The 1st RPI for August-September 2015

Dave Dewhurst - Senior Research Scientist at CSIRO in Perth, Australia

About Dave Dewhurst

Dave Dewhurst is a senior research scientist at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and is based in Perth, Australia. He has a long standing interest in clays and shales, dating from the early 1990s, where he worked on application of soil mechanics techniques to consolidation, shearing and fluid flow in accretionary wedges. After this, his work focused on permeability and physical properties of compacting clays followed by research into polygonal fault systems in fine grained rocks. He moved to CSIRO in 1998, initially working on projects involving the physics behind overpressure prediction and mechanical and microstructural properties of faults for application to fault and top seal analysis. These days he leads multiple projects investigating the links between geomechanics, rock physics and petrophysics in both overburden and gas shales, as well as working on CO2 injection and interaction with reservoirs and caprocks.

Dave was educated in the UK (going to the same school as Colin Sayers in fact!) and has a BSc (Hons) in Geology from the University of Sheffield and a PhD in Physics from the University of Newcastle, where he worked on noble gas migration during rock deformation. He did a number of post-doctoral studies on clays and shales at the University of Birmingham, the University of Newcastle, the Institut Français du Pétrole in Reuil-Malmaison and Imperial College, London before joining CSIRO.

The secret of your success in being a well known name in the rock physics community

Being slightly tongue in cheek, it probably helps being six foot eight and wearing black! It certainly gets one noticed and makes one very recognizable! However, in terms of science, part of being recognised has certainly been due to working for a long time in a niche area and presenting extensive experimental results backed by geological/physical interpretation. For much of the last twenty plus years, there were only a few people mad enough to work on the properties of shales and at CSIRO, we were lucky enough to have the facilities for extensive material characterisation over and above mechanical and ultrasonic testing. So while the mechanical and rock physics results can stand alone, a much stronger understanding of rock behaviour can be obtained through knowing composition, microstructure and physico-chemical properties and this applies to all rocks, not just shales. In addition, I am a bit of an outsider in that I am not a trained rock physicist, I have come to rock physics through geology, soil and rock mechanics, so I have brought a different perspective to rock physics results by being rooted firmly in the geology domain and making interpretations from that perspective.

Challenges you see in moving rock physics to the next level

Working across the scales from lab to field is always challenging and getting experts in their one little area to understand that their scale is not the be all and end all of science can be hard. All scales have their pros and cons, while modelling between those scales, although advancing, still has a long way to go. Understanding shale behaviour, even after 20 years, is still extremely hard, be that overburden or gas shales, as both have their own particularly awkward set of problems. For me, the broad multi-disciplinary nature of the science needed to really understand the physics behind the processes means there is no such thing as an expert in these rocks. While geo-based topics such as clay mineralogy, microstructure, geophysics, geochemistry, rock/soil mechanics and the like all help in understanding shale behaviour, there are significant overlaps with the likes of colloid science, soil physics, fluid dynamics and ceramics. Importing such knowledge into the geological domain, while challenging, could significantly improve our understanding of experimental and field behaviour as well as models in these highly variable rocks

Advice for early career scientists (rock physicists, geophysicists, etc.)

Firstly, do as much as you can to learn from other domains, learn where the crossovers are, look for the links. Try to develop as broad a multi-disciplinary background as you can. Most degrees will focus on a certain topic but will fail to develop critical concepts that cross over into other disciplines. A prime example would be to learn as much geology as possible. Many geophysicists and rock physicists never even see a rock in their whole lives! However, it is the rock and its fluids which are going to control the vast majority of the properties that are measured from seismic to log to lab scale. Geophysics, rock physics, geochemistry and the like are all tools, for sure more rigorous and quantitative perhaps than geology, but in the end they are tools for understanding the rock and fluid behaviour. Without that background geological knowledge of what makes rocks tick, interpretations mean little. I have regularly attended geophysics conferences specifically because that was not my training and every time I go, I learn something new and useful. So the message is don’t be scared of geology or disciplines you have not been taught. They are opportunities to strengthen your background knowledge and that will always stand you in good stead in your future.

Secondly, keep it simple. I see plenty of conference presentations where people either try to cram every last bit of information in or just try to blow people away with what they think is mesmerising science and page after page of equations. This does not work, at least for me anyway, and for plenty of others that I see nodding off at geophysics conferences!! Craft a coherent, contained story around a small subset of results, large clear diagrams (one to a page), few words (just prompts for you) and walk people through it slowly and simply. It is way better to get a couple of simple messages across to your audience than cram in hundreds and get none across. Always finish early to allow plenty of time for questions and feedback. Presentations are the key to getting your science across and being remembered, especially if you are not six foot eight and wearing black!!

We thank Dave for his continuous contributions to the rock physics community.

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