Dynamic Gravity Toolface Measurement via Cross-Axial Magnetometry

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Solution Overview

Problem

Conventional measurement while drilling (MWD) methods for dynamic borehole azimuth measurements are prone to magnetic interference and accuracy issues, especially near magnetic north or south, and are contaminated by vibrations and centripetal accelerations, making them unsuitable for real-time directional drilling.

Innovation Solution

The use of cross-axial magnetic field measurements in combination with accelerometer measurements to compute the dynamic borehole azimuth, eliminating the need for axial magnetic field measurements and accounting for sensor biases and vibrations, allowing for real-time dynamic borehole azimuth determination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If axial magnetic field measurements are used to compute dynamic borehole azimuth, then the measurement can be made dynamically while drilling, but the measurements are contaminated by magnetic interference from nearby drill string components

Engineering Contradiction:

Improvedynamic measurement capabilityVSAvoidmeasurement accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent extracts the problematic axial magnetic field measurement component and replaces it with cross-axial magnetic field measurements. By removing the axial component that is susceptible to magnetic interference from drill string components, the solution maintains dynamic measurement capability while eliminating the source of magnetic contamination that degrades measurement reliability.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces cross-axial magnetic field measurements as an intermediary alternative to the direct axial magnetic field measurements. These cross-axial measurements serve as a mediator that provides the necessary azimuth information without being directly exposed to the magnetic interference from nearby drill string components, thus preserving both productivity and reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If transverse accelerometer measurements are used to compute dynamic borehole azimuth, then the measurement can be made dynamically, but the measurements are contaminated by lateral vibration and centripetal acceleration

Engineering Contradiction:

Improvedynamic measurement capabilityVSAvoidazimuth measurement accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent extracts and removes the transverse accelerometer measurements that are contaminated by lateral vibration and centripetal acceleration. By eliminating these problematic measurements, the solution maintains dynamic measurement capability while removing the sources of vibration and acceleration contamination that degrade azimuth measurement precision.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent substitutes the mechanical accelerometer-based azimuth measurement system with a magnetic field-based measurement system using cross-axial magnetometers. This substitution replaces the mechanical sensing approach that is vulnerable to vibration and centripetal acceleration with a magnetic sensing approach that is immune to these mechanical disturbances, thereby achieving both dynamic measurement capability and high precision.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If static surveying measurements are used, then measurement accuracy can be maintained, but the measurements are not timely enough for real-time directional drilling

Engineering Contradiction:

Improvewell path accuracyVSAvoidmeasurement timing delay

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent transforms the static surveying measurement system into a dynamic one by implementing continuous measurements during the drilling process. The downhole measurement tool performs azimuth and inclination measurements in real-time as the drill string rotates and drilling progresses, eliminating the time delay inherent in static measurements taken after drilling stops. This dynamic approach maintains measurement precision while providing timely data for real-time directional drilling control.

Inventive Principle:

Principle #15Dynamics

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 and reliability for dynamic borehole azimuth measurements, enabling more precise directional drilling and borehole imaging, even in challenging orientations and vibration-prone conditions.

Implementation Method 1

cross-axial magnetic field measurements are utilized to compute a magnitude of a cross-axial magnetic field component

Methodology Applied

Scientific EffectMagnetic field measurement: Magnetic Field

Implementation Method 2

borehole inclination is commonly derived from tri-axial accelerometer measurements of the earth's gravitational field

Methodology Applied

Scientific EffectGravitational field measurement: Gravitation

Implementation Method 3

axial accelerometer measurements or both axial and cross-axial accelerometer measurements

Methodology Applied

Scientific EffectAccelerometer measurement: Accelerometer

Data Source

PatentUS10584575B2Utilization of dynamic downhole surveying measurements

Publication Date: 2020.03.10 SCHLUMBERGER TECH CORP

AI summary

A method for making dynamic gravity toolface measurements while rotating a downhole measurement tool in a borehole is disclosed. The method includes processing magnetic field measurements and accelerometer measurements to compute a toolface offset and further processing the toolface offset in combination with a magnetic toolface to obtain the dynamic gravity toolface. Methods for correcting dynamic and static navigational sensor measurements to remove sensor biases, for example, are also disclosed.