Abstract:

Based on the the experimental data of physical properties, components, light hydrocarbon components, carbon isotope and biomarker, physical properties and geochemical characteristics of condensate oil in the eastern Kuqa Depression,were systematically analysed. Genetical type of condensate oil and hydrocarbon charging history were confirmed. The results show that condensate oil in the eastern Kuqa Depression is typical continental oil, which is featured by low density, low viscosity, low freezing point, low sulfur content and medium wax content. Relationship between carbon isotope and biomarker indicates that condensate oil is mainly derived from Triassic lacustrine source rocks. Condensate oil and natural gas in the eastern Kuqa Depression have different origins. The condensate oil is mainly derived from the mature lacustrine source rocks, and natural gas is originated from mature to post-mature coal-measure source rocks. The maturity of condensate oil is lower than that of natural gas, and early oil suffered from gas washing. Therefore, the eastern Kuqa Depression has the charging feature of ‘early-stage accumulation of oil and late-stage accumulation of gas’. Todays condensate oil is early accumulating oil which undergone gas washing.

Key words: condensate oil, biomarker, gas washing, hydrocarbon accumulation, the eastern Kuqa Depression