NMR Diffusion Tortuosity for Acid Diversion Efficiency

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Solution Overview

Problem

Conventional methods for determining acid diversion efficiency in matrix acidizing are inaccurate and labor-intensive, particularly in heterogeneous carbonate formations, where chemical diverters fail to provide uniform stimulation.

Innovation Solution

A method using Nuclear Magnetic Resonance (NMR) to measure diffusion tortuosity in rock samples, calculating a diversion index (DI) based on tortuosity ratios in orthogonal and parallel directions to the wormhole formed by hydrochloric acid (HCl) flooding, allowing for precise evaluation of acid diversion efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional methods are used to determine acid diversion efficiency, then the process can be performed with standard equipment, but the measurement accuracy is poor and the process is labor-intensive

Engineering Contradiction:

Improveacid diversion efficiency measurement accuracyVSAvoidmeasurement efficiency

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent replaces conventional mechanical measurement methods with Nuclear Magnetic Resonance (NMR) technology to measure diffusion tortuosity. This substitution enables non-invasive, rapid, and accurate measurement of acid diversion efficiency without labor-intensive procedures, directly resolving the contradiction between measurement precision and productivity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a new measurement parameter (diffusion tortuosity measured by NMR) to characterize acid diversion efficiency. By changing from conventional measurement parameters to NMR-based diffusion tortuosity, the system achieves both high measurement accuracy and operational efficiency, eliminating the trade-off between precision and productivity

Inventive Principle:

Principle #35Parameter changes

2Reliability

If chemical diverters are applied in heterogeneous formations, then acid diversion is attempted, but the acid overstimulates high permeable sections while leaving tight rock sections under-stimulated

Engineering Contradiction:

Improveuniformity of formation stimulationVSAvoidacid distribution control

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent uses NMR measurement of diffusion tortuosity as a feedback mechanism to evaluate acid diversion efficiency in real-time. This feedback allows operators to assess whether acid has been uniformly distributed across heterogeneous formations, enabling adjustments to achieve reliable uniform stimulation while simplifying operation through clear quantitative metrics

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces complex mechanical monitoring and control systems with NMR-based diffusion tortuosity measurement. This substitution provides a simplified yet effective method to assess acid distribution uniformity in heterogeneous formations, improving both reliability of stimulation and ease of operation through non-invasive measurement

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 an accurate and efficient means to assess acid diversion efficiency, enabling targeted hydrofracking by identifying high-efficiency zones in subterranean formations.

Implementation Method 1

measuring, with NMR, a first diffusion tortuosity τd,x in an X-direction corresponding to a direction orthogonal to the wormhole; and measuring, with NMR, a second diffusion tortuosity τd,y in a Y-direction corresponding to a direction parallel to the wormhole

Methodology Applied

Scientific EffectNuclear Magnetic Resonance (NMR):

Implementation Method 2

measuring a first diffusion tortuosity τd,x in an X-direction corresponding to a direction orthogonal to the wormhole

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS12480899B2Method to measure acid diversion efficiency in matrix acidizing through NMR

Publication Date: 2025.11.25 KING FAHD UNIVERSITY OF PETROLEUM AND MINERALS

AI summary

A method to measure acid diversion efficiency in rock samples. The method includes measuring a first porosity and a permeability of the rock samples. The method includes flooding a core region of the rock sample with a hydrochloric acid (HCl) system to create a wormhole, wherein during the flooding the HCl system penetrates from a first end of the rock sample to a second end of the rock sample to form the wormhole. The method includes measuring a second porosity, a pore size distribution, and a diffusion tortuosity of the rock samples with NMR. The method includes establishing a diversion index (DI) based off a ratio between the diffusion tortuosity in a first direction and the diffusion tortuosity in a second direction. The method includes determining the acid diversion efficiency based off the diversion index.