Modelling Frequency-dependent Anisotropy Observations Made on Microseismic Data

Here we observe the dependence of anisotropy on frequency in a microseismic data set acquired from a carbonate gas field. The shear-wave splitting observations are modelled using a poroelastic model which considers fluid communication between grain size pore spaces and larger scale fractures. A grid search is performed over fracture parameters (radius, density and strike) to find the model that best fits the real data. The results show that fracture size varies from the micro-scale within the shale cap rocks, to the meter-scale within the gas reservoir, to the centimetre-scale within the non-producing part of the carbonate formation. Cumulatively, the results depict the potential for characterising fracture systems using frequency-dependent anisotropy.