Drilling the world's hottest geothermal well

Ninety-nine per cent of planet Earth has a temperature in excess of 1,000 degrees Celsius as a result of residual heat inherited from the Earth's primordial origins and the breakdown of radioactive materials. This heat can be transformed into energy -- and there is more than enough to go round.

"If we succeed in drilling for and extracting even just a small fraction of this geothermal heat, it will be enough to supply the entire planet with energy -- energy that is clean and safe." So said Are Lund, a senior research scientist at SINTEF Materials and Chemistry, in 2010.

Today, five years later, researchers and technologists from all over Europe are joining forces to pursue a common cause -- to make sure that the world's potentially most energy-rich geothermal well becomes a reality. The well will be drilled in Larderello in Tuscany, and EUR 15.6 of research funding has been earmarked for the project.

Global green energy producer Enel Green Power is heading the project called DESCRAMBLE (Drilling in dEep, Super-CRitical AMBients of continentaL Europe), where the aim is to extract the maximum possible energy from the well. The extreme heat in the rocks deep beneath northern Italy means that both pressures and temperatures will be right at the limit of what even innovative technologies can currently cope with. However, such conditions also mean that the energy output from such a well can be as much as ten times greater than for standard geothermal wells, and will help to ensure that the new well will be very profitable if the project succeeds.

"SINTEF's contribution to this EU project is to run simulations of the drilling operation and to develop a new instrument to monitor the well," says Øyvind Stamnes, a researcher and Project Manager at SINTEF ICT. Taming supercritical fluids Achieving the project's aim is a challenging assignment. No-one has previously managed to control a well under such extreme high temperature and pressure conditions. Specially developed equipment will be needed. -- "One of the major uncertainties is the presence of what we call supercritical fluids," explains physicist Roar Nybø at SINTEF Petroleum Research. At depths of two to three kilometres in the Earth's interior, ambient physical conditions change dramatically. Temperature increases. And so does the pressure. Something very special happens when temperatures reach 374 degrees and the pressure 218 times the air pressure at the surface. We encounter what we call supercritical water.

It isn't a liquid, and nor is it steam. It occurs in a physical form incorporating both phases, and this means that it takes on entirely new properties. Supercritical water behaves like a powerful acid, and will attack anything -- including electronics and drilling equipment. "In a TV fantasy series it would probably be called 'dragon water'," chuckles Nybø, whose background is as a theoretical particle physicist. Where he comes from, it's not uncommon to be contemplating even more extreme conditions than this project faces.

But the 'dragon water' has its advantages too. It can transport from depth up to ten times more energy that normal water and steam can achieve in a standard geothermal well. It also flows more easily through rock fractures and pores. If researchers can succeed in controlling the forces involved without the technology breaking down, we may be on the verge of a deep Earth technological breakthrough.

If all this wasn't enough, supercritical water can also transport valuable minerals to the surface in solution. This could provide potential incidental revenues. "The dragon of the deep may thus help us open a real treasure trove," says Nybø.

Technology transfer is the key

There's no doubt that the drilling operation requires highly advanced technical preparation. For this reason, the 'major breakthrough' must first be modelled in a specially designed simulator. This has already been developed by SINTEF for drilling operations for oil and gas, and is similar to an aircraft flight simulator.

It will now be installed with all available data about the planned well and its location. This will enable the researchers to take virtual "test flights" of the entire drilling operation.

"This approach to the exploitation of geothermal heat has much in common with oil recovery," says Nybø. "Oil exploration wells have been drilled to depths of more than ten kilometres," he says. "So there are good reasons for involving Norwegian drilling technologists in this project. Geothermal heat quite simply represents a unique opportunity for the oil and gas sector to advance its technological development. We strongly believe that this know-how can become a key Norwegian export," says Nybø, and lists the following similarities:

• Seismic technology is used to identify the correct well location.
• New equipment must be developed to withstand extreme conditions.
• The drilling operation itself.
• Getting the fluid to flow from depth through the rocks.
• Flushing the well to remove sediment.
• Recovery of the fluid (maintaining production and keeping the reservoir pressure stable throughout the lifetime of the well).

Unpredictable conditions

This isn't the first time that researchers and geologists have been looking deep into the Earth's interior to extract the inexhaustible amounts of energy it contains. Iceland has been exploiting geothermal heat for many years. The power station at Krafla has been using steam from below ground to generate electricity since 1977. Its annual production is 480 GWh, which is approximately equivalent to the annual electricity consumption of a town the size of Lillehammer.

In fact, twenty-five per cent of Iceland's energy needs are sourced from geothermal heat, while the remainder is hydroelectric.

In 2009 a team of Icelandic researchers set up some drilling equipment on the volcanic island. Their aim was to drill to 4,000 metres and establish the world's most effective geothermal well. In a frenzy of creativity, they named it DDP-1. Unfortunately, things didn't go to plan -- the geologists encountered lavas as shallow as 2,000 metres depth. But, after two years of tests and studies the well had to be shut down, without having generated any electricity at all. However, the Icelanders learned a great deal from their attempt, and have not given up in their efforts to win the race to drill the world's deepest geothermal well. They are currently planning a new well, with a new name -- DDP-2.

But their hoped for victory is now under threat from the Italians, who are armed with Norwegian oil and gas expertise and experience, and more favourable geological conditions. "Our well will encounter completely different types of rocks," explains Nybø.

"In Iceland the geology is "open" all the way down to the Earth's mantle, while in Italy the heat accumulates in so-called 'hot spots'. Areas such as this are also found in many other places in Europe, and success may lead to opportunities for the efficient exploitation of geothermal heat in many other locations around the world," he says.

Crystal ball

But to achieve this success, the supercritical water must be controlled. In order to predict as accurately as possible how this fluid will behave both at depth in the well and on its journey to the surface, the entire process has to be modelled in a so-called 'flow simulator'. Such tools have been employed in the oil and gas industry for many years to obtain more accurate predictions about how oil, gas and water are transported through subsea pipelines. After years of research, technologists have succeeded in controlling processes such as corrosion, hydrate (ice-like plugs) formation, and wax deposits in pipelines. The flow simulator 'LedaFlow' makes it possible to analyse more detailed and complex flow scenarios involving so-called 'multiphase transport', where oil, gas and water all flow along the same pipeline.

"The simulator is able to visualise waves, fluid plugs, phase transitions and hydrate precipitation, and can contribute towards reducing the risk of these factors causing operational difficulties," explains Bjørn Tore Løvfall at SINTEF Materials and Chemistry. "It also provides valuable information such as how much pressure support (gas injected into a reservoir) a well needs to deliver streamlined production. The simulator will now be used to provide a better insight into how supercritical water will behave," he says. Read more about the LedaFlow simulator here: Link to 'Stroman genome diet' (Flow at great depth).

Løvfall continues: "Today, the LedaFlow simulator is used by engineers who design, scale and operate subsea multiphase transport systems," he says. "It provides its users with a chance to "zoom in" on whatever aspect of flow they may want to visualise along a pipeline, enabling them to obtain detailed simulations of flow conditions at predefined locations.

The simulator is the result of one of SINTEF's most comprehensive research projects ever. However, for the DESCRAMBLE project it will be expanded with the aim of predicting the behaviour of supercritical water. This will entail developing an entirely separate module designed to answer questions such as how deep in the well the water makes its phase transformation, and how it behaves as it rises to the surface carrying its maximum energy load.

Developing a 'super tool'

While work on the modelling and simulation of the advanced drilling operation continues, yet another research team will be getting to grips with some completely different problems.

SINTEF ICT has a research group working under the inspiring name of 'Harsh Environment Instrumentation'. Øyvind Stamnes is a member of this group, working on the development of a specialised probe that will be lowered into the well to log and measure how the well behaves.

The drilling operation must be monitored in detail, so that if something unforeseen happens we can gain as much control of the well as possible. But how is it possible to build a system of electronics and sensors capable of withstanding temperatures of up to 450 degrees, and pressures that would destroy most instruments that we are familiar with today? One thing is certain. Such equipment is not currently on the market.

