Seismic monitoring with continuous seismic sources

Tyler W. Spackman and Don C. Lawton

ABSTRACT

The Containment and Monitoring Institute has established a Field Research Station southwest of Brooks, Alberta which will be used to study how injected carbon dioxide behaves in the subsurface, as well as to test various measurement, monitoring and verification technologies to determine their applicability for use in monitoring subsurface fluid injection projects. One technology of interest that will be tested is the use of permanent, or continuous, seismic sources.

A synthetic source function representing the sweep of a continuous seismic source was created and used to generate synthetic shot records. Additionally, a correlation routine was developed to handle multiple shot records, each originating from an individual sweep, and then remove the sweep overprint and suppress noise. Two potential correlation and stacking workflows were tested, and were found to produce comparable results. However, stacking recorded data to suppress noise before correlating with the source function produced a final shot record up to 10% faster than correlating before stacking.

To serve as a baseline dataset against which to compare data acquired using a continuous seismic source, a 2D seismic line, acquired in May 2017, was processed. A similar processing flow will be developed and semi-automated for use with continuous source data. Field work is ongoing at the Field Research Station, and includes the installation and testing of permanent sources. Based on raytracing and analysis of offset-dependent synthetic seismograms, an offset of 110 metres between the continuous seismic source and the VSP recording well will give an optimal combination of spatial coverage and angle content in recorded seismic data.

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