Geologic Pore System Characterization via Joint Inversion
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Solution Overview
Problem
Current methods for characterizing subsurface geologic regions, particularly in reservoirs, face challenges in accurately determining pore types and their volume fractions, which affects the estimation of permeability, especially in complex formations like carbonates, due to limitations in integrating sonic and NMR data effectively.
Innovation Solution
A method and system that acquire NMR and sonic data for a borehole, invert these data to determine volume fractions for shape and size-based classes of pore types, and characterize the subsurface region based on these fractions, utilizing effective medium rock physics models and machine learning techniques to improve permeability estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional separate analysis methods are used for sonic and NMR data, then the analysis process is simpler, but the measurement precision of pore type characterization deteriorates
Solution Approach 1:
The patent merges sonic and NMR data into a unified joint inversion framework. The system combines acoustic impedance from sonic data with pore size distribution from NMR data, integrating them through a pore throat radius distribution model to simultaneously characterize pore geometry and fluid properties, thereby improving measurement precision while managing complexity through systematic integration.
Solution Approach 2:
The patent creates a universal framework that handles multiple types of data (sonic, NMR) and multiple pore characteristics (size, shape, connectivity, fluid properties) within a single joint inversion system. This multi-functional approach allows the same methodology to be applied across different pore types (interparticle, intraparticle, vuggy, fracture) and different data combinations, improving precision without requiring separate specialized methods for each case.
2Measurement precision
If detailed pore geometry classification is implemented, then the reservoir characterization accuracy improves, but the difficulty of detecting and measuring increases
Solution Approach 1:
The patent introduces pore throat radius distribution as an intermediary parameter that connects observable data (acoustic impedance, NMR relaxation times) with pore geometry characteristics. By using this intermediate representation, the system can infer detailed pore geometry (shape, size, connectivity) without directly measuring each geometric parameter, thereby improving characterization accuracy while reducing measurement difficulty through indirect inference.
Solution Approach 2:
The patent transforms the measurement approach by changing from direct geometric measurement to parameter-based inference. Instead of directly measuring pore shape and size, the system uses changes in physical parameters (acoustic impedance, NMR T2 relaxation times) that are sensitive to pore geometry, allowing detailed characterization through parameter relationships rather than direct observation.
3Measurement precision
If joint inversion of sonic and NMR data is performed, then the permeability estimation accuracy improves, but the loss of time in processing increases
Solution Approach 1:
The patent performs preliminary classification of pore types (interparticle, intraparticle, vuggy, fracture) and establishes pore throat radius distribution models before the joint inversion process. By pre-defining the pore geometry framework and relationships between parameters, the system reduces the computational complexity during inversion, improving permeability estimation accuracy while minimizing additional processing time through advance preparation.
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
Enhances the accuracy of permeability estimation and reservoir characterization by integrating sonic and NMR data, providing a more detailed understanding of pore geometry and distribution, leading to improved formation evaluation and production efficiency.
Implementation Method 1
NMR measures pore size distribution and surface area to volume ratio
Implementation Method 2
sonic measurements may be used to determine aspect ratio
Data Source
AI summary
A method may include acquiring NMR data and sonic data for a borehole in a subsurface geologic region; inverting the NMR data and the sonic data to determine volume fractions for a number of classes of pore types, where the classes include shape and size-based classes; and characterizing the subsurface geologic region based on the volume fractions for the number of classes.