February 17, 2021

Team Profile:
Supercritical: What the NZ Geothermal Community Wants to Know

Melissa Climo

photo credit:

Remember how back in November 2020, at the NZ Geothermal Workshop, we presented our vision for a supercritical strategy for Aotearoa New Zealand and ran a workshop with the New Zealand geothermal community to share ideas, identify barriers to development, and ask the burning questions?

We have summarised this feedback, and yes, it's a little bit rough, and a little bit raw, but we want to share it with you anyway, because you are coming on this journey to a supercritical NZ with us.

If you're feeling curious, please have a read through.

Perhaps it will prompt an observation or question in your mind. During 2021 we'll be seeking lots more input and asking lots of questions of everyone. If you have a burning question or comment, please send us an email, or leave a comment via our Facebook or LinkedIn pages.


Written feedback from participants was collected (on post-its) and compiled. Information was collected during the workshop under six categories: Investment, Regulatory, Science, Engineering, CO2 Management, and 'Other'. During data analysis, substantial overlap was observed between categories, so the feedback is summarised below in topic-based ‘clusters’.


We did not directly ask a question about ‘why supercritical?’ but observed a high demand from participants wanting to understand the value of supercritical resources to NZ. It is clear that we need to build a narrative in regards the benefits.

“How much do you really gain from supercritical fluids for the extra expense?”

“What’s the advantage to drilling for supercritical?” “It is worth it?” “Is this even safe?”

“Why do we need to generate more power?” “Do we really need that much energy?”

“What’s the market gap that makes this viable?” “What are the financial risks?”

We need to provide a clear understanding of strategy, risks and rewards, as well as explaining clearly the relationship between existing geothermal and supercritical – what it means for both.

There may also be a perception that “new science is risky”. One commenter stated “this must be very dangerous and disturbing of nature”. It is clear we need to show the stability and reliability of geothermal – and address such perceptions.


“be aware of opportunities and build strategic relationships”

Supercritical development involves a wide range of stakeholders – partnering was seen as critical. A need for “a clear engagement plan” was highlighted including councils, tangata whenua, industry, regulators, public; as well as a comment to identify key influencers.

A few comments focused on taking stakeholders “on the journey” and taking “time to build buy-in”; especially a note that “changing any regulation takes a lot of time”.

“How to deliver easy to understand science?” Community education and involvement, and opportunities for education should be explored.

The importance of weaving in Mātauranga Māori was emphasised.


“International alignment – we are not alone“

Examples of learning from others suggested included: the oil and gas industry, deep oil and gas drilling, ultra pressure drilling (e.g. Cooper Basin), as well as data from equivalent mineral deposits.

Also – experience and lessons learnt from existing NZ geothermal should be used and trusted.


The list of suggestions included:government, R&D Tax, global climate funds, NZ industry, international finance, whenua and taonga investments, Māori and ahu whenua corporations.

A need was identified for seed funds and greater R&D funding.

Also, numbers are needed on (for example): LMRC, costs of drilling supercritical, maximum MW potential per well, ongoing costs etc.


“Who goes first? (risk vs reward)”. Comments noted the high risk and uncertainty makes investment difficult when large capital outlays are required up front – and the scale of future demand in uncertain.

“Who is the customer?” “Guaranteed market and commodity pricing would help”.

Questions were posed on how supercritical/geothermal benefit could from a disrupted electricity market (and changing low-carbon legislation). Also, how investment in geothermal sits within a broader system (e.g. grid, transmission networks) – can this be leveraged? Are existing infrastructure networks sufficient to support supercritical development?

“How do we enable wider distribution of risks and benefits?” We need to “rethink ‘ownership’”. Many comments focussed on a need for an optimal investment model. Investment is expected to require multi-sectoral investment, partnerships, and government direct investment and/or financial incentives to de-risk.


In order to set optimal regulations –resource definition is important. If supercritical is an “enormous resource”, what is the relation of supercritical to present (conventional) resources and  development - e.g. classification systems, protection vs develop. “What are the resource system boundaries at different depths?” “Could be different position to the surface boundary.”

“National level direction” and “clear regulation” is essential. The RMA / legislative reform could offer an opportunity for geothermal/ supercritical to influence/ lobby for change. Is the “RMA environmental assessment framework appropriate?”

Comments on how/what other regulations influence supercritical development e.g. national policy statements, crown minerals, surface rights, land ownership, Te Ture Whenua Act.

Do existing drilling and HTTC monitoring regulations cover supercritical depths?


