海相不同类型烃源岩有机质丰度热演化规律

Thermal evolution pattern of organic matter abundance in various marine source rocks

秦建中 金聚畅 刘宝泉

Qin Jianzhong Jin Juchang Liu Baoquan

烃源岩加水热压模拟实验和自然演化剖面实测都表明,海相不同类型烃源岩的有机质丰度热演化可分为3段:未成熟-低成熟阶段(小于0.8%)随成熟度的增加有机碳含量及生烃潜量变化不明显;在成熟阶段中晚期(为0.8%～1.3%)有机碳含量和生烃潜量随成熟度增加逐渐降低,其根本原因是油气不断大量生成和排出;在高成熟-过成熟阶段随成熟度的增加有机碳含量变化又不明显。未成熟-低成熟阶段到高成熟阶段,有机质丰度明显降低,需要进行原始有机碳含量的恢复。经不同类型源岩对比,恢复系数与生排烃潜力、干酪根类型、成熟度和有机质含量等因素有关,而与岩性关系不大。

Both simulation experiment on source rocks performed under watered, heated and pressured conditions and measurement of natural evolution sections show that thermal evolution of organic matter abundance in various marine source rocks can be divided into 3 stages, i.e. immature-low mature stage, mature stage and high mature-overmature stage. In immature-low mature stage (<0.8%),TOC and hydrocarbon generating potential change insignificantly with increasing maturity. In mid-late mature stage (= 0.8%-1.3%), TOC and hydrocarbon generating potential decrease progressively with increasing maturity, simply due to the persistent generation and expulsion of large amount of hydrocarbons. While in high mature-overmature stage, TOC varies insignificantly again with increasing maturity. The abundance of organic matter lowers significantly from immature-low mature stage to high mature stage, thus the original TOC should be restituted. Comparison of different types of source rock shows that the restitution coefficient is related to hydrocarbon-generating and-expulsing potentials, kerogen types, maturity and TOC, while it has little correlation with lithologies.

10.11743/ogg20050207