Characteristics and Main Enrichment Controlling Factors of Chang 7 Tight Oil in Xunyi-Yijun Area,Ordos Basin

Based on the data of core, well logging and oil test, etc, this paper analyzed the characteristics of tight oil and the main enrichment controlling factors of Chang 7 member through the aspects of reservoir distribution, reservoir performance and fluid properties. It is concluded that the turbidite sand body is developed in Chang 7 member and the reservoir space is tight and mainly with small pores; the crude oil has the good properties of low density, low viscosity, low freezing point, low sulfur and strong fluidity. The Chang 7 source rock is rich in organic matter with the average Ro of 0.78%, which provides a rich material basis for the formation of tight oil. The sand bodies of the Chang 7₁ and Chang 7₂ sub oil formations are thick and widely distributed, in favour of the accumulation of tight oil. However, the development of faults may destroy the accumulation of tight oil. Good preservation condition is necessary for the accumulation of tight oil in this area.