Casing Collar Locator for High-Resolution Wellbore Depth Positioning

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Solution Overview

Problem

Current methods for determining precise depth positions in well bores are inaccurate due to cable stretch and other factors, making it difficult to reliably measure depth between casing collars, especially over time and with different equipment, which affects the accuracy of downhole functions like gravity surveys.

Innovation Solution

Utilizing the innate, persistent magnetic or characteristic properties of pipe segments to generate continuous indicia of distance between casing collar locations, allowing for precise positioning of downhole tools with a tolerance of 1-2 cm, even after significant time lapses, by sensing and logging intermediate characteristic signals along the pipe segments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If odometer measurement is used to determine depth, then depth measurement is obtained, but measurement precision deteriorates due to cable stretch and other factors

Engineering Contradiction:

Improvedepth measurement precisionVSAvoidmeasurement reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent introduces an intermediary reference system (casing collar locator) that indirectly measures depth by detecting fixed physical features (casing collars) rather than directly measuring cable length. This intermediary approach eliminates the harmful effects of cable stretch on measurement accuracy.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the mechanical cable-based measurement system (odometer) with a magnetic field-based detection system (casing collar locator). This substitution eliminates the mechanical issues of cable stretch, friction, and tension that plague the traditional mechanical measurement approach.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If casing collar locator is used to augment odometer measurement, then depth accuracy between collars is improved, but device complexity increases

Engineering Contradiction:

Improvedepth accuracy between collarsVSAvoidmeasurement system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The casing collar locator serves multiple functions: it detects casing collar positions, provides reference points for depth measurement, and enables accurate positioning between collars. This multi-functionality justifies the added device complexity by delivering comprehensive measurement capabilities.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent creates a copied reference system (magnetic signature of casing collars) that replicates the physical structure's measurement function. Instead of relying on the physical cable length, it uses a magnetic field-based copy of the collar positions to establish depth references.

Inventive Principle:

Principle #26Copying

3Reliability

If traditional depth measurement methods are used, then positioning is obtained, but positioning reliability deteriorates over time and with different equipment

Engineering Contradiction:

Improvepositioning reliability over timeVSAvoidtime lapse between measurements

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent performs preliminary action by establishing a permanent magnetic reference map of casing collar positions during the initial logging run. This pre-established reference system remains valid for future measurements, eliminating the need for repeated calibration and ensuring consistency over time and across different equipment.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The magnetic signature of the casing collars creates a permanent copy of the wellbore's structural features that can be repeatedly detected and compared. This copied reference information persists indefinitely, allowing reliable positioning at any future time without degradation.

Inventive Principle:

Principle #26Copying

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 enables more accurate and repeatable downhole functions, reduces the time and cost of positioning tools, and improves the reliability of surveys by providing high-resolution depth measurements, allowing for precise repositioning after extended periods.

Implementation Method 1

The casing collar locator magnetically senses the position of casing collars where connected segments of pipe are threaded together to form the casing. The larger diameter of the casing collar and the possibility of a slight gap between the adjoining ends of the connected pipe segments creates a distinctive change in the magnetic permeability of the metal (typically steel) casing at each collar.

Methodology Applied

Scientific EffectMagnetic permeability detection: Magnetic Field

Data Source

PatentUS9540927B2High resolution continuous depth positioning in a well bore using persistent casing properties

Publication Date: 2017.01.10 MICRO G LACOSTE

AI summary

Continuous measurement indicia between casing collars of a pipe segment of a well bore casing is obtained from signals obtained by sensing innate, persistent and unaltered characteristics, e.g. magnetic permeability, of the pipe segment along its length, and using the signals to perform a downhole function, e.g. a gravity measurement, at an indicated location.