Assessment of the clastic reservoirs in northern Biru Basin,Xizang

The clastic reservoirs in the Biru-Nagqu-Sog zone in northern Biru Basin,Xizang are developed in the Lower-Middle Jurassic Xihu Group,Middle-Upper Jurassic Lagongtang Formation,Lower Cretaceous Duoni Formation and Upper Cretaceous Jingzhushan Formation.These clastic rocks are now in the late diagenetic stage.The porosity types include secondary solution openings with micropores to microthroats.The reservoir quality is better in the Jingzhushan Formation,followed by the Lagongtang Formation,whereas worse in the Xihu Group and Duoni Formation.