Spectrum’s geoscientists discuss how the evaluation of 16,000 km of modern, high quality, long-offset 2D seismic data, acquired by Spectrum in 2014 over the Sergipe Alagoas Basin, has confirmed the extension of a turbidite channel system into open acreage offered in the ongoing licensing Round 14. First published in Geo ExPro, May 2017.
This channel system has been proven to contain several billion barrels of reserves from recent exploration programmes, including the Barra, Muriu and Farfan discoveries. Integration of derived seismic attributes and potential field data has resulted in a better understanding of the main elements of the petroleum system, allowing for the identification of multiple untested play types. This evaluation demonstrates that the undrilled potential offshore Sergipe may surpass the discovered resources to date.
The long-offset 2D seismic data was processed through pre-stack time migration using conventional techniques, and through pre-stack depth migration using both conventional and broadband processing techniques. The application of these two technologies resulted in seismic data with a vertical resolution as fine as 5–10 m, allowing identification of additional levels of interest which are mostly beyond seismic resolution in the conventionally processed seismic data.
Additionally, AVO stacks and attributes have been generated over an area encompassing the Sergipe Sub-basin. A targeted pre-processing flow was used to produce conditioned-angle gathers, calibrated with existing well data, indicating numerous potential AVO anomalies.
Ship-borne gravity data has also been integrated with the seismic interpretation of a relatively clear Moho reflection on the PSDM sections, to produce a series of density models. This modelling exercise has resulted in a very clear interpretation of the crustal architecture. The outcome of the exercise will be a higher confidence in crustal architecture, leading to improved heat flow prediction and thermal maturity profiles.
Detailed evaluation of available seismic data indicates that the Sergipe deepwater plays extend further outboard to the east and south-east, where they have an added opportunity in a basin floor fan setting. To the northeast, primarily in Alagoas, channel fill sediment play, rifted basin fill, and faulted Palaeozoic sediments are all exploration targets. As part of the current licensing Round 14 and with strong indications of huge untapped potential, exploration activity, inclusive of drilling in this highly prospective area, is expected to yield continued success, with undrilled potential surpassing discovered resources.
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Offshore Brazil – Sergipe Basin Undrilled Potential Surpasses Giant Offshore Discoveries