Petroleum Potential of Rift Basins in Northern Somalia - a Fresh Look

摘要

Several wells have encountered good oil shows in the rift basins of northern Somalia, however, without finding commercial hydrocarbons to date. It is widely accepted that these basins have a similar tectonic evolution and a comparable sedimentary fill as the highly productive rift basins in Yemen from which they have been separated by the opening of the Gulf of Aden (fully established in Mid Oligocene). We present new regional tectonic maps, new basement outcrop maps, a new structural transect and new play maps, specifically for the Odewayne, Nogal, Daroor and Socotra Basins. Digital terrain data, satellite images, surface geology maps (varying scales), oil seep/slick maps, potential data (gravity), well data from ~50 wells and data from scientific publications were compiled into a regional GIS-database, so that different data categories could be spatially analyzed. To set the tectonic framework, the outlines of the basins under investigation were re-mapped, paying particular attention to crystalline basement outcrops. A set of play maps was established. We recognize at least three source rocks, five reservoirs and at least three regional seals to be present in the area (not all continuously present). Numerous oil seeps are documented, particularly in the Nogal and Odewayne Basins, indicative of ongoing migration or re-migration. Data from exploration wells seem to further support the presence of active petroleum systems, especially in the central Nogal, western Nogal and central Daroor Basins. Our GIS-based data integration confirms that significant hydrocarbon potential remains in the established rift basins, such as the Nogal and Daroor Basins. Additionally, there are a number of less known satellite basins (on and offshore) which can be mapped out and that remain completely undrilled. All of these basins have to be considered frontier basins, due to their poorly understood geology, remoteness, marketing issues and missing oil infrastructure, making the economic risks significant. However, we believe that through acquisition of new seismic data, geochemical analysis, basin modelling and, ultimately, exploration drilling these risks can be mitigated to a point where the economic risks become acceptable. We encourage explorers to conduct regional basin analysis, data integration, a GIS-based approach and modern structural geology concepts to tackle key issues, such as trap architecture, structural timing, migration pathways and breaching risks.