The members and officers of the SPWLA Tulsa Chapter are proud to revive one of the founding chapters of this prestigious International Society. Please join us as we continue to promote and advance the science of formation evaluation.
Due to Concerns over Covid19 the Tulsa SPWLA Chapter is going to a Virtual Format for the Fall 2020 Chapter Meetings / Presentations.
The Tulsa SPWLA Chapter thanks the University of Tulsa for its hospitality in hosting our Luncheon Meetings for the 2019 / 2020 season and we especially appreciate the efforts of Buford Pollett, J.D., Genave King Rogers Assistant Professor of Energy Law and Commerce without who's efforts our meeting would not have been possible.
Tulsa SPWLA Chapter - Virtual Meeting
January 20, 2021 - 11:30 am to 12:30 pm
A Link to the Webinar will be attached to the email announcement for this Presentation
Electrical Properties of Shales
Mewbourne School of Petroleum and Geological Engineering
University of Oklahoma
The determination of water saturation based on electrical resistivity logs relies on knowing the electrical properties of the reservoir rocks. However, measurements of these electrical properties for unconventional shale reservoirs are scarce in the literature. This scarcity increases uncertainties of water saturation estimates and prevents reliable hydrocarbon reserves estimations.
To improve water saturation estimates and understand the factors controlling electrical properties such as the Archie cementation exponent (m) in shales, we measured the electrical resistivity of 95 brine saturated unconventional shale samples collected from the immature, oil and gas windows of the Woodford and Wolfcamp shales. These samples were characterized by measurements of petrophysical properties such as TOC, mineralogy, and crushed rock porosity. In addition to these measurements, we have also modeled the flow of electrical current through porous media.
Measurements of resistivity on the brine saturated samples revealed that maturity exerts a minor control on the cementation exponent. The linear relationship between TOC and cementation exponent allows the computation of cementation with the knowledge of TOC.
Ali Tinni is a faculty in the Petroleum Engineering Department of the University of Oklahoma. He teaches petrophysics and reservoir engineering courses. His current research interests include fluid flow and storage as well as EOR in unconventional reservoirs. He holds Master’s and PhD degree in Petroleum Engineering from the University of Oklahoma.
Characterization of the Caney Shale, Southern Oklahoma
By Yulun Wang
Wang, Yulun; Cains, Julie; Cox, Ian; Puckette, Jim; Grammer, Mike; Pashin, Jack; Wethington, Conn and Cory Hart
Boone Pickens School of Geology, Oklahoma State University
The Meramecian-Chesterian Caney Shale is partially time-equivalent to the highly productive Fayetteville and Barnett shales, but Caney production is sparse and unpredictable. In the Ardmore and Marietta basins, the Caney Shale is over 215 m (700 feet) thick, rich in total organic carbon and in the oil window. To assess Caney production potential, depositional processes and facies must be interpreted within a sequence stratigraphic framework. Other important factors are the 3D pore architecture, petrophysical and geomechanical properties and natural fractures. Preliminary results indicate that the Caney Shale contains a variety of mixed carbonate-siliciclastic facies established based upon mineralogy, rock fabric, grain texture and dominant sedimentary and biogenic structures. Siliciclastic-rich facies are mainly massive-bedded mudstone and calcareous to muddy siltstone, burrowed to bioturbated silty mudstone, and bioturbated siltstone. Carbonate-rich rocks include packstone-grainstone, laminated carbonate and silty mudstone, packstone-rudstone, and dolomitic facies. These facies are associated with a variety of depositional processes, such as low energy background sedimentation of the siliciclastic-rich facies and high energy event deposition (e.g., turbidity current, debris flow, storms/longshore currents) of the carbonate-rich facies. Based on these observations, Caney sediments in southern Oklahoma were likely deposited on a gently dipping slope or ramp environment where lower energy deposits were episodically interrupted by high energy deposits sourced from shallower water carbonates. Vertically, facies show variable patterns, some occur repetitively, whereas others are concentrated in certain intervals or scattered throughout the section. These patterns reflect cyclic, systematic shifts in depositional processes across this region and critical for constructing a regional stratigraphic framework and mapping facies and reservoir distribution. Visible pores are not evident in core or thin sections and scanning electron microscopy reveals that pore types appear to reflect different rock fabrics. Interparticle pores dominate calcareous siltstone and carbonate-rich facies, whereas organic-rich mudstone contains a variety of pore types but is dominated by organic matter pores. On-going work includes detailed characterization of pore geometry and distribution and their relationship to rock types, and the relationships among sonic velocity, pore systems architecture, and permeability.
