Marine sources have been three sub-arrays for many years. As the drive for cost-efficiency has pushed the industry towards various types of triple source configurations, practical issues mean sources are now often two sub-arrays. This gives plenty of energy (indeed, sometimes too much energy) for shallow reflectors whilst being insufficient to recover deep reflectors – where the recoverable energy bandwidth is often limited to 20Hz or less. At the same time, shortening the shooting cycle and then deblending results in destructive interference that further reduces low end energy.
Fortunately, the Source Isolation and Source Revolution approaches – where relatively closely spaced source elements fire within a few tens of milliseconds of each other – means that they behave constructively at low frequencies – indeed, they can be thought of a one, very large, source.
Typical exploration Source Isolation configuration: 4 * small arrays. Low frequency energy is approximately the same as if a single four -or more-subarray source had been used.
- Low end signal increases as the number of output sources
- Firing time proximity means the same noise is observed, thus improving SNR significantly
- Eliminates challenge of destructive low end interference inherent in industry sim-source methods
- Reduces SPL severalfold and cuts energy density by spreading out sub-arrays – this promoting good environmental practice in the industry
- Provides unmatchable low end SNR for improved inversion, better 4D and AVO and significantly enhanced FWI capabilities