First Published: GEO ExPro, December 2019

 

Abstract

The identification and evaluation of the hydrocarbon potential of hybrid depositional systems.
According to Rystad, exploration in deep water locations have already contributed half of the discovered volumes in the first six months of 2019. In this key setting for future exploration, coast-parallel bottom currents and gravity processes are common along continental margins. The interaction of these processes can build large mixed/hybrid (turbiditic-contouritic) depositional systems which have only just been recently identified and have now begun to be studied in more detail. A number of prolific discoveries have been associated with these hybrid systems and several more are now being recognized in modern long-offset seismic data.

Mixed/hybrid deepwater turbiditic-contouritic depositional systems are only just beginning to be understood, but show great potential.

Several prolific discoveries have been associated with hybrid turbidite-contourite systems, of which the most notable is the Rovuma Basin offshore Mozambique (Maba Complex). Another significant hydrocarbon accumulation with clear seismic indications associated with a mixed system is the deepwater confined channel Barra/Moita Bonita complex (>3 Bbo in place) in the Sergipe Basin, Brazil.

Figure: (Sergipe) PSDM through a Barra well showing clear evidence for contourite drifts.

Identification of these systems relies on the recognition of a series of diagnostic criteria derived from the integration of available understanding (Sansom, 2018) and comparison with direct observations from well-established proven systems. Hydrocarbon potential evaluation includes the analysis of probable source rocks, reservoir and traps. Potential source rocks can be identified using a systematic frontier basin methodology which integrates plate tectonic reconstruction, paleographic setting, seismic character, any available well and outcrop data, and source rock characterization (Eastwell et al., 2018). To de-risk reservoir presence and quality, both depositional system features and seismic character can be used. The trapping mechanism is usually provided by the depositional characteristics of the hybrid system.

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