Closed-Loop Geothermal Heat Extraction With Passive Well Extensions
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Solution Overview
Problem
Current subterranean heat energy extraction methods are inefficient, costly, and environmentally detrimental due to the need for active fluid mining, limited temperature operation, and dependence on in-situ reservoir fluid, which restricts energy production and causes land subsidence and seismic risks.
Innovation Solution
A closed-loop passive heat extraction system using a vertical well with angled extensions, where a working fluid is circulated through a passive heat transfer device to harness thermal energy from subterranean zones, allowing for adjustable energy production and reduced environmental impact by minimizing fluid replenishment and enhancing heat exchange efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If active fluid mining is used to extract subterranean heat energy, then energy production is achieved, but land subsidence and seismic risks occur
Solution Approach 1:
The invention extracts only the thermal energy from the subterranean reservoir through heat conduction, leaving the reservoir fluid in place. The heat exchanger surfaces are in direct contact with the reservoir rock, allowing heat to be conducted from the rock to the working fluid without removing or depleting the reservoir fluid, thereby avoiding land subsidence and seismic risks associated with active fluid mining
Solution Approach 2:
The invention introduces a heat exchanger as an intermediary between the reservoir rock and the working fluid. This heat exchanger conducts heat from the reservoir rock to the working fluid without requiring direct fluid contact or fluid movement within the reservoir, thus enabling energy production while preventing the harmful effects of active fluid extraction
2Loss of substance
If reinjection of mined fluid is performed to replenish reservoir, then fluid loss is reduced, but parasitic energy load increases
Solution Approach 1:
The invention extracts only heat energy from the reservoir without removing the reservoir fluid. Since no fluid is mined, no reinjection is needed, and no parasitic energy is consumed for pumping replacement fluid. The reservoir fluid remains in place while thermal energy is conducted to the working fluid through the heat exchanger
Solution Approach 2:
The reservoir rock itself serves as the heat source, continuously conducting heat to the heat exchanger surfaces. The system operates passively without requiring external energy input for fluid circulation within the reservoir, as the natural thermal gradient drives heat conduction from the hotter rock to the cooler working fluid
3Object-affected harmful factors
If current closed-loop apparatus is used for heat extraction, then environmental impact is reduced, but production rate control becomes difficult
Solution Approach 1:
The invention makes the heat extraction system dynamically controllable by adjusting the working fluid flow rate through the heat exchanger. By varying the flow rate, the production rate can be precisely controlled to match demand while maintaining efficient heat extraction. The system transitions from being dependent on uncontrollable subsurface conditions to being actively controllable through surface operations
4Device complexity
If in situ reservoir fluid is required for operation, then system simplicity is maintained, but operational locations are restricted
Solution Approach 1:
The invention extracts heat directly from the reservoir rock without requiring in situ reservoir fluid. The heat exchanger surfaces are in direct contact with the rock formation, allowing heat conduction to occur in any geological setting regardless of fluid presence. This eliminates the restriction to areas with suitable in situ reservoirs while maintaining system simplicity
Solution Approach 2:
The heat exchanger acts as an intermediary that enables heat extraction from the reservoir rock directly, bypassing the need for in situ reservoir fluid. This intermediary approach allows the system to operate in diverse geological locations where the rock formation contains heat but may lack suitable fluid reservoirs, thereby expanding operational versatility
5Productivity
If active pumping of working fluid is used in closed-loop system, then heat extraction efficiency is improved, but system complexity and energy consumption increase
Solution Approach 1:
The system utilizes the natural thermal gradient between the hot reservoir rock and the cooler working fluid to drive heat conduction. The heat exchanger surfaces are in direct contact with the rock, allowing passive heat transfer without requiring active pumping or complex control systems. The temperature differential itself drives the heat extraction process
Solution Approach 2:
The invention replaces active mechanical pumping systems with passive heat conduction through the heat exchanger. By placing heat exchange surfaces in direct contact with the reservoir rock, the system relies on natural thermal conduction and convection rather than mechanical pumping, thereby reducing system complexity and energy consumption 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 system enables efficient and cost-effective harnessing of subterranean heat energy with adjustable production rates, reducing environmental impact and extending the lifespan of thermal reservoirs by optimizing heat extraction and minimizing fluid replenishment.
Implementation Method 1
a passive heat transfer device in the angled well, the outer casing of which is in thermal communication with the subterranean zone
Implementation Method 2
A working fluid can be circulated down an inner tubing string and across a heat exchanger in the passive heat transfer device
Implementation Method 3
The heated working fluid is then returned to the surface location where it can be used to turn turbines or perform other functions
Data Source
AI summary
A closed-loop heat exchange system and related methods for harnessing subterranean heat energy from a subterranean zone having a passive heat transfer device with multiple operational modes for targeting hotspots within the subterranean zone and adjusting the rate of energy harnessed according to consumption demands. The system can also have at least one enhanced surface section for increasing the heat exchange efficiency and/or a variable pump for controlling the rate at which the working fluid travels through the passive heat transfer device.