical calculations incorporate real rock morphological characteristics, thereby maintaining both calculation efficiency and accuracy.
Solution Approach 2:
The patent replaces traditional mechanical displacement experiments with digital imaging technology and fractal-based theoretical calculations. By substituting physical measurement systems with digital modeling systems that incorporate fractal geometry, the method achieves both high calculation efficiency and high accuracy in representing complex pore structures.
3Reliability
If traditional displacement experiment is conducted, then measured data can be obtained, but resource consumption increases due to repeated experiments needed for different conditions
Solution Approach 1:
The patent creates a reusable digital core model that can be used for multiple simulations and calculations without consuming additional physical resources. Once the digital model is created through a single CT scan, it can be used to study various displacement conditions, fluid types, and pressure gradients virtually, eliminating the need for repeated physical experiments and reducing resource consumption while maintaining data reliability.
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 method provides accurate and efficient calculation of relative permeability, reducing resource waste by incorporating rock morphology and avoiding the limitations of traditional methods, with high reliability in plotting relative permeability curves.
Implementation Method 1
scanning the sample by MicroCT-400 and establishing a digital core
Implementation Method 2
simulating a water-oil displacement in single fractal capillary
Data Source
AI summary
The invention discloses a digital imaging technology-based method for calculating relative permeability of tight core, comprising the following steps: step S1: preparing a small column sample of tight core satisfying resolution requirements; step S2: scanning the sample by MicroCT-400 and establish a digital core; step S3: performing statistical analysis on parameters reflecting the characteristics of rock pore structure and shape according to the digital core; step S4: calculating tortuosity fractal dimension DT and porosity fractal dimension Df by a 3D image fractal box dimension algorithm; step S5: performing statistical analysis on maximum pore equivalent diameter λmax and minimum pore equivalent diameter λmin by a label. The present invention solves the problems of time consumption of experiment, instrument accuracy, incapability of repeated calculation simulations and resource waste by repeated physical experiment.