“New technology will require new regulations, and understanding of issues”

Comments in hazard and safety management highlighted drilling safety, blowouts, bore closures, pipeline inspections, HTTC well (casing) monitoring, as well as potential changes to regulations and processes to ensure safe operation.  


Can we “predict environmental effects?” What are the “unanticipated environmental effects?”

Potential environmental effects noted included: noise, CO2, surface discharge, subsidence, seismicity, geological hazards, (pollution). There is a need to know: baseline environmental data, and trigger points for adverse effects.

“How do we monitor effects when it is so deep?”

Monitoring effects of resource use: Who? What? When? How?

Also, there is a need to monitor effectiveness of monitoring plans and review process.


Moving towards exploration drilling –the focus was on determining CO2 storage, processing and use options; and staying connected with regulatory changes and (dis)incentives, as well as better understanding of CO2 baselines.

CO2 emissions management was seen as essential to resolve in the 2030-2040 decade, during exploration drilling, pilot scale demonstration and feasibility testing. The focus was CO2 capture potential in NZ reservoir rocks, main trapping mechanisms, and identifying opportunities for using CO2 (e.g. agricultural products, food, pharmaceuticals).

Commenters also suggested exploring CO2 as a working fluid, and use of CO2 to adjust pH to affect scaling, scoring and permeability.


“How will reinjection of supercritical fluids work?” This was a common question.

Also, there was a desire to know more about reinjection of CO2 and other non-condensable gases.


There were a lot of questions on drilling and wells.

“Do we have rig capability?”

Drilling & logging comments included: high torque logging tools and coring tools, casing design, cement design, drill bits, depth rig, drilling fluids, well design, drill pipe failure, appropriate materials, wireline tools for high temperature and chemical conditions, logging while drilling, appropriate and reliable downhole tools – and good MWD communication.

“How do we know when to stop drilling?” Markers needed for approaching supercritical conditions.

“How do we sample fluids?”

Questions were asked about well control equipment (with one suggestion for AI-driven well control) as well as questions of wellbore integrity.

Innovation is needed to reduce well costs.

Could we “drill from existing depleted conventional wells to save on drilling costs?”


The focus for plant design was firmly on scaling and corrosions, as well as materials that can handle high temperatures and pressures. Questions were asked about silica solubility, predicting deposition and scaling risk when moving from pilot plant to full scale.

Steam purity was questioned – are the turbine etc materials appropriate?

“Can you use a closed loop system…?”

Gaps were identified in phase diagrams, predicting fluid chemistry, and thermodynamic properties for minerals phases.


What is the chemistry of supercritical fluids / the nature of deep brines?

“How can supercritical fluid properties be predicted?”

“What will come out of the ground?”

“How do supercritical and sub-critical fluids interact?”

There is a high demand for answers to these questions and more. A strong need was identified for supercritical equations of state, e.g. CO2/water dynamics.

“What is the critical point for salt saturated brines?”

Comments also reflected a desire to know about CO2 and gas concentrations/behaviour in supercritical fluids.


Do we need “different physics?” Resolution and depth of geophysical methods was questioned.

Findings supercritical targets was firmly in the 2020-2040 timing, with a need to define drill location and depth.

Suggestion to “decide on ideal fluidP/T conditions, and then search for the ‘right’ geological spot” – as well, a need to understand “resource connectedness to 20km depth” and “pick a geothermal system(s)” to start with.

How to minimise volcanic risk?


Comments acknowledged decreasing permeability with increasing pressure, and identified a need to “find” permeability and “keep it open”.

Need to understand rock properties, stresses, fractures and flow.


A need was identified for improved modelling techniques and improvement in computational power. “Models will be big, with lots of non-linearity, long solution times.”

The models wish-list included: system modelling, parallel reservoir simulation with supercritical capacity, THM models, well bore models with supercritical capability, magmatic lifecycle evolution,“how simulators”, operational planning modelling, 3D.


Do we have (will we have) skilled people and “availability of contractors”?


Supercritical fluids are not just an energy resource. As well as suggestions for using CO2 for value added products, there was a reminder to look at mineral potential in supercritical geothermal fluids e.g. rare earth elements.

Developing supercritical resources in NZ will enable cutting edge technology and process development. We should maximise innovation as we develop next generation technologies. A few comments served as reminders to look for where technological advancements could benefit other industries.

Yes, there is plenty here to keep us busy! We hope to add to this collection of ideas, issues and questions during the next few months as we talk with a wide range of stakeholders.

read more


Business Case & Opportunity
Governance & Regulation


supercritical strategy
nz geothermal workshop (NZGW)
conference presentation

Further Updates