ABSTRACT

Rocks of the Pliocene and Pleistocene Systems of the Louisiana Outer Continental Shelf are divisible into three rock facies, (i.e., massive sand, alternating-sand-shale, and massive shale). Similar to older Tertiary rocks of the inner shelf and coastal plain, these facies are genetically related to delta depositional systems. A description of the facies distribution for a discrete time interval can indicate the location of deltaic progradations and the approximate shape and seaward extent of their delta plains. The mapping technique requires a working definition of the individual rock facies to facilitate the division of log correlative time intervals into component facies. Separate isofacies contour maps are drawn simultaneously for each time interval, recognizing that deltaic progradations are shown by the massive sand isofacies map. The final lithofacies display map compiles data relating to all three rock facies and thickness contours showing the distribution of massive sand and alternating sand-shale facies.

An important inter-relationship exists between rock facies--structure--abnormal pore fluid pressure and the occurrence of hydrocarbons. Seismic techniques can reliably predict structure and abnormal pressure, and this knowledge can be qualitatively integrated into facies mapping where well control is lacking. Optimum sites for hydrocarbon accumulations can be localized by the recognition of deltas, the locale of their still stands, and favorable structural and hydrodynamic trapping mechanisms.