Solving the near-offset noise cone using rolling variable-density acquisition (RVDA)

Uniform densification is an inefficient response to offset-dependent land seismic noise. Noise is strongly offset-dependent, yet conventional acquisition designs increase sampling uniformly, expending effort across offset ranges that already exhibit acceptable signal-to-noise ratio (SNR). Wide-azimuth orthogonal layouts therefore exhibit a systematic imbalance: near offsets, where SNR degradation is most severe, are also the most sparsely sampled. This combination limits the effectiveness of subsequent processing and imaging. Rolling variable-density acquisition (RVDA) corrects this imbalance without sacrificing azimuthal symmetry or long-offset illumination. The approach preserves a standard rolling wide-azimuth base geometry to maintain aperture and azimuthal coverage, while selectively increasing sampling density within a rolling near-offset window. Receiver densification is confined to a localized subpatch of the live spread, and source densification is introduced through sparse activation in roll space (for example, firing the infill pattern every second roll in each direction), rather than by uniformly densifying the survey. The resulting effect is targeted offset rebalancing. Near- and mid-offset sampling is substantially increased, while far-offset structure and azimuthal diversity remain essentially unchanged. For a representative design, RVDA achieves near-offset sampling comparable to a uniform twofold densification with only ~33% more deployed receivers and a factor-of-two increase in effective source effort, compared with fourfold increases in both for a uniformly dense survey. Operationally, RVDA remains fully compatible with standard rolling workflows, equipment, and field practices. These results demonstrate that mitigating the near-offset noise cone does not require indiscriminate densification. By reallocating acquisition effort to the offset range where data quality degrades first, rolling variable-density acquisition restores a balanced offset spectrum for imaging, AVO, and inversion at a fraction of the cost of uniform densification.