A message from NPGS: “We are pleased to announce May 2019 NPGS Meeting on May 2, 2019. This is the FINAL dinner meeting for the season, so please join us before taking the summer break. The bar will be sponsored by Sinclair Well Products, and talk will be given by Bill Ehni. Please note, online registration ends Monday night, April 29th.”
Speaker: Bill Ehni
Topic: Adventures in Nevada Oil and Geothermal Exploration,
some answers to geologic questions with examples from White River Valley, Lake Valley, Beowawe and Wabuska
Abstract: White River Valley, in Nye County Nevada, has no oil production as of this date; however, there have been numerous good oil shows, and coupled with the presence of good source rocks and reservoir rocks, it is only a matter of time before oil production is established. The southern half of white river valley is a Tertiary graben with Paleozoic bedding dipping to the east at about 20 degrees. The 50 square mile Neogene basin created by this graben is bounded on the east by the Eagan Range with nearly 12,000 ft of displacement along west dipping normal faults and on the west by an east dipping with a minimum of 9000 ft of displacement. Mississippian source rocks in the central portion of the graben are well within the oil window and source rock analyses indicate that over 500 million barrels of oil have been expelled from the hydrocarbon kitchen.
In Lake Valley there have been 4 wells drilled for oil and gas exploration and a considerable amount of 2D seismic data. A well drilled by Amoco in1984 and drilled to a total depth of 12,750 ft (BHT 208F) encountered 2,368 ft of Mississippian rocks. Brent Energy drilled a well to a total depth of 9178 ft (BHT 226F) and encountered 1750 ft of Mississippian section. In 2010 Cabot drilled a well to 9515 ft (BHT 128F). Cabot was anticipating a 2100 foot thick section of potential Mississippian source rocks, which seems logical based on the earlier drilling results, but only found 400 ft of source rocks that were not in the oil window. These perplexing results are due to an inordinate thick section of volcanic rocks. The thick section of volcanic rocks encountered in the Cabot well probably have a significantly higher thermal conductivity which accounts for the lower bottom hole temperatures compared to offset wells. The missing Mississippian section in the Cabot well was probably eroded away, possibly by a drainage systems flowing west from the Indian Peak volcanic complex, and then subsequently filed by volcanic rocks with a relatively high thermal conductivity resulting in a thin section of Mississippian Chainman that is not in the oil window.
A curious geothermal anomaly identified in at least one publication on the Beowawe Geothermal system appears to be related to the Miocene Northern Nevada Rift. Magnetotelluric data suggests that the Beowawe system is on a northeast trending resistivity anomaly that originates near the Northern Nevada Rift. Although igneous activity associated with the Miocene Northern Nevada Rift is too old to be directly related to the Beowawe Geothermal system, it appears that secondary northeast trending structures, such as the Malpais Fault, are locally geothermally anomalous. Other northeast trending structures along the Northern Nevada Rift could be geothermal targets for additional geothermal exploration. A blind geothermal system south west of the Beowawe geysers is on trend with this resistivity anomaly and is undoubtedly related to the same northeast trend structure that controls the Beowawe geothermal system.
Bio: William J. Ehni has a Bachelors degree in Geology from Humboldt State University in 1975. He worked for 5 years in the Geysers California, 3 years at Republic Geothermal, and 3 years in Austin Texas at Geotronics Corporation. In 1985 he founded Ehni Enterprises Inc.
Click here for details or to register online and reserve your seat.
The event details are as follows:
Organization: Nevada Petroleum and Geothermal Society
Event Name: May 2019 NPGS Meeting
Date: May 2, 2019, 06:30 PM to 09:30 PM
Location: Tamarack Junction