Seismic Expression of Carbonate Platforms, East Gulf of Sirt Basin, Libya

Gunawan Juniarto¹, Carlos Diaz Merino², Andrew Wight¹, Diego Rivas¹, and Mateu Esteban^1
1REPSOL-YPF, Madrid, Spain
²Repsol Exploration Murzuq S.A. (REMSA), Tripoli, Libya

The Gulf of Sirt basin is the offshore extension of the hydrocarbon-rich Sirt basin. It is located in Northeast Libya, 600 km ESE of Tripoli.
The basin is characterized by a series of northwest-southeast oriented horsts and grabens formed by a multi-episodic rift phase during Mesozoic times. The basin is bounded along its eastern edge by the Western Cyrenaica Terrace and to the southwest by the Jahama high. It continues into the onshore Ajdabiya trough to the southeast.
Recent 2D and 3D seismic over the basin reveal a complete picture of a series of late Cretaceous to late Eocene carbonate platforms along the eastern edge of the basin. The earliest platform is upper Cretaceous and overlies an unconformity, interpreted to be Turonian in age. This platform is in turn overlain by distinct Paleocene, Lower Eocene and Middle-Upper Eocene platforms. They are north-south elongated platforms and ramps that prograde westwards. Each platform is about 80 km long and more than 20 km wide, with thicknesses ranging between 600 m to 2500 m. Platform geometry changed through time, as rate of change of accommodation space vs carbonate production varied.
Exploration for hydrocarbons is focused on the quality of reservoirs and potential seals. The quality of deeper prospective reservoirs depends most on the diagenesis experienced by these carbonates. It is important to extract the tectono-stratigraphic history of the successive platforms from the seismic. This work mainly examines how the seismic expression and interpretation of the platforms may be used to predict good reservoirs.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece