关键词: 准噶尔盆地, 南缘, 中下侏罗统, 煤型气, 生气史, 油气藏形成

Abstract: The process of natural gas generation from the Middle-Lower Jurassic coal measures in the southern margin of Junggar basin is simulated with chemical kinetic method by taking the coal-derived gas of Xishanyao formation as an example. The results indicate that the gas generation occurred mainly in Yanshan movement period, accounting for about 80% of the final gas amount, dominated by the period of Cretaceous. Corresponding to the most natural gas generation, the formation of the first-line anticlinal traps in Yanshan period is very significant. Moreover, the Himalayan movement decides the reservoir-forming condition of natural gas in this area. On the one hand, the tectonic adjustment on the first line anticlinal traps (including the continuous conservation of oil and gas in primary reservoirs and the migration toward secondary reservoirs) decides the resource perspective of natural gas in this area to a great extent. On the other hand, the second and third line anticlinal traps formed during the movement can accumulate the natural gas from the late pyrolysis of kerogen and the second cracking of crude oil.

Key words: Junggar basin, southern margin, Middle-Lower Jurassic, coal-related gas, gas generation history, reservoir formation