Yulun Wang is a post-doctoral researcher in the Boone Pickens School of Geology of the Oklahoma State University, focusing on the integrated reservoir characterization of the Caney Shale play in southern Oklahoma. Yulun was born in Panjin, which is a city powered by a major oil field in northeastern China. Driven by his curiosity about the pumpjacks in his backyard, Yulun earned his Bachelor’s degree in Petroleum Geology from Jilin University in China. He later moved to the University of Tulsa and worked with Dr. Robert W. Scott on the Lower Cretaceous shallow-marine carbonate strata in southwest Texas, which earned him a M.S. degree in Geology. Learning about the boom of unconventional resource plays at that time, Yulun became interested in characterizing these reservoirs and moved to the Boone Pickens School of Geology in the Oklahoma State University to pursue a Ph.D. degree. For his dissertation research which was mentored by Dr. G. Michael Grammer, Yulun focused on characterizing the sequence stratigraphic framework, natural fracture system, and rock mechanical properties of the unconventional “Mississippian Limestone”/STACK play in north-central Oklahoma, USA. Benefited from collaborations with industrial sponsors and the University of Miami (CSL – Center for Carbonate Research), Yulun also worked on the Wolfcamp Formation in the Permian Basin and the Vaca Muerta Formation in Argentina. Yulun was the recipient of the AAPG Grants-in-aid Award (2016, 2017) and the Oklahoma Geological Foundation Davis Geology Fellowship (2015), and was a Geology Intern at Tiptop Oil and Gas (Sinopec) (Oklahoma City, 2016).
The Tulsa Chapter appreciates Dick Merkel's October informative presentation and his continued work on the petrophysical properties of Clays.
Electrical Properties of Clays
Clay electrical properties are more complex than simply the clay diagenesis or clay morphology because the clay fabric makes its resistivity a tensor. Even before three dimensional resistivity tools were developed, tensor properties of clays could be observed with the difference between the vertical vs. horizontal wells and/or between the responses between induction vs. laterolog measurements. Modern NMR and dielectric tools and processing allows us to determine clay bound water directly. As a result, in many cases we now can separate out clay electrical properties from the response of the reservoir rock matrix. This knowledge limits the shaly sand petrophysical models that are numerically stable with these measured log electrical properties of clays.
Analysis of XRD data to determine the clay bound water volume is shown to verify NMR and dielectric VCBW inversions and can be used to calibrate deterministic clay volume models. Examples in conventional and unconventional reservoirs in the Rocky Mountains are shown with various combinations of triple combo, NMR, and dielectric logs combined with XRD core measurements. This type of analysis helps in determining free water and reservoir wettability both of which impact reservoir reserves, recoverability, and economics.
Dick Merkel is President of Denver Petrophysics LLC, which is a consulting firm dedicated to developing logging analytical techniques for petrophysical models tied to core, completion, and production data in complex reservoirs. Previously, he worked at Encana and Newfield where he worked on teams that developed reservoir models for conventional and unconventional oil and gas reservoirs in the Rocky Mountains. Prior to its closing in 2000, he was a Senior Technical Consultant at Marathon Oil Company’s Petroleum Technology Center in Littleton, CO where he worked on evaluating new logging tools and technology, and developing techniques for their application in Marathon’s reservoirs worldwide. For the past thirty years, the emphasis of his work has been on the rock physics of NMR and dielectric log and core measurements and their interpretation. Dick holds a BS in physics from St. Lawrence University and a MS and Ph.D. in geophysics from Penn State. He is a past president of SPWLA, the SPWLA Foundation, and DWLS, and is currently a member of SPWLA, SPE, and SCA.
