Assessment of Hydrocarbon Generation Potential in the Paleozoic Akkaz and Khabour Formations, Akkaz Field, Western Desert, Iraq

Thamer K. Al Ameri¹ and Mohamed Zine^2
1 University of Baghdad, College of Sciences, Baghdad, Iraq
² IHS Energy, Gloucestershire, United Kingdom

Two hundred and twenty samples of cores and cuttings collected from the Silurian Khabour and Ordovician Akkaz formations in Akkaz 1, Khleisya 1, KH5/6 and KH 5/1 boreholes were analyzed for palynological and organic geochemical studies. They revealed abundant acritarch assemblages, few spores and Chitinozoa with variable types of sedimentary organic matter. On the basis of acritarchs with tentative selections of Chitinozoa and spores the studied stratigraphic section was subdivided into Khabour, Akkas and Kaista formations in a succession of ten palynozones. These were deposited in marine environments extending from outer to inner neritic with local upwelling currents and lagoons. Maturation assessments were made on the basis of the Thermal Alteration Indices of the acritarchs while hydrocarbon generation potential was assessed by plotting organic matter types on the Bujaks (1970) graphic model. Kerogen analysis revealed total organic carbon (TOC) up to 16%, especially for the hot shale of the Akkaz formation, very low asphaltene and sulphur, saturated and aromatic hydrocarbons of more than 96% and the high peaks of C2-C20 gas chromatography indicate predominant gas generation with some light oils. The associated gases are mainly methane and ethane. The assimilation of the data has indicated source potential for wet gas and condensates from depth 2,750-3,000m and dry gas from depth of 3,570-3,650m for borehole Akkaz 1 only from the Khabour formation. While higher up some oil could be generated from the Akkaz formation in borehole Akkaz-1 and KH5/6. These potential source rocks extend towards Jordan, southwest Iraqi and Syria. Shows in equivalent strata of Tanf and Swab formations in the Akkaz-2 to Akkaz-5 wells drilled later by Syrian Petroleum Company confirm hydrocarbon generation from the high organic matter black shales and accumulation in the lower Palaeozoic of the studied areas.