NMR Permeability Estimation via Formation-Specific Pore Typing
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Solution Overview
Problem
Existing NMR logging techniques for estimating permeability in carbonate formations are limited by the use of universally applied pore sizes, which fail to accurately predict permeability due to the heterogeneity of pore systems, leading to inaccurate fluid flow predictions.
Innovation Solution
The method involves using a customized pore model for each formation by identifying statistically distinguishable peaks in the NMR relaxation time distribution, selecting pore types that contribute most to fluid flow, and calculating permeability based on the average size of these selected pore types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If universally applied NMR relaxation time cut-off values are used for pore typing, then the method is simple and consistent, but the permeability prediction accuracy deteriorates in complex carbonate formations with distinct pore types
Solution Approach 1:
The patent applies local quality by transitioning from universal pore typing to formation-specific pore typing. Instead of using the same cut-off values for all formations, the method identifies distinct pore populations in each formation and assigns specific cut-off values tailored to each formation's unique pore structure. This allows the pore typing to adapt to local characteristics of different carbonate formations, improving permeability prediction accuracy while maintaining methodological simplicity through automated identification of formation-specific pore types.
2Measurement precision
If formation-specific pore models are used to improve permeability estimation accuracy, then the measurement precision improves, but the method complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-establishing a database of formation-specific pore models and their associated cut-off values. Before performing permeability estimation on a new formation, the system prepares by identifying the formation type and selecting or creating the appropriate pore model in advance. This preliminary preparation includes analyzing formation characteristics and setting up the specific cut-off values needed, which streamlines the actual permeability estimation process and reduces on-the-fly computational complexity while maintaining high accuracy.
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 improves the accuracy of permeability estimation by considering the unique pore characteristics of each carbonate formation, reducing errors in permeability calculations compared to universal pore typing methods.
Implementation Method 1
performing nuclear magnetic resonance (NMR) measurements on a sensitive volume in the formation using an NMR tool disposed at the carrier to provide a distribution of relaxation times
Data Source
AI summary
A method for estimating a property of an earth formation includes: conveying a carrier through a borehole penetrating the earth formation; performing nuclear magnetic resonance (NMR) measurements on a sensitive volume in the formation using an NMR tool disposed at the carrier to provide a distribution of relaxation times; identifying peaks in the distribution of relaxation times; selecting at least one peak based on a characteristic of the at least one peak; and estimating the property using a relaxation time associated with the at least one peak.