ERE
Energy, Resources and the Environment

fault

I’m a Geoscientist: Sian Loveless – ‘Young Scientist Representative’ Officer

March 20, 2015

It’s I’m a Geoscientist week! Or more exactly: weeks. From March 9 until March 20, the EGU supports I’m a Geoscientist to help students engage with scientists about real science. The Energy, Resources and Environment Division of the European Geosciences Union encompasses a broad range of different ERE-related topics, from surface to subsurface, spanning all aspects of geosciences. In order to demonstrate how broad the Division actually is, and what you can do as a geoscientist to be involved with energy, resources or the environment, we asked the members of the ERE committee to introduce themselves and explain how their day-to-day work relates back to ERE.

We will end our trip past the members of the ERE committee with our Young Scientist Representative Sian Loveless. She mainly works on bringing together ERE and you (yes, you my dear YSs!).

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Sian LovelessAt my first EGU GA (General Assembly) in 2011 I took the opportunity to visit a number of Energy Resources and Environment (ERE) sessions, though they were not directly related to my PhD research. Topics within the Division of ERE tend to be of interest to academics, industry, policy-makers and the wider community as they have clear societal impacts and are therefore often rather accessible. In addition, shifts in ERE “hot topics” can occur year to year as contributors respond to evolutions in society. As an example, at the 2011 GA two presentations concerned Shale Gas; three years on, in 2014, the terminology evolved to Unconventional Hydrocarbons (to include other novel resources) and there were now a number of popular dedicated sessions.

It was the relevance of the ERE talks that attracted my attention, in particular those presenting case studies in the more novel fields of CCS (Carbon, Capture and Storage) and Geothermal Energy. Suitably impressed by these I moved to Belgium to work in Research and Development of Geothermal Energy for a technology research institute. I recommend a visit to ERE sessions to other curious researchers from across the EGU Divisions and in particular Young Scientists seeking pathways for their research.

I now spend part of my time on “strategic” or more fundamental research and part on defined geothermal feasibility and development projects. This can be a peculiar locus; trying to marry-up sophisticated in-depth research with practical challenges. A major challenge in Geothermal Energy assessment is identifying the nature of geological fault zones. Faults (and associated fractures) can be very permeable to fluids (conduits) and thus a prime target for geothermal energy, or conversely very impermeable (barriers) and should be avoided. Faults thus have significant impacts on the viability of a geothermal project. There is a marked disparity between the scale at which this problem is and can be considered. Fault permeability depends on a wide range of parameters and may vary between the two extremes even along the same fault. Rightly, much academic research is devoted to understanding these intricacies. However there is generally limited data available at depth which requires that generalisations and assumptions must be made about the nature of the fault permeability to allow progress. I see ERE sessions at the EGU GA as a tool to bring together industry and academics to present and discuss these different perspectives.

Fault in Central Greece showing highly permeability down-thrown gravel beds in the hangingwall juxtaposed against low permeability marl beds in the footwall. Juxtaposition of sediment/rock with different hydraulic properties is one of the main ways in which faults can impact sub surface fluid flow

Fault in Central Greece showing highly permeability down-thrown gravel beds in the hangingwall juxtaposed against low permeability marl beds in the footwall. Juxtaposition of sediment/rock with different hydraulic properties is one of the main ways in which faults can impact subsurface fluid flow.

Another potential function of ERE sessions is to be a platform for two-way interaction with policy-makers. Policy decisions have a critical impact on the realisation of Geothermal Energy and other green/sustainable technologies, remaining a major barrier to its adoption in many countries. As a first step we have introduced the session “ERE in Policy” to the 2015 programme in which we hope that knowledge in policy theory and practice can be efficiently and openly shared across industry, academia, research institutes, across country borders and disciplines.

As the Young Scientist Representative of the ERE Division I am interested in promoting involvement for all Young Scientists so please contact me (sian.loveless@gmail.com) with any feedback. In particular please consider submitting a blog-post related to ERE – topics can be varied, from your own research to news articles and interesting conferences that you have attended – we’d love to hear from you!

Words on Wednesday: Effects of temperature and CO2 on the frictional behavior of simulated anhydrite fault rock

February 4, 2015

Words on Wednesday aims at promoting interesting/fun/exciting publications on topics related to Energy, Resources and the Environment. If you would like to be featured on WoW, please send us a link of the paper, or your own post, at ERE.Matters@gmail.com.

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Pluymakers, A. M. H., J. E. Samuelson, A. R. Niemeijer, and C. J. Spiers (2014), Effects of temperature and CO2 on the frictional behavior of simulated anhydrite fault rock, J. Geophys. Res. Solid Earth, 119, 8728–8747, doi:10.1002/2014JB011575

Depleted oil and gas reservoirs form attractive CO2-storage sites, where prerequisites to efficient and safe CO2-storage include no leakage and no (additional) seismicity. It is thus of importance to understand the possible effects of CO2 not only on the geomechanical behavior of the reservoir- and caprock, but also of the crosscutting faults. Many of these potential storage reservoirs are topped by anhydrite caprocks (CaSO4), and thus reservoir-bounding faults are likely to contain anhydrite-derived damage material, or ‘fault gouge’. To better understand the frictional properties of anhydrite fault gouges, we have performed friction experiments on simulated anhydrite fault gouges, including effects of short-term CO2 exposure. Our main research questions were:

  1. How easy or how difficult is it to initiate movement within anhydrite fault gouges, i.e. how strong are they? What is the effect of CO2?
  2. Does anhydrite fault gouge show the potential to nucleate earthquakes (‘seismogenic potential’) at CO2-storage conditions? What is the effect of CO2?

In these experiments the samples were under a pressure and temperature similar to those at 2-4 km depth. This means an effective normal stress of 25 MPa and temperatures between 80 and 150°C. We also used different pore fluids, namely lab air, water, CO2 and CO2-saturated water. For those experiments that contained a pore fluid, the fluid pressure was 15 MPa, so the CO2 was in its supercritical phase.

cover JGR v119

Our results indicate that at these conditions, anhydrite exhibits a friction coefficient of 0.5 to 0.7, i.e. a friction coefficient typical for most rocks. However, it is important to note that the weakest samples were those containing CO2-saturated water. To avoid fault reactivation, this small (up to 15%) weakening effect should be taken into account when determining the maximum allowable injection rates and pressures into a reservoir. Furthermore, with respect to the possibility of earthquake nucleation, these results show that the presence of supercritical CO2 does not influence seismogenic potential. Only dry gouges are capable of nucleating earthquakes, and at this pressure, this only occurs at temperatures exceeding 120°C. Such high temperatures are in most areas only expected at depths exceeding 4 km, i.e. deeper than most targeted CO2 storage reservoirs. Within the investigated temperature-range, gouges that contain water (with or without CO2) exhibit very little seismogenic potential.

This research has been performed at the HPT lab of Utrecht University, the Netherlands, within the framework of CATO-2, the Dutch research program of CO2 capture, transport and storage. It has been shown as a poster presentation at EGU 2013, in the ERE division, and has been published in December 2014 in the Journal of Geophysical Research – Solid Earth.