The 4th RPI for March-April 2016

Jorg Herwanger - Vice President of Special Projects and Principal Geoscientist at Ikon Science in London, UK

About Jorg Herwanger

When I started to study Geophysics, I knew one thing for certain: “I will not work in the Oil industry”. This was just after the Exxon Valdez oil spill and at the onset of the decommissioning debate of the Brent Spar. Big Oil was evil. Geophysics to me was all about earthquakes and volcanoes, and I saw myself in the tradition of the great explorers scaling volcanoes in the Andes and diving into the Mariana trench in a submarine. If this was to be the case, I should have chosen my University more carefully, as I started to study at Clausthal University.

Clausthal University is a small college in the Harz Mountains, the eponymous location for the Hercynian Orogeny. The college has a proud mining past and a focus on applied sciences, with one of the proudest inventions being the wire rope to replace hemp ropes and metal chains in mining. No time for big picture Geodynamics research here! When I had to choose a topic for a Diplomarbeit (similar to a 1 year Masters project), I chose archaeological surveying which had become a bit of a hot topic. There was the promise of decimetre-scale scans of the subsurface using radar technology, instead of the tens-of-meter scale resolution of seismic data. Archaeology promised exciting opportunities to see roman and mediaeval artefacts scanning the Earths subsurface using geophysical techniques. The Swiss Federal Institute of Technology in Zurich (ETHZ) accepted me as an exchange student for the project. I ended up building a wooden cart to mount a Caesium magnetometer for constant terrain clearance, acquiring data from mediaeval pit houses and a Roman Garrison, and developing an inversion technique to reconstruct the shape of the pit houses. I learned a couple of things: the value of technicians in practical matters such as building a wooden cart; that inversion is a general, powerful and mathematical process; and that the Swiss railway runs on 16 2/3 Hz creating an electromagnetic field around the powerlines which is aliased when sampled at 0.1 seconds with a magnetometer. At ETHZ I also experienced generous funding for the workgroup coupled to a wise fiscal spending regime. I discovered that sufficient money is an excellent platform for doing good and worthwhile Science. Having the mountains close by allowed me to skive off the odd mid-week day for mountaineering in complete solitude. I had a great time.

During my career in the Oil industry so far, I held positions in research, worked as a consultant and assisted software sales and deployment. I believe this combination forced me to balance my views on what is required in our industry to make progress. All roles revolved around Seismic Geomechanics. As a researcher, I tried to follow what was true and pure, only to find out that as a consulting solution this may not work, solve the issue in a timeframe that is acceptable, or indeed that the data requirements were such that a specific method may not be applicable. When assisting software roll-outs, I additionally learned that most geoscientist work against very tight deadlines. In these circumstances, the true and pure solution moves even further into the future. I learned that progress needs to occur along a number of different vectors simultaneously. It is important to develop new theoretical understanding and new concepts. To make them work in practice, the new concept needs to be shown to solve a problem faster or better, simultaneously with enabling a large user base to apply and understand the new technique.

One of my colleagues put the adage “Good, fast, cheap – choose two” into the footer of his email. The reality of the current work environment requires a constant rebalancing of quality of work, depth of investigation, speed of execution, and a host of other commercial considerations. Under these circumstances, finding time to keep an inquisitive mind can be a challenge. I believe it is a challenge worth taking on. The reward is personal satisfaction.

In my current role, I am pursuing a number of goals. Firstly, I am heading the Special Projects Team at Ikon Science. My team and I carry out 3D and 4D geomechanical consulting and pilot projects using a novel fully coupled geomechanics and flow simulator. Secondly, I am working closely with the development team of the simulator as well as oil-company clients to ensure that the implemented technology is not only dazzling, but also useful in day-to-day work. Even though my main tasks revolve around 3D and 4D geomechanical simulations, I am acutely aware of the importance of high quality input data and models. To ensure quality of mechanical property models, pore pressure models and calibration data in the simulations, I work in collaboration with the consulting teams in Ikon Science and asset teams with clients that specialize in pore pressure analysis, rock physics, well-centric geomechanics and image log interpretation, model building as well as reservoir engineering and simulation.

