Evolution of the West Alboran Basin, Mediterranean, Offshore Morocco: Implications for Hydrocarbon Prospectivity

Abstract

Abstract The West Alboran Basin, lying in the westernmost Mediterranean between Morocco and Spain, contains a thick (≥ 10 km), Tertiary sedimentary fill with abundant structures and excellent coverage by vintage 2-D seismic datasets. There are good indications of a working petroleum system yet the basin is highly under-explored with only a single well on the Moroccan margin and three wells offshore Spain. It is a young basin (at oldest, latest Oligocene) and lies between the Betic and Rif fold and thrust belts, part of the Gibraltar Arc. The West Alboran Basin has typically been interpreted as a back-arc basin, however, by integrating all available data, it is proposed that it is more probably a fore-arc basin. Hydrocarbon seeps from mud volcanoes indicate the presence of thermogenic hydrocarbons. Biomarker analysis suggests oil-window maturity of the oil seeps, indicating a Lower to Middle Miocene source. Although there is strong evidence for the presence of a mature oil source rock, the areal distribution, quality, age and type of the source rock remain largely unknown. Basin modelling suggests that the Middle and Lower Miocene are mature and capable of generating substantial hydrocarbons. The distribution of suspected oil seeps is best matched by a Middle Miocene oil-prone source while biogenic gas migration modelling results in a good match between predicted pools and known gas seeps. Potential reservoirs are interpreted to comprise the deposits of various deep water environments, including turbidite fans, turbidite channels and mass transport complexes. Seismic geometries suggest the presence of such features. Numerous leads at various stratigraphic levels have been identified. The majority of these are related to mud diaper traps but, in addition, a few 4-way dip closures as well as several stratigraphic trapping configurations also occur. Overall, the well-developed structures and good indications for a working petroleum system mean that the West Alboran Basin has significant potential as a new hydrocarbon province. The next logical step is to acquire high quality 3-D seismic data to further derisk the basin.