Abstract:

Sirte Basin,an intracratonic rifted basin in North Africa,is the most important petroliferous basin in Libya.It has experienced three stages of evolution:the Early Paleozoic eratonic margin depression,the Early Cretaceous-Late Eocene rift and the post-Oligocene depression.Three sets of source rocks were developed :the Lower Cretaceous shale,the Upper Cretaceous shale and the Paleogene shale,of which the Upper Cretaceous Sirte Formation shale is the main source rock.Reservoirs occur at various horizons from the basement to the Oligocene. The Pre-Cretaceous reservoirs are dominated by clastic rocks,while the Upper Cretaceous reservoirs and their overlying reservoirs mainly consist of carbonate rocks.Cap rocks are mainly the Upper Cretaceous and Lower Eocene shale,marl and evaporite.A series of horsts and grabens in parallel with the faults were developed under the control of the NW-NE-trending normal faults.Laterally,three hydrocarbon accumulation zones in correspondence with three roughly parallel horst uplifts were recognized:the western,central and eastern zones.Vertically, two oil-bearing sequences were recognized:the pre-horst and horst fillings.According to the above analysis,three types of favorable plays occur in the Sirte Basin:type Ⅰ in the horst zone,type Ⅱ in the graben zone and type Ⅲ in the northern offshore area.

Key words: petroelum geology, play, rift valley, Sirte Basin, Libya