oa Seismic source comparison in Surat Basin, Queensland

A 2D land seismic reflection line was acquired 14-17 June 2011 in the Surat Basin, Queensland. Two source types were utilised; a heavy Vibroseis (AHV-IV 60,000 lb), and an impulsive surface source (Geokinetics proprietary Dual Synchronised Electrical Impulsive Source “onSEIS”). The recording system was OYO Geospace Seismic Recorder “GSR” cable-free nodes. The main objectives of the study were to (1) evaluate the response of the different seismic sources on the local geological framework; (2) to establish the optimal source effort for a planned 2D survey within the area. Vintage dynamite data acquired along the same line in 1984 was also used in the source effort analyses.

Qualitative analyses included visual inspection of raw shot gathers and processed brute stack sections; reflectors coherency, signal-to-noise ratio, spatial distribution, and signal penetration, were determined on raw displays. Quantitative analyse included amplitude spectra on Brute stack sections. Frequency content and signal bandwidth were critically evaluated to define which source performs better in terms of seismic resolution.

The dynamite single records showed good S/N ratio with clear reflectors at the target depths down to 1800 ms. However, the processed stack showed less bandwidth and lower imaging resolution due to the coarse source and receiver sampling during data acquisition. The onSEIS and Vibroseis signatures were comparable to the dynamite shots at the deep targets. However, the higher trace fold, longer offsets, and tighter spatial sampling for the onSEIS and Vibroseis, provided higher imaging resolutions that illuminated the entire section.