Seismic Surveys Explained
Seismic surveys are the primary tool for imaging structures beneath the seabed. By analyzing how sound waves travel through rock, geoscientists can identify potential oil and gas traps before drilling.
How Seismic Surveys Work
Generate Sound
Air guns release compressed air, creating sound waves that travel down through the water and into the seabed.
Reflect & Record
Sound waves reflect off rock layers. Hydrophones in long streamers record these reflections.
Process & Image
Supercomputers process the data to create detailed images of underground structures.
Seismic acquisition vessels tow arrays of air guns (source) and long cables containing hydrophones (receivers). As the vessel moves, it continuously fires the air guns and records the reflected signals, building up a picture of the subsurface.
2D vs 3D Seismic
2D Seismic
- Single line of data (cross-section)
- Lower cost (~$10-30k/km)
- Regional reconnaissance
- Limited structural resolution
3D Seismic
- Full 3D volume (like a CAT scan)
- Higher cost (~$50-150k/km²)
- Detailed prospect definition
- Required before drilling
Modern exploration starts with 2D surveys to identify areas of interest, then acquires 3D over specific prospects before drilling decisions.
Seismic in Cyprus
Regional reconnaissance surveys covering most of the EEZ
First 3D survey leading to Aphrodite discovery
Extensive 3D acquisition across Blocks 2, 3, 6, 8, 9, 10, 11
Additional data and advanced processing techniques
What Seismic Can (and Can't) Show
Can Identify
- • Structural traps (anticlines, faults)
- • Stratigraphic features (reefs, channels)
- • Reservoir presence and thickness
- • Potential seal (cap rock)
- • Direct hydrocarbon indicators (DHIs)
Cannot Confirm
- • Actual presence of hydrocarbons
- • Reservoir quality (porosity/permeability)
- • Fluid type (oil vs gas vs water)
- • Commercial volumes
- • Producibility
Key point: Seismic identifies potential, but only drilling can confirm whether hydrocarbons are present and commercially recoverable.