Coupling stratigraphic and petroleum system modeling tools in complex tectonic domains: case study in the North Algerian Offshore

摘要

In the eastern Algerian offshore basin, 3D basin modeling applied for facies prediction and petroleum potential 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 the Messinian salinity crisis has induced depressurization that caused oil and gas seepage from Miocene reservoirs.