# The 18th RPI for July - August 2018

### Dario Grana - Associate Professor in the Department of Geology and Geophysics at the University of Wyoming

### About Dario Grana

Dario Grana is an associate professor in the Department of Geology and Geophysics at the University of Wyoming. He received a MS in Mathematics at University of Pavia (Italy) in 2005, a MS in Applied Mathematics at University of Milano Bicocca (Italy) in 2006, and a Ph.D. in Geophysics at Stanford University in 2013. He worked as a rock physicist for four years at Eni Exploration and Production in Milan. He joined the University of Wyoming in 2013. He is coauthor of the book ‘Seismic Reflections of Rock Properties’ with Dr. Jack Dvorkin (Stanford University) and Dr. Mario Gutierrez (Shell) published by Cambridge University Press in 2014 and he has published 27 papers in peer-reviewed journals. His paper with Ernesto Della Rossa (Eni) on Bayesian petrophysical inversion using Gaussian mixture models, received 180 citations since the publication in Geophysics in 2010.

He is the recipient of the 2017 EAGE Arie van Weelden Award, the 2016 SEG. Clarence Karcher Award, the 2015 Best Paper Award in Mathematical Geosciences, and the 2014 Eni Award for New Frontiers of Hydrocarbons, together with Dr. Tapan Mukerji, Dr. Gary Mavko and Dr. Jack Dvorkin (Stanford University). His main research areas of interests are rock physics, seismic reservoir characterization, geostatistics, data-assimilation, and inverse problems for subsurface modeling. In addition to his research activity, he teaches classes in rock physics and reservoir modeling to undergraduate and graduate students and he supervises a group of five MS and PhD students and postdocs. When he is not busy with one of these activities, he generally spends his time in the office playing with Matlab.

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

During the last semester of my Masters in Mathematics, in 2006, I received an offer for an internship at Eni Exploration and Production, in Italy. I have always dreamt a career in academia, but because of the limited number of academic positions, I decided to accept the internship offer. At Eni, I had the chance to learn the basic concepts of geophysics modeling and work on interesting ongoing research projects. I quickly realized that such position offered excellent opportunities to conduct high-level research and that I had the chance to apply my knowledge in mathematics, especially inverse theory, to practical problems in exploration and production. In 2007, I accepted a full-time position at Eni in the rock physics group. My research activity focused on statistical approaches to rock physics modeling and pore pressure prediction. I had the opportunity to work with senior geophysicists from Eni as well as to collaborate with researchers from Stanford University and NTNU. The results of these research projects were presented at the SEG and EAGE annual conferences and led to my first publication in Geophysics.

In 2010, I decided to move to Stanford to complete my Ph.D. in geophysics under the supervision of Dr. Gary Mavko, Dr. Tapan Mukerji, and Dr. Jack Dvorkin. During my Ph.D., I worked on geophysical inverse methods to integrate rock physics models in seismic reservoir characterization studies. I completed my PhD in 2013 and joined the University of Wyoming as an assistant professor in the Department of Geology and Geophysics. I currently work on a broader range of seismic reservoir characterization methods with the goal of improving the accuracy of static reservoir models and quantifying the uncertainty of the model predictions. Ongoing projects include stochastic inversion methods for petrophysical property estimation, integration of seismic and electromagnetic data, history matching of 4D seismic and production data for hydrocarbon reservoirs, as well as applications to carbon dioxide sequestration and geothermal studies.

### Challenges you see in taking rock physics to the next level

Rock physics concepts, measurements, and models are used in different disciplines, such as seismic inversion, time-lapse monitoring, and reservoir modeling. The physics relations that link rock and fluid properties to their elastic and electric response (for example, porosity-velocity or saturation-resistivity) as well as the models that describe the correlation between different petrophysical properties (porosity-permeability) have been widely investigated through extensive laboratory experiments and physics theories.

My research mostly focuses on the integration of rock physics models in seismic inversion and reservoir modeling to provide a set of quantitative tools for interpretation. There are several challenges in the application of rock physics models to reservoir geophysics problems, such as the different scale and resolution of well logs and seismic data, the spatial variability of the rock physics parameters and relations, and the uncertainty quantification in the rock physics predictions. The estimation of rock and fluid properties within the reservoir requires the application of rock physics relations to the elastic model obtained from seismic inversion. However, the results of seismic inversion are in time domain and at low resolution, whereas rock physics modes are based on well log data and core measurements; therefore, accurate upscaling methods are required to reconcile seismic inversion results and rock physics model predictions.

In general, rock physics models are calibrated at the well location and assumed to be valid for the entire reservoir, but relations and parameters are not necessarily spatially invariant; rock physics models with spatially dependent parameters are not commonly adopted in seismic reservoir characterization for the lack of spatial constraints, especially in exploration studies. Finally, a complete uncertainty quantification workflow to evaluate the uncertainty in the predictions of rock and fluid properties is still missing.

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

I believe that the achievements I reached in my career are the results of different factors: excellent mentors, a strong mathematical background, and a solid experience working with real data. In exploration geophysics, there are several opportunities to conduct research at a high level, in academia and in oil and gas companies. Research is becoming more and more interdisciplinary and researchers possess different backgrounds, such as geology, physics, mathematics, engineering, and computer science. Reservoir models are very complex; therefore, geophysicists must have a solid knowledge of geology as well as a strong background in mathematical/physical modeling, geophysical acquisition and processing, rock physics, geomechanics, and reservoir engineering methods, in order to build and interpret such models. In particular, with limited hydrocarbon resources, uncertainty quantification and stochastic modeling techniques are crucial tools to improve the current reservoir models, enhancing their predictive capability and preserving their geological meaning and features. In such interdisciplinary context, finding a unique, challenging, and relevant research opportunity might be hard for students and young scientists.

The choice of the research topic and its scientific questions is often more important than the methods and tools used to solve them. I was extremely lucky to work with extraordinary scientists all over the world, and I hope I will be able to provide my contribution in advising and mentoring the next generation of geoscientists.