Over the last century, the search for clean, sustainable energy has heated up considerably. Many technologies have been exploited, some discarded, and others are still being developed. Geothermal energy is among those still being developed and shows great potential. However, like any pioneering technology, it presents certain hurdles that must be cleared before it can be widely adopted.
This chapter reviews some key challenges facing geothermal energy development and explores their impact on a project’s design, implementation, and long-term success. It also considers some practical and successful solutions.
Challenges in Geothermal Projects
Extreme Temperatures and Corrosive Fluids
Geothermal fluids often contain dissolved minerals and gases and can reach temperatures well over boiling. They create a highly challenging storage environment that can damage liner materials, increase the risk of leaks, and shorten the liner’s lifespan. The risk of thermal stress and chemical degradation is even higher in injection wells where liners are exposed to higher temperatures and pressures.
Controlling Fluid Pressure
In geothermal systems, precise control over fluid pressure must be maintained. Fluctuations in pressure can reduce the efficiency of energy conversion processes, affect the stability of underground formations, and even induce seismic activity.
Environmental Considerations
Geothermal energy is undoubtedly renewable and may even be considered “free” since it doesn’t actively consume resources. However, to be sustainable, the industry needs to work to minimize its environmental impact.
Waste Management
Byproducts of geothermal production, such as geothermal brines and sludge, often contain high concentrations of dissolved minerals and salts and can contaminate soil and water if they’re not actively managed and contained.
Land Subsidence
In some cases, geothermal fluid extraction can trigger land subsidence, where the ground sinks. Areas affected by ground subsidence can encompass multiple acres or even several square miles, where the ground may sink by as much as 50 feet over several decades. But even less dramatic subsidence can still damage infrastructure and disrupt natural habitats.
Geotextiles as Solutions
Containment and Control
- Lining Reservoirs: Impermeable geotextile liners safely store fluids so they can be used to maximize energy extraction efficiency. This includes lining surface ponds, manmade underground caverns, and other storage structures to create a secure barrier against leaks. By preventing fluid loss, geotextiles help maintain reservoir pressure, minimize the need for makeup water, and reduce the risk of land subsidence.
- Containing Waste: Geotextiles line ponds and storage facilities for geothermal byproducts such as brines and sludge, preventing them from escaping into the environment and contaminating soil or groundwater.
- Lining Injection Wells: In Enhanced Geothermal Systems (EGS), injection wells are lined with geotextiles to prevent fluids from escaping into the surrounding geological formations as they’re pushed into the fractured rock formation. The barrier helps control how fluids are distributed within the reservoir.
Environmental Remediation
When a geothermal power plant closes down, geotextiles are used to restore and protect surrounding ecosystems in a process known as environmental remediation. They’re used for:
- Remediating Contaminated Soil: Impermeable geotextiles can contain and isolate contaminated soil and prevent pollutants from spreading.
- Stabilizing Slopes: Geotextiles can reinforce slopes and minimize the effects of erosion, which reduces the risk of landslides and road collapses.
- Creating Vegetated Barriers: Geotextiles and vegetation are often used together to prevent erosion by slowing and filtering runoff.
Mitigating Induced Seismicity in Enhanced Geothermal Systems (EGS)
- Stabilizing Injection Zones: Geotextiles can reinforce critical injection zones and reduce the risks of fracturing, fluid migration, and the seismic events they trigger.
- Controlling Fluid Pressure: When geofluids are injected under incorrect pressure, the risk of seismic activity increases. Geotextiles can help control the pressure by preventing fluids from escaping into the surrounding rock.
- Pressure Relief Systems: Geotextiles can be used to construct pressure relief systems within the reservoir so excess pressure can be controlled, reducing the risk of induced seismicity.
Key Properties of Geotextiles for Geothermal Applications
High-Temperature Resistance
Many geothermal environments involve temperatures well above the boiling point. In these conditions, geotextiles must exhibit excellent thermal stability to resist degradation. Products like BTL Liners’ XR Geomembranes can tolerate these high-temperature environments.
Chemical Resistance
Many geothermal fluids have a variety of dissolved minerals and gases that can corrode some liner materials, so geotextiles used in geothermal operations must be highly resistant to these substances to maintain their integrity over time. High-performance XR geomembranes are resistant to a wide range of chemicals and suitable for many geothermal applications.
Mechanical Strength
- High pressure: Geotextiles used in geothermal projects must possess sufficient tensile strength, tear resistance, and puncture resistance to withstand the intense pressure of geothermal fluids pumped from deep reservoirs without stretching or tearing.
- Thermal expansion: Some geotextiles are vulnerable to deformation or loss of elasticity when they repeatedly expand and contract from exposure to fluctuating temperatures. This kind of degradation increases the risk of tears and leaks.
- Ground movement: Flexibility, tensile strength, and elongation allow a geotextile to accommodate stresses caused by ground movement or land subsidence without tearing or failing.
- Abrasion: Geotextiles used to line injection wells must be particularly resistant to abrasion, as they can encounter drilling debris, rough wellbore surfaces, and other materials that can cause wear and tear during the injection process.
Looking Ahead
We’ve established that geothermal projects demand innovative solutions to effectively harness the planet’s natural heat. Our next chapter will explore how and why geotextiles are used to line geothermal reservoirs.
