High-resolution land seismic acquisition with Broadsweep
Seismic acquisition techniques have steadily progressed over time to achieve higher productivity and greater data bandwidth. Vibroseis sources with new hydraulics and plate and chassis design (Bagaini, 2008; Wei, 2017) are able to generate sweeps between 1-2 Hz to 300-400 Hz (Wei, 2015). Receivers have graduated from complicated patterns to the single-point omnidirectional receiver. Trace density of surveys has increased to provide higher signal-to-noise ratio and homogeneous azimuthal and offset coverage. Vibroseis is a controllable source and its amplitude and frequency characteristics can be manipulated to shape the signal of the desired amplitude and phase spectrum. This remarkable feature of the Vibroseis source, however, remains underutilized: most of the acquisitions are performed with linear sweeps or sweeps with a very mild degree of non-linearity in the frequency- time domain. Increasing the bandwidth of seismic data has several advantages from reducing ambiguity in statics and velocity models during processing to more reliable seismic-to-well ties and seismic inversion results. The result is better reservoir characterization and reduced exploration risk. High quality data with increased signal-to-noise ratio provides for faster conventional interpretation as well as quantitative interpretation utilizing sophisticated multi-trace attributes, machine learning-based algorithms and azimuthal seismic anisotropy analysis (Curia et al., 2018). We have developed a real-time adaptive Vibroseis acquisition technology utilizing a new controller hardware and software, which takes advantage of real-time data feedback and adjusts sweep parameters to compensate for changing near-surface conditions while delivering broadband seismic data with high signal-tonoise ratio. Electronic sweeps, signals from the inertial mass and baseplate are stored, and can be used during processing to further increase data quality. This autonomous system can be used with any vibrator and without any special hardware modifications. The technology can be tuned for a particular reservoir interval to achieve maximum signal-to-noise ratio and resolution, which is further enhanced in processing. This targeted approach is especially beneficial for tight unconventional reservoirs for time-lapse hydraulic fracturing monitoring.