松辽盆地上古生界烃源岩生气潜力评价

Evaluation on Gas Generation Potential of Upper Paleozoic Source Rock in Songliao Basin

松辽盆地上古生界烃源岩有机质类型主要为Ⅲ型,热演化程度普遍达到高—过成熟阶段。松辽盆地在三叠纪经历了长期的暴露剥蚀,之后又发生快速深埋,致使上古生界烃源岩普遍发生了二次生烃过程。因此,对上古生界烃源岩生气潜力的综合评价,应该包括一次生烃和二次生烃2部分。通过生烃热模拟试验、镜质体反射率和有机碳含量的恢复,证实松辽盆地上古生界烃源岩现今生烃潜力已经很低,地质历史时期其生烃潜力体现出明显的区域性,一次生烃以盆地西部和北部地区为主,二次生烃以盆地东部为主。在上述关键参数恢复的基础上,采用热降解率法分别计算了上古生界烃源岩的一次生气量和二次生气量。计算结果显示:上古生界烃源岩一次生气量约为566.24×1012 m3,二次生烃所提供的天然气资源量为(0.97～1.29)×1012 m3;松辽盆地上古生界烃源岩二次生烃地区主要为大庆—肇州和大安—农安一带,盆地西部已经没有生气能力,北部生气区范围小,东部成为主要的有效生气区。

The type of organic matter from Upper Paleozoic source rock in Songliao Basin is type Ⅲ , and the thermal evolution is generally in high-over mature stage. A long-term exposure and erosion happens during Triassic in Songliao Basin, and then rapid deep burial happens, causing secondary hydrocarbon generation in Upper Paleozoic source rock. So, the comprehensive evaluation of gas generation potential in Upper Paleozoic source rock should include the first hydrocarbon generation and the secondary hydrocarbon generation. Based on the hydrocarbon generation thermal simulation experiment and the recovery of vitrinite reflectance and organic carbon content, it is confirmed that the hydrocarbon generation potential of Upper Paleozoic source rock in Songliao Basin is limited nowadays, but the characteristic of hydrocarbon generation potential in geological history is obviously different in each region. The first hydrocarbon generation is mainly in the western and northern parts of Songliao Basin, and the secondary one is mainly in the eastern part. According to the above recovery of key parameters,the first gas generation and secondary one are respectively calculated by the means of thermal degradation rate. The calculated results show that the first gas generation from Upper Paleozoic source rock in Songliao Basin is about 566.24 × 10^12 m3, and the gas resources produced by secondary gas generation is （0.97-1.29） × 10^12 m3 ; secondary hydrocarbon generation of Upper Paleozoic source rock in Songliao Basin mainly happens in Daqing-Zhaozhou and Da＇an-Nong＇an areas, while there is no gas generation in the western part of Songliao Basin, the scope of gas generation is small in the northern part, and the generation is efficient in the eastern part.