Gemini™ Extended Frequency Source

Increasing the signal-to-noise at low frequencies (1.5-4Hz) leads to an improvement in the resulting velocity model. This is because lower frequencies are able to penetrate rough or high contrast boundaries more effectively, thereby improving the signal to noise ratio in the data and allowing you to see clearly.

ION’s new Gemini™ Extended Frequency Source (EFS) technology is a broadband seismic source technology that is able to generate the <4Hz frequencies required to image in complex geologies where penetration of low frequencies is key.

The Gemini source is unique as it emits a broader spectrum of frequencies (2 – 80 Hz or higher) than conventional sources or other purpose built low frequency sources. These characteristics allow it to offer an alternative to conventional sources for more efficient seismic acquisition.

However, while Gemini is unique, it is also conventional, in that it is  based on airgun technology. It utilizes industry standard parts with an 8,000 cubic inch chamber and firing pressure of 2,000 psi, but its parts have been cleverly modified to better control the creation and oscillations of the source bubble.  As a result, Gemini yields a broad frequency spectrum richer in low frequencies than conventional sources.  While conventional source arrays may produce low frequencies, the signal-to noise ratio at these frequencies is very low, thereby requiring an expensive, high density of shots in order to stack up to generate an equivalent signal to noise ratio as created by Gemini.  Gemini thus offers an alternative to conventional sources for more efficient seismic acquisition and overall better data quality.

Improving the signal-to-noise ratio in the low-frequency part of the seismic spectrum allows you to hear more clearly at longer offsets.  Gemini achieves this by carefully controlling the oscillations of the bubble it creates. The final pressure of the source chamber, the volume of the source chamber, the depth of tow and the way the air is released from the chamber are all key contributors to the creation and oscillation of this bubble.  Through consistent and controlled acquisition parameterization,  source signature repeatability is also ensured.

Geologies with complex, rough or high contrast sediments such as salt bodies or chalks are often difficult to image due to poor seismic signal penetration. In addition, poor signal to noise ratios often cause the latest model building algorithms such as Full Waveform Inversion (FWI) to perform inefficiently and less effectively in a phenomena commonly referred to as cycle skipping.

With Gemini, you can achieve better low frequency signal at input. Low frequencies allow for better penetration, especially of boundaries that tend to scatter or attenuate high-frequencies.  In processing, more signal returned at the low-frequency notch means better deghosting.  In model building, better signal penetration means matching between modelled and field data using the latest inversion methodologies such as travel time or least-squares FWI can be achieved more efficiently and accurately.  Lastly, in imaging, a better velocity model results in a better migration, ultimately delivering a higher resolution, seismic image.

Gemini was designed to be compatible with standard existing vessel configurations, including: the compressors, flexible or rigid flotation systems, umbilical bell housing, controllers, etc.   This allows the majority of the existing source vessel fleet to just plug and play.

Designed to function as a single point source and not an array, Gemini’s compact profile allows for easier and safer back deck deployment and operations than a typical multi-gun array.  This is especially true in dual or triple source configurations where towing two or three point sources is clearly less onerous and has a smaller footprint than towing two or three multi-gun arrays.  Gemini’s forward primary source plus aft backup/spare configuration also ensures less downtime during seismic operations with 100% redundancy.

While the Gemini source emits a broad spectrum of frequencies (2 – 80 Hz or higher), at higher frequencies (>100 Hz), it emits less energy than a conventional air-gun array.   This  means the new source has considerably smaller behavioural threshold distances for marine mammals than conventional sources.  As a result, Gemini offers the most environmentally friendly, commercial, seismic source option available to the market today.