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.