10:40 AM - 11:00 AM
[RP-01] Using Surface Orbital Vibrators and DAS for Realizing Permanent Reservoir Monitoring – Lessons from the CO2CRC Otway Project
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Surface orbital vibrators (SOVs) combined with distributed acoustic sensing (DAS) presents a new approach to acquiring time-lapse seismic data. SOVs are AC induction motors mounted on fixed foundations, which spin eccentric weights, generating swept frequency P and S-waves (Freifeld et al., 2016). SOVs are built from off-the-shelf industrial components and unlike other rotary sources, there is no effort to provide phase-stability during rotation. A pilot geophone under the SOV allows for source-receiver deconvolution.
At the CO2CRC Otway Stage 3 Project, an SOV-DAS network was used to monitor the evolution of a 15 kT CO2-rich fluid injection. Nine SOVs were operated as seismic sources and five wells are instrumented with DAS cables cemented behind casing. This installation was the first trial of dual-motor SOVs, which feature a smaller high-frequency vibrator collocated with a larger low-frequency vibrator, design to broaden the source spectral energy. Each SOV was operated for approximately two and a half hours every other day throughout a seven-month long baseline period, followed by an almost five-month injection period. Periodic 3D VSP surveys were conducted using conventional vibroseis to serve as a benchmark for comparison to the SOV-DAS data.
The SOV-DAS system proved highly reliable, operating with an uptime of ~95%. Challenges included difficulties in maintenance and operation associated with a complex system of hardware and software. Given the small changes associated with the thin gas plume, additional challenges concerned reducing noise and artifacts to maximize the time-lapse signature of the injected plume. This paper provides an overview of the SOV-DAS system and shares some of the lessons learned from one year of operation.
At the CO2CRC Otway Stage 3 Project, an SOV-DAS network was used to monitor the evolution of a 15 kT CO2-rich fluid injection. Nine SOVs were operated as seismic sources and five wells are instrumented with DAS cables cemented behind casing. This installation was the first trial of dual-motor SOVs, which feature a smaller high-frequency vibrator collocated with a larger low-frequency vibrator, design to broaden the source spectral energy. Each SOV was operated for approximately two and a half hours every other day throughout a seven-month long baseline period, followed by an almost five-month injection period. Periodic 3D VSP surveys were conducted using conventional vibroseis to serve as a benchmark for comparison to the SOV-DAS data.
The SOV-DAS system proved highly reliable, operating with an uptime of ~95%. Challenges included difficulties in maintenance and operation associated with a complex system of hardware and software. Given the small changes associated with the thin gas plume, additional challenges concerned reducing noise and artifacts to maximize the time-lapse signature of the injected plume. This paper provides an overview of the SOV-DAS system and shares some of the lessons learned from one year of operation.
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