Exploration and targets for lithologic reservoirs in Junggar Basin,NW China

Twelve steep-slope fan-like reservoirs have been found in Junggar Basin.In the gentle-slope depositional system,such petroleum reservoirs as braided channel sandbody in Jurassic Toutunhe Formation in Well Feild Shinan 4,Shinan 21 and Shinan 26,and hydrocarbon reservoirs of Sangonghe Formation in Zhongguai High and Xishanyao Formation in Baijiahai High,have also been found.Having experienced polycyclic tectonic movements and multistage vibratory movements of lake planes,Junggar Basin has been provided with good bases for the formation of various lithologic traps.Multitudes of hydrocarbon sources and kitchens have provided abundant hydrocarbon sources for the formation of lithologic reservoirs.Multistage faulting activities and the development of multi-regional unconformable surfaces have constructed an excellent oil and gas transporting system for multi-stage hydrocarbon accumulation in the depositional traps.Therefore there is great potential for exploration of lithologic reservoirs.The identifying ratio of the lithologic reservoirs in Junggar Basin only accounts for about 4%.The reserves from such reservoirs account for less than 22% of the total proved hydrocarbon reserves.It is considered that there are currently mainly five provinces for the exploration of lithologic hydrocarbon reservoirs in Junggar Basin: Permian and Triassic steep-slope fan body in the NW margin,large gentle-slope delta front mouth bar and slumping fan of Jurassic Sangonghe Formation and Xishanyao Formation in the hinterland,channel sand body of Toutunhe Formation(or Shishugou Formation) in Luxi and Fudong slope,Jurassic-Cretaceous channel-incised valley stratigraphic-lithogic trap dominated by Chemo High,and stratigraphic-lithologic trap dominated by Jurassic structural slope belt in Western Slope of Mahu.