Fiber Optic Casing Strain Sensing for Continuous Wellbore Stress

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Solution Overview

Problem

Existing subsurface stress measurement techniques are limited to discrete points or short sections of wellbores, often requiring fracturing and providing only singular calibration points, lacking a continuous log of stress estimation along the wellbore.

Innovation Solution

A system utilizing an elongated fiber optic cable and a controller to sense strain from stress applied to the wellbore casing, enabling continuous measurement of mechanical properties and stress states over large wellbore lengths and timescales, avoiding fracturing through controlled perturbations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If hydraulic fracturing method is used to determine subsurface stress measurements, then minimum principal stress magnitude at an isolated wellbore interval can be determined, but the measurement is limited to discrete points or short sections and provides only singular calibration points

Engineering Contradiction:

Improvestress measurement accuracyVSAvoidmeasurement coverage length

Core Design Contradiction:

Measurement precisionVSLength of stationary object

Solution Approach 1:

The patent replaces traditional mechanical fracturing methods with an optical sensing system using fiber optic cables. The fiber optic cable measures strain along the wellbore, which is then converted to stress measurements, eliminating the need for physical fracturing and enabling continuous measurement along the entire wellbore length.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent transitions from discrete point measurements to continuous linear measurements along the wellbore. The fiber optic cable provides strain data at multiple locations simultaneously, creating a continuous stress profile along the wellbore length rather than isolated measurement points.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Loss of information

If traditional stress measurement methods are used, then stress can be determined at isolated intervals, but a continuous log of stress estimation along the wellbore cannot be obtained

Engineering Contradiction:

Improvestress distribution informationVSAvoidmeasurement system complexity

Core Design Contradiction:

Loss of informationVSDevice complexity

Solution Approach 1:

The fiber optic cable serves multiple functions: it acts as both the sensing element for strain measurement and the transmission medium for data. The same cable infrastructure used for other wellbore operations can be utilized for stress measurement, reducing additional system complexity while providing continuous stress information.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The fiber optic cable inherently provides the sensing capability without requiring separate measurement devices. The cable itself detects strain through optical properties, and the system uses existing wellbore infrastructure, making the measurement process self-contained and reducing overall system complexity.

Inventive Principle:

Principle #25Self-service

3Reliability

If fracturing is performed to obtain stress measurements, then calibration points can be obtained, but the process is invasive and limited to specific locations

Engineering Contradiction:

Improvestress measurement reliabilityVSAvoidwellbore formation damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces mechanical fracturing with optical strain sensing. The fiber optic cable measures strain without physically altering the formation or requiring fracturing events, thereby eliminating formation damage while maintaining measurement reliability through continuous strain monitoring.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The fiber optic cable acts as an intermediary between the stress field and the measurement system. It transduces mechanical strain into optical signals without requiring direct contact or fracturing of the formation, providing reliable stress data without causing harmful effects to the wellbore or formation.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

Enables accurate, continuous monitoring of subsurface stresses and mechanical properties, facilitating optimal wellbore design and reducing uncertainty in subsurface stress estimation, particularly useful in geothermal and hydrocarbon exploration.

Implementation Method 1

sense strain from stress applied to the wellbore casing

Methodology Applied

Scientific EffectStrain sensing: Deformation

Data Source

PatentUS12454888B2Systems and methods for determining mechanical properties in subsurface formations

Publication Date: 2025.10.28 WISCONSIN ALUMNI RES FOUND

AI summary

A system for monitoring and establishing mechanical properties of a formation may include a strain sensing system and a controller. The strain sensing system may include an elongated fiber, a light emitter, and a detector. The elongated fiber may be or may include a fiber optic cable. Monitoring and establishing mechanical properties of a wellbore may include determining a stress applied to a casing of a length of the wellbore and sensing, with the strain sensing system, a strain that may be resultant from the stress applied to the casing. Based on the stress applied to the casing and the sensed strain, the controller may determine a value related to a mechanical property of the formation extending along the wellbore.