About This Item
Share This Item
Channel sandstones are deposited in fluvial channels, fluvial-dominated deltas, submarine channels, and channel-dominated submarine fans on shelves and slopes of many basins. Excellent models of these channel-sandstone depositional environments and reservoirs are in Upper Pennsylvanian and Lower Permian sediments of the eastern shelves and slopes of the west Texas Permian basin. In dip-trending paleodrainage systems on superimposed alluvial plains, sandstone reservoirs are in single and multiple strike-oriented point bars in meander belts, and longitudinal and transverse bars in braided belts. By differential compaction these sandstone belts may produce oil where they drape over buried paleotopographic features such as reefs, structures, and sandstone bodies. Conversely, eservoirs may be found in these buried features by recognizing diversions in the trend of overlying sandstone belts. Oil and gas in sediments adjacent to channels may be trapped by nonpermeable channel-fill barriers. Seismic cross sections of meander belts can clearly show convex-downward bases.
Stratigraphic traps are in thin distributary-channel and delta-plain sandstone facies of shelf-elongate deltas on shelves. Shelf-margin lobate deltas have reservoirs in thick distributary-channel, delta-plain, and delta-front sandstone deposits.
"Packages" of fine-grained, lenticular turbidites can be correlated in submarine channels and fans. Stratigraphic cross sections reveal levees that trap oil in turbidites. Many slope-sandstone facies have been stratigraphically miscorrelated by hundreds of feet with lower sandstone formations.
Regional and local models of shelf and slope channel-sandstone systems and reservoirs and the subsurface methods that reveal them should aid research, production, and exploration geologists. This paper is an attempt to bridge the gap between research and applied geology by describing how the depositional environments of channel sandstones are recognized in the subsurface and how oil and gas are trapped in these sandstones.
End_of_Article - Last_Page 2465------------