Downhole Microseismic Monitoring At A Pilot Hydraulic Fracturing Site In Poland

A precise velocity model is necessary to obtain reliable locations of microseismic events, which provide information about the effectiveness of the hydraulic stimulation. Seismic anisotropy plays an important role in microseismic event location by imposing the dependency between wave velocities and its propagation direction. Building an anisotropic velocity model allows for more accurate location of microseismic events. In this paper we develop a workflow for a VTI velocity model construction in the absence of SH-waves in perforation shots data. SH-waves carry information about Thomsen’s γ parameter and provide constraints for microseismic events locations. We extract effective ε, δ and VP0, VS0 for each layer from P- and SV-waves arrivals of perforation shots, while the unresolved γ is retrieved from selected microseismic events’ SH-SV-waves delay time, afterwards. Finally we present an accurate locations of microseismic events recorded during a pilot stimulation job located in Northern Poland.