Modeling and interpretation of scattered waves in interstage distributed acoustic sensing vertical seismic profiling survey

Optimization of well spacings and completions are key topics in research related to the development of unconventional reservoirs. In 2017, a vertical seismic profiling (VSP) survey using fiber-optic-based distributed acoustic sensing technology was acquired. The data include a series of VSP surveys taken before and immediately following the hydraulic fracturing of each of 78 stages. Scattered seismic waves associated with hydraulic fractures (HFs) are observed in the seismic waveforms. Kinematic traveltime analysis and full-wavefield modeling results indicate that these scattered events are converted PS-waves. We have tested three different models of fracture-induced velocity inhomogeneities that can cause scattering of seismic waves: single HF, low-velocity zone (LVZ), and tip diffractors. We compare the results with the field observations and conclude that the LVZ model has the best fit for the data. In this model, the LVZ represents a stimulated rock volume (SRV). We have developed a new approach that uses PS-waves converted by SRV to estimate the half-height of the SRV and the closure time of HFs. This active seismic source approach has the potential for cost-effective real-time monitoring of hydraulic fracturing operations, and it can provide critical constraints on the optimization of unconventional field development.

Automated summary

The study focuses on optimizing well spacings and completions in unconventional reservoir development, using VSP survey data acquired in 2017 with fiber-optic-based distributed acoustic sensing technology. Scattered seismic waves associated with hydraulic fractures were observed, with the LVZ model showing the best fit for the data. A new approach was developed to estimate SRV characteristics and HF closure time, providing cost-effective real-time monitoring of hydraulic fracturing operations and critical constraints on unconventional field development.