DESC0025073

Statement of Problem: Electromagnetic geophysical investigations are a critical part of geothermal exploration, as well as an important component for exploration of critical minerals, groundwater, and monitoring of shallow infrastructure. The airborne versions of these tools are not used effectively because of the relatively high unit cost of performing these surveys over small to medium areas. This is the result of the fact that all current airborne EM systems available in the United States require large helicopters and the importation of systems from either Canada or Europe. A second issue is the limited depth of investigation of these systems, particularly the limited lower frequency range of the receiver systems utilizing natural fields. The current natural source system (Geotechĺs ZTEM) has a lower frequency limit of 30 Hz. In the areas of primary geothermal interest ľ The Basin and Range Province ľ this frequency limitation only allows mapping of the electrical resistivity structure to approximately 200m, much shallower than the stated need of 2 km. How problem is to be addressed: Drone rotocopters, combined with magnetic field sensors using feedback technology to reduce the total mass, will allow geophysical instruments to be deployed in new ways for small and medium sized projects. These exploration projects, which often require only a few hundred line-km of data collection, are not financially viable for helicopter systems but appropriately scaled for drone operations given the upcoming changes to FAA regulations concerning Beyond Visual Line of Sight operations. We propose to adopt our existing magnetic field sensors, transmitters, and data processing tools to this application, integrating them with an a hybrid drone, inertial navigation unit, a lightweight digitizer, and GPS. The data collected with this system can then be integrated with conventional MT data to extend the depth of investigation as required. This will provide the entire ecosystem to provide either high resolution shallow data at a reduced cost when compared to helicopter EM or provide support for traditional MT data acquisition on a dramatically coarser sample interval which will reduce the total cost of the deeper investigations. What is be done in Phase 1: We will build drone based semi-airborne, which uses a ground-based transmitter and airborne receivers. We will use this receiver system to collect some initial time series of the natural source to prepare for software development of motion noise mitigation software in phase 2. Commercial Applications: The initial application with be geothermal exploration, mapping the electrical resistivity structure to a depth of approximately 500 meters, extendable to 10ĺs of km with the addition of a small number of traditional MT stations. This system has applications well beyond geothermal exploration. The mapping of the earthĺs electrical resistivity structure is a critical part of the exploration of many critical minerals, including copper and lithium. The semi-airborne system, with its use of a controlled source, will be applicable to areas with noise generated by powerlines. While it will be an effective exploration tool, it also has application in the monitoring of shallow infrastructure, including tailings dams, heap leach systems, levees, quench ponds, evaporation ponds associated with powerplants, groundwater exploration, and saltwater intrusion.