陆相页岩储层孔隙分形特征——以四川盆地三叠系须家河组为例

基于氮气等温吸附、高压压汞测试结果，研究四川盆地三叠系须家河组陆相页岩孔隙结构的分形特征。分析结果表明:须家河组页岩孔隙结构复杂，基质孔隙以纳米级孔隙为主，孔径分布在2~100nm之间；须家河组页岩孔隙具有显著分形特征，分形维数在2.6~2.75之间，平均值为2.66；须家河组页岩分形维数与有机碳含量、微孔孔隙体积、比表面积正相关，与矿物含量相关性不强；页岩分形维数随热演化程度增加具有“先降后增再降”阶段性变化特征。探索性提出页岩优质储层孔隙分形维数分布范围在2.6~2.8之间，为我国陆相页岩储层定量表征及页岩气有利区评价提供新思路和手段。

Reservoir fractal characteristics of continental shale: An example from Triassic Xujiahe Formation shale,Sichuan Basin,China

Based on the nitrogen isothermal adsorption and high pressure mercury intrusion data，the reservoir fractal characteristics of continental shale from Triassic Xujiahe Formation in the Sichuan basin are analyzed.The analytical results show the following characteristics.The porosity structure of Xujiahe Formation shale is complex,and nanoscale pore is the dominant space in the reservoir matrix space with pore size of 2-100nm.The pore structure of Xujiahe shale have significant fractal characteristics,and the fractal dimension ranges from 2.6 to 2.75 with an average of 2.66.It shows positive correlations between the fractal dimension and the total organic carbon (TOC) content,microporous pore volume,specific surface area,but without strong correlation minerals content in Xujiahe shale.Fractal dimension of shale increased with the degree of thermal evolution by periodic variation characteristics of “decreasing-increasing-decreasing”.It suggested that the fractal dimension distribution of high quality shale gas reservoirs ranges from 2.6 to 2.8,with a new way and method for quantitative reservoir characterization of continental shale and favorable area evaluation of shale gas.