Promising Developments on the Island of Nevis

Drilling crew on Nevis
Drilling crew on site in Nevis (source: TEP), 22 Mar 2018.
Thermal Energy Partners is successful in finding an economic resource on the island of Nevis. Reservoir temperature predicted to be 492 °F at a depth of 3000 ft.

Thermal Energy Partners (TEP) has included details on their successful drilling efforts on the Island of Nevis. GeothermEx has confirmed that the resource drilled by TEP is economically viable and has the potential to supply market competitive power to island residents and industries.

Injection testing of TEP’s first exploration well demonstrated that the resource is highly permeable. Injection testing is used to determine the permeability of the well and the potential pumping requirements needed to inject a target amount of water into a well. The results of an injection test are usually reported in terms of an injectivity index, which is calculated by dividing the change in flow into the well (gpm) by the change in wellhead pressure (psi). For example, a well with a recorded injectivity index of 1 would have to be pumped with a pressure of 500 psi to inject 500 gpm of water into the well. TEP has not disclosed test results, but they reportedly indicate high injectivity, meaning very little pressure will be needed to inject water into the well, and also that the well has a high productivity index. The productivity index of a geothermal well is typically half that of the injectivity index and is also given in units of (gpm/psi). The productivity index tells one how quickly a well is replenished while one is pumping out geothermal water. The high injectivity and productivity encountered by the exploration well mean that TEP can expect to flow and inject large amounts of geothermal brine from each well it drills, reducing the size and expense of the wellfield.

The reservoir temperature of 492 °F (255 °C) is quite high compared to recently developed geothermal resources in the United States, where reservoir temperatures are typically 300 to 350 °F.  At these lower temperatures, not enough steam will be generated to power a typical steam turbine and binary power plants are used instead. While using binary turbines allows companies to develop lower temperature resources and increase the potential geothermal reserves, the efficiencies are considerably lower than conventional steam turbines. At 492 °F, TEP will be able to build a steam turbine and capitalize on higher conversion efficiency.

Geothermal steam turbines in the United States typically produce electricity at a marginal cost between $0.04 to $0.07 per kWh. This is far below the current average consumer cost of electricity on Nevis, which is $0.234 to $0.262. While developing a geothermal power plant on a Caribbean island will undoubtedly be more expensive than building one in the continental United States, the cost of producing electricity is still likely to be lower than what is currently available. The power produced by this project will also be much cleaner than what currently exists on the island. As of 2018, over 90% of the electricity consumed on Nevis is generated by costly – and environmentally problematic – diesel generators. TEP has an incredible opportunity to build a world-class geothermal project on the island of Nevis and provide clean, and sustainable, power for its residents. Based on my direct experience working with members of the TEP team, I’m confident that their technical skills and abilities will push this project forward.

A success on Nevis should inspire similar projects throughout the Caribbean. Please contact me to discuss future opportunities in more detail.

 

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