Through-Casing Voltage Sensor for Formation Monitoring
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Solution Overview
Problem
Current hydrocarbon recovery operations face challenges in monitoring formation changes and fluid saturations near the wellbore without disrupting ongoing production, especially in mature fields, where maintenance costs are high and continuous monitoring is necessary.
Innovation Solution
A through-casing electromagnetic formation monitoring system using voltage sensors located inside the casing string, which measure electrical properties and communicate them via fiber optic cables to an optical interrogation system, allowing for long-term, non-invasive monitoring of formation resistivity and fluid saturations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage sensors are deployed inside the casing string for formation monitoring, then continuous monitoring of formation properties is enabled without disrupting well operations, but the system complexity and deployment difficulty increase
Solution Approach 1:
The voltage sensor assembly is nested within the casing string, allowing the sensor to be deployed inside the existing wellbore infrastructure without requiring new boreholes or disrupting production operations. The sensor package travels through the casing on a deployable support structure that can be inserted and retrieved through the same casing opening.
Solution Approach 2:
A deployable support structure acts as an intermediary mechanism, enabling the voltage sensor to make temporary contact with the casing inner surface for measurement purposes, then retracting to avoid interference with well operations. This mediator allows the sensor to access the formation through the casing without permanent installation.
2Measurement precision
If sensors are placed in contact with the casing inner surface to measure electrical properties, then formation resistivity and fluid saturation measurements are obtained, but the risk of corrosion and electrical interference increases
Solution Approach 1:
The deployable support structure serves as an intermediary between the voltage sensor and the casing, allowing the sensor to measure electrical properties at the casing inner surface without being in permanent contact. This temporary contact arrangement reduces exposure to corrosive wellbore environment and minimizes electrical interference from continuous casing interaction.
Solution Approach 2:
The support structure transitions from a retracted state during deployment to an extended state during measurement, then retracts after measurement. This dynamic positioning allows the sensor to optimize measurement contact only when needed, minimizing exposure to harmful factors during non-measurement periods.
3Ease of manufacture
If the wellbore is shut in to deploy sensors outside the casing, then sensor installation is simplified, but production is interrupted and maintenance costs increase
Solution Approach 1:
The voltage sensor assembly is nested within the casing string for deployment, eliminating the need to shut in the wellbore or remove the sensor from the well. The entire sensor package can be inserted through the casing opening while the well remains operational, maintaining production continuity.
Solution Approach 2:
The deployable support structure enables the sensor to self-deploy and self-position within the casing without requiring external intervention or well shutdown. The sensor system serves itself by using the existing wellbore infrastructure (casing opening) as the deployment pathway.
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 continuous, cost-effective monitoring of formation properties without interfering with well operations, providing insights into fluid displacements and optimizing production and injection practices, even in existing wells, by deploying sensors within the casing string.
Implementation Method 1
a fiber optic cable coupled to an electro-optical transducer within the voltage sensor
Data Source
AI summary
A through-casing formation monitoring system may include a casing string positioned within a wellbore, a power source electrically coupled to the casing string, a voltage sensor electrically coupled to an inner surface of the casing string such that the voltage sensor allows a continued operation of the wellbore, a fiber optic cable coupled to an electro-optical transducer within the voltage sensor, and an optical interrogation system configured to measure an electric potential applied to the electro-optical transducer via the fiber optic cable.