About a decade ago, the Alaska Energy Authority in concert with Ormat Technologies, Inc. looked into the possibilities for geothermal energy from the Mount Spurr volcano some 150 km west of Anchorage, AK.
The plan was to eventually generate 50 – 100 MW on a daily basis to feed into the Southcentral Alaska (Railbelt) electrical grid.
A series of holes were drilled into eastern leases farthest from the volcano. They found conglomerate, gravel, broken rock and other debris that were too permeable to support a hot pressurized system. Yes, some of the rock was hot, but it was too porous to support a pressurized system. Further drilling was suspended in 2012 pending analysis of the first set of wells on the easternmost set of leases.
Alaska Railbelt Energy
Here in Southcentral Alaska, the Railbelt refers to everything connected by the Alaska Railroad. Generally this includes a moderately straight line from Seward in the south to Fairbanks in the north.
Electricity in the Railbelt is produced by six separate and occasionally cooperating electric utilities. Over 90% of the generation is powered by natural gas produced from Cook Inlet. There is some wind in the system. There is some hydroelectric in the system. There is also a long fought over clean coal plant near Healy. Total daily production of electricity in the Railbelt is around 750 – 800 MW. We have no operating coal or nuclear generation in the Railbelt though there is a lot of coal in Alaska.
The system is interconnected so that member utilities can sell excess production to one another. It is referred to as an islanded system as it does not connect to the larger electric grid in North America.
Over the last decade, there has been a push by local greens, the congressional delegation, and the state legislature toward adoption of renewable energy such as big hydroelectric, wind, geothermal, biomass and tidal. Most of the renewable options are not economically viable unless subsidized by a government at some level.
In the mid-2000s, the Alaska legislature passed a resolution establishing a goal of 50% of all electricity in Alaska to be produced by renewable means by 2025. At the time, it made some sense with oil and natural gas prices near or above historic highs. Most experts thought they would not do anything but stay the same or increase.
The most popular forms of renewable energy (at least to governments) are typically solar and wind, both of which are highly variable in output depending on weather and time of day. As such, both require spinning backup as large as or larger than what is expected to be produced from the renewable methods. They both also require massive storage so as to keep output as constant as possible. Geothermal on the other hand is relatively stable and output constant as long as the fluids keep being pumped into the heat source and hot fluids cycled through generation systems.
With this in mind, the Alaska Energy Authority started working with Ormat Technologies, LLC on a proposed geothermal plant taking advantage of heat flow from the Mount Spurr volcano. Ormat is a world class geothermal energy recovery company that has done quite well in the current push for increasingly green energy. Ormat has a history here in Alaska, having provided stand-alone power plants along the Trans-Alaskan Pipeline System (TAPS). It also has a small geothermal operation for the University of Alaska at Fairbanks at Manley Hot Springs in the interior.
The first geothermal lease sale in the Mount Spurr area was in 1983. One of 16 tracts received a bid. The lease for that tract was terminated in 1992. Two new tracts were offered in 1986. Both received bids. Leases expired and were terminated in 1996 and 1990. Respectively. The reason for lack of development at this time was the global collapse of oil prices in the mid-1980s.
In 2008, Ormat purchased exploration rights on 15 of 16 offered lease tracts to the east of Mount Spurr for around $3.3 million US. The terms of the leases were 10 years and deliverables established in state law.
The lease site is very close to a major power generation plant and natural gas pipeline hub at Beluga, making it relatively easy and inexpensive to tie into the Railbelt electrical grid.
Lease sites are essentially at the southern foot of Mount Spurr. They include Chakachamna Lake, formed by a flank collapse of Mount Spurr itself, rivers eastbound to Cook Inlet. There has been some interest in a hydroelectric plant using water from Chakachamna Lake over the years. The Chakachamna area is well within the volcanic hazard area of Spurr.
Much of the area was recently glaciated leaving the rock debris one would expect after the glaciers withdraw. Lower elevations are gently sloping with thickets of alder. Fish include all five species of Pacific Salmon present in Alaska, though due to the coldness of the water, numbers are relatively low. Wildlife includes moose, caribou, wolf and bear.
Mount Spurr is located some 150 km west of Anchorage. Its last two eruptions were Plinian in nature out of Crater Peak in 1953 and 1992. In 2004, increased seismicity was followed by a short-lived crater lake at the top of Spurr itself. There were also a few short lahars that did not reach the valley floor below. Crater Peak is a satellite cone on the south flank some 3 km from the main peak. https://volcanocafe.wordpress.com/2013/11/28/mount-spurr-the-closest-volcano-to-anchorage/
Volcanic hazards to the proposed generation plant include but are not limited to flank collapses, debris avalanches, lahars, directed blasts, pyroclastic flows, ballistic rock, tephra and ash. The debris avalanche that created the Chakachamna Lake traveled some 20 km south of the flank of the volcano.
The exploration area includes steep slopes of the volcano itself leading to some concern about proper siting of the drilling operation by the State of Alaska Department of Natural Resources (DNR). DNR was also concerned about induced earthquakes caused by injection and removal of fluids by an operating geothermal plant.
