Speaker: Dr. Roger M. Slatt & Zin Zhang
Topic: Advances in Understanding Woodford and Other Unconventional Resource Shales
The Institute of Reservoir Characterization (IRC) within the School of Geology and Geophysics at University of Oklahoma (OU) has been studying local unconventional resource shales for the past seven years through a consortium of major to independent companies (STACK-MERGE-SCOOP Consortium). Major emphasis has been on the Woodford Shale, but more recently has expanded into Sycamore and Meramec strata in outcrops, core, wells, and some 3D seismic reflection. During this time a standard workflow has evolved from its initial publication (Slatt et al., 2011) to its present integrated form (Fig. 1). Our workflow has placed major emphasis on studying the rocks (outcrop, core, cuttings) and applying our findings to the subsurface plays and exploration/development activities of drilling and seismic. We also focus on building our workflow using relatively inexpensive equipment in a cost-effective way.
Most of our examples in this paper relate to the Woodford. However, we also have had the opportunity from time to time of examining in varying detail most of the popular producing and potential economic resource shales in North America and some from international areas (China, Colombia, Venezuela, Tunisia, and Saudi Arabia), thus adding to our experience base. Detailed field studies are found principally in the various theses and dissertations that are referenced herein (for example: Amorocho, 2012; Chain, 2012; Killian, 2012; Slatt, and Rodriguez, 2012; Molinares, 2013; Serna-Bernal, 2013, Cardona,2014; McCullough, 2014; Tréanton, 2014; Ali, 2015; Becerra-Rondon, 2015; Bontempi, 2015; Hasbrook, 2015; Zou, and Slatt, 2015; Maynard, 2016; Turner, 2016 and Turner et al., 2016; Zhang, 2016; Ekwunife, 2017; Galvis, 2017 and 2018; Ghosh, 2017; Ghosh, et. al., 2018; Castro, 2018).
This paper is intended to summarize the methodology and instrumentation developed in IRC (irc.oucreate.com) for geological characterization of unconventional resource shales. Changes in our workflow since 2011 include addition of X-ray fluorescence spectroscopy (XRF)—-a powerful correlation and identification tool which has only gained significant application and appreciation over the past few years (Turner, 2016; Turner et. al, 2016), especially when combined with an easy to use, inexpensive ‘rebound hammer’ to estimate rock hardness (Becerra-Rondon, 2017). Institute students have completed shale characterization studies of 31 M.S./Ph.D. theses and dissertations, so we consider our workflow as a stable, routine, built upon a large amount of data, and a relatively inexpensive way to provide a realistic geological screening and geological modeling workflow, particularly for detecting ‘sweet spots’, favorable horizontal well landing zones, wellbore stability, fluid flow simulation, and volumetric analysis.
Advanced seismic techniques have been especially useful in detecting fracture intensity and azimuth. Using the Barnett Shale as an example, a attribute-based AVAz workflow was employed and validated using wide azimuth data. The seismic data is migrated into eight azimuths. Prestack structure-oriented filtering is applied to the seismic amplitude data for noise reduction. Spectral peak magnitude, envelope, and P-wave impedance inversion were computed on each azimuthally-limited seismic volume. Then, 2D-flattened computed attributes and seismic amplitude along picked horizons were extracted and input into the AVAz workflow. The results indicate intensity, orientation, and confidence of azimuthal anisotropy effects on seismic velocity and amplitude which can be referred to smaller scale vertical natural fracture.
Roger M. Slatt currently holds the Gungoll Family Chair in Petroleum Geology and Geophysics at the University of Oklahoma (OU) and is Director of the Institute of Reservoir Characterization. He was Director of the School of Geology and Geophysics and Eberly Family Chair Professor at University of Oklahoma from 2000-2006, and the Ward Chair Professor of Reservoir Characterization from 2007-10. He formerly was Head of the Department of Geology and Geological Engineering at Colorado School of Mines (1992-2000) and Director of the Rocky Mountain Region Petroleum Technology Transfer Council (1995-2000).
