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The question of upscaling

Do lab results on small rock samples describe the behavior of kilometer-sized geological formations?

This question on “upscaling” is crucial in better understanding earthquakes, or long-term efficiency of geothermal energy production. We ask Frank van Bergen, research manager at the Rijswijk Centre for Sustainable Geo-energy (RCSG) about this:

Q: Say again. What is this “question of upscaling”?
A: Upscaling is about how we can apply our understanding of the behavior of small (hand sized) rock samples used in conventional lab testing to describe the behavior at larger scales. In an ideal experiment you can control all the parameters, and you are able to vary just one of these parameters to investigate its influence. Controlling this is difficult enough in conventional lab tests, using samples typically smaller than 10 cm. Let alone at larger scales, for which controlling the environment gets increasingly difficult. At the km-scale relevant for subsurface geo-energy applications (geothermal energy, subsurface storage), controlling parameters for scientific testing can be very challanging, and requires significant, large-scale infrastructure. Because of this, bridging our understanding gained in experiments performed at small scales (nm – dm), with that needed at large scales of actual subsurface operations (hm – km) is notoriously difficult. So to question of upscaling is how to go about that. 

Q: What will you do in Rijswijk to help address this? 
A: To bridge this gap it really helps to perform experiments at intermediate scales, i.e. at 1 to 100 meter scale. In particular because 1-100 meter is the typical, minimum meshsize used in many computer models aimed at describing the impact of large-scale subsurface operations, while using small-scale lab tests data (mm-dm samples) as input. So: can we use these lab data, even at meshsize scale? 

RCSG provides an experimental environment where this can be tested. At RCSG, experiments can simulate subsurface operations and subsurface response at 1 to 400 meter scales. Moreover, such experiments can be performed in natural formations, under controlled conditions of pressure, temperature, and flow rate. To do this at meter-, or even subsurface scale (>100 meter) is something few other laboratories can offer.

Frank, standing on a 6 meter tall, 1000 bar pressure vessel at the Rijswijk Centre

“We can better apply our understanding from conventional lab experiments, at the km-scale where such understanding is needed”

Q: Why is that important? 
A: Experimenting at this scale is essential to mature innovative technologies for subsurface use. Or to understand the impact of the nano- or micro-scale processes found to govern lab-scale rock samples, at the much larger scale relevant for geo-energy applications. Particularly that is important for true, physics-based understanding of the impact of our subsurface activities. 

And remember, Einstein said that ”No amount of experimentation can ever prove me right; a single experiment can prove me wrong”. If it does not work in a controlled environment, it probably does not work on a larger scale the way you thought it worked.

Q: What could we do we do with the results, that we couldn’t before?
A: We can better apply our understanding from conventional lab experiments, at the km-scale where such understanding is needed. This helps to steer or even predict the impact caused by using the subsurface for geo-energy-related applications.

Q: Sounds wonderful! When can you start?
A: The laboratory is already an open innovation lab infrastructure and is open to help out with excellent research ideas– just approach us directly or via EPOS-NL for free-of-charge access. Within EPOS-eNLarge, we plan to extend current research capabilities further, to fit the research goals of the partners and the project.

Learn more about EPOS-eNLarge plans and researchers