By Kim Gunn Maver, Ola Michael Vestavik, Jørgen Peter Rasmussen, and Carl-Emil Larsen in First Break, Vol 41, Issue 9, Reservoir Engineering & Geoscience.

Introduction: Many Geothermal District Heating (GeoDH) systems are based on local favourable geological conditions with a doublet concept for heat extraction. The doublet design consists of a deviated production well and injection well drilled from a single drilling pad or a few kilometres apart with geothermal fluid production from an adequate reservoir section, which is usually sustained by downhole production pumps (geodh.eu). The main benefits of geothermal energy are provision of local, baseload and flexible renewable energy with a very limited environmental footprint, reliable and long-term energy diversification of the energy mix, and protection against changing fossil fuels prices (geodh.eu). A study from 2012 of60 geothermal fields from 14 countries representing 70% of the worldwide installed capacity (11,000 MW) showed a success rate in each field fluctuates widely in the exploration phase from 33% to I 00% with a mean of 68% (Sanyal and Morrow, 2012). More recently Rystad Energy (2022) has reviewed the geothermal drilling success and found it is variable and very dependent on the specific location of the well and the industry’s maturity in the relevant country. Success rates in Germany and Hungary often exceed 90%, but similar rates in the Netherlands are as low as 70%. The success rate of these geothermal projects is dependent on the geological parameters of the geothermal reservoir such as permeability, porosity, geochemistry, and temperature as well as a heat loss when the fluids return to the surface. A new solution to utilise geothermal energy is proposed using a single well closed looped system with the patented dual vacuum pipe technology which can reliably provide healed fluids with very limited geological requirements. Operational risk and maintenance needs are low and the system can further strengthen the use of geothermal energy in district heating as part of the transition to a green ‘zero’ emission society. As the system is closed no fluid circulates outside the pipes and the heat is harvested at the subsurface.

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