AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Modeling Hydrocarbon Generations of the Basrah Oil Fields, Southern Iraq; Based on Petromod with Palynofacies Evidences
(1) Palynology and Petroleum Geology College of Science, University of Baghdad, Baghdad, Iraq.
(2) Ministry of Oil, Oil Exploration Company, Baghdad, Iraq.
(3) USGS, Denver, CO.
Timing of tectonic events are taken on larger subsidence lines in the burial thermal diagram of the 1D PetroMod software modeling output of seven wells of four main oil field producers in southern Mesopotamia; namely Majnoon (Mj), West Qurna (WQ), Nahr Umr (NR) and Zubair (Zb) . Within these timing, two main petroleum generation phases are cleared. The first phase was 100% transformation ratios possessed from Jurassic Formations of Sargelu, Najmah and Sulaiy within temperature effect of 120-140°C, during times of 80-30 million years ago. The second phase was 53-90% transformation ratios possessed from Lower Cretaceous Ratawi and Zubair Formations within temperature effect of 100-120°C, during times of 15 million years ago. Trap formation is taken from the abrupt subsidence lines during the Upper Cretaceous time at 65-60 million years ago, which conform to the Global Cretaceous/Tertiary Event of its effect on the Arabian Plate for the first phase and during the Miocene time at 20-10 million years ago and which conform with the closing phase of the Alpine Orogeny effect on north east Arabian Plate for the second phase.
Palynofacies of the Jurassic-Lower Cretaceous strata has confirmed main phase of oil generation and expulsion for the first phase of the model with vertical migrations along faults and compression joints in the anticline crest to charge the already existed Middle and Upper Cretaceous traps from palynofacies IX of the Sulaiy Formation, while the hydrocarbon generated by the second phase of the model are of very low expulsion efficiency from palynofacies VII and V and hence stored in stratigraphic traps of mainly clastic strata of the same formation as the case in Zubair Formation. Very little generation possessed from Shuaiba to Ahmedi Formations. No generation from Rumaila Formation and upward in the stratigraphic succession.
The stratigraphies of the effective source rocks for those generations in Basrah oil fields are based mainly on palynomorphs of the dinoflagellate cysts and spores that have indicated Tithonian-Berriassian age for the Sulaiy Formation as generation and expulsion phase and Barremian-Aptian with probable early Albian ages for the Zubair Formation as generation phase only.