STRUCTURE, SEDIMENTATION AND HYDROCARBON ACCUMULATION OF THE NEO-TETHYS PASSIVE MARGIN BASINS: EXAMPLES OF THE GIANT GAS FIELDS FROM (ULTRA-)DEEP-WATER EASTERN MEDITERRANEAN AND EAST AFRICA

The percentage of PP reserves discovered from the (ultra-)deep-water is over 50% while the field number percentage is less than 13% since 2010, which make the (ultra-)deep-water become a hot area. The giant fields from the (ultra-)deep-water area mainly locate in east Africa, south Atlantic and eastern Mediterranean with the percentage of PP reserves 53.8%, 34.8% and 11.4% respectively. The giant gas fields from the east Mediterranean and east Africa area locate within the Neo-Tethys passive margin basins . Comparative studies on structure, sedimentation, reservoir and hydrocarbon accumulation can help us better understand the Neo-Tethys passive margin basins. In the east Mediterranean, Neo-Tethys passive margin basin, represented by the Levant basin, involves a stable passive margin tectonic and sedimentary environment until the collision between the Arabia and Turkey plate resulting in the SW-direction lateral activation of the regional strike-slip fault (eg. Dead Sea Fault) and normal faults. The salt diapir does not develop as the salt is too young (Miocene) and less influenced by the Nile Delta. The onshore uplift occurs post-Miocene, which does not contribute to the main reservoir (Miocene Tamar sand). The upper cretaceous source rock migrate upward to the Miocene sand reservoir along the fault and sealed by the upper Messinian salt. In the east Africa, Neo-Tethys passive margin basin, represented by the Ruvuma basin, involves post Madagascar rift and drift stages, a relative stable passive margin tectonic and sedimentary environment bounded by Davies Fracture Zone to the east and East Africa Rift System to the far-West. The salt diapir develops as the result of the gravity collapse, triggering the Cenozoic shallow-water normal fault and the deep-water thrust fault. The Mozambique onshore uplift occurs in late Eocene, which contribute the main reservoir (Eocene to Pliocene sand) from the Ruvuma river. The lower-mid Jurassic source rock migrate upward to the Neogene sandbody reservoir, especially in the Oligocene sand, along the rift-period normal fault and drift-period thrust fault, and sealed by the Cenozoic mudstone. The better structural (salt diapir, earlier uplift, et al) and sedimentary (river infilling, gravity collapse, et al) environment of the Rovuma basin deserve to have a larger reserves.