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AAPG GEO 2010 Middle East
Geoscience Conference & Exhibition
Innovative Geoscience Solutions – Meeting Hydrocarbon Demand in Changing Times
March 7-10, 2010 – Manama, Bahrain

Petroleum System of the Mesozoic Sab’Atayn Basin of Yemen

Mustafa A. As-Saruri1; Rasheed Baraba'1

(1) GD of Studies and Research, Petroleum Exploration and Production Authorithy, San'a, Yemen.

The Mesozoic Sab’atayn basin was elongated along the ancient Najd fault system (NW/SE) in the Upper Jurassic time and had continued up to the Lower Cretaceous. It is filled with syn- and post rift sediments and includes good source and reservoir rocks. The first petroleum discovery in Yemen was happened in 1984 in the Marib sector of the basin. This was followed by second discovery in Shabwah sector in 1986. However, based on the available data, the Hajr sector indicates good hydrocarbon potential, but no productive field was reported yet. The predominant source rock is the rich bituminous shale of the Madbi Formation (Kimmeridgian/Lower Tithonian) which involves Lower and Upper Madbi Shales Members and found throughout the all sectors of the basin. The main reservoir rocks are found in several stratigraphic levels, but the sandstone of the Alif Member of the Sab’atayn Formation (Middle/Upper Tithonian) represents the main reservoir in the Marib sector. In addition, there are several reservoirs are not studied in detail up to date in all stratigraphic levels (fractured basement, Kuhlan, Shuqrah Formations). The fractured metamorphic basement and the turbidite within the Lam Member of the Madbi Formation compose the main reservoirs in the Shabwah sector of the basin. The Tithonian salt was only developed in this basin and represents good seal in all sectors of the Sab'atayn basin.

Lithostratigraphic correlations in surface and subsurface sections as well as paleogeography of the depositional environments show the differences and the characterization of the hydrocarbon system in the Sab'atayn basin and distinguish the lateral and vertical variation and facies changes.
The main tectonic trend is NW/SE (Najd Trend), which displays good role through the structuring of the hydrocarbon play. The traps are characterized by structural elements represented by horst, tilted fault blocks and less stratigraphic traps. Two source rock types are identified in the Sab'atayn basin; in which bituminous rich shale of Madbi Formation is of type I and type II kerogens. The organic carbon content is between 1-10% and the hydrogen index reaches 800 mg HC/g TOC. The shale and bituminous limestone of the Layadim and Safir Member of the Sab'atayn Formation contains good source rock including type II and type III kerogens and the organic carbon content is ranging between 0.8 and 4%.