不同加热温度下松辽盆地北部低熟页岩油生烃特征与演化规律

Hydrocarbon Generation Characteristics and Evolution Patterns of Low-Maturity Shale Oil in the Northern Songliao Basin under Different Heating Temperatures

摘要: 松辽盆地北部嫩江组与青山口组发育巨厚层富有机质页岩，低熟页岩油资源潜力巨大，但针对其加热过程中生烃特征与动态演化规律的系统研究仍较薄弱，制约了勘探有利区优选与资源量精准评价。本研究以齐家–古龙凹陷和三肇凹陷为重点研究区，系统采集不同层位、不同有机碳含量的低成熟度页岩样品，设计生油率测定实验、封闭体系热演化实验以及边生边排热演化实验等，揭示不同温度下低熟页岩的生烃特征及变化规律。研究表明：① 松辽盆地北部低熟页岩干酪根类型为I-IIa型，研究区油页岩生油潜力有利区的地球化学参数指标为：TOC > 4%，含油率 > 3%，热解烃S₂ > 25 mg/g，氢指数HI > 350 mg/g；② 封闭体系下，生油量呈现先升后降的变化规律，350℃~400℃为生油高峰阶段，对应成熟度1.08%~1.74%，有机质转化率达68.2%；③ 半开放体系下，生油量随温度升高持续增加，350℃~400℃增幅大，占总量78%，对应成熟度0.95%~1.53%，有机质转化率达71.7%。

Abstract: The Nenjiang and Qingshankou formations in the northern Songliao Basin host thick, organic-rich shales with significant potential for low-maturity shale oil resources. However, systematic studies on the hydrocarbon generation characteristics and dynamic evolution during thermal maturation remain insufficient, which constrains the optimization of exploration sweet spots and accurate resource assessment. This study focuses on the Qijia-Gulong and Sanzhao sags as key areas, systematically collecting low-maturity shale samples from different layers and with varying total organic carbon (TOC) contents. Experiments including oil yield determination, closed-system thermal evolution, and semi-open (generation‑and‑expulsion) thermal evolution were designed to reveal the hydrocarbon generation characteristics and variation patterns of low-maturity shales under different temperatures. The results show: (1) The kerogen in low-maturity shales of the northern Songliao Basin is predominantly type I-IIa. The geochemical parameter thresholds defining favorable zones for oil shale potential in the study area are: TOC > 4%, oil yield > 3%, pyrolysis hydrocarbon S₂ > 25 mg/g, and hydrogen index HI > 350 mg/g. (2) Under closed-system conditions, oil generation first increases and then decreases; the peak oil generation window occurs at 350˚C~400˚C, corresponding to a maturity of 1.08%~1.74% R_o, with an organic matter conversion rate of 68.2%. (3) Under semi-open system conditions, oil generation continuously increases with rising temperature. The temperature range of 350˚C~400˚C exhibits a sharp increase, accounting for 78% of the total oil generated, corresponding to a maturity of 0.95%~1.53% Ro and an organic matter conversion rate of 71.7%.