Geothermal energy is one of the hottest (no pun intended) prospects within the world of energy. At its heart, the Earth is one big hot rock and globally we’re beginning to realise just how much we can tap into that heat as a source of energy production. But how is this linked to the oil and gas sector?
Well, increasingly, it’s being found that abandoned oil wells house the potential to be used in geothermal energy production. The team here at TriStone Holdings, a prominent UK oil investment company, wanted to explore this developing area in a little more detail.
What Is Geothermal Energy?
First, though, let’s look at what geothermal energy actually is and how it works. Geothermal energy refers to the heat energy stored within the earth’s subsurface. The thermal energy housed within the earth’s crust itself originates from the decay of radioactive materials. If this thermal energy is tapped, it can be used to drive steam turbines and subsequently produce electricity.
It’s one of the most effective renewable energy sources and has long since been used in highly volcanic countries like Iceland. If you’ve ever been to the Blue Lagoon attraction near Reykjavik, then that water is warmed as a result of geothermal energy. In fact, Iceland sources a remarkable 66% of its primary energy from geothermal sources, with the energy being used for everything from electricity production to the heating of pavements in winter months.
How Can Abandoned Oil Wells Be Used?
Usually, when onshore wells are no longer economically viable in terms of production, they’re simply abandoned. This means wherever there’s active production, there’s a good chance that there are a huge number of abandoned oil wells located nearby. This method is suitable for abandoned wells where condition and integrity is still good (its cement and casing remains in good condition) and where both temperature and flow rate make it feasible.
If such conditions are met, then fluids can be pumped into the well where they’re then heated by the surrounding rock, and then either piped nearby or used in steam-electricity generation. Typically, though, wells tend to be best suited for heating rather than electricity generation, so the ideal abandoned wells for this are those near where there’s a specific heat demand. This method, whether used in heat production or electricity generation, is known as the conversion method. There’s also one other major option known as coproduction.
The coproduction method entails utilising active oil wells rather than abandoned wells. As an oil well produces oil over time, its level of production decreases. As this happens, the levels of water within the well increase. This water is usually extracted before being re-injected as a means of increasing production again. The potential for geothermal energy production comes from the fact that that water coming to the surface is very hot (as it stems from that area of hot rock beneath the surface).
Usually, though, this heat energy doesn’t get utilised in any useful way, the water just goes straight back into being re-injected. Coproduction centres around extracting the heat potential of that water before then re-injecting it. Essentially, it’s a case of not wasting any energy!
These so-called ‘double wells’ present an especially attractive proposition for those wells in the latter stage of their production lives, and mean that they can stay economically advantageous for longer than they otherwise would. This isn’t a nascent technology per se, and it has been used for the past couple of decades now, but given the increasingly pressing issues surrounding sustainability, coproducing wells will no doubt become more common, moving forward.
As global industry looks towards implementing more sustainable energy sources, the option of using oil wells for geothermal production seems an increasingly attractive one. This is another example of how the oil industry is adapting to the times, and how both the onshore and offshore sectors can be used in innovative and unexpected ways. Another topic worth checking out is how offshore platforms are being used to create coral reefs – it’s incredible!