To stay connected with the wider geoscience community, I am an active member of EAGE, PESGB, SEG and SPE. I served as an EAGE Distinguished Lecturer from 2007-2009, EAGE Education Tour (EET-V) Lecturer in 2011-2012, and I am a member of the EAGE Education Committee. For the EET-V, I wrote the eponymous book on “Seismic Geomechanics”.

Inversion processes had a great allure to me, and I was very pleased when I had the opportunity to earn a PhD at Imperial College, London to work on inversion of electric and seismic crosswell data. I carried out experiments at a fractured rock test site in Cornwall that had previously been used for hydrological studies of fluid flow in fractured rock. The aim of my work was to investigate whether geophysical techniques could be used to identify and characterize fracture zones. The test-site proved to have extraordinarily anisotropic rocks, caused by a combination of finely laminated mudstones and fractures. Anisotropic seismic traveltime tomography was already well developed and I could build on the wealth of existing knowledge and research software at Imperial. Evaluating the electric measurements proved more of an issue. At the time, we did not understand whether anisotropy of electric resistivity could be resolved by using tomographic techniques, and I decided that the best way to find out was by trying. The answer was that resistivity anisotropy was an order of magnitude larger than the seismic anisotropy, that neglecting anisotropy in the inversion process caused serious artefacts, and that zones of seismic anisotropy were also electrically anisotropic. I never figured out conclusively whether the observed anisotropy was pre-dominantly caused by fractures, by fine-scale layering or by aligned anisotropic minerals.

I am reminded of this conundrum when following the current debate on azimuthal seismic anisotropy for reservoir characterization, where the question is whether the root cause of anisotropy is a difference in horizontal principal stresses or steeply inclined aligned fractures. What amuses me in this discussion is how much easier it is to pose the fundamental question than to solve it. Since the root causes of anisotropy and ways to determine anisotropy in the subsurface are important questions, every contribution is proffered as the solution and a great amount of posturing ensues.

During my PhD, I never managed to complete the anisotropic resistivity tomography work satisfactorily. I therefore found a grant to finish the work as a PostDoc, against the explicit advice of my PhD advisor. His words of wisdom were that the “oil industry may forgive you doing a PhD, it will not forgive you doing a PostDoc”, implying that it gets harder to find a job after doing a PhD and nearly impossible after going down an academic route first. Good thing that I never planned to work in the Oil industry. Life proved me wrong, and I did join numerous colleagues as a geophysicist into the Oil industry. And my supervisor was right – finding a first job was hard and I got a lot of needless questions about my age and lack of practical experience when applying. On the other hand, the knowledge I gained during that time on second rank (resistivity) tensors came in very handy later when I started working with second rank stress and strain tensors!

Your pathway for success in becoming a well known name in the rock physics community

If I had only three words to summarize why I am reasonably well known in the field, I’d choose luck, perseverance and curiosity.

Luck came to me in various guises. Firstly, I got lucky with projects. On the first day in my first job in the oil and gas industry, I was given a plot of shear-wave splitting observations in the shallow overburden superimposed on the subsidence bowl above the Valhall field. The fast shear waves were very clearly aligned with the contour lines of the observed subsidence. I was told to go away and find an explanation. I figured I had to learn some geomechanics to understand the subsidence bowl. Studying rock physics models would allow me to relate the changes in stress/strain during the formation of the subsidence bowl to velocity changes, which in turn could explain the observed shear-wave splitting. The ideas that I formed at the time are still at the core of my current work. The second bit of luck was having colleagues, both at Schlumberger and with clients, who were willing to share knowledge, bits of computer programmes, time, their address book and access to data. I don’t want to single out any colleague in particular – many of them will appear as co-authors in publications or will be mentioned in the acknowledgements. The third bit of luck was having a string of managers who gave me the freedom necessary to develop ideas, concepts and products that did not always follow a GANTT chart or a product life-cycle management programme. These managers opened doors at the right moment and took on battles on my behalf that I could not have fought myself. Finally, on the point of luck, I hasten to mention that the harder you work, the luckier you get.

