Hydrocarbon Accumulation Process and Exploration Potential of Shizigou-Yingdong Area, Western Qaidam Basin

Abstract

Abstract In recent years, with the successful drilling of Sha37 and Sha 40 wells and discovery of Yingdong No.1 oil field, great breakthrough had been achieved in Shizigou-Yingdong area. And hydrocarbon exploration in Shizigou-Yindong tectonic belt is also blooming. However, contrast with the great achievement in exploration, research on hydrocarbon accumulation process is still weak and exploraiton potential is not clear. In this paper, several advanced methods are adopted to research the hydrocarbon process including QGF and QGF-E analysis on core sample, TSF analysis on oil sample and laser confocal scanning on component analysis of hydrocarbon inclusion. The results of analysis on hydrocarbon inclusion and oil sample by new methods showed that there were mainly two stages (N21 and N23-Q) of hydrocarbon accumulation in this area. Early hydrocarbon charging is mainly low maturity oil and latest charging is high maturity oil and gas. Meanwhile, new concept and dynamic model of structure evolution in western Qaidam baisn demonstrated that the inverse "S" shape structure were formed controlled by Alyn Tagh and East Kunlun strike slip fault. Structure of Shizigou-Yingdong area were first formed in the west and developed eastward. Hydrocarbon accumulation are mainly controlled by regional fault and preservation conditions. The footwall of fault and the eastern part of Yingdong tectonic belt are favorable for hydrocarbon accmulation. The new understanding on hydrocarbon accumulation process and favorable enrichment prediction has great significance to the further exploration and well deployments. Introduction Shizigou-Yingdong area located in the western Qaidam basin, where several oil fields including Gasikule, Youshashan, Shizigou and Wunan had been discovered before 2000(Fig.1). There were not big oil or gas fields discovered in the last decade until Yingdong oil field was discovered in the year of 2010. Yingdong oil field is not only one of the biggest discoveries of CNPC, but also one of the richest oil fields in China. In order to research the hydrocarbon accumulation process and exploration potential in this area, large amount of core and oil samples of Yingdong area and adjacent oil fields were collected and analyzed in our laboratory. After observation and datailed analysis of oil/gas inclusion in reservoir core sample, conventional geochemistry analysis of oil samples, dynamic analysis of tectonic movement, formation and evolution of Shizigou-Yingdong tectonic belt, the two stages of hydrocarbon charging history and accumulation process is identified.