NMR Logging Tool Electromagnetic Model Correction

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Solution Overview

Problem

Nuclear magnetic resonance (NMR) logging data is affected by undesired effects such as stimulated echo, over/under prepolarization, inter-band interference, molecular diffusion, and temperature, which cannot be accurately described by theoretical formulations, leading to inaccuracies in petrophysical parameter determination.

Innovation Solution

The development of precise electromagnetic models that account for tool design and environmental variables, combined with spin dynamics simulations, to simulate and correct for these effects, ensuring more accurate NMR logging data interpretation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If theoretical formulations are used to describe NMR logging data, then the processing is simple and fast, but the accuracy of petrophysical parameter determination deteriorates due to undesired effects

Engineering Contradiction:

Improveaccuracy of petrophysical parameter determinationVSAvoidcomplexity of data processing

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent introduces an intermediary correction process that bridges the gap between simple theoretical formulations and accurate measurements. The system applies correction factors derived from simulated echo trains to compensate for undesired effects, allowing the use of simple theoretical models while achieving high accuracy through the intermediary correction step.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent performs preliminary simulations to generate correction factors before actual NMR logging. By pre-calculating the effects of undesired phenomena (stimulated echo, diffusion, etc.) through spin dynamics simulations, the system prepares correction data in advance that can be applied during actual logging operations, improving accuracy without adding real-time complexity.

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If calibration is performed to remove undesired effects, then measurement accuracy improves, but the number of repetitions required increases significantly

Engineering Contradiction:

Improveaccuracy of NMR logging dataVSAvoidcalibration time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent creates a virtual copy of the NMR logging environment through spin dynamics simulations. Instead of performing repeated physical calibration measurements, the system simulates the logging process under various conditions to generate correction factors, replacing time-consuming physical calibration with computational modeling.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent replaces the mechanical calibration process (repeated physical measurements) with a computational approach. Spin dynamics simulations substitute for physical calibration repetitions, using numerical models to predict and correct undesired effects without requiring extensive field calibration measurements.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If tool calibration is extended to multi-dimensional space of variables, then the accuracy of accounting for undesired effects improves, but the calibration becomes practically impossible

Engineering Contradiction:

Improveaccuracy of effect correctionVSAvoidfeasibility of calibration

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent segments the complex multi-dimensional calibration problem into manageable components. The spin dynamics simulation systematically varies individual parameters (diffusion coefficients, T1/T2 times, echo spacings) separately to generate correction factors for each effect, making the intractable multi-dimensional calibration problem solvable through sequential single-parameter analysis.

Inventive Principle:

Principle #1Segmentation

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 enhances the accuracy of petrophysical parameter determination, including hydrocarbon saturation and fluid distribution, thereby improving drilling operations by providing more precise data for targeting hydrocarbon-rich regions.

Implementation Method 1

nuclear magnetic resonance (NMR) logging. By tuning a radio frequency (RF) pulse to the correct frequency or bandwidth, one may elicit a resonant response from hydrogen in formation materials

Methodology Applied

Scientific EffectNuclear magnetic resonance: Resonance

Implementation Method 2

computing a set of one or more spin echoes based, at least in part, on the set of one or more simulation results and the B0/B1 model

Methodology Applied

Scientific EffectSpin echo: Echo

Data Source

PatentUS11143781B2Accounting for tool based effects in nuclear magnetic resonance logging data

Publication Date: 2021.10.12 HALLIBURTON ENERGY SERVICES INC

AI summary

An electromagnet model or models are created to generate the static and radio frequency magnetic fields of an NMR downhole logging tool. The magnetic field distributions are then used in spin dynamics (SD) simulations to model the impacts of various effects on NMR logging data, effects that cannot be accurately describe by theoretical formulation alone. The accuracy of the electromagnetic model and the SD simulation may be verified against experimental observations or trial logging runs. Simulation of electronic circuit, molecular diffusion, tool motion can all be incorporated in the SD simulation. The NMR data inversion process can be modified according to echoes obtained from SD simulation to obtain more accurate petrophysical parameters.