Repurposing Hydrocarbon Wells for Geothermal Applications
Insights from Our Interview with Christi on EGS, Storage, and Europe’s Energy Transition
Christi is a Geothermal Resource Engineer and PhD Researcher, specializing in deep geothermal systems, closed-loop systems, well repurposing (especially converting old oil/gas wells for geothermal use), Enhanced Geothermal Systems (EGS), and Deep Borehole Heat Exchangers (DBHE).
What if the thousands of oil and gas wells scattered across Europe could become the backbone of the geothermal transition?
In our recent interview with Christi, a leading researcher involved in the TRANSGEO project, we explored the technical, economic, and regulatory realities of repurposing hydrocarbon wells for geothermal applications ,
particularly for Enhanced Geothermal Systems (EGS), thermal storage, and district heating integration.
From case studies like Groß Schönebeck to regional analysis in Lausitz, Christi offered a grounded and technical perspective on what works and what doesn’t in well repurposing.
Let’s break it down.
1. Well Selection: Not Every Abandoned Well Qualifies
Repurposing an oil or gas well is not as simple as plugging in a heat exchanger and turning on the pumps. According to Christi, the workflow begins with rigorous screening.
Critical Selection Criteria
In Germany’s case, three factors are fundamental:
Subsurface temperature, Without sufficient temperature, the economics collapse.
Wellbore diameter, The bottom-hole casing must be greater than 7 inches. Wells with less than 7” casing diameter are typically disqualified because modification for liner casing production becomes technically limiting.
Well age, Wells older than 30 years are generally avoided due to integrity risks.
Additionally, partially abandoned or fully abandoned wells often face regulatory or structural challenges that make conversion impractical.
“Out of 1,000 abandoned wells, you might find none that are viable,” Christi emphasized.
The idea that thousands of wells automatically translate into geothermal potential is misleading. Viability is rare , and highly site-specific.
2. Technical Modifications: Integrity is Everything
The biggest technical hurdles revolve around:
Well completion modifications
Long-term well integrity
Casing–reservoir fluid interaction
Hydraulic stimulation performance
Germany currently applies five geothermal technologies:
Shallow to medium-depth ,Borehole Heat Exchangers
Hydrothermal systems
Enhanced Geothermal Systems (EGS) (still under development)
Aquifer Thermal Energy Storage (ATES) (research stage)
Borehole Thermal Energy Storage (BTES) (research stage)
While shallow systems are mature, deeper EGS and storage systems remain under research and demonstration.
3. Lessons from Groß Schönebeck: EGS in Practice
At Groß Schönebeck, a former gas exploratory well E GrSk 3/90 , was successfully converted into an EGS injection well. This stands as a field example of how repurposing can work when geological conditions align.
Using:
3D geological modeling
Reservoir simulation
Cross-flow testing between injection and production wells
Engineers designed multi-stage fracture concepts for fracture-dominated EGS systems.
However, Christi was clear:
Repurposing does not automatically improve heat extraction or well longevity.
Its purpose is to add value to existing infrastructure rather than abandon it.
Performance largely depends on the effectiveness of hydraulic stimulation and fracture geometry.
In short: repurposing is an economic optimization strategy , not a performance miracle.
4. The Economic Reality: Where the 50–60% Savings Come From
The primary economic advantage is obvious:
Drilling has already been done.
Avoiding new drilling can reduce capital expenditure by 50–60%, making projects financially attractive , but only under the right conditions.
Key Cost Drivers
Heating distribution infrastructure
Integration into district heating systems
Electricity price benchmarks (~12 cents)
Heating energy prices (~30 cents)
Government offtake structures (e.g., affordability constraints in Indonesia)
Christi estimates the “impact advantage” of repurposing at around 50% compared to greenfield geothermal development.
But without district heating demand or viable offtake pricing, economics quickly become strained.
5. Storage & Hybrid Systems: ATES and BTES Potential
Beyond power and heat production, storage systems are emerging as a promising use case.
ATES and BTES technologies are particularly attractive in:
Northern Europe
Canada
These regions have:
Strong seasonal heating and cooling demand
Existing wells with bottom casing diameters greater than 7 inches
District heating infrastructure
However, BTES requires multiple wells in a network for effective storage functionality. Single-well applications are limited.
In former oil and gas regions, these systems could help:
Balance seasonal energy demand
Stabilize district heating networks
Lower heating costs
But again , infrastructure integration is key.
