HYDROCARBON GENERATION POTENTIAL OF THE LOWER PALAEOZOIC SUCCESSION, WESTERN IRAQI DESERT
Thamer AL-Ameri & Diear Baban Department of Geology. College of Sciences. University of Baghdad
Two hundred and twenty samples of cores and cuttings collected from the Khabour and Akkas Formations in Akkas-1. Khleisya-1 and KH5/6 boreholes were analyzed for palynological and organic geochemical studies. They revealed abundant acritarch assemblages and a few spores and Chitinozoa with variable types from organic matter.
On the basis of acritarchs with tentative selections of Chitinozoa and spores, the stratigraphic section subdivided into the Ordovician Khabour. and Silurian Akkas and Upper Devonian Kaista formations in a succession of ten palynozones w ithin a stratigraphic framework. Formations of this section were deposited in marine environments extending from outer to inner neritic with local upwelling currents and lagoons, especially in boreholes Akkas-1. KH5/ 1 and KH5/ 6.
Maturation assessments are on the basis of the Thermal Alteration Indices (TAI) of the acritarchs Diexallophasis denticulata- Orthosphaeridium ternatus and Baltisphaeridium constrictum. organic matter types were represented on the Bujaks (1977) graphical model. Thompson Kerogen types and the total organic carbon (TOC) upto 1.0% to interpret hydrocarbon generation potential.
The location of each level in the diagrams have indicated source potential for wet gas and condensates from depths 2750 - 3000 meters and dry gas from depths of 3570 - 3650 meters for borehole Akkas-1 only from the Ordovician kabour Formation, while higher up from the Silurian, some oil could be generated from the lower Silurian Akkas formation in borehore Akkas-1 and K.H5 6 with immature organic matter in borehole khleisya -1. These potential source rocks are extended southwest towards Jordon and southwest Iraqi Desert.
Key Words: Lower Silurian, Western Iraq, Hydrocarbon generation, Palynomorphs, Palynostratigraphy. Palaeoenvironment.