Biomarker characteristics and oil accumulation period of Well Sutan 1 in Qaidam Basin, China

Abstract

The hydrocarbon accumulation history of 2536.5 m–2697.0 m of Well Sutan 1was studied, and the geological and geochemical data including the homogenization temperature of fluid inclusion and the geochemical characteristics of the crude oil were analyzed. The results showed that the crude oil had the properties of a high degree of evolution. The precursor type was mainly high terrestrial plants. Among them, crude oil from depths of 2620.67 m, 3640.57 m and 2697 m had been charged with crude oil with aquatic organism. The crude oil was deposited in weak oxidizing to oxidizing environment with fresh to slight saline water, which is better for preservation and transformation of organics. The characteristic of fluid inclusion with Well Sutan 1 showed that there were at least three occasions of filling of oil and one of filling of gas. Also, petroleum accumulation existed in the crude oil on two occasions. The reservoir forming time of the first charge with oil was about 142 Ma, and the second charge with oil was about 107 Ma, which is tectonic inversion of the Yanshanian Orogenic Movement in the Late-Early Cretaceous.

Keywords

• Qaidam Basin
• Well Sutan 1
• Biomarkers
• Inclusion