Abstract: This paper highlights the reservoir sand body, petrology, pore structure, petrophysical properties and their effects in Yanan delta by way of macroscopic and microscopic study, including thin-section and cast thin-section analysis data, etc. Inte-grating with petroleum exploratory progress of the delta, this paper proposes statistically that Chang-4+5, Chang-6' and Chang-6?oil layers in target area are better than other layers. In general, the microfacies-developed zone of distributary channel in thedelta front is the most favorable for hydrocarbon prospecting.In spite of belonging to low porosity and low permeability reservoirwith compaction and dominated by intergranular dissolved pores and intergranular residual porosity, Yan'an delta still has greaterpotentials for petroleum development compared with the similar domestic fields.

Key words: delta, reservoir, characteristic, Yan'an