The Feasibility and Dangers of Injecting Seawater into Earth's Mantle: A Geothermal Energy Myth

The idea of utilizing geothermal energy through the injection of trillions of gallons of seawater into the superheated areas of the earth's mantle has been proposed as a potential source of renewable power. However, this concept, despite its allure, faces significant challenges and dangers, primarily due to the rapid clogging of equipment and the immense maintenance costs involved.

Short-Term Feasibility

A temporally brief proposal to inject seawater into superheated areas of the earth's mantle for geothermal energy production seems promising. Yet, the reality on the ground is far more grim. The equipment used for injecting seawater and extracting energy from the steam would be clogged by the minerals and salt in the seawater within days, not years or months. This issue underscores the critical challenge of maintaining such systems over extended periods.

Practical Maintenance Issues

During my summer internship at The Geisers geothermal field, one of the few dry steam geothermal sources in the world, maintenance of the turbines became a significant problem. Due to the presence of boron deposits, blades would accumulate until they were ripped off by centrifugal force, leading to vibrations in the turbines. These vibrations were significant enough to disrupt operations, and rotating the turbines to hit another blade with a sledgehammer was a workable yet imperfect solution.

The operators had to find a costly solution to the blade damage problem due to the remote and challenging location of maintaining such systems. Each new blade loss would reduce efficiency, making the continued operation of the damaged rotor financially impractical over time. The massive costs of replacing rotors were a critical barrier to sustaining operations.

Exploring Unocal's Experience

My employer, Unocal, was also developing a superheated saline water reservoir in the Philippines. Despite the theoretical potential, the practical difficulties were evident. The water, produced through wells, was flashed at the surface to be used to drive turbines. However, well casings were reported to be heavily clogged with mineral deposits, leaving only a half-inch opening after just one month. Consequently, the expensive well had to be abandoned, highlighting the severe limitations of using seawater in geothermal systems.

Theoretical vs. Practical Dangers

The idea of localised cooling of the lava/magma through such an injection of seawater is both dangerous and currently unfeasible. While the concept may seem straightforward on paper, the reality of the geological and thermodynamic impacts is far more complex. Even a short-term injection can lead to significant and rapid clogging, severely impacting the efficiency and viability of the geothermal energy production process.

Before considering such a contentious proposal, it is imperative to conduct detailed scientific impact assessments, including thermodynamic and geological studies. Until these assessments provide clear and reliable evidence, the idea remains a mere myth with more theoretical promise than practical application.

Conclusion: The challenges in maintaining geothermal systems, especially those involving seawater, far outweigh the potential benefits of such a proposal. The practical issues faced during the operation of these systems, combined with the significant maintenance costs, make the idea of large-scale seawater injection into the earth's mantle a non-viable proposition. Until substantial scientific validation is provided, this concept should remain in the realm of theoretical debate.