Hydraulic Fracturing-driven Infrasound Signals -A New Class of Signal
for Subsurface Engineering
Abstract
Fluid injection into subsurface causes rock deformations, which give
rise to mechanical waves in the surrounding rock. This article focuses
on the infrasound signals (2-80 Hz) recorded by hydrophones during a
meso-scale (~10 meter) hydraulic fracturing experiment
at depth of 1.5 kilometer. We present a full-waveform-based data-driven
workflow to map the spatiotemporal evolution of the infrasound sources
produced during hydraulic fracturing. The infrasound source locations
are compared against the simultaneously created microseismic source
locations. Orientation of the infrasound source point cloud strongly
agrees with natural fracture orientation, as inferred from the discrete
fracture-network modelling. Finally, we arrive at a conceptual model of
fluid-injection driven infrasound generation in subsurface and posit
that the reopening of natural fractures is the main mechanism of the
infrasound generation. A joint analysis of signals from microseismicity
and infrasound sources can improve subsurface fracture imaging.