SIMULATION OF HYDROCARBON GENERATION AND EXPULSION CHARACTERISTICS OF SOURCE ROCKS IN QAIDAM BASIN

The characteristics of hydrocarbon generation and expulsion of the source rocks in Qaidam basin were experimentally studied by means of the hot pressure physical simulation method and the hydrocarbon expulsion threshold theory. Based on the simulation results, a chart for distinguishing the hydrocarbon expulsion threshold was established. The study results indicate that: ① Under the geological background, the existing of water medium favors the hydrocarbon generation and expulsion; ② There existed a critical depth for hydrocarbon expulsion in the geological history. Hydrocarbon could be expulsed in a large scale only after the source rocks entered into the threshold; ③ The processes of hydrocarbon generation and expulsion from coal, argillaceous rocks and carbargillite can be respectively divided into three stages, including generation and expulsion of gaseous hydrocarbon, liquid hydrocarbon and heavier hydrocarbons, high temperature cracking gas; ④The source rocks of lower Ganchaigou group of the Tertiary entered the hydrocarbon expulsion threshold in the depth of about 2250 m. The calculation shows that the hydrocarbon generation ratios, hydrocarbon expulsion ratios, hydrocarbon remaining ratios and hydrocarbon generation and expulsion ratios for the above three kinds of source rocks are 10～500 kg per ton, 0～25 kg per ton, 5～280 kg per ton, and 100～800 m\+3 per ton, respectively.