Optical Fiber Wellbore Strain and Temperature Monitoring
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Solution Overview
Problem
Existing methods for monitoring wellbores and formations are insufficient in detecting deformation, strain, and fluid leaks, particularly in subterranean systems like carbon dioxide storage reservoirs, as they do not provide a comprehensive indication of leaks or fluid flow.
Innovation Solution
A system comprising a borehole string with optical fiber sensors and distributed temperature sensing (DTS) or discrete temperature sensing (DDTS) systems, which measure strain and temperature along the borehole string, allowing for the calculation of strain profiles, identification of elevated strain regions, and correlation with temperature measurements to detect fluid leaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fiber optic techniques are used to measure strain and temperature in a wellbore, then strain and temperature measurement capability is improved, but the ability to detect fluid leaks and deformation remains insufficient
Solution Approach 1:
The patent combines fiber optic strain sensing with distributed temperature sensing (DTS) into an integrated monitoring system. The strain sensor and temperature sensor are merged into a single comprehensive system that simultaneously measures both parameters along the wellbore, enabling correlated analysis to detect fluid leaks that neither sensor could identify alone.
Solution Approach 2:
The system uses temperature as an intermediary parameter to enhance leak detection. By correlating temperature measurements with strain measurements, the system indirectly detects fluid leaks through their thermal signature, transforming the temperature field into a diagnostic tool for identifying leakage locations.
2Device complexity
If a single type of sensor is used for wellbore monitoring, then device complexity is reduced, but the completeness of deformation and leak detection is insufficient
Solution Approach 1:
The fiber optic cable serves multiple functions simultaneously: it acts as both the strain sensing element and the temperature sensing medium. This multi-functionality allows the system to monitor both mechanical deformation and thermal conditions using a single integrated platform, reducing the need for separate sensor systems while comprehensively capturing wellbore behavior.
Solution Approach 2:
The system transitions from single-point measurements to distributed measurements along the entire length of the wellbore. By implementing continuous strain and temperature sensing along the wellbore length, the system adds the spatial dimension to monitoring, enabling identification of deformation and leak locations at any position rather than at discrete points.
3Measurement precision
If wavelength shift measurement is used to detect strain, then strain detection sensitivity is improved, but thermal effects on strain measurement increase measurement error
Solution Approach 1:
The system implements feedback by continuously measuring temperature along the wellbore and using this information to correct strain measurements. The temperature data provides real-time feedback about thermal conditions, which is then used to compensate for thermal effects on the fiber optic strain sensor, maintaining measurement accuracy under varying temperature conditions.
Solution Approach 2:
The system extracts and separates the thermal component from the strain measurement. By independently measuring temperature and then removing its contribution from the total wavelength shift, the system isolates the mechanical strain signal from thermal interference, obtaining accurate strain measurements despite temperature variations.
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 system effectively monitors wellbores and formations, providing a complete picture of integrity and fluid flow, enabling early detection of leaks and deformation, thus allowing for timely remedial actions and changes in production practices.
Implementation Method 1
the plurality of measurement units configured to cause a wavelength shift in an interrogation signal received in the at least one optical fiber sensor due to at least one of a strain and a deformation of the borehole string
Implementation Method 2
at least one distributed temperature sensing (DTS) sensor and a distributed discrete temperature sensing (DDTS) sensor disposed along a length of the borehole and configured to measure a temperature at a plurality of locations along the length
Data Source
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AI summary
A system for monitoring a borehole includes: a borehole string configured to be disposed within the borehole and configured to direct a fluid into the earth formation for storage in the earth formation, the fluid including carbon dioxide; at least one optical fiber sensor disposed on the borehole string at a fixed location relative to the borehole string, the optical fiber sensor including a plurality of measurement units disposed therein along a length of the optical fiber sensor, the plurality of measurement units configured to cause a wavelength shift in an interrogation signal received in the at least one optical fiber sensor due to at least one of a strain and a deformation of the borehole string; and a processor configured to transmit the interrogation signal to the at least one optical fiber sensor, and calculate at least one of the strain and the deformation based on the wavelength shift.