富有机质页岩生烃阶段孔隙演化及分形特征

为明确富有机质页岩孔隙演化规律，以鄂尔多斯盆地三叠系延长组不同成熟度(RO值介于0.53%~1.09%之间)黑色页岩为研究对象，通过扫描电镜、氮气吸附和X-射线衍射等技术手段对页岩储层的纳米孔隙及热演化特征进行研究，并依据FHH分形模型探讨了页岩孔隙分形特征及热演化规律。结果表明：页岩孔隙总体积和比表面积主要受控于中孔(2~50nm)和大孔(＞50nm)，并与TOC含量有较好的相关性；随着RO值的增加，页岩孔隙总体积先下降，再略微上升，比表面积先下降，再明显回升，这是压实作用和生排烃作用共同作用的结果。RO值与有机质孔发育程度密切相关，是中孔的最大贡献者。页岩孔隙的分形维数普遍较高，随着热演化程度的加深整体呈增大趋势，且与孔体积及平均孔径显著负相关，与比表面积正相关，表明页岩孔隙结构趋于复杂，吸附能力提升。

The porous evolution and fractal dimension of the organic-rich shale at the stage of hydrocarbon generation

To study the micro pore shale thermal evolution，this paper takes Triassic black shale of different maturity (RO=0.53%-1.09%) in Ordos Basin as the research object，characterizingshale pore evolution by scanning electron microscopy，N2 adsorption method,X-ray，and exploring the fractal characteristics of shale based on the thermal evolution of the FHH fractal model.The results show that as the maturity of organic matter increases，the pores of organic matter increase，the average pore size decreases,the total pore volume，mainly controlled by the volume of the large pores and mesoporous pores，decreases first and then slightly increases; and the specific surface area first decreases and then increases，which is in accordance with the evolution trend of the mesoporous volume.The above phenomena may be closely related to compaction and hydrocarbon generation and expulsion byorganic matter.Furthermore,the pore size of organic matter is closely related to RO and is the largest contributor to mesopores.The fractal dimension (calculated by FHH model)which is negatively correlated with pore volume and average pore size，and positively related to specific surface areaincreases generally(between 2.513 and 2.745)，indicating that shale pore structure tends to be complex，and the adsorption capacity is improved.