The same philosophy needed to be applied to the receiver side. The receiver side however, which often uses geophone arrays, or bulky and expensive nodes, has lagged behind, slowing down the survey as they are unable to match the speed of these new, fast-moving sources. If we look at how conventional surveys have evolved to higher densities on the source side in the last few decades, we can see that conventional vibroseis source fleets have been ‘scattered’ and replaced by denser single point sources, often using some flavor of simultaneous shooting schemes, bringing an increased autonomy, and delivering considerable efficiency compared to conventional source fleets (Howe et al., 2008). This has been achieved by increasing either source efficiency or receiver channel counts to their limits. In the last decades, the oil and gas industry has recognized the value of increasing trace density, and seismic surveys of tens of millions of traces per km2 are gradually becoming the norm. Trace density is defined by the number of pair source-receivers per unit of surface and can be increased by either increasing the source or the receiver density. Higher trace density seismic surveys have been associated with a better definition of the subsurface for several decades, whether in terms of imaging or seismic attributes which are ultimately linked to rock and fluid properties (Ourabah et al., 2015). Cable-less autonomous nodes are natural successors for cable systems, and removed some of those constraints, but were still not small, light, and low cost enough to enable them to release their full potential in any terrain at any scale.
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