The 22nd RPI for March-April 2019

Mark G. Kittridge - Petrophysical Consultant, Occidental Oil & Gas Corporation

Founder and Principal Petroleum Engineer, MUREX Petrophysics & Rock Physics, LLC.

About Mark G. Kittridge

Mark Kittridge is currently a Petrophysical Consultant with Occidental Oil & Gas Corporation, as well as Founder and Principal Petroleum Engineer at MUREX Petrophysics & Rock Physics, LLC. He earned both BSc and Professional degrees in Geological Engineering from the Colorado School of Mines (1986) and then a MSc in Petroleum Engineering from The University of Texas at Austin (1988). He spent his career primarily in large integrated oil & gas companies, never holding a title of ‘rock physicist’ or ‘researcher’, working at the E&P coal face as a Petrophysical Engineer (1988 – 2010), applying the sound fundamentals instilled by Shell. The early years at Shell taught me how to solve practical problems, using multi-scale data, in both mature (brownfield) assets, including tertiary (CO2) recovery projects, as well as active primary (re-)development (greenfield) assets, both onshore and offshore. I learned that data gathering costs money and must add value, and integrated interpretive products that reached beyond the wellbore were sought after by many of my colleagues.

In 1998 I had an opportunity to start looking at well data in a large GoM deepwater producing asset, where I was told there was an issue with geophysical well ties. The manager who brought me this problem also mentioned “… the geophysicist says the problem has nothing to do with the well (log) data …”. And so this chance opportunity put me on the path to a future in seismic rock physics. I found that the attention to petrophysical detail learned early in my career paid dividends as I tried to divine rock and fluid properties information relevant to the geophysicist prospecting with a varied collection of seismic attributes. For the remainder of my Shell career, I was fortunate to work with an incredible team of researchers on truly integrated seismic (attribute) interpretation problems around the globe, largely focused on deepwater siliciclastic targets, but also some carbonate reservoirs. In 2006 I was named Principal Technical Expert (PTE) for QI Petrophysics, and held that role until I left Shell in 2010. Following Shell, I spent time at ConocoPhillips, Ikon Science, and Hess in both technical leadership and individual contributor roles before starting my current position (2018) with Oxy.

I have been able to publish on a variety of topics in SPE (Formation Evaluation) and in Interpretation, and have contributed conference papers in SEG, SPE, EAGE, and SPWLA. In addition to those papers in print, there are a variety of presentations made along the way, most notably in SEG post-convention workshops. I have also been involved with delivering workshops and conferences for SEG (chaired the 2008 Summer Research Workshop), SPE (2009 Advanced Technology Workshop), and SPWLA (research workshops, technology committee 2015-present). I was named an SPWLA Distinguished Speaker (2014-15) and was awarded the SPWLA Distinguished Technical Achievement award in 2017. My primary interests are in the areas of seismic petrophysics, rock and fluid physics model development, multi-scale and multi-physics data integration, and (most recently) geomechanics for unconventional reservoirs. I have also been delivering a 1-day “Petrophysics Meets Geophysics” workshop for SPWLA during the Annual Symposium.

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

I expect that, when compared to the previous RPI’s collected here, my path to (any?) notoriety in rock physics is largely attributable to mentors along the way, a passion for problem solving at the intersection of geology and petroleum engineering, and good fortune (i.e. luck). Growing up along the front range of the Rocky Mountains outside Denver, Colorado, I developed a strong interest in geology, and in middle school met my first mentor (Mrs. Berrong) in Earth Science class. Her weekly quizzes provided motivation, played to my competitive nature, and I earned an invite to the spring field trip, where I was introduced to the famous I-70 geology outside Golden. It was then I knew I was going to work with rocks in the oilfield. Years later, in my last semester at The School of Mines, another significant mentor (Dr. Craig Van Kirk) was instrumental in my placement for graduate school, and assured me that petroleum engineering was the natural next step for me. And in the final act, I landed at The University of Texas at Austin, in a brand new Petroleum Engineering building (1986), and was taken in by two more outstanding thinkers and mentors, Dr. Larry Lake, and Mr. F. Jerry Lucia, who was then working at the BEG. I spent two glorious years in Austin and on the slopes of the Algerita Escarpment, realizing that Dr. Van Kirk was right: there was a natural intersection where geology and (petroleum) engineering intersect. And the good fortune? In addition to the amazing mentors, oil was selling for under $10/bbl in May, 1986 when I left Mines.

