PROPERTIES AND STUDY ON THE ALTERATION OF HEAVY OIL OF JURASSIC IN WU-XIA AREA,JUNGGAR BASIN

The heavy oil reservoir mainly distributes near the Wu-Xia fault belt or on the structural high part which lies in the top wall of the fault in Wu-Xia Area of Junggar Basin.By analyzing its physical and geochemical properties,we find some characteristics of the heavy oil.Such as:the density,viscosity and acid value of heavy oil are very hight;The wax and sulphur content are relatively low,partial hopanes,steranes and homosteranes,and n-alkanes,free carotene suffer serious loss;While tricyclic terpanes,pregnanes and homopregnanes are in high content.Based on these characteristics as well as the distribution of normal crude oil,heavy oil and oil sand,it is considered that the heavy oil in this region is mainly of secondary origin.Additionally,the alteration of heavy oil would be divided into biodegradation,oxygenation,water washing and diffusion respectively,of which the biodegradation and oxygenation are the most important.Finally,the accumulation model of heavy oil is established,which provides theoretical basis in predicting the distribution of heavy oil in the Wu-Xia area.