赵迪斐;郭英海;解徳录;苏驰;杨玉娟;于一帆;

• 1:中国矿业大学资源与地球科学学院
• 2:中国矿业大学煤层气资源与成藏过程教育部重点实验室

摘要：

为研究页岩储层孔隙结构特征,以重庆南川三泉剖面泉浅1井、綦江观音桥剖面、涪陵B井和石柱打风坳剖面等龙马溪组页岩储层样品为例,通过低温氮吸附实验数据建立FHH分形模型,讨论分形维数与孔隙结构参数、TOC质量分数的相互关系.结果表明:样品孔隙以微孔为主,孔径分布集中在40nm以下,具有明显的分形特征,分形维数介于2.760~2.850之间,相关因数大多超过0.99,反映复杂的孔隙结构与较强的非均质性;部分样品显示明显的双重分形特征,以甲烷分子自由程为界可将纳米孔分为渗透孔隙和吸附孔隙,吸附孔隙阶段分形维数变化范围在2.881~2.917之间,渗透孔隙阶段分形维数变化范围在2.791~2.823之间;孔隙体积和平均孔径与分形维数具有负相关性,BET比表面积与分形维数呈明显的正相关关系,即平均孔径越小、孔隙体积越小、BET比表面积越大,分形维数越接近于3;TOC质量分数也与分形维数呈明显的正相关关系,是分形维数的重要影响因素.通过分形维数可以定量评价储层孔隙的复杂程度和非均质程度,为储层评价和页岩气在纳米孔隙中的赋存和运移机理研究提供思路.

关键词： 页岩储层;孔隙;分形维数;氮气吸附法;FHH分形模型

Abstract: The fractal model for shale reservoir pores can indirectly reflect the characteristics that is difficult to observe directly.Using samples taken from Quanqian1 well from Sanquan profile in Nanchuan and Guanyinqiao profile in Qijiang,the based structural features were studied by low-temperature nitrogen adsorption experiments and the FHH fractal model was established.The relationship between fractal dimension values and pore structure parameters,TOC content were discussed.The results shows that the shale pores were mainly distributed in micropore under 40 nm and have obvious fractal characteristics.The fractal dimension lies between 2.76~2.85 with correlation coefficient higher than 99%reflecting the complex pore structures and strong heterogeneity.Some samples shows dual fractal feature and the pores can be divided into seepage pore and absorption pore bounded by methane molecular free path.The fractal dimension D1 for absorption pore(2.881~2.917)is higher than D2 for seepage pore(2.791~2.823).The relationship between pore volume,average pore radius and fractal dimension were negatively correlated and the relationship between specific surface area and fractal dimension were positively correlated which shows that the smaller the average pore size,pore volume is and the bigger the specific surface area is,the fractal dimension is more close to 3.There is a positive correlation between the fractal dimension values and TOC content which shows that the TOC content is an important influencing factors of fractal dimension values.The fractal dimension value can be used to evaluate thecomplexity and heterogeneity of reservoir pore quantitatively.It provides support for new reservoir evaluation methods and shale gas occurrence and migration mechanism in nano-pore research.

Keywords: shale reservoir;pore;fractal dimension;low-temperature nitrogen adsorption;FHH fractal model

基金项目: 国家重点基础研究发展计划(973计划)资助项目(2012CB214702);; 中国矿业大学大学生创新创业基金资助项目(201415)

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