Dr. Margaret A. Lessenger


Dr. Lessenger is a petrophysicist with broad experience in petroleum geology and geophysics. She has a proven track record of solving difficult petroleum exploration and production problems using creative and innovative approaches based on sound scientific and engineering principles. Ms. Lessenger specializes in unconventional resource petrophysics, integrated petrophysical data analytics, basin-scale sequence stratigraphy, sedimentology, basin analysis, petroleum system basin modeling, and stratigraphic simulation modeling.


2016 to Present - Petrophysicist - Rimrock Petrophysics and Analytics, LLC, Golden, Colorado, USA

  • Petrophysical consulting focusing on integrated analyses and analytics for petroleum exploration and development.

  • 2011 to 2015 - Petrophysicist - Newfield Exploration

  • Exploration and new ventures petrophysics utilizing core and log data for tight oil play development and petrophysical support for Uinta Basin Green River and Wasatch asset teams.
  • Lead petrophysicist for Greater Monument Butte Field, Uinta Basin. Integrated specialty logging and core analyses for petrophysical support for reservoir characterization, optimized field development and waterflood injectivity and down-spacing pilot. Ongoing petrophysical support for mulit-rig drilling program.
  • Developed new operations petrophysical model and worked with development team to implement a streamlined petrophysical workflow for optimized completions, waterflood pattern reviews and OOIP assessments. Created model to evaluate reservoir potential for both movable oil and water calibrated to single-zone tests, specialty logging data and core analyses.
  • Led team effort to understand fluid sensitivity of Uinta Green River reservoirs using core flood experiments, core NMR, and pore-scale imaging techniques. Results saved Newfield $5 million in completions costs in the first year, significantly reduced carbonate scale in newly completed wells and reduced formation damage.
  • Currently utilizing downhole NMR T1-T2 and T2D map and dielectric data, core NMR, USBM measurements, SARA, and pore-scale imaging (FEI/Lithicon) to better characterize variable wettability of reservoirs. Work is leading to a new understanding of how to interpret volumes of oil and water in micro- and macro- pore size fractions from downhole NMR and dielectric data. Results give new insights into a problematic producing reservoir unit.
  • Developed an eFacies model for triple-combo data that characterized reservoir rock quality and facilitated stratigraphic interpretation within complex lacustrine fluvial-deltaic system.
  • Developed a stratigraphic-based electrical property (m and n) model for the Greater Monument Butte Field saturation model based on analysis of dielectric data.
  • Mentored geologists, petrophysicts, engineers and geophysicists.
  • Initiated an experimental study of waterflood chemistry optimization for reservoirs with variable wettability for Newfield with Dr. Mohammad Piri, University of Wyoming.
  • Developed and coordinated ongoing standard and specialty logging and coring programs for field development and assessment of new plays.

  • 2006-2011 - Petrophysics - Williams Exploration and Production

  • Developed petrophysical models used by development geologists and completions engineers integrating open-hole logs, specialty logging and core analyses for improved OGIP and pay identification. Validated model using production results, production logs, zonal flowbacks and partial completions. (Piceance Basin)
  • Coordinated and analyzed routine and specialty core analyses for improved petrophysical models for tight gas and shale gas fields leading to better completion decisions. (Piceance and San Juan Basins).
  • Developed and applied an inverse model for shaly-sand Simmandoux models solving for electrical properties (Rw, 'm', 'n' and Rclay) as a function of stratigraphy and depositional facies. Validated results using core and specialty log data. This effort led to increased confidence in our petrophysical calculations for completions and OGIP determinations. (Piceance Basin)
  • Developed a specialty logging program to evaluate and calibrate the "Top of Gas" determination in multiple fields leading to increased optimization of EURs. (Piceance Basin)
  • Provided on-going petrophysical support for a multi-rig drilling program. (Piceance Basin)
  • Evaluated and developed a shale gas play leading to a multi-TCF addition to Williams Production portfolio. Developed play using shale petrophysical modeling, triple combo and specialty logs, core analyses, thin section and SEM analyses, stratigraphic correlations, interpretation of geochemical parameters, calculation of minimum horizontal stress profile for completions design, and estimation of OGIP. (Niobrara, San Juan Basin)

  • Petroleum Geology & Geophysics

  • Exploration experience in the Rocky Mountains and offshore Gulf of Mexico.
  • Correlated well logs and analyzed cores for high-resolution and basin-scale sequence Stratigraphic studies for domestic and international petroleum companies.
  • Proven and consistent prospect generator in the offshore Gulf of Mexico. Work led to a new field discovery for Superior Oil (Galveston Island Block 313; produced 22 bcf and 485 bbls condensate). Another prospect became a new field discovery for another company (South Timbalier Block 198; produced 82 bcf and 1376 bbls condensate).

