Bai Xuefeng, Feng Zihui, Zhang Xiaochang, Huo Qiuli, Jin Wei, Sun Jing, Zeng Huasen
State Key Laboratory of Continental Shale Oil, Daqing, 163712, Heilongjiang, China.
Daqing Oilfield Co., Ltd., Daqing, 163712, Heilongjiang, China.
Sci Rep. 2025 Aug 9;15(1):29186. doi: 10.1038/s41598-025-14009-9.
Diamondoids are an important industrial material for biomedicine and equipment manufacturing. In addition to chemical synthesis methods used in industry, direct separation from petroleum is also a potential approach. Therefore, studying the quantity and formation mechanism of diamondoids in crude oil has attracted attention. The Gulong shale oil in the Songliao Basin is accumulated in-situ and has not been affected by migration, fractionation, or biological modification; therefore, it provides a natural laboratory for studying the genesis of diamondoids. This article explores the content and formation mechanism of diamondoids in Gulong shale oil through absolute quantification and chromatography-mass spectrometry analysis techniques. The results show that (1) the total diamondoid content in the Gulong shale oil is 45-1,059 µg/g, including 45-1005 µg/g of adamantane and 0-53 µg/g of diamantane. The maximum diamondoid content in shale oil is about 10 - 20 times that in conventional oil. (2) The content of diamondoids in shale oil is controlled by thermal evolution with thermal maturity at Ro < 0.8%, 0.8%-1.2%, 1.2%-1.4%, and > 1.4%, the diamondoid content exhibits four changing characteristics: low value, essential stability, slow increase, and rapid increase, respectively, indicating that the shale oil has undergone rearrangement, cracking, and other reactions to form diamondoids under high temperatures and pressures. (3) The content of diamondoids in shale oil is closely related to the catalytic effect of clay minerals; the diamondoid content in shale oil with high thermal maturity is 1.26 - 1.35 times higher than that in tight oil, confirming that the catalytic effect of clay minerals in shale is conducive to the formation of diamondoids. (4) The content of diamondoids in shale oil is significantly affected by reservoir pressure; under high thermal maturity, the shale oil with a reservoir pressure coefficient of 1.5 has a higher diamondoid content than that with a pressure coefficient of 1.3 by 1.4 times. In particular, the appearance of diamantane implies that high-pressure conditions are favorable for the formation of high-grade diamondoids. Finally, a formation and evolution model of diamondoids in the Gulong shale oil was established, which shows four stages with different formation mechanisms, including primary, inheritance, generation, and enrichment.
金刚烷类化合物是生物医药和设备制造领域的一种重要工业材料。除了工业上使用的化学合成方法外，从石油中直接分离也是一种潜在的方法。因此，研究原油中金刚烷类化合物的含量及其形成机制受到了关注。松辽盆地古龙页岩油为原地聚集，未受到运移、分馏或生物改造的影响，因此为研究金刚烷类化合物的成因提供了一个天然实验室。本文通过绝对定量和色谱 - 质谱分析技术，探究了古龙页岩油中金刚烷类化合物的含量及形成机制。结果表明：（1）古龙页岩油中金刚烷类化合物的总含量为45 - 1059 μg/g，其中金刚烷含量为45 - 1005 μg/g，双金刚烷含量为0 - 53 μg/g。页岩油中金刚烷类化合物的最大含量约为常规油的10 - 20倍。（2）页岩油中金刚烷类化合物的含量受热演化控制，当热成熟度Ro分别小于0.8%、0.8% - 1.2%、1.2% - 1.4%和大于1.4%时，金刚烷类化合物含量呈现出低值、基本稳定、缓慢增加和快速增加四个变化特征，这表明页岩油在高温高压下经历了重排、裂解等反应形成金刚烷类化合物。（3）页岩油中金刚烷类化合物的含量与黏土矿物的催化作用密切相关；高热成熟度页岩油中金刚烷类化合物的含量比致密油高1.26 - 1.35倍，证实了页岩中黏土矿物的催化作用有利于金刚烷类化合物的形成。（4）页岩油中金刚烷类化合物的含量受储层压力的显著影响；在高热成熟度下，储层压力系数为1.5的页岩油中金刚烷类化合物的含量比压力系数为1.3的页岩油高1.4倍。特别是双金刚烷的出现意味着高压条件有利于高等级金刚烷类化合物的形成。最后，建立了古龙页岩油中金刚烷类化合物的形成与演化模型，该模型显示了四个具有不同形成机制的阶段，包括原生、继承、生成和富集。
