Exploring Augustine

GeoAlaska files 2023 plan, will use non-intrusive subsurface geophysical measurements

Kay Cashman

Petroleum News

On June 9 Anchorage-based GeoAlaska LLC filed a revised plan of exploration with Alaska's Division of Oil and Gas for Mount Augustine. It was initially filed on May 15. The division approved the plan on June 14.

Mount Augustine is an active stratovolcano on Augustine Island in Cook Inlet a little over 68 miles southwest of Homer. Mount Augustine with its shallow magma chamber is believed to have geothermal potential.

Anchorage-based GeoAlaska was established in May 2020 by Paul Craig for the purpose of developing geothermal resources in Alaska.

Geothermal energy is generated by tapping into the heat produced by volcanic activity, and it can be used to generate electricity. It's considered a clean and sustainable energy source because geothermal energy does not emit greenhouse gases or pollutants, and it has the potential to provide a reliable source of energy. It's one of the few renewable energy sources that can provide 24/7 baseload energy, as it can operate continuously, regardless of weather conditions or time of day. Other renewable energy sources, such as solar, wind, tidal and hydro, are intermittent and dependent on seasonal occurrence and weather conditions.

GeoAlaska currently holds a geothermal exploration permit (ADL 394080) on the southern part of Augustine Island.

This summer GeoAlaska intends to collect and analyze geophysical data on and around its permit holdings, using non-intrusive subsurface geophysical measurements.

The goal is to gather and interpret scientific evidence to reduce subsurface uncertainty and objectively assess the presence of a working hydrothermal system.

If such a system is suggested by the geophysical data analytics, then GeoAlaska will evaluate the commercial merits of drilling one or more temperature gradient wells on Augustine Island during summer 2024 to confirm subsurface hydrothermal parameters.

The - resulting data and interpretations could ... result in carbon neutral energy production that will provide long term energy security for the Alaska Railbelt region, benefiting some 65% of all Alaskans," GeoAlaska said.

Jurassic units

The company's current geothermal model +involves reservoir(s) that may be fed by fluid upflow from the heat source underlying the current main volcanic center and/or in-situ heating of the reservoir fluids by thermal conduction from the hot rocks within and around the magma conduit. The shale units are anticipated to provide an impermeable seal isolating the heated waters in the reservoir from the cooler meteoric waters and seawater above."

If GeoAlaska is correct, the reservoir dynamics would reduce heat loss from the reservoir through thermal convection involving these cooler waters.

The location and orientation of the shale unit appears to be "optimally configured to reduce convection between the seawater and the reservoir formations underlying the shale unit," GeoAlaska said.

The goal of the exploration efforts at Augustine will be to identify the presence of a resistivity contrast between high resistivity bodies below and low resistivity anomalies above which could represent a trapped hydrothermal system and identify vertically oriented low density anomalies which could represent structural features such as fractures or dykes.

Gravity and MT surveys

GeoAlaska's 2023 plan of geophysical exploration at Augustine Island includes a Gravity Survey and MT Survey.

The company plans to start the surveys on July 28. Their current assumption is that MT will take 24 days and gravity will take an additional seven days.

A gravity survey is a geophysical method used to measure the variations in the Earth's gravitational field caused by differences in density of the underlying rocks. This survey involves measuring the acceleration due to gravity at various points on the Earth's surface and using these measurements to create a map of the subsurface density variations.

MT survey usually refers to a Magnetic Resonance Sounding (MRS) or Magnetotelluric (MT) survey. It is a geophysical method used to study the electrical conductivity of subsurface rocks and soils.

Using state-of-the-art tools for 3D subsurface imaging, GeoAlaska intends to map the underground geologic structures and fluid pathways. Each investigation adds information, refines the image, and reduces economic risk.

GeoAlaska plans to obtain 192 gravity survey stations and 29 MT survey stations.

The objectives for the geophysical gravity surveys are to conduct a ground-based gravimetric survey over approximately 11 square kilometers on the south flanks of Mount Augustine.

Stations will be spaced at ~250 meters, depending on local topography and terrain conditions, for a total of 192 total station locations.

Survey stations have been classified in first, secondary and - nice to have' categories to focus the team during the allotted time.