Geothermal Exploration Basics, and Why Geothermal Trails Solar and Wind

By Dan Patrick

Geothermal is a proven technology with power plants online now that went into operation nearly 5 decades ago. Is it complex? Somewhat, but so are wind and solar farms and their accompanying cyclic power production. When a geothermal plant goes online, it operates for many decades, 24-7, silently and reliably, on a small footprint, with nearly zero emissions.

So why not geothermal? Mostly because so many of us don't understand it. It's easy to visualize solar panels producing electricity. There is little understanding of how it truly works, but there's a panel and wires, and the magic of the production is accepted. Windmills are even easier to understand, because it's easy to understand the idea that physical motion can be converted to electricity. Geothermal, no pun intended, is specifically NOT on the surface, but literally underground and most people don't really know what it is or how it works.

To understand geothermal a little better, let's look at a key stage of the process to bring a geothermal power plant online - geothermal exploration. Geothermal Exploration is the stage that establishes where exactly is a suitable place to drill and extract heat (the heat is used to convert water to steam and run turbines and generators - physical motion).

Geothermal exploration uses existing data, then adds more data from surface testing and then adds more data from underground testing to make a virtual model of the resource that is progressively more accurate. When a resource and drilling locations are determined to be suitable, power plant design begins. When the plant goes online, you can run your toaster on it and forget about where the power came from.

What are the stages of geothermal exploration?

Reviewing existing data

Over time, the United States Geological Services may have performed studies on the geology of a region, as well as private companies looking to develop geothermal energy in the past. Often, data collected in the past can be used to a greater extent now than when it was collected by applying modern data analysis techniques that were not previously available to geothermal exploration projects. Using existing data is the first step due to the low cost. This stage is also called a 'desk analysis' because no field work is involved.

Gather new Data through Surface Testing

Unless the data in the desk analysis proves a resource unsuitable, additional data will be needed to advance the model of the geothermal resource. There are many types of tests that may be included in this phase, involving examination of the physical features at the surface, gravity measurements, magnetic properties and seismic surveys.

Well Siting and Design

The geothermal exploration model is now based on past data plus new data, and is used to determine sites to test underground via drilling and sampling. The underground testing is required to confirm surface surveys and to test against specific power production goals.

Drilling and Logging

Drilling exploration involves taking samples and enables more detailed analysis of various parameters of heat transfer, porosity and other parameters.

Production Testing

Using any of several methods and lasting from a few hours to several weeks, physical testing of the wells is used to improve the modeling by actually testing the production characteristics of the well. At this point, the model determines whether a site is appropriate for drilling 'production' wells, wells that would be used to directly extract heat for turning water to steam and creating electricity!

This is a short version of the steps involved in geothermal exploration, but interestingly, they are similar at the top level to evaluating and progressively modeling a solar or wind 'resource area'. The main difference is that the resource is under your feet and harder to visualize without a level of understanding of the process. The correlating benefit of being underground is that when a geothermal plant is in operation, it doesn't cover entire hillsides or plains.

Before you automatically think Solar and Wind are the only big renewable energy alternatives, learn more about Geothermal Energy and Geothermal Exploration from Mannvit Engineering, geothermal energy experts from Iceland, where clean energy sources provide 95% of the country's needs. - Patrick Sullivan.

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