Stimuli-Responsive Nanofluids for Geothermal Fracture Control
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Solution Overview
Problem
In Enhanced Geothermal Systems (EGS), non-uniform fracture networks lead to short-circuiting of working fluids due to high conductivity and injectivity in certain fractures, necessitating improved tracer fluids and stimulation methods to characterize and control subsurface permeability effectively, especially in high-temperature environments where conventional tracers are underdeveloped.
Innovation Solution
Development of stimuli-responsive heat transfer nanofluids that increase viscosity at high flow velocities and can form gels under specific conditions, utilizing surface-treated nanoparticles with responsive polymers and functional groups to control hydraulic conductivity and prevent flow through 'fast paths' in EGS reservoirs, thereby acting as both enhanced heat transfer fluids and tracer fluids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional tracer fluids are used in EGS, then the system is simple to operate, but the tracer fluids cannot effectively characterize subsurface permeability in high-temperature environments
Solution Approach 1:
The patent modifies the chemical parameters of tracer fluids by incorporating temperature-stable compounds and adjustable viscosity agents, enabling the fluid to maintain its tracer functionality across high-temperature EGS conditions (175-300°C) while allowing viscosity adjustment to match different fracture network characteristics
Solution Approach 2:
The patent creates composite tracer fluids by combining base fluids with specialized additives including temperature-stable tracers, viscosity modifiers, and fracture-characterization agents, resulting in a multi-functional fluid that can simultaneously withstand high temperatures and effectively characterize subsurface permeability
2Temperature
If nanofluids with high nanoparticle concentration are used, then thermal conductivity increases, but viscosity increases excessively worsening thermal performance
Solution Approach 1:
The patent optimizes nanoparticle concentration parameters and selects nanoparticle materials with surface treatments that minimize aggregation, achieving enhanced thermal conductivity while controlling viscosity increases to remain below the threshold where thermal performance deteriorates
Solution Approach 2:
The patent applies surface treatments to nanoparticles that create localized hydrophilic or hydrophobic regions, improving nanoparticle dispersion and reducing viscosity increases while maintaining thermal conductivity enhancement benefits
3Productivity
If fracture network is non-uniform, then injectivity is high in certain fractures, but fluid takes fast pathways causing short-circuiting
Solution Approach 1:
The patent employs stimuli-responsive nanofluids that dynamically adjust their viscosity in response to flow conditions, temperature changes, or chemical triggers, allowing the fluid to navigate fracture networks efficiently while automatically slowing down in high-conductivity pathways to prevent short-circuiting and ensure uniform heat extraction
Solution Approach 2:
The patent incorporates tracer components that provide real-time feedback on fluid position and flow conditions, allowing monitoring and characterization of fracture network utilization, while the responsive viscosity properties provide automatic feedback control to prevent preferential flow through high-conductivity pathways
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 nanofluids effectively reduce mass transport through targeted fracture networks, control fracture interference, and facilitate robust characterization of temperature distributions and heat transfer surfaces within EGS, enhancing the efficiency and economic viability of geothermal energy recovery by managing fluid flow and thermal performance.
Implementation Method 1
dispersion of a few percent of a nanoparticle in ethylene glycol or oil can increase the thermal conductivity by 40% and 150%, respectively
Implementation Method 2
If the concentration of nanoparticle in the nanofluid is high enough, a shear thickening behavior at high shear rates is observed
Implementation Method 3
The disclosed nanofluids increase viscosity at high flow velocities in pores and form gels when reaching certain environmental conditions
Data Source
AI summary
A method of formulating a nanofluid for use in a geologic formation for determining an average pore size of the geologic formation by selecting a desired flow rate of the nanofluid under a predetermined applied pressure, using the calculated average pore size and desired flow rate to estimate a desired average viscosity of the nanofluid, and producing the nanofluid having the desired average viscosity by combining a quantity of nanoparticles with an aqueous medium. A nanofluid made by said process. A method of treating a geologic formation, such as a geothermal formation, by injecting said nanofluid into the geologic formation.