Thermal evolution and hydrocarbon generation of organic matter in shales via sequential high-pressure hydrous pyrolysis: Implications for in-situ conversion of unconventional resource

IF 7.7 2区工程技术 Q1 CHEMISTRY, APPLIED

Fuel Processing Technology Pub Date : 2025-09-11 DOI:10.1016/j.fuproc.2025.108327

Fengtian Bai , Clement N. Uguna , Will Meredith , Colin E. Snape , Christopher H. Vane , Chenggong Sun

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引用次数: 0

Abstract

Understanding kerogen transformation under geological conditions is critical for optimizing the in-situ conversion (ISC) process of organic-rich unconventional resources. Sequential high-pressure hydrous pyrolysis was employed to investigate the geological thermal evolution and hydrocarbon generation mechanisms of organic matter in immature Huadian (Type II₁ kerogen) and Fushun (Type I kerogen) shales. Experiments progressed through four thermal stages, that is Stage 1 (350 °C, 6 h), Stage 2 (350 °C, 24 h), Stage 3 (380 °C, 24 h), and Stage 4 (420 °C, 24 h), with comprehensive analysis of hydrocarbon products by gas-chromatography mass-spectrometry and solid residues by vitrinite reflectance (Ro) and Rock-Eval pyrolysis. The results revealed that the hydrocarbon-generation potential of these two shales declined sharply with a Ro of 0.78–1.23 %, correlating with peak oil generation. Type I kerogen (Fushun) exhibited higher reactivity, generating twice the cumulative oil yield (normalized by TOC) compared to Type II₁ (Huadian) and transitioning earlier to oil dominance. Biomarker evolution (OEP decline, sterane/hopane isomerization) in expelled oil and declining gas dryness index (C₁/ΣC₁–C₅) correlated strongly with the maturity of organic matter, enabling non-destructive ISC monitoring. Compared to typical temperatures used in ex-situ retorting (520 °C), the kerogen conversion was completed at lower temperatures of 350–420 °C in this study, validating prolonged heating as a viable low-energy ISC strategy. However, high-pressure conditions in geological formations may impede hydrocarbon expulsion efficiency, leading to the retention of viscous bitumen and thus necessitating engineered solutions for effective oil recovery. This research enriches the understanding of high-pressure pyrolysis mechanisms of immature/low-maturity unconventional resources and establishes a geochemical framework for optimizing ISC in recovering the oil from these source rocks, ultimately contributing to advancing sustainable exploitation of unconventional resources.

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页岩有机质序贯高压水热解热演化与生烃：对非常规资源就地转化的启示

了解地质条件下的干酪根转化是优化富有机质非常规资源原位转化过程的关键。采用序次高压水热解方法，研究了华甸（ⅱ1型）和抚顺（ⅰ型）未成熟页岩有机质的地质热演化和生烃机制。实验通过了1阶段（350°C, 6 h）、2阶段（350°C, 24 h）、3阶段（380°C, 24 h）和4阶段（420°C, 24 h）四个热阶段，通过气相色谱-质谱法对烃类产物进行了综合分析，通过镜质体反射率（Ro）和岩石热解对固体残留物进行了综合分析。结果表明，这两种页岩的生烃潜力急剧下降，Ro值为0.78 ~ 1.23%，与生油峰值有关。ⅰ型干酪根（抚顺）表现出较高的反应性，其累积产油量（按TOC归一化）是ⅱ型干酪根（华甸）的2倍，且较ⅰ型干酪根（华甸）更早过渡到以油为主。排油中生物标志物的演化（OEP下降、甾烷/藿烷异构化）和天然气干燥指数（C1/ ΣC1-C5）的下降与有机质成熟度密切相关，从而实现非破坏性ISC监测。与非原位重整中使用的典型温度（520℃）相比，本研究中干酪根转化在350-420℃的较低温度下完成，验证了长时间加热是一种可行的低能耗ISC策略。然而，地质地层中的高压条件可能会阻碍排烃效率，导致粘性沥青的滞留，因此需要有效采油的工程解决方案。本研究丰富了对未成熟/低成熟非常规资源高压热解机理的认识，并建立了烃源岩中油气ISC优化的地球化学框架，最终为非常规资源的可持续开发做出贡献。

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来源期刊

Fuel Processing Technology 工程技术-工程：化工

CiteScore

13.20

自引率

9.30%

发文量

398

审稿时长

26 days

期刊介绍： Fuel Processing Technology (FPT) deals with the scientific and technological aspects of converting fossil and renewable resources to clean fuels, value-added chemicals, fuel-related advanced carbon materials and by-products. In addition to the traditional non-nuclear fossil fuels, biomass and wastes, papers on the integration of renewables such as solar and wind energy and energy storage into the fuel processing processes, as well as papers on the production and conversion of non-carbon-containing fuels such as hydrogen and ammonia, are also welcome. While chemical conversion is emphasized, papers on advanced physical conversion processes are also considered for publication in FPT. Papers on the fundamental aspects of fuel structure and properties will also be considered.