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Extending Permeable Fracture Imaging at Newberry to Depth: Added Receiver-Coverage Area and Seismic Velocity Control J. EPPINK, P. MALIN, T. FLURE, F. HOROWITZ, A. MATHEWS, H. ONTIVEROS, A. STROUJKOVA, S. VALENZUELA T. FLEURE, W. MCLAIN, S. PASCHALL, C. SICKING A. T. CHEN, Z. WANG, ANDBONNEVILLE, [Duke University, USA] |
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In September 2025 we conducted a 3-week, 1,320 seismic ground level receiver, Permeable Fracture Imaging survey at the Newberry geothermal area, Oregon. The aim was to extend a previous, 2023, 982 receiver, PFI survey from ~2.2 km to over 3 km. The extension included adding (1) more receivers to cover a broader area (and hence adding depth) and (2) refining the seismic velocity-depth profile using surface vibroseis, behind casing distributed acoustic sensing (DAS), and a downhole propellant-sourced check shot (hence adding absolute travel time resolution and accuracy). We received support for both the 2023 and 2025 surveys from the Advance Research Project Agency – Energy (ARPA-E), and in 2025, from our industrial partner, Mazama Energy. The PFI method uses hundreds of time-synced seismic recorders to observe episodes of small seismic movements in connected permeability structures – the fluid filled joints, fractures, fracture zones, faults, and fault zone that are geothermal drilling targets. The signals are enhanced by stacking time-distance adjusted seismic signals for a subsurface volume of voxels. The voxel size depends on the density of receivers – roughly 36/km2 in both surveys. The depth penetration of PFI depends on uniform coverage over the target area plus a buffer area, the width of which needs to be ~1 times the depth of the target. In 2023 the area was 27 km2 , yielding a PFI depth of 2.2 km. In 2025, by adding 338 receivers at the same density, the area increased to 37 km2 and PFI depth to more than 3 km. In both cases, the resulting resolution was roughly 30x30x30 m voxels. The spatial accuracy of the PFI method depends on an accurate 3D seismic velocity model. This includes the need to know the varying thicknesses and velocities of near-surface sediments (such adjustments are known in O&G seismic reflection methods as “static corrections”) and the velocity profile all the way down to the bottom of the PFI target. To address this requirement, in the 2025 survey we employed (1) 3-D vibroseis-source profiling recorded into the 1,320-receiver surface net, (2) several ~200 m deep borehole sensors, (3) a 2,736 m long, cemented behind casing, DAS cable and (4) a propellant check shot at 3000 m depth. The vibroseis-to-surface net and ~200 m borehole receivers covered the upper velocity structure. The propellant check shot recorded on the DAS covered the mid and deeper velocity structure. The processing of the resulting terabyte volume of passive and active-source seismic data is currently in progress. We expect a significant improvement in the 2025 survey of PFI depth and location accuracy over what was possible with the 2023 data.
Topic: Emerging Technology