乌伦古地区石炭系烃源岩生烃潜力评价

Hydrocarbon Potential Evaluation of Carboniferous Source-Rocks in Wulungu

准噶尔北缘乌伦古地区下石炭统姜巴斯套组为一套有机质丰度较高、干酪根类型以Ⅰ—Ⅱ型为主的火山岩系烃源岩,虽然评价为中等—好烃源岩,但其热演化过程复杂,主生烃期不清楚,影响了对其生油气潜力的认识。在地层剥蚀厚度恢复的基础上,开展了烃源岩沉积埋藏史及热史研究,恢复了烃源岩热演化生烃过程。为了评价石炭系火山岩系烃源岩生烃潜力,开展了不同岩石类型、不同成熟度烃源岩封闭体系生烃模拟实验。结果表明,火山物质含量较少的凝灰质泥岩的生烃产率明显高于沉凝灰岩。当初始成熟度Ro为1.34%时,凝灰质泥岩仍具有一定的二次生烃能力。在烃源岩生烃潜力评价的基础上,结合油气成藏期和圈闭形成期认为,乌伦古地区应该以寻找与石炭系晚期生烃(二次生烃)区域相匹配的火山岩或中生界圈闭作为下步勘探的方向。

The Wulungu Carboniferous Jiangbasitao formation in the northern margin of Junggar Basin is a set of volcanic source-rocks with high organic matter abundance and the corresponding kerogen is mainly dominated by TypeⅠ-Ⅱ. Although it is identified as medium-high quality source-rocks,the hydrocarbon potential evaluation of source-rocks is limited by the complex thermal evolution processes and unclear main hydrocarbon-generation stage. Based on the restoration of strata erosion thickness,the depositional-burial and thermal histories are researched to restore the thermal evolution hydrocarbon-generation processes of source-rocks. The hydrocarbon simulation experiments of source-rocks in a closed system with different rock types and maturities are carried out to evaluate the hydrocarbon potential of Carboniferous volcanic source-rocks. Research demonstrates that the hydrocarbon-generation rate of tuffaceous mudstone with low content of volcanic material is significantly higher than that of sedimentary tuff.When the initial maturity( Ro) is 1. 34%,the tuffaceous mudstone is characterized by certain secondary hydrocarbon generation capacity. According to the hydrocarbon potential evaluation,hydrocarbon accumulation and trap-forming stages,the volcanic or Mesozoic traps in Late Carboniferous Hydrocarbon area are the next orientation for exploration in Wulungu.