Upcoming Lectures and Meetings

Utah State Geologist – Dr. Rick Allis – September 5, 2013

Speaker: Dr. Rick Allis, Director of the Utah Geological Survey and State Geologist of Utah
Title: Basin-Centered Stratigraphic Reservoirs – Potential for Large Scale Geothermal Power Generation in the U.S.
When: Thursday September 5, 2013 (2:30 p.m.)
Where: Davidson Mathematics and Science Center, Room 104, on the UNR campus: http://www.unr.edu/around-campus/maps

Abstract: Recent growth in the installed geothermal power capacity of the U.S. has utilized binary plants mostly located on moderate-temperature hydrothermal systems. Many of the more attractive and accessible systems have been developed or are under investigation, and blind hydrothermal systems are difficult to locate. These moderate temperature systems are typically small (< 10 km2 in area) and power plants are often 10 – 30 MWe in size. If the U.S. is to achieve 5 – 10 GWe growth in geothermal capacity during the next decade as advocated by the Dept. of Energy Geothermal Technologies Office, it requires 100 MWe-scale power developments. This size power plant requires reservoir volumes of ~ 10 km3 for developments producing at near the installed capacity for at least 30 years. The modest success of EGS pilot projects since 1980, and the small size of moderate-temperature hydrothermal reservoirs in the western U.S. suggest limited potential for power growth in the next decade from these types of reservoirs.

Stratigraphic reservoirs in high heat flow basins of the western U.S. have the potential to sustain 100 MWe-scale power developments and contribute the required growth. These sub-horizontal reservoirs need to have a temperature of at least 175°C for a levelized cost of electricity of US$ 100/MWe-hour, and are likely to be at 3 – 4 km depth in basins where the heat flow is at least 80 mW/m2. A review of porosity and permeability data from both oil reservoirs and groundwater aquifers suggests the high permeabilities required for geothermal production wells (100 mDarcy) are not uncommon. Modeling with reservoir transmissivities of 3 – 10 Darcy-meters yields power densities in the range 3 – 10 MWe/km2 of reservoir area. In the eastern Great Basin, large areas of Paleozoic carbonates underlie Tertiary– Quaternary fill in basins and appear to be the most attractive reservoir target.

NPGS Meeting – Dr. Rick Allis – September 5, 2013 (RSVP by Sept. 3)

What: Nevada Petroleum & Geothermal Society Dinner Meeting
Speaker: Dr. Rick Allis, Director of the Utah Geological Survey and State Geologist of Utah
When: Thursday September 5, 2013 (cocktail reception hosted by Boart Longyear at Skyline Bar at 6:30 p.m., dinner at 7:00 p.m.)
Where: Ramada Reno Hotel, 1000 East 6th Street, Reno
Cost: NPS members $20, Non-members $23, Students $10
RSVP: RSVP by Tuesday, Sep 3 with the following link: https://docs.google.com/forms/d/1WnAKdocCpT6NjJHxzhCdT37uD1v9OiL8t-dXS8Xue4M/viewform

Title: Our Transforming Energy Sector – a Utah Perspective on Trends and Changes
Abstract: The changes occurring in Utah’s energy industries mimic many of the recent national trends in energy substitution. Oil production has doubled during the last 10 years, and at present rates will reach Utah’s historic peak oil production in about 10 more years.  Natural gas production is at record levels, but coal production has declined to levels last seen 25 years ago as new electricity generation is gas-fired.  Declining petroleum consumption since 2005, and substitution of coal for gas in electricity generation has caused state CO2 emissions to decline to levels last reached during the late 1990s.  Renewable electricity generation has increased to 6% of Utah’s total generation due mainly to new wind and geothermal plants.  This talk will speculate on future trends, and will address the issues and possibilities of nuclear power, oil shale development, carbon sequestration, geothermal power from hot basins, and development constraints due to limited water availability.

GSN Meeting Lecture – Greg Dering – September 11, 2013

Email from Laura Ruud, GSN: “Please join the GSN Winnemucca Chapter for their September meeting.

Presenter: Greg Dering, Nevada Bureau of Mines and Geology
Location: The Martin Hotel, 94 West Railroad St., Winnemucca, NV
Date: Wednesday the 11th of September
Time: Refreshments at 6:00 pm, Appetizers at 6:30, Talk at 7:00
Title: Structural Controls of the Tuscarora Geothermal Field, by Greg Dering and Dr. Jim Faulds, Nevada Bureau of Mines and Geology

Abstract: Detailed geologic mapping, structural analysis, and well data have been integrated to elucidate the stratigraphic framework and structural setting of the Tuscarora geothermal area. Tuscarora is an amagmatic geothermal system that lies in the northern part of the Basin and Range province ~90 km northwest of Elko, Nevada. The geothermal area is dominated by late Eocene to middle Miocene volcanic and sedimentary rocks, all overlying Paleozoic metasedimentary rocks. A geothermal power plant was constructed in 2011 and currently produces 18 MWe from an ~170°C reservoir in argillite and silty limestone. Analysis of drill core reveals that the subsurface geology is dominated to depths of ~700-1000 m by intracaldera deposits of the Eocene Big Cottonwood Canyon caldera, including blocks of basement-derived megabreccia.

Two distinct structural settings at different scales appear to control the geothermal field. The regional structural setting is a 10-km wide complexly faulted left step or relay ramp in the west-dipping range-bounding Independence-Bull Run Mountains normal fault system. Geothermal activity occurs within the step-over where sets of east- and west-dipping normal faults overlap in a northerly trending accommodation zone. The distribution of hot wells and hydrothermal surface features, including boiling springs, fumaroles, and siliceous sinter, indicate that the geothermal system is restricted to the narrow (< 1 km) axial part of the accommodation zone, where permeability is maintained at depth around complex fault intersections. Shallow up-flow appears to be focused along several closely spaced steeply west-dipping north-northeast-striking normal faults within the axial part of the accommodation zone. These faults are favorably oriented for extension and fluid flow under the present-day northwest-trending regional extension direction indicated by previous studies of GPS geodetic data, earthquake focal mechanisms, and kinematic data from late Quaternary faults.

The recognition of the axial part of an accommodation zone as a favorable structural setting for fluid upflow may be a useful exploration tool for developing drill targets in both fossil and active epithermal systems. The presence of several high-temperature systems in northeastern Nevada demonstrates the viability of electrical-grade geothermal activity in this region despite low present-day strain rates as indicated by GPS geodetic data. Geothermal exploration potential in northeastern Nevada may therefore be higher than previously recognized.

Food and drinks are sponsored by Boart Longyear.

Please contact Andy Jansen, andy.jansen@newmont.com or Peter O’Byrne, peter.o’byrne@newmont.com for more information.”

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