We wish to Thank Chelsea Newgord for her excellent Presentation during our September Virtual Meeting
A New Workflow for Joint Interpretation of Electrical Resistivity and NMR Measurements to Simultaneously Estimate Wettability and Water Saturation
Chelsea Newgord, Artur Posenato Garcia, and Zoya Heidari
The University of Texas at Austin
Wettability of rocks can be assessed from interpretation of borehole geophysical measurements such as electrical resistivity and Nuclear Magnetic Resonance (NMR). These wettability models often require additional inputs (e.g., water saturation, porosity, and pore-geometry-related parameters), which are difficult to obtain independently. Consequently, a multi-physics workflow that integrates resistivity and NMR measurements can reduce the number of input parameters, resulting in a more accurate and robust wettability assessment. The objectives of this work are (i) to introduce the workflow for joint interpretation of resistivity and NMR measurements to simultaneously estimate wettability and water saturation, and (ii) to verify the reliability of estimates of wettability and water saturation by comparison to experimentally measured contact angles, Amott Indices, and gravimetrically assessed water saturation.
The new workflow for assessing wettability and water saturation combines non-linear resistivity- and NMR-based rock physics models. The inputs to the resistivity-based wettability model include the resistivity of the rock-fluid system and brine, porosity, and pore-geometry-related parameters. The NMR-based wettability model requires the transverse (T2) responses of the rock-fluid system, of the saturating fluids, and of water-wet water-saturated and oil-wet oil-saturated rocks. To verify the reliability of the new integrated workflow, we perform resistivity and NMR measurements on core samples from different rock types, covering a range of wettability and water saturation levels. These measurements are inputs to the non-linear models, which are simultaneously solved to estimate wettability and water saturation for each core sample. We verify the reliability of wettability estimates by comparison to the Amott Index and contact angle measurements, and the water saturation estimates by comparison to the gravimetrically measured water saturation.
We successfully verified the reliability of the new method for joint interpretation of resistivity and NMR measurements to estimate wettability and water saturation of limestone and sandstone core samples. For water saturation levels ranging from irreducible water saturation to residual oil saturation, we observed an average relative error of 11% between the gravimetrically assessed and the model-estimated water saturation. It is challenging to estimate water saturation in rocks with multi-modal pore-size distribution uniquely from the interpretation of NMR measurements. The introduced integrated workflow improved the accuracy of water saturation estimates in rocks with complex pore structure. For the wettability ranging from oil-wet to water-wet, we observed an average absolute difference of 0.15 between the experimentally measured Amott Index and the model-estimated wettability. These model-estimated wettability values were also consistent with the contact angle measurements. It should be noted that the new workflow relies on physically-meaningful and measurable parameters, which minimizes calibration efforts. Furthermore, the multi-physics workflow eliminates the non-uniqueness associated with wettability and water saturation estimates obtained from independent interpretation of NMR and resistivity measurements.
Chelsea Newgord recently received her MS in petroleum engineering from The University of Texas at Austin. She currently works in the Formation Evaluation group at ExxonMobil in Houston. Previously, she worked as a reservoir geophysicist at Sigma Cubed Integrated Reservoir Services in Denver from 2012–2017. She holds a BS degree (2012) in geophysical engineering from Colorado School of Mines, with minors in geology and public affairs. She was designated as a Distinguished Speaker for 2018–2019 and 2019–2020 by SPWLA. She is a member of SPWLA, SPE, and SEG. Her research interests include core analysis, formation evaluation, and multi-disciplinary reservoir characterization.
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