Fiber Optic Strain Sensing for Hydraulic Fracture Mapping
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Solution Overview
Problem
Current strain sensing technologies in hydraulic fracturing operations face challenges such as low sensitivity, inaccurate data, and computationally intensive data interpretation, making real-time adjustments difficult, and are prone to damage during perforation, leading to increased costs and limited fracture monitoring capabilities.
Innovation Solution
A fiber optic cable assembly with a gel or thermoset material providing high strain sensitivity and reliability, coupled with a computing device performing real-time linear inversion of strain data to determine fluid distribution and fracture orientation, allowing for accurate and timely adjustments during fracturing operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If traditional strain sensing cables are used during hydraulic fracturing, then the sensing coverage area is limited, but the sensitivity and accuracy of strain measurement deteriorate
Solution Approach 1:
The sensing system is divided into multiple distributed sensing points along the fiber optic cable, with each segment independently measuring strain at its location. This segmentation allows the entire fracture network to be monitored with high precision at multiple locations simultaneously, resolving the contradiction between coverage area and measurement precision.
Solution Approach 2:
The patent transitions from point-based sensing to distributed continuous sensing along the fiber optic cable length, adding a spatial dimension to the measurement. This dimensional change enables simultaneous high-precision measurements across the entire sensing coverage area, eliminating the trade-off between area and precision.
2Loss of time
If real-time data interpretation is performed during fracturing operations, then the response time is reduced, but the computational requirements and complexity increase
Solution Approach 1:
The system pre-calculates and stores the relationship between strain measurements and fracture parameters before the fracturing operation begins. During real-time operation, only simple lookup and interpolation operations are needed, dramatically reducing computational complexity while maintaining real-time response capability.
Solution Approach 2:
The patent creates simplified computational models that replicate the complex fracture behavior relationships in advance. These model copies enable real-time data interpretation using lightweight computations instead of full-scale complex simulations, reducing both time and computational requirements.
3Measurement precision
If strain sensing cables are deployed close to the fracture zone for accurate measurement, then the measurement accuracy improves, but the risk of cable damage during perforation increases
Solution Approach 1:
The fiber optic cable is deployed in the annular space between the casing and formation, serving as an intermediary sensing location that is close enough to capture fracture-induced strain accurately but far enough from the perforation zone to avoid direct damage. This intermediary position resolves the contradiction between measurement accuracy and cable reliability.
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
The solution enables accurate real-time strain measurement and fracture mapping, reducing uncertainty and computational requirements, allowing for proactive fracture control and minimizing the risk of well interference by accurately predicting fracture behavior and optimizing fluid and proppant distribution.
Implementation Method 1
A fiber optic cable may be deployed in an annular space between a casing and the formation to measure strain in the formation
Data Source
AI summary
A system can calculate estimated strain data for a fracture in a geological formation at each of a plurality of selected locations detectable by a strain measurement device. The system can receive real strain data from the strain measurement device for the geological formation. The system can perform an inversion to determine a probable distribution of fluid volume and hydraulic fracture orientation in the geological formation based on the estimated strain data and real strain data. The system can determine adjustments for a fracturing operation based on the inversion.