Time-Lapse Data Acquisition of Passive Seismic and Active Seismic at the Same Time

Abstract

Abstract Microseismic analysis plays a key role in hydraulic fracture monitoring for developing shale plays and avoiding unwanted fracture development. Meanwhile, active seismic (or 4D seismic) monitoring is widely used for delineating temporal change associated with fluid injection and production. For continuous analysis of both passive and active seismic at the same time, we introduce an approach to simultaneously aquire seismic signals from microseismic and from active seismic sources ACROSS (Accurately Controlled, Routinely Operated Signal System). We perform test data acquisition with two ACROSS sources in Kashiwazaki, Japan to obtain high signal-to-noise ratio (S/N) of ACROSS data and passive seismic signals after the suppression of ACROSS data. The ACROSS source was operated with sweep cycle of exactly 200 seconds and with frequencies ranging between 5 and 50 Hz. Permanent geophone data at 1.5 km and 5.5 km from the ACROSS sources confirmed highly repeatable ACROSS signals with 2 hour stack and 1 day stack, respectively. The results indicated that the transmittability of ACROSS signal is sufficient enough for daily-basis active-seismic analysis. On the other hand, motions related to ACROSS source were clearly suppressed by subtracting "weight-averaged" ACROSS data, and subtle motions from passive seismic were uncovered. The ground motions of lower than 50 micro kines (5 X 10-7 m/s) were extracted at just 70 m away from the ACROSS source. Since continuous microseismic observation is possible at most of the receiver locations, our proposed technicque should provide opportunities for passive and active seismic surveys at the same time and may be highly beneficial for shale or other tight reservoir characterization.