煤与煤层气地球化学指标判别沉积环境研究进展

    Research progress on discriminating sedimentary environments using geochemical indicators of coal and coalbed methane

    • 摘要: 为精准重建成煤期沉积环境,支撑煤炭资源评价与煤层气勘探开发,本文系统综述了利用煤与煤层气地球化学指标判别沉积环境的研究进展,重点构建并阐述了四类核心指标的环境指示机理,包括通过B、Sr/Ba比值表征盐度,V/Cr、V/(V+Ni)比值判别氧化还原条件、硫元素反映水体性质的微量元素,借总量及Eu、Ce异常揭示物源与古环境的稀土元素,能指示气体成因与古植被的碳/氢/氧稳定同位素,以及可溯源成煤植被与氧化还原环境的正构烷烃、萜类化合物等生物标志物。同时,本文对比分析了国内外在该领域的研究特色,国内研究的显著特点是将地球化学指标与区域构造演化相结合,且强调多学科交叉;而国外更注重微观机理研究与定量模型构建,并广泛应用分子有机地球化学方法。当前研究仍存在指标多解性、次生改造干扰及埋深>2 000 m的深部煤层研究薄弱等问题,未来需构建“元素-同位素-分子”多指标耦合模型,加强深部煤层气地球化学研究与技术创新,为资源勘探及古环境重建提供更可靠的理论支撑。

       

      Abstract: To accurately reconstruct the sedimentary environment during the coal-forming period and support coal resource evaluation as well as coalbed methane (CBM) exploration and development, this paper systematically reviews the research progress on discriminating sedimentary environments using geochemical indicators of coal and CBM, while focusing on constructing and expounding the environmental indication mechanisms of four categories of core indicators: among them, for trace elements, Boron (B) content and Sr/Ba ratio are used to characterize salinity, V/Cr and V/(V+Ni) ratios are applied to distinguish redox conditions, and sulfur (S) element reflects the properties of water bodies; rare earth elements (REEs) employ total REE content and Eu/Ce anomalies to reveal provenance and paleoenvironment; stable isotopes, specifically stable carbon (C), hydrogen (H), and oxygen (O) isotopes, can indicate gas genesis and paleovegetation; and biomarkers refer to biomolecules such as n-alkanes and terpenoids that are capable of tracing coal-forming vegetation and redox environments. Meanwhile, this paper compares and analyzes the research characteristics of this field at home and abroad. A prominent feature of domestic research is the integration of geochemical indicators with regional tectonic evolution, with emphasis on interdisciplinary collaboration. In contrast, foreign research focuses more on the study of micro-mechanisms and the construction of quantitative models, and extensively applies molecular organic geochemistry methods. Current research still faces challenges, including the multi-solution nature of indicators, interference from secondary transformation, and insufficient research on deep coal seams with a burial depth >2 000 m. In the future, it is necessary to establish a “element-isotope-molecule” multi-indicator coupling model, strengthen geochemical research and technological innovation on deep CBM, so as to provide more reliable theoretical support for resource exploration and paleoenvironment reconstruction.

       

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