Seismic studies of the near-surface at the CaMI Field Research Station, Newell County, Alberta

J. Helen Isaac, Donald C. Lawton

We reassessed the processing and analysis of the two S-wave seismic surveys that were acquired at the CaMI Field Research Station (FRS) in the summer of 2018. We refined the S-wave depth/velocity model derived from refraction statics analysis of the S-wave fixed array data by limiting the offsets in the analysis. The new model shows a 19-26 m thick near-surface layer with velocities ranging from 222 to 288 m/s. Below this layer is bedrock having S-wave velocities between 885 and 930 m/s. The depths to bedrock compare well with the actual bedrock depth at the injection well location. The profile of the near-surface S-wave velocity corresponds well with the refractor depth profiles obtained through refraction analysis of 2D P-wave data.

We also improved the imaging of the S-wave streamer data by reprocessing the data. We rebinned the CDPs and applied updated stacking velocities. We also applied pre-stack trace mixing and post-stack f-x deconvolution because of the very short receiver spacing of 1 m and low fold. The resulting reflector is more continuous and better focussed. However, we found that the observed time structure is highly sensitive to the stacking velocities, as they are so low.