6. Regulatory Complexity: A Cross-Border Challenge
Within Central Europe, regulations differ widely. Each country:
Protects well integrity differently
Has distinct liability frameworks
Applies unique permitting procedures
Liability for legacy wells remains one of the biggest non-technical barriers.
Christi stressed the need for:
Minimum integrity standards
Transferable technical criteria
A consortium-based approach
Scalable frameworks adaptable at local levels
While subsurface physics may be similar across borders, governance is not.
7. TRANSGEO’s Core Lesson: No Universal Workflow
One of the most important insights from the TRANSGEO pilot feasibility studies is this:
Reservoir characteristics are not transferable.
Engineering workflows cannot simply be copied from one site to another.
Each project requires:
Site-specific modeling
Demand-side evaluation
At least two economically viable geothermal reservoirs
At least two possible energy applications within a single well
District heating demand must already exist — or be realistically deployable.
Without demand, even technically viable wells fail economically.
8. Future Outlook: Massive Opportunity, Tough Reality
Europe has thousands of oil and gas wells.
The opportunity is immense.
But the real question is:
How many countries are willing to commit those wells to geothermal conversion?
Scaling depends on:
Policy commitment
Regulatory harmonization
District heating expansion
Financial risk-sharing models
Emerging technologies like closed-loop systems could further accelerate adoption. Christi noted that closed-loop systems are effective , but currently limited to around 100 kW, primarily for heating rather than electricity generation.
Supercritical or superhot rock concepts, requiring two to three wells, could push boundaries further , though these remain technologically and economically complex.
Final Reflection: From Abandonment to Asset
Repurposing hydrocarbon wells is not a silver bullet. It does not automatically increase productivity or extend well life.
What it does is transform stranded infrastructure into potential geothermal assets.
But viability is rare. Out of 1,000 abandoned wells, none may qualify.
The transition depends not just on geology — but on policy, economics, district heating networks, and national commitment.
The geothermal transition will not be powered by theory alone.
It will be powered by selective, strategic, economically viable conversions.
And as Christi’s insights reveal, the future of repurposed wells lies at the intersection of engineering realism and political will.
At Alphaxioms, we continue to explore how oil and gas repurposing can unlock geothermal value , not through assumptions, but through rigorous technical assessment and economic discipline.
Repurposing Hydrocarbon Wells for Geothermal Applications
Insights from Our Interview with Christi on EGS, Storage, and Europe’s Energy Transition
What if the thousands of oil and gas wells scattered across Europe could become the backbone of the geothermal transition?
In our recent interview with Christi, a leading researcher involved in the TRANSGEO project, we explored the technical, economic, and regulatory realities of repurposing hydrocarbon wells for geothermal applications ,
particularly for Enhanced Geothermal Systems (EGS), thermal storage, and district heating integration.
From case studies like Groß Schönebeck to regional analysis in Lausitz, Christi offered a grounded and technical perspective on what works and what doesn’t in well repurposing.
Let’s break it down.
1. Well Selection: Not Every Abandoned Well Qualifies
Repurposing an oil or gas well is not as simple as plugging in a heat exchanger and turning on the pumps. According to Christi, the workflow begins with rigorous screening.
Critical Selection Criteria
In Germany’s case, three factors are fundamental:
Subsurface temperature, Without sufficient temperature, the economics collapse.
Wellbore diameter, The bottom-hole casing must be greater than 7 inches. Wells with less than 7” casing diameter are typically disqualified because modification for liner casing production becomes technically limiting.
Well age, Wells older than 30 years are generally avoided due to integrity risks.
Additionally, partially abandoned or fully abandoned wells often face regulatory or structural challenges that make conversion impractical.
“Out of 1,000 abandoned wells, you might find none that are viable,” Christi emphasized.
The idea that thousands of wells automatically translate into geothermal potential is misleading. Viability is rare , and highly site-specific.
2. Technical Modifications: Integrity is Everything
The biggest technical hurdles revolve around:
Well completion modifications
Long-term well integrity
Casing–reservoir fluid interaction
Hydraulic stimulation performance
Germany currently applies five geothermal technologies:
Shallow to medium-depth ,Borehole Heat Exchangers
Hydrothermal systems
Enhanced Geothermal Systems (EGS) (still under development)
Aquifer Thermal Energy Storage (ATES) (research stage)
Borehole Thermal Energy Storage (BTES) (research stage)
While shallow systems are mature, deeper EGS and storage systems remain under research and demonstration.
