Transient Electromagnetic Resistivity Imaging via Ex-Vz Derivative Ratio

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Solution Overview

Problem

The conventional electrical source transient electromagnetic method faces challenges in accurately calculating full-period apparent resistivity due to the binary relationship between horizontal electric field and vertical induced voltage components, and the influence of emission source shape on accuracy.

Innovation Solution

The method involves observing horizontal electric field and vertical induced voltage, calculating their first derivatives, and using their ratio to determine full-period apparent resistivity, followed by time-depth conversion for improved imaging accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the conventional calculation method based on Bz component is used, then the full-period apparent resistivity can be calculated, but the imaging accuracy deteriorates when the emission source bends or fluctuates

Engineering Contradiction:

Improvefull-period apparent resistivity calculation accuracyVSAvoidemission source shape adaptability

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent changes the calculation parameters from using only the Bz component to using the ratio of ex (horizontal electric field) to vz (vertical induced voltage). This parameter change eliminates the monotonic relationship requirement and makes the calculation independent of emission source shape, thereby resolving the contradiction between calculation accuracy and adaptability to different source configurations

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent extracts and eliminates the emission source shape influence from the calculation process by using the ratio of ex to vz. This extraction removes the harmful factor (emission source shape variability) that causes accuracy deterioration, allowing accurate full-period apparent resistivity calculation regardless of whether the source is straight or bent

Inventive Principle:

Principle #2Taking out (Extraction)

2Adaptability or versatility

If the ex and vz components are used for calculation, then the emission source shape influence is eliminated, but the direct calculation of full-period apparent resistivity becomes impossible due to binary relationship

Engineering Contradiction:

Improveemission source shape independenceVSAvoidfull-period apparent resistivity calculation difficulty

Core Design Contradiction:

Adaptability or versatilityVSDifficulty of detecting and measuring

Solution Approach 1:

The patent applies preliminary action by calculating the first derivatives of ex and vz with respect to time before performing the ratio operation. This preliminary differentiation step transforms the binary relationship components into forms that can be directly ratioed to obtain full-period apparent resistivity, thereby resolving the calculation difficulty while maintaining emission source shape independence

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces the first derivative operation as an intermediary step between measuring ex and vz and calculating the full-period apparent resistivity. This intermediary transformation converts the difficult binary relationship into a solvable form through the derivative ratio, enabling direct calculation while eliminating emission source influence

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of manufacture

If the monotonic relationship between field value and resistivity is required, then the calculation can be performed, but the applicable observation components are limited

Engineering Contradiction:

Improvecalculation simplicityVSAvoidobservable component utilization

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The patent inverts the conventional approach by not requiring a monotonic relationship between field value and resistivity. Instead, it uses the ratio of derivatives of ex and vz, which fundamentally changes the calculation paradigm from direct monotonic mapping to derivative ratio-based calculation, thereby enabling utilization of components that were previously unusable

Inventive Principle:

Principle #13The other way round (Inversion)

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 imaging accuracy by eliminating the influence of emission source shape and allows for precise resistivity distribution mapping.

Implementation Method 1

The electrical source transient electromagnetic method uses a long wire with two ends grounded as the emission source, and observes the secondary electromagnetic field signals in a certain range on both sides of the wire

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS20260086260A1Electrical source transient electromagnetic data imaging method, device and system thereof and storage medium

Publication Date: 2026.03.26 INSTITUTE OF GEOLOGY AND GEOPHYSICS CHINESE ACADEMY OF SCIENCES

AI summary

An electrical source transient electromagnetic data imaging method, a device and a system thereof and a storage medium are provided. The method includes following steps: step S1, observing horizontal electric field ex and vertical induced voltage vz at a same measuring point; step S2, respectively obtaining first derivatives of time t for the horizontal electric field ex and the vertical induced voltage vz; step S3, calculating full-period apparent resistivity according to the first derivatives; and step S4, performing time-depth conversion according to the full-period apparent resistivity to realize apparent resistivity depth imaging.