Japan Organization for Metals and Energy Security (JOGMEC), Chiba, Japan.
Alberta Energy Regulator, Edmonton, Canada.
Sci Rep. 2023 Jun 19;13(1):9904. doi: 10.1038/s41598-023-35259-5.
High total organic sulfur (TOS) content (i.e., Type IIS kerogen) is well known to significantly influence kerogen transformation but the effect of TOS content on the evolution of organic porosity has only rarely and indirectly been investigated. This study demonstrates that organic porosity is generated at lower thermal maturity in mudstones containing Type IIS kerogen relative to those with Type II kerogen. To our knowledge this phenomenon has not been previously demonstrated. The implications are relevant for the characterization of organic-rich mudstones as cap rocks, hydrocarbon reservoirs, and disposal reservoirs for CO or nuclear waste because pore systems control storage volumes and matrix fluid flow. Five thermally immature core samples were selected from three organic-rich mudstone units with low to high TOS content: the late Devonian Duvernay Formation (Canada), middle late Miocene Onnagawa Formation (Japan), and early Jurassic Gordondale member of the Fernie Formation (Canada). Hydrous pyrolysis was used to artificially mature splits of the immature samples to four maturity stages, upon which petrophysical and organic geochemical properties were measured and compared to baseline immature samples. Most porosity growth in Type IIS samples occurred below 0.70% VRo, but in Type II samples was broader and robust until 1.1% VRo.
高总有机硫（TOS）含量（即 II 型干酪根）众所周知会显著影响干酪根转化，但 TOS 含量对有机孔隙演化的影响很少被直接研究过。本研究表明，与含 II 型干酪根的泥岩相比，含 II 型干酪根的泥岩在较低的热成熟度下生成有机孔隙。据我们所知，这种现象以前尚未被证明过。这一现象对富含有机质泥岩作为盖层、烃类储层和 CO 或核废料处置库的特征具有重要意义，因为孔隙系统控制着储层体积和基质流体的流动。从 TOS 含量较低到较高的三个富含有机质泥岩单元中选择了五个未成熟的岩心样品：晚泥盆世 Duvernay 组（加拿大）、中晚中新世 Onnagawa 组（日本）和早侏罗世 Fernie 组的 Gordondale 段（加拿大）。水热裂解用于将未成熟样品的分裂物人为地成熟到四个成熟阶段，然后测量其岩石物理和有机地球化学性质，并与基础未成熟样品进行比较。II 型样品中的大部分孔隙生长发生在 0.70% VRo 以下，但在 II 型样品中则更广泛且稳健，直到 1.1% VRo。
