Low-frequency Vibroseis: current achievements and the road ahead?
Extending the seismic signal frequency towards low frequencies has become almost standard on seismic projects, owing to the benefits it provides in terms of vertical resolution, signal penetration, inversion workflow results or ease of interpretation. Vibroseis is preferred to explosives not only for its productivity, but also for the control it allows over frequencies generated. While Vibroseis equipment has been improved in recent years, discrepancies are observed in the equipment and methods used, in particular in the design of low-frequency sweeps. A desire for lower frequencies seems also to guide the development of some vibrators, at the expense of technical complexity, higher cost and reduced performance at higher frequencies. However, if the need for broader frequencies is not questioned, the right level of low-frequency energy necessary for imaging and interpretation purposes is still not clearly defined by the industry, at the risk that the current focus for more powerful lower frequencies could be a temporary trend. This paper discusses achievements in equipment and methods, and speculates on the future of low-frequency Vibroseis.