Hydrocarbon Generation, Expulsion and Migration in Geisum and Tawila Oil Fields-Southern Gulf of Suez

By

Selim A.Hamid El Srogy¹, Iman Hussein Helal¹, Esam Ismail Amer², Hossam Ali Mohamed²

(1) Geisum Oil Co., Cairo, Egypt (2) StratoChem, Cairo, Egypt

 Geisum and Tawila fields are located in the southern province of the Gulf of Suez and produce oil from the pre-rift Eocene, the lower Senonian sandstones, fractured Precambrian basement, and the post-rift Miocene Kareem and Belayim sandstones. The study aims at determining the main source rock units and oil characterization for better understanding the time of generation, explusion, and migration pathways of hydrocarbons. Three main source rock units are investigated. The first source type is found in the Upper Senonian carbonate-rich sediments, the Brown Limestone. The second source includes clastic-rich sediments, the Miocene Rudeis Formation. The third type is the clastic-rich lower Senonian Matulla / Wata Formations. The bulk composition for the crude oils shows two separate oil groups. The first group is the Geisum oils which are charged from the Brown Limestone, a marine carbonate-rich source. The second group is the Tawila oils which appear to be charged from Miocene and the Lower Senonian, clastic-rich sources. The hydrocarbon migration routes show that the main reservoirs in the Geisum field are charged from the Brown Limestone in the flank of the basin located south-west of Geisum. The Tawila oils seem to be charged from the Rudeis and Matulla/Wata rocks in the basin located south of the field. In addition, the hydrocarbon migration pathway may charge undiscovered prospects within the Geisum and Tawila concessions. The correlation between the calculated expelled and trapped hydrocarbons and the proven reserves in Geisum and Tawila indicate that nearly half of the estimated reserves are not discovered yet.