oa Petroleum System of the Mesozoic Sab’Atayn Basin of Yemen

The Mesozoic Sab’atayn basin was elongated along the ancient Najd fault system (NW/SE) in the Upper<br>Jurassic time and had continued up to the Lower Cretaceous. It is filled with syn- and post rift<br>sediments and includes good source and reservoir rocks. The first petroleum discovery in Yemen was<br>happened in 1984 in the Marib sector of the basin. This was followed by second discovery in Shabwah<br>sector in 1986. However, based on the available data, the Hajr sector indicates good hydrocarbon<br>potential, but no productive field was reported yet. The predominant source rock is the rich bituminous<br>shale of the Madbi Formation (Kimmeridgian/Lower Tithonian) which involves Lower and Upper Madbi<br>Shales Members and found throughout the all sectors of the basin. The main reservoir rocks are found<br>in several stratigraphic levels, but the sandstone of the Alif Member of the Sab’atayn Formation<br>(Middle/Upper Tithonian) represents the main reservoir in the Marib sector. In addition, there are<br>several reservoirs are not studied in detail up to date in all stratigraphic levels (fractured basement,<br>Kuhlan, Shuqrah Formations). The fractured metamorphic basement and the turbidite within the Lam<br>Member of the Madbi Formation compose the main reservoirs in the Shabwah sector of the basin. The<br>Tithonian salt was only developed in this basin and represents good seal in all sectors of the Sab'atayn basin.<br>Lithostratigraphic correlations in surface and subsurface sections as well as paleogeography of the<br>depositional environments show the differences and the characterization of the hydrocarbon system in<br>the Sab'atayn basin and distinguish the lateral and vertical variation and facies changes.<br>The main tectonic trend is NW/SE (Najd Trend), which displays good role through the structuring of the<br>hydrocarbon play. The traps are characterized by structural elements represented by horst, tilted fault<br>blocks and less stratigraphic traps. Two source rock types are identified in the Sab'atayn basin; in<br>which bituminous rich shale of Madbi Formation is of type I and type II kerogens. The organic carbon<br>content is between 1-10% and the hydrogen index reaches 800 mg HC/g TOC. The shale and<br>bituminous limestone of the Layadim and Safir Member of the Sab'atayn Formation contains good<br>source rock including type II and type III kerogens and the organic carbon content is ranging between 0.8 and 4%.