Seismic Net Pay Estimator

Estimate minimum detectable net pay thickness from seismic tuning analysis. Determines if thin reservoir intervals are visible on seismic data and evaluates detectability based on amplitude response and tuning effects.

Net Pay Tuning Detectability Thin Beds

Input Parameters

Seismic Properties

Hz
Peak frequency of seismic data
m/s
P-wave velocity in reservoir
%
% of tuning amplitude (10-50% typical)

Impedance Contrast

%
Sand-shale impedance difference
R ≈ ΔZ / (2 × 100)

Well Calibration

m
Net pay from well logs (optional)

Quick Presets

Results

Theory & References

Tuning Wedge Concept

Quarter-Wavelength Rule

Seismic tuning occurs when layer thickness equals λ/4, where reflections from the top and base of a layer constructively interfere to produce maximum amplitude.

  • Below tuning (h < λ/4): Amplitude increases linearly with thickness (composite wavelet response)
  • At tuning (h = λ/4): Maximum amplitude (peak constructive interference)
  • Above tuning (h > λ/4): Amplitude decreases as top and base reflections separate

Thin Bed Reflectivity

Below Tuning Behavior

For beds thinner than tuning thickness, the amplitude is proportional to net pay:

  • Composite response: A = 2R × sin(2πh/λ)
  • Linear approximation: A ≈ (4πRh)/λ for h << λ
  • Detection limit: Minimum thickness producing measurable response (≈ λ/30)
  • Key insight: Thin beds produce weak but detectable signals if impedance contrast is sufficient

Detection Strategies

  • High frequency data: Improves vertical resolution (smaller λ)
  • Well calibration: Tie well net pay to seismic amplitude
  • Amplitude extraction: Extract RMS or peak amplitude along horizon
  • Spectral decomposition: Isolate frequency components sensitive to thin beds
  • AI/EI inversion: Convert amplitudes to impedance for direct thickness estimates