Abstract:

The relationship between oil layer distributions and key reservoirforming factors indicates that the westward monocline is the foundation of structurallithologic trap type; Nose uplift structure determines oil distribution; Distributary channel sand body is the main reservoirs; Interchannel mudstone is the barrier and cap of oil accumulation; Diagenesis is a key point for storage capability of sand bodies; The massive interconnected sandstone on the bottom of Chang 2 formation is like a large inverted hopper that can accumulate oil for the upper entrapment. The influence degree of each geologic element is defferent for each sublayer. The strongest element is called key element of hydrocarbon enrichment. The key element is also the poorest element and changes with the place of middle sedimentary cycle.The key elements of hydrocarbon enrichment of Chang 211 and Chang 212, Chang 222 and Chang 23, Chang 213 and Chang 221 are the sand body distribution of distributary channel, mudstone barrier or cap and the shape of noseshaped uplift, respectively, forming oil distribution in a row, in disperse and as strings, respectively.

Key words: Jiyuan area, enrichment law of oil, key element of hydrocarbon enrichment, noseshaped uplift, Ordos Basin