As I have noted
on this blog, many people, including the realist (seemingly pessimistic) Art
Berman, have long seen closed-loop geothermal as overhyped. While it may have a
small role to play in the energy transition, the technology is likely limited
by physics from gaining a larger role.
Eavor is the originator of the
Eavorloop, its own closed-loop advanced geothermal system. One of its first
pilot commercial projects, its well-hyped Geretsried geothermal project in
Germany, has faced limitations not adequately foreseen. Eavor also cancelled
its upcoming project in Hannover, in Northern Germany.
Closed-loop geothermal is a type
of conduction geothermal where the fluids convey heat to a working fluid via
conduction. In contrast, convection geothermal involves producing hot fluids
directly to run steam turbines. Many in the industry have long noted the
limitations of conduction geothermal. It is simply harder to make the economics
work for conduction geothermal.
GeoExPro’s Henk Kombrink
interviewed Eavor’s CEO Mark Fitzgerald in May. Kombrink had previously been
critical of Eavor’s level of secrecy about the Geretsried project and its
unexpectedly low output of its first loop, expected to be at 2 MWe, but only
measured at 0.5 MWe. Fitzgerald was hired as CEO in October 2025. He said he
wanted the company to be more transparent. He also explained that they stepped
away from being the operator of the Geretsried project and wanted to focus
instead on being a technology provider. He believes another company more
experienced at operating projects should take the helm as operator. As part of
this change of strategy, they also reduced their team from 147 to about 80.
Kombrink notes some details about why the output is so low. It was due to
clogging with cuttings and unexpected communication between loops. Poor cement
jobs were implicated. The output should be as designed if all the loops were
drilled and functional.
“…it is already widely known that the company only
completed six loops instead of the planned twelve. What was new to me was that
it is actually 3 to 4 loops that are contributing to flow. Two loops
experienced clogging by rock fragments to such an extent that the cleaning
operation could not alleviate the problem. The third loop is only contributing
to a limited extent.”
“We believe that we have proven the concept. We now have
to prove commerciality,” is what he reiterated a few times during the
conversation.
The company reported in
mid-October that the two drilling rigs at Geretsried had been released.
Kombrink noted in the interview that the company had burned through its funding
of about 350 Euros for the project. He is also not quite sure they could say
they had proven the concept, given the problems.
Think GeoEnergy reported then:
“Although the milestone validated many technical aspects
of Eavor’s closed-loop concept, challenges in execution prevented the project
from reaching its operational targets. A few months after the start of
electricity supply, the company disclosed that the Geretsried site only
achieved between 0.5 to 2.0 MWe of gross power generation, with practically no
power delivered to the grid.”
“Isar Loisach Naturwärme (ILN), the district heating
company founded by Stadtwerke Geretsried, expressed disappointment that the
project has been further delayed.”
They signed a heat offtake
agreement for district heating in 2024, but the lack of heat due to the low number of loops and now incorrect sizing of components, including the ORC system, presents operational issues.
In a late October article in
GeoExPro, Kombrink expressed more doubts about Eavor’s failed project in
Germany and its concept in general. Lack of circulation and fluid loss problems
would have to be fully solved before the concept could work as designed. One of
the big problems with closed-loop geothermal and Eavor’s concept in particular
is that drilling and cementing wells, laterals, and sidetracks is expensive as
well as technically challenging. He expressed doubt that they will find an
operator willing to proceed with the rest of the Geretsried project. Kombrink
expressed doubt about Eavor’s viability going forward after the clear project
failure. He thinks it may be years or even decades before closed-loop
geothermal becomes viable, if ever.
Back in May of 2026, Eavor did
provide a technical update on the Geretsried project on its website. The early
part of the drilling encountered severe problems, which they later improved, as
recounted below:
Extreme drilling dynamics and dysfunction
“The combination of deep hard rock, long laterals, high
friction, and difficult hole conditions created severe shocks, vibration, and
torque dysfunction. This did not just slow rate of penetration; it also damaged
tools, shortened bit life, and increased trips out of hole. As the campaign
progressed, we improved the bit and BHA design, adjusted drilling parameters,
changed the fluid system, improved lubricity and hole cleaning, and used
drilling dynamics mitigation tools. Those changes translated into better ROP,
longer bit runs, and fewer drilling dysfunction issues in the later wells.
Ultimately, we were able to drill the last lateral pair in a single run from
each rig.”
Bit life improved, ROP improved,
and Eavor’s magnetic ranging technology, used to connect the two wellbores in
the loops, proved to be successful and faster than other magnetic ranging
efforts.
As they recount below, the biggest problem by far was hydraulic communication:
“Hydraulic communication between the two rigs through
previously drilled lateral pairs”
“This challenge was by far the most impactful. Following
the sidetracking of the second lateral pair, hydraulic communication (fluid
flow) between the two rigs was measured. The root cause was poor cement jobs on
both cased “motherbores”, enabling a significant annular fluid channel behind
the casing, which connected all the lateral pairs to each other. Fluid could
freely flow down previously drilled laterals and up to the other rig.”
“Efficient Eavor-Loop construction depends on two rigs
drilling in parallel; each lateral pair is drilled by two rigs simultaneously
and intersected, starting with the lowermost lateral and then repeating from
the “bottom up”. Each previously drilled lateral pair is supposed to be sealed
(hydraulically isolated) from the next lateral pair which is drilled uphole (in
the direction towards the surface within the cased motherbores). However,
inadequate isolation in the cement behind the casing created hydraulic
communication between the two well systems/rigs. Once that happened, pressure,
mud, and cuttings could move freely between the inlet and outlet patterns
through previously drilled lateral pairs.”
Below are the company’s loop
models.
Eavor also points out that
compared to other EGS geothermal projects and other forms of energy, it is
heavily weighted toward Capex. One of its advantages is the low Opex once a
project is completed as designed and online. However, completing a project as
designed is currently the biggest challenge.
Until these technical challenges
are overcome, the concept will remain uncommercialized. They believe they can
commercialize and stress that Gertsried is a first-of-a-kind (FOAK) project
with FOAK problems that can be overcome in subsequent testing. However, with
the lackluster results and loss of capital, Geretsried can only be seen as a
technical and economic failure at present.
References:
The
end of Eavor? With the rigs having departed from Geretsried and the Hannover
project cancelled, what remains of the Eavor project pipeline? Henk Kombrink.
GeoExPro. October 31, 2026. The
end of Eavor? - GeoExpro
Eavor
withdraws drilling rigs from the Geretsried geothermal project site in Germany.
Carlo Cariaga. Think GeoEnergy. October 16, 2026. Eavor
withdraws drilling rigs from the Geretsried geothermal project site in Germany
Eavor
stepping away from operator role in Geretsried: That’s what Eavor’s CEO Mark
Fitzgerald said during an exclusive interview with us that addressed the
company’s recent project in Germany as well as the new strategy it has now
embarked on. Henk Kombrink. May 13, 2026. Eavor
stepping away from operator role in Geretsried - GeoExpro
Technical
Update from Geretsried: What we built, what we learned, and what comes next. Matt
Toews. Eavor. May 21, 2026. Technical
Update from Geretsried: What we built, what we learned, and what comes next -
Eavor