ICE 2022


For optimal, cost-effective imaging, a seismic acquisition design should be an integrated solution that in addition to geometry parameters, also considers the seismic energy source and its role in spatial sampling. In the past, seismic surveys for deeper targets (>2 km depth) used large explosive seismic sources (2-4 kg of explosives) deployed in deep shot holes (12-18m) with sparse spatial sampling. In areas where drilling deep shot holes was difficult, multiple shallower shot holes with smaller charges were used to generate the equivalent energy of a single large, deep source, but these were still deployed at the same spatial sampling interval as the larger charges. What if better seismic data could be acquired via better spatial sampling, without sacrificing deep imaging? This has been a successful approach with Vibroseis sources where surveys are now acquired with a single Vibroseis and single sweep at a much smaller spatial sampling interval than was used when multiple Vibroseis and multiple sweeps were used at each shot location. This case study examines methodologies for implementing this technique for explosive surveys. While often explosive source performance is analyzed on shot records, a more statistically relevant analysis can be done by comparing fully processed seismic lines, as used by interpreters. However, a challenge in comparing different sources this way is that not only are the source parameters different, but often the acquisition parameters (source interval, receiver interval, recording channels) and the processing flow are different. This can complicate comparisons of source charge size and depth analyses as differences in these other parameters will affect results. In order to accurately compare just the changes in sources, seismic lines can be decimated to matching acquisition parameters and reprocessed. This is the approach taken in this case study, where four 2D seismic lines from the Magdalena Valley, Colombia with various source parameters were decimated to the same acquisition geometry, and then reprocessed to accurately compare and identify the best cost/benefit source options. Furthermore, new developments in miniaturizing seismic sources are enabling smaller spatial sampling on surveys with explosive sources without negatively affecting costs. In Canada, several field trials have been conducted utilizing new miniaturized sources that can be deployed as shallow as 1m and still provide good energy at depth (Crook et. al., 2021, Brost, 2021). By reducing cost per source, more source points per km2 can be recorded, resulting in a smaller station interval and better subsurface sampling. We will show a comparison of miniaturized sources vs. conventional sources in Canada to illustrate how improved subsurface imaging can be achieved with miniaturized seismic sources. Acknowledgements The authors would like to acknowledge and thank Gran Tierra Energy for permission to publish results from the Colombian study and Suncor Energy Inc., Imperial, and Orica for permission to publish results from the Canadian study. References: Brost, D. 2021, Tactics for Explosive Deployment Deep Basin Seismic Exploration: GeoConvention, Technical Program Abstracts. Crook, A. et. al., Case Study: The use of miniaturized seismic sources for reduced environmental impact 2021, 82nd EAGE Annual Conference & Exhibition, Expanded Abstracts.