What is Geothermal Energy


Geothermal energy comes in the form of natural hot water or steam that is generated under the Earth’s surface. This heat derives from the formation of our planet and the radioactive decay of materials. It increases with depth, causing an increase in temperature at a rate of 25-30 °C/ km on average (geothermal gradient). Hot fluids circulating within the permeability of the rock underground are pushed upwards due to its lower density and can create a network of fractures carrying these fluids full of energy. In some cases, these fractures reach the surface and create natural hot springs. In many other cases, the network of fractures stop underneath the surface and consequently, it is necessary to drill a well to intercept them and produce hot water or steam. 


How Geothermal Energy plays its part in the Energy Transition


Steam and hot water can be used to drive turbines connected to electricity generators. First used in Italy in 1904, geothermal has been a consistent and growing source of energy in recent years. According to Statista, the installed capacity of geothermal energy reached 14 GW in 2020 worldwide. The World Energy Council considers it possible to produce up to 8.3% of the electricity worldwide with geothermal resources, supplying 17% of the planet’s population. The United States and Iceland are worldwide leaders in the production of geothermal energy, due to their geological position. Geothermal energy is mostly produced along the borders of the tectonic plates, where there is sufficient tectonic activity generating the largest systems of fractures and faults and enhancing the geothermal gradient.


The British Geological Survey describes geothermal energy as a “carbon-free, renewable, sustainable form of energy that provides a continuous, uninterrupted supply of heat that can be used to heat homes and office buildings and to generate electricity”. Geothermal energy generates only 17% of the CO2 in comparison to a natural gas plant and it is not an intermittent source of energy like wind or solar.


How the Oil & Gas industry can help


In many cases, it is necessary to drill a well to access these natural reserves. This is why the oil and gas industry is in a competitive position to leverage its knowledge and know-how to lead geothermal energy production and bring in further improvements in terms of efficiency and footprint. It is not uncommon for a hydrocarbon reservoir to have temperatures similar to their geothermal counterparts (in cases where the geothermal gradient or depth are not particularly high in a geothermal reservoir or not particularly low in a hydrocarbon one). As the oil & gas industry has been exploiting reservoirs for almost two centuries, they have already developed the technology able to deal with hot downhole temperatures. Such technology and expertise can then be transferred to geothermal applications and be further upgraded if necessary.


How AnTech’s CTD technology can be applied to drilling geothermal wells


We already have all the technology and experience in-house to deliver a geothermal drilling service. Coiled Tubing Drilling (CTD) is ideally suited for this type of application as it is the best technique to achieve an underbalanced drilling regime, which is particularly beneficial when you hit fractures while drilling. In this way, the fractures will not be invaded by the drilling fluid and carrying particles, which may settle in the fractures and compromise the flow of the geothermal fluid into the wellbore. CTD is the only way to fully achieve underbalanced conditions because it has a closed-loop circulation system and consequently the reservoir never needs to be put in an overbalanced regime, unlike in conventional drilling when making up the pipes for example. 


For a geothermal well to be successful, the most productive fractures must be intercepted. This means that the wellbore must be placed very accurately within the fractured reservoir. The reservoir might have a homogeneous structure with very little gamma and resistivity character. We can work successfully in this situation due to our proprietary synthetic porosity software, RockSense. RockSense is a unique and powerful geosteering tool, measuring synthetic porosity in real-time and at-bit, not 20-30 ft behind the bit where sensors are placed, with inch-level resolution. In this way, the directional driller can detect and respond to the presence of a fracture or a change in formation as soon as the bit passes through it. This will deliver an optimally placed wellbore with the highest possible production rates.


Our downhole equipment is already rated to 165°C and consequently able to drill many geothermal reservoirs. Our engineers have the necessary expertise to upgrade the temperature rating of the electronics components of our tools if needed, to be able to drill deeper and hotter geothermal reservoirs.


Get in touch with us to learn more how AnTech’s technology and how we can make your geothermal project successful.


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