Supercritical fluid found near magma chambers has the potential to power thousands of homes.
Electricity generated from supercritical volcanic fluids sourced from next to an active magma chamber may seem like science fiction, but it might well be the future of renewable energy, at least in some volcanically active regions. A project centered on drilling into the outer edge of a potential volcano to develop a super efficient geothermal power station is ongoing in south-western Iceland.
The Iceland Deep Drilling Project, a partnership between the Icelandic government and a number of private energy companies, began in 2009 and is attempting to source and research the potential use of supercritical fluids for geothermal energy generation.
Supercritical geothermal fluid is a mixture of water and a variety of minerals that is heated under immense pressure to a point that the distinction between gaseous and liquid phases of the fluid is blurred. While in this phase, the geothermal fluid is able to gain several times more enthalpy (total heat content) and transfer its mass much faster than a standard fluid with the same chemistry.
This huge increase in enthalpy and mass transfer opens up the possibility of massively more productive geothermal power stations. In Iceland, a source of this uniquely powerful geothermal energy has been found next to an active magma chamber along a landward extension of the Mid-Atlantic Ridge.
The IDDP2 (Iceland Deep Drilling Project 2) test well ÛÒ aptly named ÛÏThorÛÛÒ was drilled to a final depth of 4.7 kilometres on Jan. 25, 2017. The drilling of this borehole, into the outer edge of a magma chamber underneath the Reykjanes Peninsula, began in August 2016. The goal of the well and overall project is to investigate the feasibility of producing geothermal energy from supercritical geothermal fluids on an economic scale.
Standard geothermal energy generation is the process of producing electricity from turbines powered by groundwater, or injected surface water, heated into steam by natural heat radiating from the Earth’s core in volcanically active regions. The water and steam that powers these turbines is known as geothermal fluid and generally heated to around 200 degrees Celsius. Geothermal energy is theoretically completely renewable. Even in circumstances where the exploited fluid is taken directly from a reservoir with a finite quantity of liquid or a very low permeability, a process of water reinjection back into the ground can ensure the source of geothermal fluid is never completely exhausted.
Currently, the power-generation potential of geothermal energy is limited by the energy-carrying capacity and relatively low heat of the geothermal fluid. Multiple wells are needed in a small area to make an economically viable power station. By investigating new types of high-energy fluids, such as those under exploration by the IDDP, geothermal energy has the potential to be a far more efficient and widespread source of renewable electricity that it currently is.
The supercritical fluids sought by the IDDP project team are created by the interaction between groundwater and an active magma chamber five kilometers underneath the Reykjanes Peninsula. The intense heat and pressure created by this magma chamber heats the nearby ground water to more than 400 degrees Celsius ÛÒ far hotter than a standard geothermal fluid source. At this temperature and pressure, super-heated fluid enters a supercritical phase, which has the same low density as a gas yet flows as easily as a liquid. Exploiting these properties, along with the massively larger energy-carrying capacity, may allow the construction of a geothermal well up to 10 times as powerful as is currently possible. This huge leap in energy production could allow a geothermal single well to power thousands of homes.
As well as providing an enhanced source of geothermal energy, it is hoped that the unique situation of both the well and the fluid, next to an active magma chamber, will provide new geological information as well as a potential source of rare minerals due to the composition of the fluid.
The idea for the project began as the result of an accident. The unwanted intrusion of a planned super-deep geothermal well in Krafla, nearby the current IDDP2 site, into an active magma chamber in 2009 brought IDDP scientists’ attention to the unusual supercritical fluids found just above the chamber. A brief test of the energy capacity of these fluids brought up from this well revealed that, had it been linked to a generator, the well would have produced more than 36 megawatts of electricity (more than 10 times that of an average geothermal well). This means a single well of this type could power nearly 6,000 homes.
The current temperature at the base of the IDDP2 well is 427 degrees Celsius and may increase when high pressure steam is later injected into the well. This makes it the hottest drill hole in the world and may allow energy generation from extremely high-energy fluid from the well. This high energy, supercritical fluid could form a large part of the future of renewable energy for many countries in similarly active volcanic zones.
With such extreme conditions come extreme technical challenges for the project team. Among the most difficult aspects of the project, according to information released by HS Orka, a company involved in the operation, is the difficulty of drilling into the complex and unknown geology of the Mid-Atlantic Ridge as it extends into the peninsula where little is known about the subsurface stratigraphy (how the rocks are layered). Another challenging issue is the highly corrosive nature of the fluids, which requires the design of extremely resistant drilling equipment and well casings.
While the conditions required to develop such a productive geothermal well are not necessarily found everywhere in the world, there is still a high potential for such technology to be introduced in many other locations globally where geothermal energy is already generated, such as the United States. The website of project partner HS Orka states that the technology ÛÏcould be applied elsewhere in high temperature geothermal fields.Û
A new study by ETH Zurich, which models the fluid reservoir underneath the IDDP2 well, also has shown that such fluids may be far more widespread that previously thought. A similar European project, DESCRAMBLE, underway in Italy’s Tuscany region, also seeks to investigate the potential for exploiting the fluids adjacent to a super deep volcanic reservoir.
However, while the prospect of drilling into and producing energy almost directly from a potential volcano may seem incredibly exciting from a scientific and renewable energy point of view, it is not without detractors. There has been concern from the public that such drilling, and the associated injection of high-pressure water into the ground, may trigger earthquakes or even a volcanic eruption.
There also has been a history of geothermal drilling triggering earthquakes, such as happened during a similar super deep geothermal well drilling project near Basel, Switzerland. This project was abandoned in 2005 after drilling was linked to a 3.4-magnitude earthquake that damaged several buildings. The risk of such drilling trigging a volcanic eruption however, due to accidentally penetrating a magma chamber, is likely to be extremely low due to both the incredibly dense magma found in Iceland and the very small potential impact of the borehole on a chamber.
In spite of the perceived risk associated with geothermal wells, the IDDP project has the potential to open up a new and truly powerful source of clean and renewable energy for the future. Following the completion of the project well, the IDDP team is conducting research and testing on the well with the next step being the undertaking of fluid flow tests and handling experiments to examine the well’s productive capacity. According to a recent news release from the project team, the actual usability of the well for electricity generation will not be clear until 2018.
Robert Galvin is a geologist who works in a scientific outreach capacity with the Copper Coast Geopark in southeastern Ireland.