Characteristics and controlling factors of the large carbonate petroleum province in the Tarim Basin, NW China

A comprehensive analysis of hydrocarbon accumulation conditions and typical reservoirs reveals that a large carbonate petroleum province is formed around the Manjiaer depression in the Tarim Basin and it consists of Ordovician non-structural petroleum reservoirs. Multi-type litho-stratigraphic reservoirs are stacked vertically and connected laterally along the paleo-uplift slopes, with a large area. Reservoirs are intensively heterogeneous, extensively developed and distributed in layers along the top of different-scale sequence boundaries. Hydrocarbon phase and physical properties are diverse and the distribution pattern is “lower gas, upper oil”. The oil/gas/water output alters and declines quickly, and 20%-30% high-efficiency wells provide more than 70% of the production. The stable paleo-uplift, widely developed heterogeneous reservoir, multi-stages of hydrocarbon accumulation are the basic forming and distribution conditions of the large carbonate petroleum province. The paleo-uplift near the hydrocarbon kitchen is developed stably and controls the reservoir distribution, migration and accumulation. The special characteristics of carbonate reservoirs result in the wide and discontinuous distribution of irregular fracture-cavity hydrocarbon pools. The enrichment of hydrocarbon is controlled by reservoirs, which are the main controlling factor of the formation and distribution of the large petroleum province. Multi-stages of accumulation and adjustment of hydrocarbon are universal and result in the large area and diversity of the oil and gas.