Impact of Near-surface Velocities on Surface Microseismic Signal, a Case Study in the Fayetteville Formation

A near-surface velocity map is derived, using data from active shots, acquired in the frame of a surface microseismic survey, targeting the Fayetteville shale formation. This near-surface velocity map shows strong velocity variations with velocities ranging from a few hundreds of metres per second to approximately 1500 m/s.

The visibility of the S-wave expression on the vertical component of surface geophones was investigated. It was found that only one-third of the events showed a visible S-wave arrival, and this arrival was below the level of noise for the other two-thirds of the events. When the S-wave is observed, it is seen preferentially in areas where near-surface velocities are larger and attenuation is lower.

The use of only P-waves appears to be widespread in surface microseismic processing. This study suggests, through the derivation of a near-surface velocity map, that near-surface attenuation could be one factor justifying this approach.