[S-TT42] Applying optic fiber sensing to earth science

[STT42-P05] Continuous reservoir monitoring system based on portable active seismic source (PASS) and borehole DAS data

*Takeshi Tsuji¹, Ahmad Bahaa Ahmad², Hitoshi Tsukahara³, Fumitoshi Murakami³, Naoshi Aoki³, Susumu Abe³, Takuya Miura⁴, Takao Nibe⁴ (1.Graduate School of Engineering, The University of Tokyo, 2.Graduate School of Engineering, Kyushu University, 3.JGI, 4.JAPEX)

Keywords:Portable Active Seismic Source PASS, Distributed Acoustic Sensing, Continuous Monitoring, CO2 geological storage, Geothermics, Volcano monitoring

To continuously monitor the CO2 storage and geothermal reservoirs, we have developed a Portable Active Seismic Source (PASS) system. The PASS generates chirp signals with a wide frequency range, which is configurable to suit the imaging or monitoring target. Although our seismic source is small, stacking of the signals continuously generated by the PASS enhances the signal-to-noise ratio of the seismometer data far from the source. The smaller size and lower cost of the PASS allow its deployment in many places to continuously monitor geological formations, including reservoirs, with high spatiotemporal resolution. To achieve continuous monitoring, the distributed acoustic sensing (DAS) is another crucial technology. Based on the DAS, we can continuously record the signal from the PASS in an extensive area including the boreholes and offshore environment. Here we report several applications of our PASS and DAS system at fields (including deep borehole). We used several types of PASSs in the field. The chirp signals from our PASS unit (4 cm diameter motor), generated by eccentric rotation of a mass smaller than 10 g with a frequency range of 20–60 Hz (19N at 50Hz), propagated a horizontal distance of 1 km. When we used larger PASS (630N at 50Hz) and recorded the signal by the borehole DAS, we confirmed the PASS signal propagation to 1 km depth. Because the depth of CO2 storage reservoir is ~1km, we could use our PASS for the continuous monitoring of stored CO2. Currently we are optimizing the size of PASS for each potential CO2 storage site.