|

Seismic Acquisition Basics

Byadmin

Seismic Acquisition Basics

Introduction

Seismic acquisition is the first step in the seismic workflow. It involves generating energy, recording wavefields, and designing surveys that capture the subsurface with the right resolution, coverage, and signal quality. Good acquisition design ensures that downstream processing and interpretation deliver reliable geological results.

1. Key Components

Seismic acquisition relies on several essential elements:

• Sources

Generate seismic energy. Common types:

  • Vibroseis (land)

  • Dynamite (land)

  • Air guns (marine)

• Receivers

Record returning seismic waves. Examples:

  • Geophones

  • Hydrophones

  • Ocean‑bottom nodes (OBN)

• Recording Systems

Digitize and store seismic data with proper sampling and dynamic range.

• Survey Geometry

Defines how sources and receivers are arranged. Controls:

  • Fold

  • Offset distribution

  • Azimuth coverage

  • Bin size

Survey geometry directly impacts resolution and imaging quality.

2. Acquisition Parameters

Key parameters that determine data quality include:

• Fold

Number of traces contributing to each subsurface bin. Higher fold improves signal‑to‑noise ratio.

• Offset

Distance between source and receiver. Critical for AVO, velocity analysis, and imaging.

• Azimuth

Direction of source‑receiver pairs. Multi‑azimuth improves fault imaging and fracture detection.

• Sampling

Temporal and spatial sampling must meet Nyquist criteria to avoid aliasing.

• Bin Size

Defines horizontal resolution. Smaller bins capture finer geological detail.

3. Land vs. Marine Acquisition

Land Acquisition

  • Uses vibroseis trucks or dynamite

  • Terrain, access, and permitting affect layout

  • Often irregular geometry

Marine Acquisition

Two main types:

• Streamer Acquisition

  • Long hydrophone streamers towed behind a vessel

  • Efficient for large 3D surveys

  • Limited by feathering and shallow‑water noise

• Ocean‑Bottom Nodes (OBN)

  • Nodes placed on the seafloor

  • Excellent for full‑azimuth and long‑offset coverage

  • Ideal for complex imaging (salt, carbonates)

4. Challenges

Seismic acquisition faces several operational and technical challenges:

  • Noise — cultural noise, swell noise, wind, machinery

  • Terrain — mountains, deserts, swamps, urban areas

  • Weather — storms, currents, temperature extremes

  • Environmental Restrictions — protected areas, wildlife, permitting

  • Logistics & Cost — large crews, vessels, and equipment

Good planning and QC mitigate these issues.

Conclusion

Seismic acquisition is the foundation of the entire seismic workflow. Well‑designed surveys with proper geometry, sampling, and QC ensure high‑quality data for processing, interpretation, and reservoir characterization. Strong acquisition design leads to better images, more confident decisions, and reduced exploration risk.

Similar Posts