After receiving his Ph.D. in 1970 from the University of Alaska, he taught geology for 8 years at Memorial University of Newfoundland and Arizona State University. He then spent 14 years in the petroleum industry with Cities Service Research, ARCO Research, and ARCO International Oil and Gas. Co. before joining Colorado School of Mines in 1992. He has published over 100 papers and abstracts, and has made numerous presentations on the subjects of petroleum geology, reservoir geology, seismic and sequence stratigraphy, shallow marine and turbidite depositional systems, geology of shale, glacial and Pleistocene-Quaternary geology, and geochemical exploration. He sits on various professional society committees, has organized technical conferences for American Association of Petroleum Geologists (AAPG), and teaches short courses for industry and AAPG on the “Introduction to the petroleum geology of deep-water (turbidite) depositional systems” and on “Principles of geologic reservoir characterization”. He also offers a global, web-based course on “Introduction to geologic reservoir characterization” to people from many different countries. He has taught his two courses in many places in the U.S., as well as in many countries, including Colombia, Mexico, Indonesia, Malaysia, Australia, Angola, India, New Zealand, Scotland, and England.
While employed in the international oil and gas industry, he had the opportunity, as Director of Reservoir Evaluation, to study numerous oil and gas fields and exploration prospects worldwide, and to make recommendations to senior management for international investment. Many of Dr. Slatt’s publications have dealt with the subject of exploration for, and development of deepwater submarine fan (turbidite; basin floor fan) oil and gas reservoirs. He is considered an expert on deepwater submarine fan exploration and development, and has worked in both industry and as a consultant on many such reservoirs globally. In late 2006 he completed co-authoring a book titled: Introduction to the Petroleum Geology of Deepwater Settings, published by American Association of Petroleum Geologists. He also completed a book in late 2006 (and updated as 2nd edition in 2013) titled Stratigraphic Reservoir Characterization for Petroleum Geologists, Geophysicists, and Engineers, published by Elsevier. Also in 2006, he organized the 26th Annual Gulf Coast Assoc. Sedimentary Geologists (GCSSEPM) conference, titled Reservoir Characterization: Integrating Technology and Business Practices, and was chief editor of a CD book comprised of papers from that conference. Since 2002, he has taught a web-based course semi-annually for AAPG titled Introduction to Geologic Reservoir Characterization. In recent years, Dr. Slatt and a team of students and colleagues have developed a comprehensive program in unconventional gas shale geology.
In 1996 he received the AAPG Distinguished Service Award. In 1999 he was the Esso Australia Distinguished Lecturer in Petroleum Geology. In 2001-2, he was an AAPG Distinguished Lecturer, giving a presentation titled “Outcrop/behind outcrop characterization of deepwater (turbidite) petroleum reservoir analogs: why and how”. He offered the same presentation as an SPE Distinguished Lecturer in 2003. In 2003, he was awarded with AAPG Honorary Membership. In 2006 he received the AAPG Grover Murray Distinguished Educator Award. In 2007 he received the Society of Exploration Geophysicists (SEG) Special Commendation Award “in recognition of meritorious service rendered the scientific community, the earth sciences and exploration geophysics”. In 2011 he received the Jules Braunstein award for co-authoring the Best Poster at the AAPG Annual National Convention. The poster was titled Multiscale brittle-ductile couplets in unconventional gas shales: merging sequence stratigraphy and geomechanics. In addition to teaching, he currently manages a well-subscribed consortium of oil and gas industry companies on the geology of resource shales. In 2017, he was a co-author of the winning oral presentation Torres et.al., (2017) Identification of Potential Lacustrine Stratigraphic Intervals in the Woodford Shale, Oklahoma, Using MultiAttribute 3D Seismic Displays and a Supervised Neural Network at the AAPG Mid-Continent meeting in Oklahoma City.