The Evolution of Geothermal

You can only operate a geothermal power plant in the presence of abundant geothermal energy, right? Wrong! Well, sort of.

Geysir, Iceland
Source: Personal Collection

Historically, the building and operation of geothermal power plants has been tightly restricted to geothermally active areas. Think places like New Zealand, Iceland and the Philippines, where energy literally comes bubbling out of the ground in the form of hot springs, geysers and steam. These areas are usually found on the boundaries of the huge tectonic plates that make up the earth’s lithosphere. Along the borders of these plates, geothermally heated aquifers often flow relatively close to the surface, and these sources of energy are simply begging to be harnessed. The problem is, however, that the areas where these conditions exist make up less than 10 percent of Earth’s dry land.

What About the Cool 90 Percent?

Here is the good news. Geothermal energy originates below the earth’s crust, where the steady decay of naturally radioactive materials produces heat continually. Theoretically, this source of energy is available virtually everywhere, albeit at a greater depth than in the previously mentioned, geothermal areas. The total amount of thermal energy within a depth of 10 km from the earth’s surface is estimated to be 50,000 times greater than all the natural gas and oil resources in the world.

Efforts to harness this hidden energy are already being made in various places across the globe, using a new technology called Enhanced Geothermal Systems (EGS). The method essentially expands traditional geothermal energy production through the use of hydraulic fracturing. It consists of drilling a well to a depth of about 3 to 10 km, where temperature levels are usually between 70 and 315°C. In contrast to EGS, traditional geothermal power plants usually only require wells that are 2 to 3 km deep, in order to reach the same temperature levels. Upon reaching this depth, water is pumped into the dry layers of hot rock at high pressure, which causes the rocks to break and thus increases their permeability. Cold water is then pumped down through an injection well, where it flows through the hot rocks before returning back to the surface as steam, through a separate well. The steam is then run through a turbine where it produces electricity, before it is cooled and condensed, and pumped back into the ground.

The EGS Process
Source: EERE

An Earth-Shaking Prospect

This technology offers a number of different benefits. First of all, it introduces a vast supply of geothermal energy potential to areas that have hitherto been considered too cold for such ventures. The EGS technology also enjoys many of the same benefits associated with traditional geothermal energy production. It is a steady, renewable source of energy and geothermal plants require very little land space per MW produced, in comparison to other types of power plants. However, drilling in itself is a messy and expensive business, and as the technology is still in its infancy, the upfront cost of an EGS project remains very high.

The technology also has to deal with the issue of induced seismicity, as the injected water can act as lubricant on highly stressed layers of rock near geological fault lines. In 2009, a $60 million EGS venture was cancelled in Basel, Switzerland, due to a flurry of earthquakes that were generated as a result of the project. While the momentum of EGS has been lessened by setbacks such as the Basel shutdown, as well as the under-delivery of other ongoing projects, the potential benefits that the technology promises are hard to negate. Proponents of EGS are still willing to brace the significant learning curve that lies ahead, before the technique becomes both technologically refined and cost competitive, and geothermal becomes a global source of renewable energy.

 

Hydraulic Fracturing Revisted…

This blog entry is a specific reply to a previous blog entry about hydraulic fracturing.

I believe the oil and gas industry’s greatest challenge going forth is educating the public and attempting to right the past wrongs of the industry. We shall see if they ever achieve that end but the use of diesel fuels by BJ Services and Halliburton after voluntarily agreeing not to use diesel fuel is a perfect example of the poor choices that have plagued the oil and gas industry in terms of public perception. These actions are very near-sighted and could ultimately cost the industry the ability to produce oil and gas domestically (see no offshore oil production from Florida because of spills in places like California 40 years ago and the inability to obtain leases in ANWR).

The EPA has already performed a study on hydraulic fracturing for contamination. It was performed in 2004 and the result was no evidence of contamination could be found though it was for coalbed methane reservoirs and not all tight gas reservoirs. In addition, field data was not a priority as it was “a fact-finding effort based primarily on existing literature”. However, we are doing it all over again because of questionable injection fluids used by the previously mentioned companies. So not only are these companies endangering a vast resource and a very large revenue stream for them but they are using tax dollars to re-perform a study that was performed a mere 6 years ago.

My favorite issue is who is ultimately responsible IF contamination is occurring. The reservoirs are from 3,000 feet to over 9,000 feet below the surface in the Marcellus shale (average depths are 5,000-8,000 feet), other shales like the Haynesville can be even deeper. There is no fresh water aquifer that is close to that. There is also very little chance the fracture propagates from 5,000 feet to 200 feet to reach the fresh water wells. I spoke with a Baker Hughes employee who estimates the fractures in the tight formations propagate a couple hundred feet or more but nothing approaching 1 mile. So how is the contaminated fluid reaching the fresh water aquifers?

I believe it is poor well completion techniques. For environmental as well as economic reasons, a well is “cased” with thick steel and then cement is used outside the steel to eliminate the chance that fluids traveling up and down the wellbore will enter the subsurface in an undesired location. It is possible if not probable that the leaking that is occurring is due to completion techniques rather than fracturing itself. If that is the case, who is legally responsible for the leak? Is it the well completion company (Baker Hughes, Schlumberger, etc.), the operator (ExxonMobil, Shell, etc.), or the fracturing company (Halliburton, Schlumberger, etc.)? The completion company and fracture company need not be the same on any given well.

As the previous blog mentioned, the “recipes” for the fracturing fluids are proprietary. As a result, no one really knows what types of fluids are being injected. The previous blog stated

“Although not knowing precisely what makes up the mixture means nothing to the reservoir, it means a lot to those concerned with the potential environmental impacts.”

I disagree with the first point. True, the rocks themselves have no feelings or senses of course but the fluids injected are absolutely relevant to production. They can alter rock characteristics and fluid flow in the reservoir. As a result, the “recipe” is important from a production standpoint. However, the value of importance is up for debate because we do not know what any “recipe” is/was and therefore cannot develop best practices. The fracturing companies themselves might be performing those studies but the fracturing company is not the producing company. There is a real problem here from a public welfare as well as optimum recovery standpoint that needs to be addressed.

I do not believe the fracturing itself is causing contamination but I am very disappointed that my oil and gas brethren continue to unnecessarily risk public ire to make a few dollars today while ignoring tomorrow. I am very saddened the government is forced to use more tax dollars on an already studied topic. I personally think the answer should be disclosure and/or regulation of the fluids themselves and nothing more. Of course given the oil industry’s history, there is obviously doubt about whether they will actually obey such a regulation. The actions of so few can have very large consequences for so many.