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Magdalena Fan Confined Slope Channel Architecture: Lessons Learned about Reservoir Quality from Seismic Expression of Slope Entrenchment, Bypass and Levee Development in Mixed Sand-Mud Atlantic Margins

Cronin, Bryan T.; Castillo, Jaime1; and Martinez, J.
1[email protected]

Confined slope channel complexes form a major style of reservoir in circum- Atlantic Tertiary and Cretaceous locations. These 5-8km wide, 60-150m deep complexes have a wide range of fill architecture, linked to variable initiation, bypass, filling and reactivation styles, in different types of deep-water slope settings. The fill style of confined slope channel complexes, distinct from aggradational basin floor or lower slope sinuous leveed channels, with which they are also compared in this paper, is characterised by seismically resolvable features. Firstly the scale is within the narrow dimensional range. Secondly, they have the characteristics of both slope entrenchment and erosion and bypass, usually associated with canyons, and with master levee development, more typical of smaller scale leveed channels. Their fills form a range continuum from (1) low net; gross complexes, with early residual bypass or slump lags, followed by alternating laterally derived slumps and isolated or moderately-well connected underfit channels with their own ‘inside’ levees; through (2) moderate N:G complexes with better connectivity between channel elements, including confined sheets formed by underfit channel frontal and crevasse splays, all within the broader channel complex fill; through (3) moderate N:G complexes with significant sand bypass downdip, which has potential upside for lower slope sand sheet plays beyond the channel mouth, and to breaching of master levees on the slope to give crevasse splay plays as stratigraphic traps laterally equivalent to the large complexes; through (4) moderate-high N:G confined channel complexes with many of the characteristics of (3) with the additional confined to channelized sand sheets in the main complex fill passing upwards into late stage underfit channels.

The Magdalena Fan, including its feeder slope and upper rise areas, is characterised by a wide range of confined slope channel complexes. Detailed work on the seismic architecture has been undertaken, with the aim of finding the best fit between seismic architecture and potential reservoir quality. One of the complexes has been penetrated, to find that it fell into the finer-grained end of number (2) above, and development strategies are currently underway.


AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013