Methods and systems for heat transfer using formation fluids
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Solution Overview
Problem
Geothermal systems face challenges in efficiently extracting heat from subsurface rock formations due to the cooling of geothermal fluids as they flow through cooler shallow rock formations, leading to decreased heat transfer efficiency over time.
Innovation Solution
A closed-loop geothermal system with a control valve and temperature sensor is used to regulate the flow of geothermal fluid, allowing discharge when the fluid temperature drops below a predetermined level, and reintroducing hotter fluid to maintain heat transfer efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If geothermal fluid flows continuously through the wellbore, then heat transfer occurs, but the fluid temperature drops below effective levels over time
Solution Approach 1:
The system dynamically adjusts the flow regime by switching between continuous flow and discharge/ refill cycles based on real-time temperature monitoring. The control valve transitions from fully open to closed positions, creating variable flow conditions that maintain temperature above minimum thresholds while extending operational duration.
Solution Approach 2:
The temperature sensor continuously monitors geothermal fluid temperature and provides feedback to the control system. When temperature drops below the minimum threshold, the control valve closes to prevent further cooling, and when temperature rises above the maximum threshold, the valve opens to discharge fluid. This closed-loop feedback control maintains temperature within optimal ranges.
2Temperature
If the control valve remains closed to maintain temperature, then heat transfer efficiency is preserved, but fluid flow and heat extraction are reduced
Solution Approach 1:
The system employs periodic discharge and refill cycles rather than continuous flow. The control valve alternates between open and closed positions based on temperature thresholds, creating a pulsating flow pattern. During closed periods, heat transfer efficiency is maintained; during open periods, fluid is discharged and replaced with hotter reservoir fluid, preparing for the next efficient heat extraction cycle.
3Temperature
If the control valve opens frequently to discharge cool fluid, then temperature is maintained, but system complexity and operational control increase
Solution Approach 1:
The control system automatically regulates valve operation based on pre-programmed temperature thresholds without requiring manual intervention. The temperature sensor continuously monitors conditions and the control valve responds autonomously, allowing the system to self-regulate flow based on thermal conditions. This reduces operational complexity while maintaining effective temperature control.
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
The system maintains near-equilibrium heat transfer efficiency by automatically adjusting fluid flow, slowing the decline in power generation over the system's lifecycle.
Implementation Method 1
The temperature sensor is configured to measure a first temperature of the geothermal fluid within the casing string
Implementation Method 2
The control valve is configured to control the flow of geothermal fluid out of the annulus
Implementation Method 3
A first end of the casing string is open. A portion of the casing string penetrating the geothermal heat source is perforated permitting geothermal fluid to flow from the geothermal heat source into an annulus formed between the closed-loop geothermal system and the casing string
Data Source
AI summary
Methods and systems are disclosed herein. A method may include operating a closed-loop geothermal system disposed in a well. The well includes a wellbore penetrating the geothermal heat source, a casing string, a control valve, and a temperature sensor. An annulus is formed between the closed-loop geothermal system and the casing string. The method includes measuring, using the temperature sensor a first temperature of the geothermal fluid. The method includes opening, when the first temperature is lower than a first predetermined temperature, the control valve in order to discharge geothermal fluid from the annulus.