Geothermal loop in-ground heat exchanger for energy extraction
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Solution Overview
Problem
Geothermal energy systems face limitations due to reservoir porosity and permeability issues, leading to costly and unpredictable fracturing, as well as significant well scaling and corrosion problems that severely impact performance and can result in catastrophic failures.
Innovation Solution
A closed-loop coaxial heat exchanger system is introduced, featuring an outer tubular casing and an inner tubular portion with an injection space, where a working fluid is injected at a lower temperature and exits at a higher temperature, facilitating heat transfer from a geothermal reservoir to the surface for energy extraction, while mitigating scaling and corrosion through design features like insulation and expandable components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If reservoir fracturing is employed to overcome porosity and permeability limitations, then heat extraction capability is improved, but operational cost and time increase significantly
Solution Approach 1:
The invention extracts the working fluid circulation system from the reservoir matrix and places it directly in the wellbore as a closed-loop heat exchanger. This eliminates the need for reservoir fracturing while maintaining heat extraction capability, as the heat exchanger directly contacts the reservoir through the wellbore without requiring enhanced permeability pathways.
Solution Approach 2:
The closed-loop working fluid acts as an intermediary between the reservoir and the surface heat extraction system. The working fluid circulates in the annular space of the heat exchanger, absorbing heat from the reservoir through the outer casing and delivering it to the surface, thereby eliminating the need for direct reservoir fracturing.
2Productivity
If reservoir fracturing is employed to enhance contact area, then heat transfer efficiency is improved, but cost and predictability worsen
Solution Approach 1:
The invention removes the dependency on reservoir fracturing by extracting the heat exchange function into a dedicated wellbore-installed heat exchanger system. This provides predictable and controllable heat transfer efficiency without the cost and uncertainty associated with fracturing operations.
Solution Approach 2:
The invention changes the operational parameters from relying on reservoir permeability enhancement to controlling heat transfer through the heat exchanger design parameters (annular space geometry, working fluid flow rate, heat exchanger material properties), thereby achieving predictable and cost-effective heat transfer efficiency.
3Productivity
If open well configuration is used for fluid circulation, then heat extraction is enabled, but scaling and corrosion problems increase
Solution Approach 1:
The invention extracts the working fluid circulation from the open well configuration and implements it as a closed-loop system. The working fluid is contained within the heat exchanger annular space and does not directly contact the reservoir, thereby eliminating scaling and corrosion issues while maintaining heat extraction productivity.
Solution Approach 2:
The heat exchanger structure serves as an intermediary barrier between the reservoir and the working fluid circulation system. This allows heat transfer from the reservoir through the outer casing to the working fluid in the annular space without direct contact, preventing scaling and corrosion on the circulation system components.
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 solution enhances geothermal energy extraction efficiency by maintaining consistent heat transfer and reducing operational costs, while preventing mechanical failures by addressing scaling and corrosion issues, thus providing a more reliable and sustainable energy production method.
Implementation Method 1
the outer shell tube casing (7) that is in contact with the naturally occurring hot reservoir (4)... heat is transferred from the reservoir across the outer wall of heat exchanger to the working fluid
Data Source
AI summary
A geothermal loop in-ground heat exchanger for energy extraction including an outer tubular casing and an inner tubular portion spaced from the outer tubular casing to define an injection space wherein a working fluid is injected into the injection space at a first temperature, T1 while the heat exchanger is located in a geothermal heat reservoir and the working fluid exits through the inner tubular portion at a second temperature, T2 which is greater than T1.