Perseverance is perhaps more straightforward than luck. Some projects take a lot of willpower and cunning to be successful in the end. In my experience, it is important to find a theme and then play variations on the theme. Let me explain by retracing my career path highlighting some of the variations on a theme. In my case the theme is “Seismic Geomechanics”. The excellent multi-component seismic product development group in which I was first developing ideas on the link between seismic observations and geomechanical models disappeared due to a slowdown in multicomponent seismic business. I therefore had to park my work on shear-wave data, my first passion. Instead I started to look more at time-lapse seismic data and its relationship with production induced geomechanical effects. During this period I started to think more about the process of building 3D geomechanical property models, and wondered why seismic inversion models were not used more often in this process. So the next variation on my theme became the accurate calculation of 3D mechanical property models, especially the importance of facies models in the construction of mechanical property models. To summarize the secret to my success here was “to stick to my guns”, persevering in the pursuit of my ideas while accepting to step sideways when necessary.

Curiosity is arguably the foundation necessary for luck and perseverance to flourish. Without curiosity perseverance can easily turn into a pointless slog, and luck needs to be tempted to attach itself to you. Applied geophysics is a discipline in which the underpinning physical principles are very well understood. In order to do innovative work it is essential to tease out the missing links and new applications. This works by being curious, and by taking perceived wisdom with a pinch of salt.

Challenges you see in moving rock physics to the next level 

A particular area where I see potential for a big step forward is to extend the realm of rock-physics into mechanical properties. This journey has of course already started, but there is a lot of room for improvement. One example is the determination of strength properties via rock-physics templates. There are common underlying mechanisms that influence both elastic wave speeds and rock strength. For example, stronger cement and an increase in number density of grain-to-grain contacts result in both faster and stronger rock. To predict velocities, we have a fairly comprehensive set of rock-physics equations, whereas for strength properties the standard across the industry is still to use correlations, i.e. an equation that does not link back to the underlying physics of the observed relationship. I believe that this will change over the next 5-10 years.

A related and harder question is to formulate rock-physics models that define the stress-strain relationships beyond elastic deformation. There is of course a large body of literature formulating stress-strain relationships for plastic and visco-plastic deformation. This body of literature has, however, its own set of parameters and notation. These parameters are not yet linked conclusively to mineral composition, porosity, cementation, and other petro-physical quantities typically used in rock-physics models.

I would also like to take this opportunity to point out a non-technical field where I see a future challenge for rock-physics. In the recent past, I have reviewed an increasing amount of papers, both for conference and journal publications, where rock-physics was applied in a formulaic manner. In these manuscripts the outputs from one process form the input to the next process without the necessary critical thought as to whether (i) the process applies and (ii) the input data warrant the application of the process. The challenge I see in taking rock-physics forward is the following: How do we, as a rock-physics community, manage to create a large and informed user base, and avoid the creation of “rock-physics borgs”?

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

This is a hard question, as the answer depends very much on the personality of the early career scientist. Amongst my many colleagues and friends there are no two career paths that are the same.

Some of my most clever friends have started their career as field engineers, and thus developed a deep practical knowledge that informs their later work, focussed on practical solutions. Others have started in software support. This has taken them into client offices around the world and forced exposure to a large amount of different geological settings and client mindsets, again benefitting their later careers. And then there are my colleagues that have started as scientists. This is probably the minority, as very few companies have dedicated research departments.

As a general principle, I would say take opportunities when they come. Note that many opportunities can only be spotted as such in hindsight. Therefore be prepared to be surprised and don’t be afraid to take an assignment that does not really “make sense” at the onset. Throughout remain curious, engaged and cheerful. 

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