Authors of this report summarize the results of integrated geologic characterization of the Frontier Formation along the Moxa Arch in southwestern Wyoming in four major areas of study: (1) stratigraphic and depositional systems, (2) diagenesis of reservoir sandstones, (3) disttribution of natural fractures, and (4) horizontal stress orientation. The authors describe the geological elements that were found to be important in characterizing these low-permeability sandstone reservoirs.

Structurally complex, heterogeneous, tide-dominated deltaic reservoirs in the Lower Misoa Formation (lower Eocene C members) in the LL-652 area of Lagunillas field in the Maracaibo Basin, Venezuela, have produced 166 million stock-tank barrels (MMSTB) of oil but have a low recovery efficiency of 22 percent. These reservoirs will contain more than 900 MMSTB of unrecovered mobile oil when primary recovery operations at the current 80-acre well spacing end.

The origin of thousands of playa basins on the Southern High Plains of Texas and New Mexico has been attributed to eolian deflation, evaporite or carbonate dissolution and subsidence, piping, or animal activity. Shallow-seismic data from three ephemeral lake (playa) basins in the Texas Panhandle, collected as part of a hydrogeological study of High Plains playa and interplaya environments, demonstrate that subsidence has figured prominently in the formation of these three basins.