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ABSTRACT: Evidence for Recent Migration of Geopressured Fluids along Faults in Eugene Island, Block 330 from Estimates of Pore Water Salinity


We estimated the pore water salinity of reservoir sands in the Eugene Island Block 330 Field using SP logs from about 50 wells. Our results show: (a) shallow reservoir sands (depths less than 1600 m) have higher salinities than deeper sends (depths greater than 2000 m); (b) salinity systematically increases with distance from the fault zone; (c) salinity estimated from SP logs taken after 1986 are higher than salinities calculated from SP logs taken in the early 1970s in shallow reservoir sands; and (d) salinity estimates for deeper reservoir sands do not vary with the age of the SP log. Pore water salinities estimated from SP logs are consistent with salinities measured from well head samples in the region. We interpret these results as evidence for recent expulsion of low salinity geopressured fluids along faults into sand layers in the overlying hydropressured Plio-Pleistocene section. Lower salinities and the absence of changes in salinity with age of the SP log implies that deeper reservoir sands are in hydrologic contact with the geopressured zone or have experienced an infusion of low salinity fluids during the production history of the South Eugene Island Block 330 Field.

AAPG Search and Discovery Article #90941©1997 GCAGS 47th Annual Meeting, New Orleans, Louisiana