Mesozoic Sedimentary Cover of Puntland State of Somalia and Its Hydrocarbon Potential

Abstract

The Mesozoic sedimentary sequence of NE Somalia (Puntland State) consists of Jurassic and Cretaceous succession and geologically correlates well with coeval, petroleum-rich stratigraphic units of southern Arabia region across the Gulf of Aden. This suggests that the two regions belonged to one landmass during the Mesozoic Era and shared similar tectono-stratigraphic and sedimentologic evolutions. The geologic similarity and the ever-increasing global demand of fossil fuels raised the exploration interest of Somalia, in general, and of northern states, in particular. This presentation addresses the lithostratigraphic sequence of the northeastern part of the country (Puntland) and its hydrocarbon potential. The oldest Mesozoic unit is ?Early Jurassic Adirgrat Formation; a medium to coarse-grained arkosic sandstone that blankets over the Precambrian basement rocks. The post-Adigrat Mesozoic sequences change laterally from the northwest (Al-Mado Basin) to the southeast (Hafun Margin). In the Al-Mado Basin, the strata are represented by Toarcian to Portlandian mixed carbonate-clastic sequence (Al-Mado Group) and Aptian to Maastrichtian mixed clastics & carbonates (Tisje Fm.). The Jurassic strata of the Hafun Margin consist of carbonates of the Pliensbachian to Callovian Hamanlei Fm. and overlying marls of the Uarandab Fm. whereas its Cretaceous System includes Cotton & Mustahil formations. Available paleogeographic and stratigraphic data indicate that the Hafun Margin is a southward extension of the Arabian carbonate platform of the Tethys Ocean. Although Permian (e.g., Khuff Fm.) to Cretaceous (e.g., Natih Fm) sequence represents the Arabian platform, the Jurassic Hamanlei Fm. forms the oldest carbonate strata in NE Somalia. Thus, in the latter, the carbonate platform was established in the Jurassic Period and continued until the end of the Mesozoic Era with intermittent stratigraphic breaks due to tectono-eustatic changes comparable to those recorded in Arabia. Exploration wells in the study area proved existence of mature hydrocarbon system with thick and extensive geologic units of potential reservoirs, source rocks and appreciable stratigrpahic and structural traps. It is envisaged here that the Mesozoic fill of the study area preserves an appreciable amount of hydrocarbons and awaits an extensive exploration activity. This high potentiality is not only confined to Puntland State of Somalia but also extends to the rest of Somalia, including offshore areas.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015