Zhao Ya, Zeng Qianghao, He Taohua, Teng Juan, Xiao Daxing, Yang Shukun, Zhang Xiaqi, Wen Zhigang
Key Laboratory of Exploration Technologies for Oil and Gas Resources (Yangtze University), Ministry of Education Wuhan, 430100, China.
Hubei Key Laboratory of Petroleum Geochemistry and Environment, Yangtze University, Wuhan, 430100, China.
ACS Omega. 2024 Jul 11;9(29):32033-32051. doi: 10.1021/acsomega.4c03837. eCollection 2024 Jul 23.
In the Gaoyou Sag located within the Subei Basin, the hybrid shales from the second member of the Funing Formation (Ef) have been identified as a prolific source of shale oil production, despite their characteristically low organic matter content (TOC < 1.5%). This observation suggests that specific macerals within these hybrid shales demonstrate a pronounced hydrocarbon generation potential, thus unveiling a new frontier for shale oil exploration endeavors. In this study, 16 samples were rigorously extracted from both mudstone and hybrid shale strata within the Ef. An exhaustive suite of organic and inorganic geochemical analyses was conducted on these specimens. The analyses elucidated several key findings: (1) The maceral composition within the hybrid shales is predominantly comprised of alginite, solid bitumen, and inertinite. Remarkably, the variability of alginite content within the hybrid shales is more pronounced than that observed in high-TOC mudstones. High-TOC mudstones are characterized by a preponderance of lamalginite and a paucity of telalginite, leading to a diminished aggregate hydrocarbon potential. (2) Biomarker ratios (e.g., sterane/hopane, C tricyclic terpane/αβ C hopane, C tetracyclic terpane/C tricyclic terpane, etc.) suggest a primary derivation from lower aquatic organisms, with a secondary contribution from terrigenous organic matter within the hybrid shales. (3) The accretion of macerals is governed by an intricate set of factors, including the input of terrigenous detritus, paleosalinity, and paleoproductivity. (4) Alginite is identified as the principal constituent responsible for hydrocarbon genesis in hybrid shales. The proliferation of alginite facilitates the concurrent enrichment of shale oil and organic matter within the hybrid shales of the Subei Basin, illustrating a cooperative mechanism underlying the accumulation of shale oil and organic matter. This indicates that even hybrid shales with scant organic content exhibit considerable potential for shale oil exploration.
在苏北盆地的高邮凹陷，阜宁组二段（Ef）的混合页岩已被确定为页岩油的高产来源，尽管其有机质含量通常较低（总有机碳含量<1.5%）。这一观察结果表明，这些混合页岩中的特定显微组分具有显著的生烃潜力，从而为页岩油勘探开辟了新的领域。在本研究中，从Ef的泥岩和混合页岩地层中严格提取了16个样本。对这些样本进行了一系列详尽的有机和无机地球化学分析。分析得出了几个关键发现：（1）混合页岩中的显微组分主要由藻质体、固体沥青和惰质体组成。值得注意的是，混合页岩中藻质体含量的变化比高总有机碳泥岩中更为明显。高总有机碳泥岩的特征是层状藻质体占优势而远源藻质体稀少，导致总体生烃潜力降低。（2）生物标志物比值（如甾烷/藿烷、三环萜烷/αβ藿烷、四环萜烷/三环萜烷等）表明主要来源于低等水生生物，混合页岩中陆源有机质有次要贡献。（3）显微组分的堆积受一系列复杂因素控制，包括陆源碎屑输入、古盐度和古生产力。（4）藻质体被确定为混合页岩中烃类生成的主要成分。藻质体的大量存在促进了苏北盆地混合页岩中页岩油和有机质的同时富集，说明了页岩油和有机质聚集的协同机制。这表明即使是有机含量稀少的混合页岩在页岩油勘探方面也具有相当大的潜力。
