Abstract: The dominating factors controlling hydrocarbon accumulation of Neogene are determined by analyses of the source-reservoircap rocks and traps in Yiliping area. The result shows that the source rock assumes dark mudstone in $N^{1}_{1}$ zone and $N^{2}_{1}$ zone, dominated by humic-type organic matter of relatively low abundance, maturity threshold depth of 2 800 m; the reservoir rock is characterized by siltstone; the traps are anticline and faulted anticline. The major hydrocarbon-generating stage of Neogene source rock well matches the period of trap formation, shaping the original hydrocarbon accumulation mode of internal storage, according to study of the structural evolution history, sedimentation history and hydrocarbon generation history. It is concluded that Jianshan and Jianshishan in this area could be regarded as exploration targets in the near future.

Key words: Qaidam basin, source rock, reservoir, trap, hydrocarbon accumulation mode