Geo-steering via EM Gap Impedance Resistivity

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Solution Overview

Problem

Current wellbore drilling operations face challenges in accurately geo-steering due to incomplete and inaccurate geological information, often relying on minimal tools like measurement-while-drilling (MWD) tools or expensive 'look-ahead' technologies, which can result in undesirable wellbore trajectories.

Innovation Solution

The method and system utilize electromagnetic (EM) signals to measure gap voltage and current across a gap sub in a downhole tool, determining gap impedance and formation resistivity to steer the tool, enabling more precise geo-steering based on real-time resistivity data.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If measurement-while-drilling (MWD) tools with total gamma ray radiation measurements are used to identify formations, then the cost is minimized, but the geological information becomes incomplete and inaccurate

Engineering Contradiction:

ImprovecostVSAvoidgeological information accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent uses gap impedance measurements as an intermediary parameter to infer formation resistivity. The gap impedance serves as a mediator that provides information about formation properties without requiring direct formation contact or expensive dedicated resistivity tools, thus improving measurement accuracy while keeping costs low.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces mechanical/direct-contact formation evaluation methods with electromagnetic field-based gap impedance measurements. By using EM fields to probe formation resistivity through the gap sub, the system achieves more accurate geological information without the complexity and cost of traditional look-ahead technologies.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If look-ahead technologies based on sonic or resistivity data are used to geo-steer, then the wellbore trajectory accuracy is improved, but the cost becomes very expensive

Engineering Contradiction:

Improvewellbore trajectory accuracyVSAvoidcost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent makes the EM telemetry system multi-functional by using it for both data transmission and formation resistivity measurement. The same EM signals used for communication also provide geological information through gap impedance variations, eliminating the need for separate expensive look-ahead tools while maintaining trajectory accuracy.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent changes the measurement parameter from direct formation contact methods to electromagnetic gap impedance. By monitoring changes in gap impedance caused by formation resistivity variations, the system achieves accurate geo-steering information at lower cost, effectively substituting expensive sonic or resistivity tools with a modified EM telemetry approach.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If bare minimum tools are used in bottom hole assembly, then the cost is reduced, but the geological information becomes incomplete leading to undesirable wellbore trajectory

Engineering Contradiction:

ImprovecostVSAvoidwellbore trajectory control

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent implements feedback by continuously monitoring gap impedance measurements and using this information to adjust wellbore trajectory in real-time. The EM telemetry system provides ongoing geological feedback that enables dynamic geo-steering decisions, improving trajectory reliability without adding significant tool complexity or cost.

Inventive Principle:

Principle #23Feedback

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 provides improved accuracy in wellbore trajectory control by correlating gap impedance with formation resistivity, allowing for more effective geo-steering and potentially extending wellbore life while reducing costs associated with expensive technologies.

Implementation Method 1

transmitting a first electromagnetic (EM) signal from the downhole tool to a computing system at the surface

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

determining a formation resistivity at a first location in the wellbore based at least partially upon the gap impedance

Methodology Applied

Scientific EffectElectrical resistivity: Electrical Resistance

Data Source

PatentUS11719048B2Geo-steering using electromagnetic gap impedance data

Publication Date: 2023.08.08 SCHLUMBERGER TECH CORP

AI summary

A method for steering a downhole tool includes receiving an electromagnetic (EM) signal from the downhole tool. The downhole tool is in a wellbore in a formation. The EM signal comprises a gap voltage and a gap current that are measured across a gap sub in the downhole tool. The method also includes determining a gap impedance based at least partially upon the gap voltage and the gap current. The method also includes determining a first formation resistivity at a first location in the wellbore based at least partially upon the gap impedance. The method also includes steering the downhole tool based at least partially upon the first formation resistivity.