Abstract: The lithology, mineral composition, physical property, oil bearing and oilwater relationship of Yanchang Formation are analyzed by using data of drill core, well logging, testing and production performance, the relationship of characteristic of pore structure, mobile fluid saturation and physical property, are studied, too, the relationship and affecting factors among electri property, physical property and oil bearing summed up, and the interpretation model of porosity, permeability, oil saturation etc. is given. The research indicates that the reservoir beds of Yanchang formation are characterized by the little rock particles, rich cementing material, small porous throat, multifold porous forms and complex composition in microcosmic, which are the essential reasons to make it form the characteristic of low porosity and low permeability. Through the research of “four quality”, the new conception of acoustoelectric integration index is proposed, the lower limit reference criterions of “four quality”for Chang 2&3,Chang 4+5,Chang 6 and Chang 8 formation established to divide oil layer, acquifer and dry layer accurately.

Key words: reservoir geology, Yanchang Formation, well logging, acoustoelectric integration index, Ordos Basin