3D survey design end-to-end walkthrough

Part 3 — Survey geometry design

Learning objectives

Chain together §3.1–§3.7 to produce a concrete design from target requirements
Compute bin size, aperture, line intervals, and fold from user inputs
Estimate channel count and crew productivity
Recognise which input most constrains the design (typical bottleneck: fold or aperture)

Everything in §3.1–§3.7 comes together in a single design. Given the target (depth, dip, area) and the bandwidth you want (V, f_max) and the fold you need, a consistent 3D design falls out of the formulas.

The design sequence:

Bandwidth: λ_min = V / f_max.
Bin size: Δx = min(λ_min/3, V/(4 f_max sinα)). Round down to a standard bin.
Aperture: A = z · tan(θ_max).
Survey outline: target + 2A on each side.
Line intervals: SLI and RLI ≈ 8–12 × Δx (classical; modern nodal can be more efficient).
Offsets: max offset X_max ≈ z · tan(35°) captures enough AVO angle for most targets.
Fold: scale patch size until fold target is reached.
Channel count: patch L × patch W / (bin²). Big number.

What typically binds

For deep (>3 km) steeply-dipping targets (salt, thrust belts) the binding constraint is aperture: it balloons the survey. Each additional 10° of θ_max adds ~15% to survey size at depth. For mid-depth (1–3 km) targets the binding constraint is fold: getting 40+ fold uniformly across a large survey requires substantial channel count. For shallow (<500 m) high-resolution work the binding constraint is bin size: Δx may need to drop to 6.25 m, quadrupling the channel budget.

Sanity-checking your own design

Before handing the design to a field planner, answer three questions honestly:

Does my bin size support imaging at the steepest dip I quoted? (Δx ≤ V/(4 f_max sinα))
Does my aperture extend the survey by 2z · tan(θ_max) in every direction?
Does my template + patch give the fold target across the full-fold area (not just at the centre)?

If any answer is "no", one of your bin size, aperture, or channel count is too small. That’s where the budget conversations start.

References

Cordsen, A., Galbraith, M., Peirce, J. (2000). Planning Land 3-D Seismic Surveys. SEG Geophysical Developments 9.
Vermeer, G. J. O. (2002). 3-D Seismic Survey Design. SEG Geophysical References 12.
Stone, D. G. (1994). Designing Seismic Surveys in Two and Three Dimensions. SEG Geophysical References 5.
Bouska, J. (1995). Cube management — 3D acquisition design. The Leading Edge, 14(1), 53–57.