  • 2000 - 2005
  • Senior Scientist, Platte River Associates, Inc., Boulder, Colorado

  • 1993 - 2000
  • Assistant Research Professor, Genetic Stratigraphy Research Group, Dept. of Geology & Geological Engineering, Colorado School of Mine

  • 09/1988 - 1993
  • Graduate Studies, Dept. of Geology & Geological Eng., Colorado School of Mines

  • 01/1990 - 06/1990
  • Research Consultant, Elf Aquitaine, Research Lab, Pau, France Stratigraphic modeling and field seminars.

  • 01/1986 - 09/1988
  • Graduate Studies, Dept. of Geophysics, Colorado School of Mines Research Assistant for Dr. Ed White and Dr. Frank Hadsell.

  • 12/1984 - 12/1985
  • Exploration Geophysicist, ARCO Exploration and Production, Denver, Colorado

  • 06/1982 - 11/1984
  • Explorationist, Superior Oil Company, the Woodlands, Texas

  • 06/1981 - 06/1982
  • Geophysicist, Superior Oil Company, Geoscience Lab, Houston, Texas


    Ph.D. Geology, Colorado School of Mines, Golden, CO, USA, 1993
              Dissertation: Forward and Inverse Simulation Models of Stratal Architecture
              and Facies Distributions in Marine Shelf to Coastal Plain Environments.

    M.S.   Geophysics, 1988, Colorado School of Mines
              Thesis: An Expert System to Evaluate Geologic Risk for Petroleum Exploration

    B.S.   Geophysical Engineering, 1981, Colorado School of Mines
              With Highest Scholastic Honors


    Lessenger, M., Merkel, R., Medina, R., Ramakrishna, S., Chen, S., Balliet, R., Xie, H., Bhattad, P., Carnerup, A., Knackstedt, M., 2015, Subsurface fluid characterization using downhole and core NMR T1T2 maps combined with pore-scale imaging techniques, 56th Annual SPWLA Symposium, July 18-22, 2015, and Petrophysics, v 56, no 4, p. 313-333.

    Lessenger, M., Merkel, R., Sullivan, B., and Burton, D., 2013, Application of dielectric and standard logging suites to characterize the stratigraphic and lithologic variations in Archie parameters within the Green River Formation of the Greater Monument Butte Field, Uinta Basin, Utah, USA, 54th Annual SPWLA Symposium, June 22-26, 2013.

    Lessenger, M., Sullivan, B., Woolf, K., and Burton, D., 2016, Fluid sensitivity analyses in tight sandstones - when rocks behave badly, 2015, AAPG Memoir 110: Imaging Unconventional Reservoir Pore Systems, (in press).

    Merkel, R. and Lessenger, M., 2014, Characterizing the oil reservoirs in the Uinta Basin, SPE 169510-MS Conference Paper.

    Merkel, R. and Lessenger, M., 2016, Advanced log interpretation in field development, 55th Annual SPWLA Symposium, June 25-29, 2016.

    Ramakrishna, S., Merkel, R., Balliet, R., Lessenger, M., 2013, Mineralogy, porosity, fluid property, and hydrocarbon determination of oil reservoirs of the Green River Formation in the Uinta Basin, Petrophysics, June, 2013. Also presented at the 53rd Annual SPWLA Symposium, June 16-20, 2012.

    10 other publications in the areas of stratigraphy, stratigraphic modeling, inverse modeling, seismic stratigraphy, and borehole geophysics.


    Cross, T.A., and Lessenger, M.A., Method of predicting three-dimensional stratigraphy using inverse optimization techniques, United States 6754588.

    Cross, T.A., and Lessenger, M.A., Method for predicting stratigraphy, stratigraphic simulation modeling, inverse modeling, and seismic stratigraphy, United States 6246963


    2016 SPWLA Distinguished Speaker

    Numerous professional oral papers and posters for the Society of Petrophysicists and Well Log Analysts, Society of Petroleum Engineers, American Association of Petroleum Geologists, Society of Exploration Geophysicists, American Geophysical Union, International Association for Mathematical Geology, and local well-logging and geophysical societies in Denver, Houston, Boston, New Orleans, Oklahoma City, and Casper.



    2016          Co-chair SPWLA Spring Topical Conference on NMR

    2016          Steering Committee for SPE Low Permeability Symposium (Petrophysics)

    2011-2012 Board of Directors, DWLS; Informal technical advisor to DWLS Workshop organizers

    2010-2011 Co-founder of Williams Women.s Geoscience Forum linking women geoscience professionals with women
                       geoscience students at the Colorado school of Mines.