Mon, Nov 13|
Petroleum Club of Fort Worth
FWGS November Luncheon
Weak Interfaces in Unconventional Reservoirs: How They Effect Hydraulic Fracturing and the Geologist’s Role in Classifying Them by John Degenhardt, Ph. D., P.G.
Time & Location
Nov 13, 2017, 11:30 AM – 1:00 PM
Petroleum Club of Fort Worth, 777 Main St, Fort Worth, TX 76102, USA
Time: 11:30 am Buffet, Noon Speaker Presentation
RSVP online by Friday, November 10th at noon on the FWGS website www.fwgs.org.
Cost: $27 with RSVP, $30 with no RSVP, student members eat free with RSVP (Student Members please directly email the FWGS Secretary to RSVP).
Reminder: FWGS is charged for all RSVP's, so if you RSVP and do not attend you will be contacted concerning payment.
Unconventional rocks are vertically thinly layered and laterally heterogeneous at many scales. Their pervasive layering results from geologic processes of deposition that is influenced by cyclical variations in sea level and compounded by the addition of materials that are transported by bottom-current processes (turbidites, debris flows, linked debrites and others). In addition, mudstone systems deposited in sediment starved (i.e., deep marine) depositional settings may contain large volumes of microbial-derived early diagenetic cements (calcite, dolomite, ferroan carbonates, silica, authigenic clays, iron sulfides), organic matter, and biogenic debris (fish bones, microfossils) which, because of their specific geochemical interactions and reaction potentials, all contribute to the heterogeneity of the layered system. In some reservoirs, bed parallel ash beds, mineralized veins, and fault deformation surfaces are also present, which further adds to the layered-heterogeneity of the system.
In general, sequences of organic and biogenic-rich sediments juxtaposed to mineral-rich sediments comprise a mechanical system that is far from homogeneous or isotropic, and although the complex rock fabric of organic-rich mudstones have been well described for geologic applications, they have been poorly quantified for engineering and completion applications. Given the importance of hydraulic fracturing for producing from unconventional reservoirs, the challenge (and opportunity) for geologists is to translate the commonly described features of the rock fabric in a manner that helps engineers to define the system in a mechanical way. For example, the characterization and potential use of ductile-brittle couplets for optimizing drilling orientations and predicting hydraulic fracturing in mudstone reservoirs was proposed by Slatt et al. 2011. This represents an important first step in the effort to suitably characterize the features of unconventional reservoirs for engineering applications. Beyond this, the properties of ductile-brittle (soft-hard) couplets have been characterized in core and found to contain interfaces, or surfaces of contact that are inherently weak. They are prone to fail in shear and they may have an initial hydraulic conductivity that promotes high leakoff during hydraulic fracturing. On this basis, their geologic characterization can be considered an additional step to facilitating the integration of geology and engineering.
To this end, we have developed a methodology for evaluating these interfaces, defining their type and pervasiveness along the length of the core, and measuring their properties (friction, cohesion, and hydraulic conductivity). By mapping them in relation to their geologic origin, type and properties across the region of interest, we are able to provide a better geologic model of the region and better engineering information on how to drill and complete the reservoir system for maximizing hydrocarbon production.
After earning a BS degree in Geology from Texas A&M University in 1987, John joined Texaco’s Exploration and Production Technology Division as a Reservoir Technologist. Working in the Heavy Oil Recovery Group, he was engaged in the investigation of phase-change phenomena at the steam-liquid interface in the Kern River Field and other mature steam floods in California, as well as in-situ combustion processes in Bellevue Louisiana. While at Texaco, he earned an MS degree in Planetary Geology from The University of Houston, during which time he became involved with research on meteorite impact processes and impactites from meteorite craters at NASA’s Johnson Space Center. John left Texaco in 1997 and returned to Texas A&M to pursue a doctorate in Geomorphology, which he earned in 2002. His research involved one of the first applications of ground penetrating radar to the subsurface investigation of alpine rock glaciers, and was carried out in the San Juan Mountains near Telluride and Ouray Colorado. The results of this work was used to develop ice-rock deformation models and to identify potential water sources near prospective manned landing sites on Mars. After completing post-doctoral work as a Research Scientist at Texas A&M, John accepted a dual-chair faculty position at Sam Houston State University, where he remained for four years. He joined W. D. Von Gonten & Company as a Senior Consulting Geologist in January 2010 and worked primarily on shelf and deep water Gulf of Mexico assets and California offshore fields as well as various onshore domestic basin plays including Niobrara, Midland and Delaware Basins, Williston and Anadarko Basins, and DJ and Powder River Basins. Currently, John serves as Lead Laboratory Geologist for W. D. Von Gonten Laboratories.
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