3. Lessons from Groß Schönebeck: EGS in Practice
At Groß Schönebeck, a former gas exploratory well E GrSk 3/90 , was successfully converted into an EGS injection well. This stands as a field example of how repurposing can work when geological conditions align.
Using:
3D geological modeling
Reservoir simulation
Cross-flow testing between injection and production wells
Engineers designed multi-stage fracture concepts for fracture-dominated EGS systems.
However, Christi was clear:
Repurposing does not automatically improve heat extraction or well longevity.
Its purpose is to add value to existing infrastructure rather than abandon it.
Performance largely depends on the effectiveness of hydraulic stimulation and fracture geometry.
In short: repurposing is an economic optimization strategy , not a performance miracle.
4. The Economic Reality: Where the 50–60% Savings Come From
The primary economic advantage is obvious:
Drilling has already been done.
Avoiding new drilling can reduce capital expenditure by 50–60%, making projects financially attractive , but only under the right conditions.
Key Cost Drivers
Heating distribution infrastructure
Integration into district heating systems
Electricity price benchmarks (~12 cents)
Heating energy prices (~30 cents)
Government offtake structures (e.g., affordability constraints in Indonesia)
Christi estimates the “impact advantage” of repurposing at around 50% compared to greenfield geothermal development.
But without district heating demand or viable offtake pricing, economics quickly become strained.
5. Storage & Hybrid Systems: ATES and BTES Potential
Beyond power and heat production, storage systems are emerging as a promising use case.
ATES and BTES technologies are particularly attractive in:
Northern Europe
Canada
These regions have:
Strong seasonal heating and cooling demand
Existing wells with bottom casing diameters greater than 7 inches
District heating infrastructure
However, BTES requires multiple wells in a network for effective storage functionality. Single-well applications are limited.
In former oil and gas regions, these systems could help:
Balance seasonal energy demand
Stabilize district heating networks
Lower heating costs
But again , infrastructure integration is key.
6. Regulatory Complexity: A Cross-Border Challenge
Within Central Europe, regulations differ widely. Each country:
Protects well integrity differently
Has distinct liability frameworks
Applies unique permitting procedures
Liability for legacy wells remains one of the biggest non-technical barriers.
Christi stressed the need for:
Minimum integrity standards
Transferable technical criteria
A consortium-based approach
Scalable frameworks adaptable at local levels
While subsurface physics may be similar across borders, governance is not.
7. TRANSGEO’s Core Lesson: No Universal Workflow
One of the most important insights from the TRANSGEO pilot feasibility studies is this:
Reservoir characteristics are not transferable.
Engineering workflows cannot simply be copied from one site to another.
Each project requires:
Site-specific modeling
Demand-side evaluation
At least two economically viable geothermal reservoirs
At least two possible energy applications within a single well
District heating demand must already exist — or be realistically deployable.
Without demand, even technically viable wells fail economically.
8. Future Outlook: Massive Opportunity, Tough Reality
Europe has thousands of oil and gas wells.
The opportunity is immense.
But the real question is:
How many countries are willing to commit those wells to geothermal conversion?
Scaling depends on:
Policy commitment
Regulatory harmonization
District heating expansion
Financial risk-sharing models
Emerging technologies like closed-loop systems could further accelerate adoption. Christi noted that closed-loop systems are effective , but currently limited to around 100 kW, primarily for heating rather than electricity generation.
Supercritical or superhot rock concepts, requiring two to three wells, could push boundaries further , though these remain technologically and economically complex.
Final Reflection: From Abandonment to Asset
Repurposing hydrocarbon wells is not a silver bullet. It does not automatically increase productivity or extend well life.
What it does is transform stranded infrastructure into potential geothermal assets.
But viability is rare. Out of 1,000 abandoned wells, none may qualify.
The transition depends not just on geology — but on policy, economics, district heating networks, and national commitment.
The geothermal transition will not be powered by theory alone.
It will be powered by selective, strategic, economically viable conversions.
And as Christi’s insights reveal, the future of repurposed wells lies at the intersection of engineering realism and political will.
You missed: Inside the Geothermal Startup Mind: The Strategy, Funding & Sacrifices Behind Teverra’s Growth
At Alphaxioms, we continue to explore how oil and gas repurposing can unlock geothermal value , not through assumptions, but through rigorous technical assessment and economic discipline.
Alphaxioms appreciates Christi's insightful and indepth analysis on what it takes on turning Oil and gas wells into Geothermal Energy.
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