Hydrocarbon source rocks in North Tarim Basin can be divided into three petroleum systems such as Cambrian Ordovician system

Tertiary Jurassic system and Carboniferous Permian system.The last one is an inferred system.The first system is a reformed residual one

and also the most important one.The early subsystem(∈-P)was an unified system with Manjar Depression as its oil generation centre;the late subsystem(∈-K)had multiple hydrocarbon generation centres and formed separate branch systems.The second system is the main gas producing realm with Kuqa Depression as its hydrocarbon generation centre.The flat gypsolith and mudrock formed in Late Cretaceous Early Tertiary are regional cap rocks.So it is considered that Cambrian Ordovician petroleum system with good preservation condition is favourable for oil exploration;Tertiary Jurassic petroleum system is an important gas exploration realm for its late hydrocarbon generation

weak reformation and good gas preservation and accumclation conditions.