Sedimentary facies of Chang 8 oil unit in Zhengning-Yichuan area of Ordos Basin

This paper studies the favorable reservoir facies and the main control factors on hydrocarbon accumulation as well as resources potential of Chang 8 oil unit in Yanchang formation of Zhengning-Yichuan area in the southeast of Ordos Basin on the basis of a large amount of regional geological data and previous researches by using sedimentology method,drilling and logging data,and the research achievements of neighboring formations and sedimentary facies.It is determined that this oil unit had developed delta and lacustrine facies,comprising two main subfacies of shallow lake and delta front.The main sedimentary sources came from the northeast and the south.The distribution of sedimentary facies can be predicted according to sedimentary source direction.This study may guide the determination of favorable zone and future exploration and development.