February 16, 2022

Team Profile:
Experimental Studies of Supercritical Fluid-Rock Interactions

Peter Rendel

photo credit:
Peter Rendel

How do fluids and rocks interact under supercritical conditions?

The exploration and use of supercritical fluids are dependent on accessible and high-quality geochemical data. Understanding fluid-rock interactions that occur under supercritical conditions provides thermodynamic constraints. These can then be incorporated into numerical models in order to better define supercritical resources and predict how they will behave when utilised.

Now that our high temperature experimental reactors are up and running, we’ve been working on addressing this knowledge gap. We presented preliminary results of this work as a conference paper and oral presentation at the New Zealand Geothermal Workshop.

In the paper, we shared results from a fluid-rock interaction experiment between supercritical water and NZ basement greywacke at 500˚C and 210 bars. Extensive mineral alteration was observed on the surface of the rock. There were changes in the mineral colour and an increase in surface roughness due to the dissolution and re-precipitation of minerals.

You can read the results by downloading the paper and some highlights are shown below.  

Numerous cavities and porosity after reaction show that there has been complete dissolution of quartz from the rock.   
SEM-EDS maps of the rock surface before (left) and after (right) reaction. The change from red-coloured grains into purple-coloured grains represents the loss of sodium (red) from the original albite and replacement by potassium (blue) and calcium(green). Other primary phases like pyroxene and chlorite are altered to clinopyroxene, hornblende and clay phases (e.g. illite).
SEM-EDS maps of the rock surface before(left) and after (right) reaction. Silica (red) is depleted, with the surface roughness of the reacted block emphasised by the shadows (black). Aluminium (green),and sodium (blue) are also depleted.

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new publication
experimental geochemistry
water-rock interations
supercritical conditions
high temperature & pressure

Further Updates