Hydrocarbon Indicators
Evidence for a mature working petroleum system comes from the following indicators.
Well shows
Geochemical anomalies
Seismic DHI's
Beach strandings of tar are a regular occurence in Seychelles. The tars geochemistry correlate to the local stratigraphy (see source rock analysis report).
Well Shows
The three Amoco wells all encountered hydrocarbon shows at various depths as indicated below.
This table describes the different shows in the three wells. It can be seen that all the wells had shows of migrant oils and headspace gas and Reith Bank even had 0.7 ppm of Benzene in a drill stem test which is believed to indicate proximity to an accumulation.
Sniffer Survey
In 1983, together with a seismic programme, Amoco undertook a gas sniffer survey which came up with some interesting anomalies as shown here.
An airborne fluorescence survey
was undertaken by Enterprise Oil in 1991 and this again came up with some interesting anomalies. It is also interesting to note that Enterprise flew over the three Amoco wells which had been drilled over ten years earlier and still came up with some anomalies over them.
Satellite seep survey
Recently PetroSeychelles commissioned a satellite seep survey which was done by Infoterra and this also came up with some interesting seep anomalies.
Seismic DHI's
Direct indicators of hydrocarbons are also evident on seismic data in the form of gas chimneys, flat spots with phase reversals and chemosynthetic reef buildups among others.
All these support the fact that oil and gas have been generated and trapped in the Seychelles waiting to be discovered.