Shell, and fortunate timing, then provided the formative time that gave me the opportunity to develop skills in rock physics, while trying to develop and deploy novel Seismic Petrophysics workflow(s). Absolutely critical to my ability to operate at this new intersection with (quantitative) geophysics was my training as an engineer, and the years of operational experience in Petrophysics. I learned that careful attention to detail(s), core-based measurements, model calibration, and model transport – all common to Petrophysics – were equally applicable and, perhaps even more relevant, in rock physics and quantitative interpretation. The geophysicists in the team came to appreciate the time and effort spent to carefully work the well data, agonize over the semantics of reservoir fluid type(s), worry about the reservoir petrophysics inputs to fluid replacement, and question the veracity of every measured shear log. In the end, we developed a series of sequential, but always iterative, Seismic Petrophysics workflows that I believe are repeatable and globally applicable. They are grounded in geology, and recognize that good rock physics should be based on real rocks, and geologic characteristics amenable to model transport using well-based data. In my experience, we will always have vastly more well-derived rock physics data than lab-measured rock properties data. Petrophysicists willing to carefully QC and make up (sorry, ‘forward model’) shear log(s), take a deliberate approach to the application of fluid replacement modelling using robust reservoir petrophysics inputs, and develop geologically-sensible rock physics models will always be in demand by the QI geophysical community.

There are several things that I have done which I believe are useful, and hope will continue to find application in Seismic Petrophysics. I have shown the utility of a dry-rock modulus approach to modelling the elastic properties of conventional reservoir rocks, and developed a specific model for quartz-dominated siliciclastic reservoir rocks that continues to perform very well in global studies. This approach has also helped bring attention to the importance of compositional variability in siliciclastic reservoir rocks, trying to move beyond the original emphasis on ‘clay’ content as the primary variable perturbing velocity-porosity behavior. Dry-rock modulus diagnostics are also now a recognized component of fluid replacement modelling, and a means to robust QC and composition-based oversight of the fluid substitution workflow. Following from the early work in clastics, I have also tried to bring some focus, and a workflow, to evaluating the potential role of pore shape(s) in conventional carbonate reservoir rocks. Results from this work show that progress and insights come first by abandoning the fatuous view that Wyllie and his time average is the starting point for pore shape characterization in carbonates. The role of pore shape(s) on dry-rock moduli are then the final step in a careful evaluation that recognizes mineral-specific properties and use model(s) that actually account for pore shape.

Challenges you see in taking rock physics to the next level

In 1992, Blangy made the following statement: “The seismic amplitude information is rich yet goes mostly unused … and I believe that petrophysics appears to have been the ‘weak link’ in quantitative seismic lithology interpretation.” (emphasis from original) And today, nearly 30 years later, I would agree, but qualify his view by saying that today we still miss the opportunity for pragmatic rock physics built on multi-scale data derived from the deliberate application of quantitative seismic petrophysics workflows. Too often, what passes for rock physics analyses are a collection of cross-plots, made using original raw well log digi’s of data, painted on a backdrop of model recipes, commonly selected because ‘they are in the handbook’, or applied because ’those are what are available in the software’. Selecting a ‘famous’ (named) model recipe to match well data, where for example a ‘quartz’ default was applied during analysis and the reservoir rock is a lithic arkose (Folk), yielding dry-rock properties (moduli, Poisson ratio) incompatible with quartz, but matched with physically unrealistic or unrealizable model parameters, is not rock physics. Real rational rock physics should aspire to be a key element of seismic petrophysics (workflows), where we adhere to “The purposeful application of rock physics theory, as calibrated by laboratory and well measurements, to the interpretation of seismic data.” (Pennington, 1997). In this manner, the seismic petrophysics workflows deliver rock physics results that are truly data-driven, are amenable to integration of both local and geologically-sensible (global) analog data, and the model(s) applied are selected based on local geology, with an understanding of both the importance and sensitivity of key model parameter(s). In so doing, I believe that we have the opportunity to fully address Blangy’s challenge to the petrophysical (and engineering) community. The challenge is to engage the individual and demand his/her active participation in the deliberate application of the workflow. Nate Silver, writing in The Signal and the Noise, reminds us “Data-driven predictions can succeed – and they can fail. It is when we deny our role in the process that the odds of failure rise. Before we demand more of our data, we need to demand more of ourselves.

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

Find what you are passionate about, and work passionately every day at what you do. Always be willing to take on a new role, and embrace the natural evolution in your career and skills development. Mentors will be around you – find them, and learn from them every day. Recognize that every career path is the result of some luck, and the intersection of hard work and personal determination. It is very difficult to script an entire future or career path – look at each assignment or role as an opportunity on an evolutionary path, learn, and prepare for the next step(s) in your career.

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

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