Cook Inlet tectonics are driven by the impact of the Pacific Plate into the North American Plate. South and west of roughly an east – west line through Anchorage, the impact is a classic subduction region, with the Pacific Plate bending under the Alaska Range, the Alaska Peninsula and throughout the length of the Aleutians. This subduction provides magma for all Alaskan Peninsula and Aleutian volcanoes. The line of volcanoes stops roughly abeam Anchorage with Mount Spurr and to its immediate north, Mount Hayes.
As you go east from Anchorage, tectonics is dominated by the impact of the Pacific Plate into southern Alaska. This impact has steadily built up southern Alaska with the delivery of multiple terranes into the region. New terranes tend to be squeezed between the Pacific Plate and the North American Plate with the line of east – west movement being the Denali Fault. Some terranes are over 250 km west from the point where they were delivered to Alaska. The major volcanic entity in this part of the state is the Wrangell Volcanic Field, a group of huge shield and stratovolcanoes. https://volcanocafe.wordpress.com/2014/04/14/wrangell-volcanic-field/
The most recently delivered terrane is the Yakutat, sometimes called a microplate. Directly north of the region it was delivered, it has mostly halted Pacific Plate subduction, and is weakly subducted. It is this weak subduction under the thick North American Plate that delivered magmas to the Wrangell Volcanic Field.
West of that region, there is what appears to be a portion of the Yakutat terrane that is flat plate subducting under the North American Plate. This is referred to as the Yakutat Slab. Interestingly, it has all but shut down active volcanism in the region it is below. The buoyant slab appears to be acting as a squeegee under the thicker plate, sweeping mantle fluids from above it, and south under Cook Inlet, where those fluids are imaged as signals in topography (subsidence) and gravity. The basin under upper Cook Inlet is being pulled down from beneath.
As with any major subduction region, Alaska is home to major fault lines and earthquakes. The major fault line north of Anchorage is the Denali Fault, which is a strike – slip region, moving as much as 10 m per large quake. To the west of Anchorage in the vicinity of Mount Spurr, there is the Castle Mountain – Lake Clark fault system. Like the Denali Fault, its motions are also strike – slip though there is less movement than farther north as the region transitions to full subduction as we move south. Movement on either side of the Castle Mountain – Lake Clark Fault system is in the vicinity of 24 – 36 m / 10ka.
The entire region is highly folded with significant sedimentary sands and rock layered with other rocks making it an excellent oil and natural gas province. Finally, the entire region is heavily glaciated, with over a kilometer of ice covering Anchorage and upper Cook Inlet as recently as 5,000 years ago.
Ormat had a two phase plan with exploration starting in 2008 leading to plant design and permitting by 2015 and operations beginning in 2018. Geothermal plants are capital intensive at the beginning but generally require no fuel and save money over time.
In a presentation made to the Chugach Electrical Cooperative, the largest electrical utility in the Railbelt in 2012, Ormat described what they had done.
There was non-intrusive exploration in the four eastern leases in summers of 2009 and 2010. Two exploration holes were drilled in September 2010. These were relatively shallow only going to around 300 m. Results of this drilling was positive. A third deep hole was drilled in summer 2011 to a depth of around 1,200 m. These results were not so positive. While they did find heat, they did not find the expected hard basement bedrock. Instead, they found relatively permeable conglomerate that would have been problematic to run a pressurized system through. Temperatures of the deeper well were colder than expected.
The eastern leases were chosen because they were closest to infrastructure (roads and transmission), outside the known volcanic hazard zone, and had faults that could possibly accommodate a geothermal resource (Lake Clark Fault among others).
Geologic modeling predicted a low likelihood of finding a commercially viable geothermal resource in the eastern region. Data still supports possible existence of a commercial resource in the more difficult to develop central region.
Their most recent efforts (as of 2012) were trying to find a location in the central region that satisfied their requirements – reasonable likelihood of finding a commercial resource; mitigating volcanic hazards; and affordable connection to roads and transmission. As an aside, up here in Alaska, the cost to build transmission runs about a million dollars US a mile ($625 k US / km).
The discovery of conglomerate and cooler than expected temperatures from the 2011 hole forced Ormat to revise their geologic model. There is some concern that cold glacial water from the surface is mixing with the hot hydrothermal water system below that part of the volcano.
One way around this is to simply drill deeper holes and see what they find. Ormat has developed systems as deep as 2,500 m. But drilling deeper means exploration gets more expensive and requires a larger drilling rig. An article in the Oct.30, 2011 issue of Petroleum News estimated the total cost of the deeper drilling operation in the vicinity of $11 million US.
Electricity out of the new plant is estimated at 12 cents / kwh (kilowatt hour) or two cents more expensive than electrical generation out of the system the geothermal plant was projected to replace.
If those nails in the economic coffin were not sufficient, the project now has to compete with relatively inexpensive natural gas at Henry Hub spot prices between $2.56 – 2.88 US / million Btu as of this writing. At the time the State of Alaska was pursuing Mount Spurr, we were looking at a spot price between $7 – 9 US / million Btu, with electricity being sold at around 13 cents US / kwh.
It has been a while since we have heard from Ormat. I expect the historically low natural gas prices along with the worldwide glut for the forseeable future has shelved this project for the time being.