Advanced Micro-seismic Monitoring Methods

Micro-seismic monitoring is a widely used tool to map fracture propagation during hydraulic fracture stimulation. The capability to model, monitor, and measure the resulting fracture network is essential for optimal production. Using a sample dataset recorded from a set of surface sensors, we demonstrate the use of empirical matched filters to first detect low threshold events and then apply Bayesian-based location methods to yield locations along with robust error estimates. The error estimation is useful in relating the observed seismicity distribution to geologic models and distinguishing between features reflecting actual geologic structure as opposed to artifacts caused by sensor geometry and other sources of error. The velocity model is estimated using all available data and refined using Green’s function derived from ambient noise. Next, we explore the use of full waveform modeling using adjoint methods to define the micro-seismic focal mechanism, which distinguishes between tensile and shear mechanisms in the underlying fractures. The results (locations and focal mechanisms) are compared with the known geology (such as lithologic changes and fracture orientations) of the site and with standard techniques (P/S amplitude ratio and first-motion focal mechanisms) to evaluate the validity of these methods.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California