Geochemical characteristics of Chang 9(1)source rocks of upper Triassic Yanchang formation in Zhidan-Ansai area, Ordos Basin and its significance for tight oil exploration

摘要

The average total organic carbon (TOC) content of Chang 9(1)source rocks is 4.85%, and the main kerogen type is II1, and the average pyrolysis peak temperature is 452 degrees C in Zhidan-Ansai area, Ordos Basin. These show that Chang 9(1)source rocks have reached good to excellent level and peak hydrocarbon generation stage. Chang 9(1)source rocks were formed in semi-deep lacustrine sedimentary environments of fresh-brackish water and weak oxidation-reduction. The discovery of Chang 9(1)source rock extends the oil exploration field of Yanchang Formation, especially in Zhidan area, it is a favorable area for further exploration in Chang 9 reservoir.