Thermal maturity modelling for the pre-Miocene source rocks in Ras Garra area, Suez rift Basin, Egypt

Abstract

The main potential source rocks in the Ras Garra area of the Suez rift Basin are thought to be the pre-Miocene formations, Duwi, Esna, and Thebes, from the oldest to youngest. The total organic carbon content (TOC) ranges from 6.0 to 7.0 wt %, suggesting very good hydrocarbon generative potential. The hydrogen index (HI) ranges from 600 to 700 mg HC/g TOC and the kerogen is of type I/II. Burial and thermal maturity modelling indicates that the pre-Miocene source rocks started the oil generation as early mature stage in Langhian (14.3 Ma), and mid-mature stage in Pleistocene (2.4 Ma). The early mature stage is characterized by the depth to maturity of 1400 m, burial maximum temperature up to 87 °C and vitrinite reflectance (VR) up to 0.7% Ro. The mid-mature stage is characterized by the depth to maturity of 3007 m, burial maximum temperature up to 120 °C and vitrinite reflectance up to 0.75% Ro. The hydrocarbon generation and expulsion history is divided into two phases and Duwi source rock passed the second phase of hydrocarbon generation, and expulsion with transformation ratio (TR) of 29%. From 0.8 Ma until the present, the hydrocarbon generation and expulsion rates have been increased and the generated and expelled hydrocarbons are mainly oil with minor gases. The results show that the most important factor affecting the maturity of the source rocks and hydrocarbon generation and expulsion rates is the durations of early and mid-mature stages.