泥页岩烃—孔隙—表面的关系及其对残留烃评价的意义

The Relationships Among Hydrocarbon-Pore-Surface in Shale Rocks and Their Significance for the Evaluation of Residual Hydrocarbons

泥页岩中残留烃具有多种赋存态,且赋存态与赋存空间紧密相关,残留烃的研究必须同时关注赋存态和赋存空间。残留烃的不同赋存态在本质上是由于残留烃组分以及孔隙和表面性质的多样性造成的,导致不同赋存态烃的剥离条件具有差异,基于这种差异,提出有机溶剂抽提—化学湿氧化的相继处理方法分离游离态烃、物理吸附烃和化学结合态烃。泥页岩中存在多种类型的孔隙和表面,气体吸附法、压汞法、化学吸附法和成像方法的配合才能够全面表征泥页岩的孔隙结构。通过分析每一步处理前后烃参数和孔隙结构表征参数的变化特征可以建立烃—孔隙表面的关系,而烃和矿物在分子层面和微观尺度相互作用的研究有助于进一步丰富烃—孔隙—表面的关系,这对于深刻理解残留烃的赋存机理和流动特征具有重要意义。

Development of shale oil and gas has prompted people to think about the occurrence space and occurrence states of residual hydrocarbon in shale. There are three occurrence states of residual hydrocarbon in shale： free, adsorbed and dissolved. The contribution of different state hydrocarbon remains uncertain. The occurrence space for hydrocarbon includes pore and surface. Pore can be divided into macropore, mesopore, micropore; and surface can be distinguished between the external and internal surface. Filling and adsorption of hydrocarbon in/on different spaces vary a lot. Furthermore, characteristics of hydrocarbon and organic matter, and the burial and evolution process could complicate the relationships among hydrocarbon, pore and surface. In summary, research on residual hydrocarbon in shale must focus on occurrence state and space simultaneously; Rock-Eval pyrolysis and organic solvent extraction are effective quantitative methods for residual hydrocarbon evaluation, and calibration of characteristic parameters is of great significance. Union of N2 adsorption, mercury intrusion and EGME adsorption methods could achieve the pore structure characteristics of shale comprehensively. These quantitative evaluation methods are the basis for the research on relationships among hydrocarbon, pore and surface. This paper recommended progressively use of organic solvents and wet chemical oxidation methods＇ which can separate free hydrocarbon, physical adsorption hydrocarbon and chemical bonding hydrocarbon gradually, and then we could establish the relationship among hydrocarbon, pore and surface by the combination of residual hydrocarbon and space quantitative characterization methods. Research on the interactions between hydrocarbon and minerals in molecular level and micro-scale will enrich the relationship among hydrocarbon, pore and surface, and it has great significance for us to understand the occurrence mechanism and flow characteristies of residual hydrocarbon in shale.