Overview

The Alboran Basin in the Moroccan Mediterranean Sea is a syn-orogenic to post-orogenic basin. It is bounded to the west by the Gibraltar arch comprised between the Moroccan Rif and the Spanish Betic Chains Belts, which resulted from the collision between the Iberian and the African Plates.

Database

Since 1974, 10 901 km of multi fold 2D seismic lines have been acquired in the area. During 1983-1985 periods, two exploration wells were spudded.

Tectonic and sedimentary evolution

The geodynamic evolution of the Alboran Sea started in Oligocene - Early Miocene time with the collision of the African and European Continental Plates. The development of overthrusted nappes to the north (Ronda nappe in Spain) and to the south (Beni - Bousera nappe in Morocco), was an important consequence of this convergence. During the Early and Middle Miocene, the Alboran basin was influenced by extension tectonics. In Late Miocene (end of Tortonian), an intensive compressive phase produced imbrications and thrust faults which were occasionally marked by large amplitude movements. This followed by collapse, which created a basin expansion. The later movements have reorganized the basin setting in a way that continues up to present.

Petroleum systems

Source Rocks

The presence of shaly marine sediments in the Tertiary stratigraphic section is an indication of the presence of potential organic rich beds, which are related to the high sedimentation rate and confined environment.  Geochemical analyses carried out in 2000 on the Messinian outcrops in the northern part of the Rif foreland revealed TOC values of about 2 % and HI = 429 of immature sediments. Nevertheless, we assume that in the deep offshore areas, these shales would be sufficiently buried to be in the oil or gas window.

Reservoir rocks

Reservoirs have been identified in turbiditic type deposits, which may include sandstones whose porosity is about 20 % as shown in the log study of Miocene sandy beds of the El Jebha - 1 well.

In the eastern portion of the Mediterranean Domain, even the Miocene section is relatively reduced, the same reservoirs, as in the western basin, are expected.

Seal rocks

The shaly Mio - Pliocene formations are sufficiently thick to form a good seal for any Miocene reservoir.

Play concepts

The main attractive target is represented by the Miocene turbiditic sandstones, which could be sourced either vertically or laterally from the interbedded shales. Various types of traps are defined:

  • Hanging wall anticlines ;
  • Unconformity Messinian traps ;
  • Mini-basin fans, related to the paleohighs ;
  • Combined stratigraphic and structural traps created by the inversion of the mini-basins fans.

Conclusion

The Mediterranean offshore domain is an interesting exploration frontier area with good traps in which turbiditic sandstones are expected to present the main exploration targets.

New 3D seismic acquisition and adequate reprocessing of the 2D vintage data will improve greatly the prospectivity of the area.