Provenance study of potential Oligocene reservoirs in Nile Delta and offshore Mediterranean

Abstract

This study aims to investigate the provenance of the Oligocene sandstones exposed at Gebel Qatrani Formation at the Fayum Province and analogues subsurface Oligocene sandstone intervals cored from 2.7 to 5.12 km at the Nile Delta. The analysis and quantification of heavy mineral assemblages revealed that the two sites maintain similar heavy mineral suites but with variable concentrations and different patterns. The provenance reliable heavy mineral indices indicate that the exposed Oligocene sandstones at Gebel Qatrani Formation are much more mature than those of the Oligocene sandstone intervals at the Nile Delta. The lower and the upper members of Qatrani Formation display heavy mineral contents indicating more maturation than the middle member which reflects an influx of less mature sandstone. The middle member may reflect a tectonic reconfiguration of the hinterland during its deposition. The reliable heavy mineral indicators of the Oligocene sandstones at the Nile delta maintain their higher values at different depths along the entire wells indicating a significant rejuvenation of the source area and hence sand supply from a source(s) that was not far distant. In contrast, Habbar-1 well sand samples (cored from 3.8 to 4.5 km) display the highest pyroxene values along with considerable contents of amphibole, mica, sillimanite, and kyanite indicating transport from a shorter distant source including a metamorphic one. Thirty seismic cross sections are interpreted and used to construct isopach maps which revealed the diagenetic effect of the heavy mineral suits with depth. That will subsequently affect the reserving characteristics of Oligocene sand intervals. Moreover, according to the estimated petrophysical parameters, the Oligocene intervals in Habbar-1 and Port Fouad Marine Deep-1 wells are very promising.