DAS characterization of an unconventional shale reservoir using guided waves

Unconventional shale reservoirs can act as waveguides if their velocity is lower than their surroundings. Using DAS, we can record such guided waves as unaliased signals originating from both cross-well perforation shots and microseismic events. When S-type guided waves propagate through previously stimulated fractured areas, their dynamic and kinematic properties are strongly affected. We can use this effect to estimate the horizontal growth of the fractures. In addition, shear-mode splitting of guided waves is a powerful indicator of microseismic event location, and we use this property to constrain whether the event originates in the reservoir or outside it.