Geothermal heat mining system
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Solution Overview
Problem
Current geothermal energy extraction technologies face challenges in reliably tapping large geothermal reservoirs due to geological limitations and technical difficulties, such as induced seismicity, difficulty in controlling fracture networks, and increased drilling costs, especially at greater depths and high temperatures.
Innovation Solution
A geothermal heat mining system utilizing a single primary borehole with a secondary fluid loop in thermal contact with the reservoir, allowing for controlled heat transfer through a downhole device that manages fluid flow to optimize heat extraction, reducing the need for hydraulic fracturing and minimizing seismic risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hydraulic fracturing is used to create fracture networks in hot dry rock, then heat transfer efficiency is improved, but induced seismicity and safety risks increase
Solution Approach 1:
The system divides the single borehole into multiple functional zones with separate fluid loops (primary loop for heat extraction, secondary loop for reservoir contact). This segmentation allows heat transfer without requiring hydraulic fracturing of the entire reservoir, thereby improving productivity while reducing seismicity risks.
Solution Approach 2:
The patent introduces a secondary fluid loop as an intermediary between the borehole and the geothermal reservoir. This intermediary enables heat transfer through thermal contact without direct hydraulic fracturing, resolving the contradiction between heat transfer efficiency and seismicity reduction.
2Productivity
If multiple boreholes are drilled for injection and production, then heat recovery capacity is improved, but drilling costs and complexity increase
Solution Approach 1:
The patent merges injection and production functions into a single borehole by creating separate fluid loops (primary and secondary) that operate within the same borehole structure. This combining approach maintains heat recovery capacity while significantly reducing drilling complexity and costs.
Solution Approach 2:
The single borehole is designed to perform multiple functions: it serves as both injection and production well, houses both primary and secondary fluid loops, and provides both heat extraction and reservoir contact. This multi-functionality resolves the contradiction between productivity and device complexity.
3Temperature
If drilling depth is increased to access deeper geothermal reservoirs, then heat temperature and energy density are improved, but drilling difficulty and costs increase
Solution Approach 1:
The system establishes a single deep borehole infrastructure first, then implements multiple fluid loops within this pre-drilled structure. This preliminary action of drilling one deep borehole rather than multiple shallower ones reduces drilling difficulty and costs while maintaining access to high-temperature reservoirs.
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 enables efficient and controlled geothermal energy extraction from a single borehole, allowing for deeper access to geothermal reservoirs while reducing seismicity and drilling costs, and can produce energy continuously by managing heat transfer and fluid flow effectively.
Implementation Method 1
A secondary fluid loop can be located down the primary borehole and entirely subsurface. The secondary fluid loop can be in thermal contact with the geothermal reservoir.
Data Source
AI summary
A geothermal heat mining system can operate within a single primary borehole in a geothermal reservoir. A primary fluid loop can include a cold working fluid line leading into the primary borehole and a hot working fluid line coming out of the primary borehole. A secondary fluid loop can be located down the primary borehole, where the secondary fluid loop is in thermal contact with the geothermal reservoir and is entirely subsurface. A downhole heat mining device can control a rate of heat transfer from the secondary fluid loop to the primary fluid loop by selectively controlling fluid flow through the primary fluid loop, the secondary fluid loop, or both.