--> ABSTRACT: The Deposition and Distribution of Organic-Rich Muds by Modern Turbidity Currents on the Western European Passive Margin: Analogues for the Deepwater Petroleum Systems, by Hunt, James E.; Wynn, Russell B.; Stevenson, Christopher J.; #90135 (2011)

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The Deposition and Distribution of Organic-Rich Muds by Modern Turbidity Currents on the Western European Passive Margin: Analogues for the Deepwater Petroleum Systems

Hunt, James E.1; Wynn, Russell B.1; Stevenson, Christopher J.1
(1)Marine Geoscience, National Oceanography Centre, Southampton, United Kingdom.

Modern deepwater turbidite systems have shown the deposition of large volume unconfined turbidity currents on the Western European passive margin. The modern core dataset held at BOSCORF at the NOC has allowed the detailed study of deposits from nine deepwater abyssal plains in order to critique the depositional processes affecting the turbidites.

The turbidite muds pose significant heterogeneities within potential reservoir intervals. The turbidite muds from the modern Western European passive margin also contain >2% TOC. Thus, these deposits could present analogues for potential hydrocarbon sources from turbidite muds. Understanding the processes of deposition and controls on distribution from these modern systems is important; since this detail can be applied to analogous ancient systems representing regions under petroleum exploration or development.

There are several processes that will be evaluated:

+ Linked debrite development.

+ Mudcap ponding into basin depocentres.

+ Mudcap remobilisation.

Linked debrites can pose significant heterogeneities in turbidite reservoir intervals. This dataset has enabled an important advance in the understanding of the role that mud (clay and fine silt) has to play in their formation. The present study also demonstrates a classification scheme in mud-rich systems compared to previous work.

Metre-thick mudcaps have been observed to thicken in subtle basin lows. Previous studies have eluded to deposition from highly concentrated non-turbulent (laminar) flows. Grain-size and geochemical vertical and spatial profiles indicate that fluid turbulence is instead the primary transport mechanism for sediment dispersal. However, during sedimentation yield-strength fluids are generated as the fine-grained material consolidates. This is then able to flow under laminar flow conditions and redistribute the mudcap preferentially into the basin lows.

On basin margins there is additional evidence to suggest that the rapid deposition of metre-thick mudcaps has led to destabilisation of the accumulation. This has led to remobilisation of the mudcap deposit as a yield-strength mudflow.

Understanding the architectures of these turbidite muds and the controls on their distribution is captured here in an unparalleled core and geophysical dataset. The hope is that the heterogeneities resolved in the present study can be used to aid petroleum system evaluations both from reservoir and source rock perspectives.

 

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.