GeoAlaska LLC, established in 2020, focuses on harnessing geothermal energy in Alaska to provide carbon-free, baseload electricity. In March 2023, Ignis Energy Inc., a partner company of Geolog International B.V., joined forces with GeoAlaska to offer technical and project management expertise. Since 2021, GeoAlaska has identified two promising geothermal sites on state-owned land near Alaska’s South Central Railbelt Region: 10,830 acres on Augustine Island and 6,376 acres on Mt. Spurr. This brochure highlights the geothermal potential of the Augustine Island site, which lies within the seismically active Pacific Ring of Fire.
Southcentral Alaska is strategically positioned for geothermal development, with its proximity to volcanic activity in the Cook Inlet basin. As Alaska’s electricity market increasingly emphasizes renewable energy, House Bill 50, passed in May 2024, has created favorable conditions for geothermal exploration. Despite high energy consumption and some of the highest electricity costs in the U.S., Alaska has no significant geothermal power plants.
The Railbelt region, serving about 75% of Alaska’s population, is vital for the state’s economic growth. In 2020, 82% of the Railbelt’s electricity came from fossil fuels. However, Alaska’s Renewable Energy Portfolio Standard (RPS), established in 2022, aims to shift the state to 30% renewable power by 2030 and 80% by 2040. With concerns over the long-term reliability of natural gas supplies in the Cook Inlet region, geothermal power from Augustine Island could replace coal-fired plants, reducing carbon emissions by 1.7 million tonnes annually. A 2023 survey showed that 82% of Alaskans support geothermal as a future carbon-neutral energy solution.
Augustine Island, also known as Augustine Volcano, is an andesitic stratovolcano located in southwestern Cook Inlet, about 175 miles southwest of Anchorage. The volcano began erupting between 40,000 and 75,000 years ago, with its most recent eruption in 2006.
Augustine’s volcanic structure is complex, characterized by a shallow magma chamber estimated to be around 4 km deep with temperatures reaching 840°C. Above the magma chamber, a degassing zone exists at approximately 1 km below sea level, where gases escape, indicating ongoing magmatic activity. The island’s core is composed of fractured, fluid-saturated igneous rock, contributing to its volatile nature. The southern flank of Augustine Volcano reveals sedimentary rocks from the Upper Jurassic Naknek Formation, uplifted and altered by volcanic forces (picture 1). This formation, consisting of siltstone and fine sandstone, provides insight into the island’s volcanic history, showing evidence of both volcanic and sedimentary processes. These geological features highlight Augustine Volcano’s dynamic and active nature, with its shallow magma chamber playing a central role in the island’s ongoing volcanic processes.
The generated model revealed a sector with a convergence of low resistivity and high-density volumes on the southern flank of Augustine Volcano that could represent a working hydrothermal system, underlying a geothermal clay cap.
Two geophysical surveys were conducted at the Mt. Augustine prospect: a 2023 survey with 28 AMT stations and 215 gravity measurements, and a 2024 MT survey with 40 standard MT measurements (picture2). The data from these surveys were jointly inverted using CGG’s RLM-3D code, combining different geophysical data types to better constrain the geophysical models. The surveys identified a clay cap with low permeability that acts as a ‘lid’ on the geothermal reservoir. This cap, with resistivities of 1-10 ohm-m, typically lies hundreds of meters thick above the volcanic reservoir, with temperatures at its base around 250°C. The conceptual model (picture 3) developed from these findings, illustrated a geothermal system with a clay cap over a deeper reservoir, similar to the Kakkonda geothermal field in Japan.
Based on the current dataset, potential power generation at the Mt. Augustine prospect was calculated using both power density and volumetric methods, with results averaged for further analysis. Due to the uncertainties typical of greenfield prospects like Mt. Augustine, a Monte Carlo simulation with 10,000 iterations was used to reduce uncertainty. The P50 value was estimated at 204 MWe, with a P90-P10 range of 167 MWe to 243 MWe, and these estimates will be refined as GeoAlaska gathers more data.
Development efforts are guided by an evolving business plan updated as new data emerges, with economic evaluations including internal rate of return (IRR) and net present value (NPV).
