3. Reservoir and source rock properties
The best reservoir properties are found in the fractured carbonates of
the Zebbag Formation, a dual porosity systemrecognized as the primary
target in the area. Porosity values range from 8 to 16% and permeabilities
from 10 to 500 mD. The sandy layers of Sidi Aich Formation show
an average porosity of 20% and a permeability range from 150 to
250 mD. The sandy and sandstone layers of Melloussi Formation have
good porosity values ranging between 12% and 21%. The sandstones
layers of M'Rabtine Member have porosity values of between 12 and
19% and a permeability of 130mD. Reservoir units are sealed by overlying
and intra-formational evaporates and shales (Fig. 2). The main
source rock characterizing this area is the Callovian black shale of
KechemElMiitMemberwith TOC value up to 1.7% and oil potential between
3 kg and 12 HC/T rock. The kerogen types are oil to oil-gas prone.
The maturity of the Callovian black shale is increased due to enhanced
subsidence (Fig. 3). According to the basin modeling of the Jeffara
area, the Kechem El Miit Middle Jurassic source rock entered the main
generation phase in the Late Miocene or Pliocene (Dey et al., 2002).
The intercalated black shale of Nara Formation is considered as potential
source rock in this area with TOC values up to 1.3% and oil potential
ranging from 1.5 to 39.5 kg HC/T rock (Dey and Inoubli, 2000; Dey
et al., 2002).