A Conceptual Geologic Model for the Newberry Volcano EGS Site in Central Oregon: Constraining Heat Capacity and Permeability through Interpretation of Multicomponent Geosystems Data

Newberry Volcano, a voluminous (500 km3) basaltic/andesitic/rhyolitic shield volcano located near the intersection of the Cascade volcanic arc, the Oregon High Lava Plains and Brothers Fault Zone, and the northern Basin and Range Province, has been the site of geothermal exploration for more than 40 years. This has resulted in a unique resource: an extensive set of surficial and subsurface information appropriate to constrain the baseline structure of, and conditions within a high heat capacity magmatically hosted geothermal system.

In 2012 and 2014 AltaRock Energy conducted repeated stimulation of an enhanced geothermal systems (EGS) prospect along the western flank of the Newberry Volcano. A surface based monitoring effort was conducted independent of these stimulation attempts in both 2012 and 2014 through a collaboration between NETL, Oregon State University and Zonge International. This program included utilization of 3-D and 4-D magnetotelluric, InSAR, ground-based interferometric radar, and microgravity observations within and surrounding the planned EGS stimulation zone. These observations as well as borehole and microseismic stress field and location solutions provided by AltaRock and its collaborators, in combination with well logs, petrologic and geochemical data sets, LIDAR mapping of fault traces and extrusive volcanics, surficial geologic mapping and seismic tomography, have resulted in development of a framework, subsurface geologic model for Newberry Volcano.

The Newberry subsurface geologic model is a three-dimensional digital model constructed in EarthVision that enables lithology, directly and remotely measured material properties, and derived properties such as permeability, porosity and temperature, to be coregistered. This provides a powerful tool for characterizing and evaluating the sustainability of the site for EGS production and testing, particularly within the data-dense western portion of the volcano. The model has implications for understanding the previous EGS stimulations at Newberry as well as supporting future research and resource characterization opportunities. A portion of the Newberry area has been selected as a candidate site for the DOE FORGE (Frontier Observatory for Research in Geothermal Energy) Program through a collaboration between Pacific Northwest National Laboratory, Oregon State University, AltaRock Energy and additional partners. Thus, the conceptual geologic model presented here will support and benefit from future enhancements associated with that
effort. --Mark-Moser et al. 2016