Coupling stratigraphic and petroleum system modeling tools in complex tectonic domains: case study in the North Algerian Offshore
Résumé
In the eastern Algerian offshore basin, 3D basin
modeling applied for facies prediction and petroleumpotential
assessment shows that most favorable zones for reservoir development
and hydrocarbon occurrence are located at a maximum
distance of 60 km from the coastline. The lack of well
data in this area is partly compensated by a large data set of
geophysical and geological (G&G) data such as multichannel
seismic (MCS), magnetism, wide angle velocity models, and
geological outcrops; they represent important constraints for
3D dynamic modeling. Facies distribution model is
constrained by sequence and environment evolution through
time that is defined from onshore outcrops. 2D structural reconstitution
and thermal modeling were also undertaken with
ArcTem software. The structural interpretations highlight the
occurrence of north-verging ramps during the Quaternary
which played an important role in HC generation and migration.
Three source rocks have been considered for maturation
modeling with Temis Flow software, Burdigalian, Langhian,
and Tortonian. They are found to be in gas window in the deep
areas and locally in oil window at shallower structured zones.
The modeling results indicate that the main fluid discharge
was focused toward the southern border of the offshore basin
where recent thrust faults (parallel to the margin) are located.
In order to test the role of these faults in terms of hydrocarbon
migration and trapping, two scenarios are considered according
to whether they were sealed or not. In both cases, the 2D/
3D simulations depict overpressures (2,000–4,000 psi) in the
pre-salt sedimentary package. However, the hydrocarbon
charge is most efficient with the sealing faults for the lower
Langhian and lower Messinian reservoirs. The hydrocarbon
potential depends mostly on the lateral extension of seals, their
sealing capacity and the organic carbon (TOC) content of
potential source rocks. Besides, the sea drop of about 1,
000 m during theMessinian salinity crisis has induced depressurization
that caused oil and gas seepage from Miocene
reservoirs.