"We know that when the well reaches its maximum temperature, all known measuring instruments will stop functioning," says Stamnes. The electronics will encounter temperatures high enough to cause short circuits due to excessive leakage flows," says Øyvind Nistad Stamnes.

So how do you get around that? With a combination of custom-designed high-temperature electronics enclosed in a kind of thermos flask. Or in technical language -- A Dewar flask. The container must be well insulated to protect the measuring instrument which has to record conditions in the well over periods of several hours in ambient temperatures of 450°C, and 250°C in the interior of the container.

"You could say that our approach involves developing instruments enclosed in space suits," explains Stamnes. Building electronics for high-temperature applications is nothing new to researchers at SINTEF ICT. They've been looking into this since the 1990s. But the challenge now will be to assemble an array of components that can all withstand the high temperatures -- with something of a safety margin built in as well. "For example, there are no batteries on the market that can withstand temperatures greater than 200°C.. So we're working together with manufacturers to produce batteries that are safe to use at even higher temperatures," says Stamnes.

The project was launched in Pisa in Italy in mid-May, and drilling is planned to start in autumn 2016. If everything goes as planned, this well once completed will provide ten times the output of a standard shallow geothermal well.

The project will give a radical boost to the competitiveness of green, geothermal energy because the drilling costs for a well of this type are between 30 and 50 per cent of the total costs. "This makes for exciting times here at SINTEF ICT," says Stamnes as he returns to his lab to continue working on the "space suit for sensors" on which the entire project relies.

FACTS: An inexhaustible source

Low-temperature geothermal energy involves the extraction of geothermal heat from between 150 and 200 metres below the surface. At these depths, the temperature is between six and eight degrees Celsius. Such energy is extracted using ground source heat pumps combined with energy wells, and is currently produced in large volumes. High-temperature geothermal heat has tremendous potential because it represents an inexhaustible, and virtually emissions-free, energy source.

Heat energy can be found in a variety of rocks in the Earth's crust. The deeper we drill, the hotter it gets. About half of the heat at depth originates from primordial heat derived from the Earth's mantle (the layer immediately below the crust) and core. The remaining fifty per cent is derived from the continuous breakdown of radioactive material in the Earth's crust. All this heat is transported towards the surface through the overlying formations.

Oil companies are currently making healthy profits from the recovery of oil from reservoirs at depths of 5,000 metres, where temperatures can reach up to 170 degrees Celsius. At deeper levels, drilling operations and materials integrity are faced with major challenges. Steel becomes brittle, and materials such as plastics and electronics either fail or start to melt. Normally, electronics only function for a short time at temperatures greater than 200 degrees Celsius. These problems must be resolved if the extraction of high-temperature geothermal heat is to become a going concern.

Facts: A democratic source

One of the unique properties of geothermal heat is that it exists all over the world. Potentially, everyone on the planet can exploit this democratic energy source that is both stable and independent of variations in climatic conditions at the Earth's surface. The depths to which we have to drill to achieve the desired temperatures will vary from country to country. This is due to variations in the thickness of the Earth's crust and the geothermal gradient. Here in Norway, temperature increases by about 20 degrees per kilometre, while in other parts of the world, this may be as high as 40 degrees per kilometre. The average is about 25. Countries currently leading the way in the generation of electricity from geothermal sources are the USA, the Philippines, Mexico, Indonesia and Italy. Iceland is lower down the list at number eight.

Facts about the DESCRAMBLE project The aim of the project is to achieve a ten-fold increase in output compared with traditional, shallow geothermal wells. For comparison, the Krafla geothermal energy plant on Iceland generates 480 GWh annually. This is equivalent to the electricity consumption of a town the size of Lillehammer. Participating countries: Italy, Germany and Norway. The Norwegian research partners are SINTEF ICT located in Oslo, and SINTEF Petroleum Research in Trondheim and Bergen. Coordinator: Italy's Enel Green Power, represented by Ruggeri Brentani Duration: 36 months following project kick-off in May Total budget: EUR 16,615,957, funded via the EU programme Horizon 2020.