The interpretation of 2-D and 3-D seismic and suites of well logs from submarine fans known to be important reservoirs lacks an important companion, namely detailed studies of major outcrops. Such studies can provide data to construct synthetics that may be sufficiently comparable to subsurface information to provide a guide to interpretation and a framework for understanding the reservoir architecture.

Outcrops of coarse-grained, sand-rich fans are rather common. However, tectonic tilt normally prevents lateral correlation of many features which commonly are larger than the outcrop. In addition, resulting fan models are not very applicable to fine-grained fans. Studies of the Mississippi Fan (DSDP Leg 96), the salt-withdrawal basins in the northern Gulf and the adjacent basin floor south of the Sigsbee Escarpment, combined with the non-tilted Permian Tanqua Karoo in South Africa, provide an excellent framework for exploration- and reservoir- scale investigations of fine-grained basin-floor fans.

Basin-floor fan deposits start with an updip-pinching-out channel complex at the base of slope where the erosional characteristics typical of the continental slope change into depositional characteristics. Amalgamated channel sandstones with remnants of shale-rich levee deposits result in a somewhat complex tortuosity of the fluid flow. Downdip, the complex changes into one or more individual leveed channels. Major massive channel sands are surrounded by rather clean levee deposits (low-resistivity, low-contrast, thin-bedded sandstones) that can be very oil prone. Further down dip, the channels become less channelized and lose their confining influence to the head of density currents, and sheet sand deposition results. The sheet sands are wide and thin, but as a total deposit they form major reservoir sand thicknesses. The complexity of the vertical and lateral continuity of these sands is not well understood, which results in miscommunication between geologists1 geophysicists and reservoir engineers.

End_of_Record - Last_Page 12---------------