川东北地区侏罗系凉高山组页岩储层孔隙结构及分形特征

Pore structure and fractal characteristics of shale reservoirs in Jurassic Lianggaoshan Formation, northeastern Sichuan Basin

李琦 陈睿倩 商斐 李玲 白昕

LI Qi CHEN Ruiqian SHANG Fei LI Ling BAI Xin

1. 中国石油大学(北京)油气资源与工程全国重点实验室, 北京 102249; 2. 中国石油大学(北京) 地球科学学院, 北京 102249; 3. 中国石油勘探开发研究院, 北京 100083

1. State Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum (Beijing), Beijing 102249, China; 2. College of Geosciences, China University of Petroleum (Beijing), Beijing 102249, China; 3. Research Institute of Petroleum Exploration and Development, CNPC, Beijing 100083

川东北地区侏罗系凉高山组作为四川盆地页岩油重点勘探层段，因勘探程度较低，目前页岩储层特征尚不明确。利用X射线衍射矿物分析、扫描电子显微镜分析、高压压汞、低温氮气吸附等实验，深入探究其储集空间类型与分形特征。研究区凉高山组页岩矿物组成主要为黏土矿物(平均含量51.57%)，其次为长英质矿物(平均含量47.11%)，碳酸盐矿物极少(平均含量2.69%)。储集空间类型主要包括黏土矿物层间孔、石英与长石粒间孔以及微裂缝，低温氮气吸附曲线形态接近国际理论与应用化学联合会页岩孔径划分方法中的Ⅳ类，指示狭缝型孔隙。按照压汞曲线形态及储层物性参数特征，将研究区页岩储层分为四类，从Ⅰ到Ⅳ类，排驱压力、中值压力增大，最大进汞饱和度减小，储层非均质性增强。“FHH”模型显示孔隙表面分形维数DN1大于孔隙结构分形维数DN2，表明孔隙表面的复杂程度高于内部；“含水饱和度法”计算结果显示大孔隙分形维数D1平均值为2.991 2，小孔隙分形维数D2平均值为2.679 2，大孔隙分形维数更接近于3且分布更集中，表明非均质性更强的大孔隙对储层的贡献更大。相关性分析显示，D1与矿物组分含量(石英、黏土矿物)、孔喉结构参数存在相关性，证明大孔隙是研究区页岩储集与空间的主要贡献者。通过定性与定量分析对川东北地区凉高山组页岩进行储层评价，为后续该地区有利勘探层段评价与优选提供了思路。

The Jurassic Lianggaoshan Formation in the northeastern Sichuan Basin is a key exploration target for shale oil. However, due to limited exploration in this area, the shale reservoir characteristics remain unclear. Experiments such as X-ray diffraction mineral analysis, scanning electron microscopy analysis, high-pressure mercury intrusion, and low-temperature nitrogen adsorption were conducted to systematically study the storage space types and fractal features of the Lianggaoshan Formation shale reservoir. The primary mineral composition of the Lianggaoshan Formation reservoir in the northeastern Sichuan Basin is clay minerals, with an average content of 51.57%, followed by feldspar and quartz minerals at an average of 47.11%, while carbonate minerals are scarce, averaging 2.69%. The dominant storage space types mainly include interlayer pores of clay minerals, intergranular pores between quartz and feldspar, and micro-fractures. The low-temperature nitrogen adsorption curve of the Lianggaoshan Formation shale aligns with type Ⅳ in the classification system of the International Union of Pure and Applied Chemistry, indicating slit-type pores. Based on the morphology of mercury intrusion curves and reservoir physical properties, the reservoir is divided into four types. From type Ⅰ to type Ⅳ, drainage pressure and median pressure increase, whereas maximum mercury saturation decreases, leading to enhanced reservoir heterogeneity. The “FHH”model calculations show that the pore surface fractal dimension (DN1) is greater than the pore structure fractal dimension (DN2), indicating that the pore surface exhibits greater complexity than the internal pore structure. The average fractal dimension D1 of large pores, calculated using the water saturation method, averages 2.991 2, while that of small pores (D2) averages 2.679 2. The larger pores have a fractal dimension closer to 3 and exhibit a more concentrated distribution, indicating that highly heterogeneous large pores contribute more significantly to the reservoir. Correlation analysis shows that there is a correlation between D and the contents of minerals (quartz and clay minerals) as well as pore-throat struture parameters, proving that large pores are the main contributers to the shale reservoir space in the study area. Through qualitative and quantitative analyses, this paper conducts a reservoir evaluation of the Lianggaoshan Formation shale in the northeastern Sichuan Basin, offering insights for the subsequent evaluation and selection of favorable exploration intervals in this area.

中国石油西南油气田分公司科技计划项目“川东北地区侏罗系下统凉高山组页岩油气地质特征研究”(JS2022-90)资助。

https://doi.org/10.11781/sysydz2025020323