IGC 2024, Reykjavik, and the Reverse Enthalpy Methodology (REM)

It has been a great pleasure to present at #IGC2024 in Reykjavik on the work I have been helping the GEN srl. team with (i.e. the Geological and Engineering Network, based in Rome) on the Reverse Enthalpy Methodology (REM). 

REM is a technique they have already put to good use in several countries of southern Europe, and we are working with Rose Subsurface Assessment to compose a dedicated course.  It works out of mathematical principles first developed for the oil and gas industry by the likes of Peter Rose, but modifies them for the many important differences and nuances symptomatic of geothermal deployment.  The GEN team are a network of diverse geological and engineering experts with long experience in geothermal geoscience (geological, geophysical, & geochemical), drilling, facilities engineering, and environmental impacts.  

The methodology is a way of reversing back from assumption of a particular geothermal development scenario & size, to give the chance of commercial success – and how many exploration & development wells a project can take and still be profitable.  This in relatively immature areas for geothermal development - which has been a historical problem holding back developments in new areas.

It is technology and use agnostic – i.e. suitable for heat, power, and any kind of geothermal technology – as long as you have enough data points to draw on analogues.  It empirically relates the MW (MWt or MWe) per an estimated dimension of a geothermal field, as a function of temperature (or enthalpy as appropriate), in analogues, to compare with the project area under investigation.   

Usually that dimension is area, but there are options to use other things (e.g. aquifer volumes, closed loop hole length in reservoirs).  It is a function of how many data points you have for a particular dimension.  Importantly though, it provides a place to start. It uses detailed geoscientific analysis to capture project uncertainty in a building block of well deliverability (i.e. flow rates averaged over time), and from there, the probabilistic range of well count required to meet the designated plant capacity.  

The aim is not to give “the answer” but to sensibly frame a plant capacity size estimation, and from geological knowledge of an area, ascertain what a project can bear in terms of plant sizes and well counts and still be profitable. In places where there are decades of data and well penetrations and the geoscience is well known, there are far more sophisticated methods to adopt and to model in detail, because the data is present - but where geothermal deployment is just beginning, this method gives geothermal investors the tools they need to look at an area's geoscience, compare it with appropriate analogues around the world, and chisel some financial metric footholds in the geothermal cliff-face.

The beauty of working around a designated capacity, is that armed with a probabilistic distribution of associated well count it enables the NPV (net present value) and EMV (expected monetary value) economic analysis in relatively immature areas, which is so often so very difficult.  It gives an "anchor". That economic analysis leads to the “dry hole tolerance” – how many wells the project can tolerate and still be profitable, and the chance of commercial success.  That is what financiers like to know – the chance of technical success on its own is not enough.   It’s not being able to do something that matters to them or the final customer – it is being able to do something profitably. 

There is no permanent tie to that initial estimate of designated plant capacity – if the initial iteration REM results of commercial success and well counts are not favourable or fitting with corporate plans, there is scope to readjust the designated capacity size informed by the initial results and progress to a new iteration of development concept and/or capacity to repeat analysis.  And to do so several times if necessary – to end up with a plant capacity size that is appropriate to the geoscience of the project and to the mandates of those investing in it. 

Such analysis works well with modular system based approaches that help limit costs, and the focus on development concept also eases classification into emerging UN geothermal classification schemes.  And if the area you are looking at cannot yield a desired plant capacity size for a sensible well count, the method will help tell you so, and save finding out the hard way. It also provides a clear knowledge of when, if after good efforts without success, it is time to walk away. Knowing when to stop can be as important as knowing whether to start.

For any company involved in geothermal – drilling companies, geothermal power plant and district heating builders, big engineering houses – it is a way of showing to your customers - how they can work meaningfully through technical uncertainties, risks, and economic decision trees to come up with a sensible geothermal project approach in any given area.  Or if you work within a state framework in a country where geothermal development for either heat or power is still new, it is a way of looking quantitatively to appropriate analogues in other places to help steer “how to start” where you are. With real estimates of spend, uncertainty and chance of success. 

It was a pleasure to meet up with so many at IGC, and I will be writing up a fuller account of the conference from a Paetoro Consulting UK Ltd perspective shortly.  I will also aim to write up a fuller summary of the REM technique for LI, to add to publications in process.  In the meantime don’t hesitate to get in touch should you be interested in knowing more. 

As mentioned, we are in the process of finalising a dedicated course with Rose Subsurface Assessment , so should you have lots of young keen geothermal experts in your organisation, help is at hand to arm them with information to assist potential clients - in knowing how to attack geothermal projects in newer areas methodically and intelligently from geoscientific, engineering, and commercial perspectives.

Regards,

Dave

(My thanks also to Roberto Gambini for taking some snaps as I presented)