The 13th RPI for September-October 2017

Boris Gurevich - Professor of Geophysics at Curtin University, Perth, Australia

About Boris Gurevich

Boris Gurevich obtained his Diploma (Russian equivalent of MSc) at Lomonosov Moscow State University in 1981 and started his career at the Moscow Institute of Geosystems. His early work included numerical analysis of NMR signals, and application of pattern recognition software to direct detection of hydrocarbons from seismic reflection data. It is in the Institute of Geosystems that he first met Sergey L. Lopatnikov who inspired Boris’s interest in poroelasticity. This subject became Boris’s long term obsession. His first steps in this area were focused on quantification of dispersion and attenuation due to mesoscopic flow in thinly-layered poroelastic systems. This research formed the basis of Boris’s PhD thesis (1988).

In 1990s, after visiting research appointments at University of Karlsruhe (Germany), Birkbeck College and Elf Geoscience Research Centre (both in London), Boris joined the Geophysical Institute of Israel, where he combined his continued interest in poroelasticity with development and application of multifocusing imaging.

In 2001 Boris was appointed Professor of Geophysics at Curtin University, where his research expanded into a large variety of rock physics topics, such as effective stress laws, stress dependency of rock properties and solid/fluid layered systems. At the same time, he continued to work on the topic of wave-induced fluid flow, studying such systems as patchy saturation; flow between pores and fractures; squirt flow; and heavy oil rocks. He has also collaborated with colleagues who specialise in seismic data processing and analysis. This collaboration led to a number of interesting studies, such as development of new algorithms for estimation of azimuthal anisotropy from vertical seismic profiles, and modelling the seismic time-lapse response of CO2 injected into a reservoir rock.

Pathways or recipes for your success in becoming a well-known name in the rock physics community

There is no one pathway or recipe but there are several principles that I think have helped me in the course of my career:

We are standing on the shoulders of the giants. This may be a cliché but I really think insights you get from reading some old papers are indispensable. But even more crucial for me was inspiration I got from some amazing scientists, not necessarily working on the same topics. I have been lucky to have met a great number of such people, but in particular I would mention late Leonid Girshgorn (who inspired me to study geophysics in the first place), Sergey Goldin and Mike Schoenberg.

It is important to keep in mind that, to quote a maxim often attributed to Einstein, a theoretical model must be as simple as possible to explain the observations but not simpler. Using models more complex than necessary may involve interesting and intriguing math but is quite harmful. For instance some people try to formulate the seismic inverse problem using equations of dynamic poroelasticity. Even if we assume that all the geological formations can be adequately described by these equations (which is unlikely), this makes the problem even more ill-posed than the elastic inverse problem, and greatly increases the uncertainty of the result.

Also, a specific point that I owe to my supervisor, Sergey Lopatnikov. He taught me to always look for an analytical closed-form solution even where the result is easily obtained numerically. Analytical solutions may only exist in some limiting cases, but they provide insights that are hard to obtain from a table of numbers or even a line graph (which is always computed for particular parameter combinations).

Finally I should mention importance of clear scientific communication. I have always strived to write very detailed papers, and even when writing about complex theoretical arguments,give lots of intuitive explanations. I am sure I have not always succeeded, but I think it is very important to appeal to a general geophysical audience rather than niche experts…

Challenges you see in taking rock physics to the next level

The following challenges are close to my heart

    • Connecting theoretical advances in rock physics with lab measurements and field observations. Over the last 70 years the poroelasticity community has developed a range of very sophisticated theoretical models, but their application in the industry and even experimental validation is rather limited. For instance, except in a few special situations such as gas chimneys or heavy oil, we still do not understand the physical reasons behind seismic attenuation in the sedimentary crust. There are a number of reasons for this, especially the narrow frequency band of seismic measurements and the frequency / scale relationship that make it impossible to explore the frequency dependence of rock properties without changing the size of the measured volume. But recent advances in laboratory measurements make it possible to explore the frequency dependency of elastic properties of the same sample and we need to seize this opportunity to connect theory at least with lab measurements.
    • With a few notable exceptions, rock physics has not kept pace with the oil and gas shale revolution. We need to fill this gap or will be left on the sidelines.
    • Rock physics theory is grounded in the fundamental principles of physics and mechanics. This is all very good, but we all know these models have way too many parameters to be useful for geophysical inversion. In my view, this parameter space can be considerably reduced by relating the rock physics models to the processes that created these rocks in the first place. Linking rock physics to geology, is in my view, one of the grand challenges for our community in the 21st century.

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

    • Look around. Don’t just focus on your narrow subject. Key to many problems in rock physics lie in other fields such as materials science, mechanics of composite materials, scattering theory, ocean acoustics, soil and rock mechanics. Many insights can be gained from interaction with experts in geology, seismic imaging, petroleum engineering and earthquake seismology.
    • At some point in my early career I read in Physics Today some advice from an accomplished physicist to junior colleagues and students: don’t just focus on minimally publishable results; try to tackle really important and challenging problems. This sounded great and inspirational but how do you get there if you don’t know where to start (and often lack the big picture to know what problems are really important)? I guess in the hindsight you do it step by step. You may be making small steps but they are directed towards a bigger goal.
    • For an applied field like exploration geophysics the above principle translates into tackling problems that are relevant to our industry. Our models might not be applicable tomorrow but thinking about potential applications in the future can help guide your research direction.
    • Don’t focus on the most fashionable topic of the day. This may look attractive but unless you are a genius it will be hard to make tangible progress, at least at the start. Try to find a topic that you feel is important but does not attract the attention it deserves.

We thank Boris for his continuous contributions to the rock physics community