Sand Distribution Within a Topographically Complex Basin — From Channelized Sheets to Onlap Margins: Grès D’Annot, SE France
David A. Stanbrook1, Jamie K. Pringle2, and Julian Clark3
1Maersk Alie og Gas A/S, Denmark
2School of Physical Sciences & Geography, Keele, United Kingdom
3Chevron, San Ramon, CA
Common stratigraphic-trap reservoirs in the Gulf of Mexico and along the margins of the Atlantic, often in salt-provinces, are found within channelized (e.g. Tahoe) or basin margin settings (e.g. Auger, Mars). Frequently within the same topographically complex mini-basin, high net:gross channel and lower net:gross basin-margin environments occur concurrently. Deciphering the lateral and distal relationships between these environments is key to understanding reservoir connectivity.
The Grand Coyer Sub-Basin (Grès d’Annot, SE France) outcrops demonstrate lateral and distal facies changes in a confined basin with complex paleotopography from a relatively thin-bedded unit, the Marnes Brunes Inférieures, to the thicker-bedded Grès d’Annot. The relationship between these two units in this confined, topographically complex sub-basin has implications for subsurface reservoir characterisation;
1) High net:gross sandstone bodies terminate rapidly with little draping onto palaeoslopes. Lower net:gross sandstone bodies tend to drape onto palaeoslopes, 2) Cyclical, ~50m thick, high- and low- net:gross sedimentary intervals appear to be unpredictable in both their repetition and in their distribution in the sub-basin, 3) Channel sinuosity tends to increase as the basin is progressively filled, 4) All formations erode underlying intervals and have implications for reservoir seal, 5) Steep slopes in the underlying palaeoslopes result in remobilised, chaotically deposited material creating complex palaeotopography later in-filled with turbidity-current derived sediment.
AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery