Time-lapse Refraction Seismic Monitoring

A novel seismic technique for reservoir monitoring has been developed and tested in a resent field trial at the Peace River heavy oil field in Alberta, Canada. By measuring time shifts on first arrival head-waves from a refracting layer below the reservoir, the method aims to produce high-resolution areal maps of reservoir time shifts at a much lower cost than conventional 4D seismic. Good lateral resolution is achieved by numerically redatuming the wave field recorded at surface to a datum just above the reservoir. Preliminary results show plausible one-way time-lapse time shifts in the reservoir of the order of 2 ms, caused by variation in reservoir fluid pressure in the vicinity of active steam injectors.