| Title | Geothermal Well Targeting and Monitoring Using Seismic Tremors from Fluid-Filled Fracture: The PFI Method |
|---|---|
| Authors | Peter Malin |
| Year | 2026 |
| Conference | World Geothermal Congress |
| Keywords | 9 |
| Abstract | The Permeable Fracture Imaging (PFI) method uses hundreds of nodal seismic recorders to observe episodes of small seismic tremors in connected, fluid-filled fractures. These included the fluid filled joints, fracture zones, faults, and fault zone, all of which are geothermal drilling targets. The signals are enhanced by stacking time-distance adjusted tremor signals for a subsurface volume of voxels. The voxel size depends on the density of receivers – roughly 20x20x20 m when receivers are spread at roughly 40 points per square km. While a recently established technology in Oil & Gas exploration, including hydraulic fracture and reservoir monitoring, PFI is a new innovation in geothermal well targeting and stimulation and well-to-well fluid-flow monitoring. We have conducted 2 pilot PFI surveys in the Newberry Volcano Geothermal Field using PFI methods – a 982 node survey in 2023 and a 1323 node survey in 2025. The 2023 survey imaged a 1.6x1.6 km square area down to ~2.1 km depth; the 2025 survey extended this area down to ~3.5 km. The 2023 survey was conducted during a period of very low industrial and other seismic noise, the 2025 survey included periods of very high surface noise and well-to-well pumping. With extensive signal processing of the 2025 data – including velocity model control using a borehole propellant source and surface vibroseis profiling, we were able to obtain geologically and operationally valuable images for planning drilling and evaluating well-to-well flow. We will display these and other related results in our WGC 2026 Poster. |