Petroleum System and Exploration Potential of the West Alboran Basin

By

 Lung-Chuan Kuo¹, R. A. Mountfield¹, Y.M. Chevalier¹, G.A. Haddad¹, A.C. Weinzapfel¹, M.O. Strickland¹

(1) Conoco Inc, Houston, TX

 The offshore West Alboran Basin, which covers ca. 3000 sq. km., lies between the Moroccan and Spanish continental shelf, in the hinterland of the Rif-Betic fold-thrust belt. Conoco recently acquired 3200 km of 2D seismic, gravity, and magnetic data, as well as swath bathymetry and seabed piston cores, in order to evaluate the tectonic evolution and hydrocarbon potential of this little-explored basin.

The new seismic data reveal a coherent sedimentary column up to ca. 12 km in the basin, which is much greater than that estimated in previous studies. Mud volcanoes and mud diapirs, which originate near the base of the section, occur throughout the basin center. The roots of some of these are clearly associated with early rifting, which possibly started during Early Miocene. Several large, E-W-trending half grabens developed at this time are the most likely locations for source rock deposition. Deposition of the likely reservoir sand facies occurred mainly during Middle Miocene.

The presence of thermogenic gas and oil seeps in several seabed cores provides strong evidence for the presence of a functioning petroleum system in this basin. Oil and gas expulsion started in Late Miocene, which coincides with the initial phases of structural deformation within the basin. The Messinian shales as well as interbedded Middle Miocene shales provide seals for hydrocarbon accumulation.

Evaluation of the key exploration risks of this petroleum system continues with the results defining our future course of action.