Expandable Casing for Closed-Loop Geothermal Heat Transfer Enhancement
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Solution Overview
Problem
Closed-loop geothermal systems face challenges in extracting sufficient heat from the subsurface due to limitations in the flow of geothermal fluid and the 'airgap' distance between rock and the downhole heat exchanger, which affect long-term energy production efficiency.
Innovation Solution
The use of an expandable casing section within an enlarged wellbore to increase the volume and contact surface area accessible to the downhole heat exchanger, enhancing thermal connectivity and geothermal fluid access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a standard wellbore diameter is used, then the construction is simpler and costs are lower, but the volume of geothermal fluids accessible to the heat exchanger is limited
Solution Approach 1:
The wellbore construction is divided into multiple stages: initial wellbore creation, enlargement to first pre-determined diameter, insertion of casing string with expandable section, expansion to second larger diameter. This segmentation allows the system to achieve large volume access while managing construction complexity through phased implementation
Solution Approach 2:
The casing string includes an expandable casing section that can change diameter from the first pre-determined diameter to the second larger diameter. This dynamic adjustment allows the wellbore volume to be increased after initial construction, enabling greater geothermal fluid access without requiring complete reconstruction
2Area of stationary object
If the wellbore diameter is increased, then the contact surface area between rock and heat exchanger increases, but the construction difficulty and cost increase
Solution Approach 1:
The initial wellbore is drilled to a first pre-determined diameter that is sufficient to accommodate the casing string and allow for future expansion. This preliminary action prepares the wellbore for subsequent enlargement without requiring excessive initial construction effort
Solution Approach 2:
The expandable casing section allows the wellbore diameter to be increased from the first pre-determined diameter to the second larger diameter after the heat exchanger is in place. This dynamic expansion increases the contact surface area between rock and heat exchanger while avoiding the need for complete wellbore reconstruction
3Productivity
If geothermal fluid flow is increased, then heat extraction efficiency improves, but the system requires larger wellbore volume to accommodate the increased fluid movement
Solution Approach 1:
The expandable casing section enables the wellbore volume to be increased from the first diameter to the second larger diameter, providing sufficient space for increased geothermal fluid flow while maintaining heat extraction efficiency
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 improves heat transfer efficiency by increasing the volume of geothermal fluids accessible, promoting better heat extraction and maintaining consistent power generation over time.
Implementation Method 1
expanding the expandable casing section within the first portion
Implementation Method 2
The fluid conduit is configured to channel cool working fluid from the uphole heat exchanger to the downhole heat exchanger and hot fluid from the downhole heat exchanger to the uphole heat exchanger
Data Source
AI summary
Methods and systems for constructing an enhanced closed-loop geothermal system for heat transfer from a region of a subsurface. The method may include obtaining a first wellbore extending from a surface and penetrating the region of the subsurface. The method further includes enlarging at least a first portion of the first wellbore to a first pre-determined wellbore diameter and inserting a casing string having an expandable casing section into the first wellbore such that the expandable casing section is disposed within the first portion. The method also includes expanding the expandable casing section within the first portion and inserting a closed-loop geothermal system having a fluid conduit into the first wellbore yielding the enhanced closed-loop geothermal system.