基于氮气吸附实验与分形FHH模型分析页岩孔隙结构特征——以鄂尔多斯盆地华池地区长7段为例

Analysis of shale pore structure characteristics based on nitrogen adsorption experiment and fractal FHH model: a case study of 7th member of Triassic Yanchang Formation in Huachi area, Ordos Basin

安成 柳广弟 孙明亮 游富粮 王子昕 曹玉顺

AN Cheng LIU Guangdi SUN Mingliang YOU Fuliang WANG Zixin CAO Yushun

中国石油大学(北京) 地球科学学院，北京 102249 油气资源与探测国家重点实验室，北京 102249

College of Geosciences, China University of Petroleum (Beijing), Beijing 102249, China State Key Laboratory of Petroleum Resource and Prospecting, China University of Petroleum (Beijing), Beijing 102249, China

孔隙结构是页岩储层研究的重点，对页岩油的赋存具有重要影响。选取鄂尔多斯盆地华池地区延长组7段的10块泥页岩岩心样品，通过扫描电镜观察及低温氮气吸附实验，结合分形FHH模型，计算分形维数，对研究区泥页岩的孔隙结构进行定量化表征，并在此基础上探讨分形维数与孔隙结构参数、含油性参数的关系，确定长7段泥页岩孔隙发育的主要影响因素。华池地区长7段泥页岩有机质丰度高，属于好—极好烃源岩，含油性与可动性较好，多达到中含油级别，主要由石英与黏土矿物组成；储集空间以粒间孔、粒内孔及少量有机质孔为主，孔隙形态有两类，分别为平行板状狭缝形+单边狭缝形及墨水瓶形+平行板状狭缝形，孔径以微孔和中孔为主，宏孔发育较少。多数样品具有分形特征，表征小孔隙的分形维数D1介于2.264 7~2.714 9之间，表征大孔隙的分形维数D2介于2.373 3~2.777之间。其中，D2同比表面积、孔体积、平均孔径及S1的相关性较好，可以表征孔隙结构发育特征和页岩的含油性；而D1仅可表征页岩油的可动性。泥页岩的孔隙发育主要受控于有机碳及石英含量，与长石含量有一定的关系，黏土矿物含量不是主要的影响因素。

Pore structure, as the focus of shale reservoir research, has important influence on the occurrence of shale oil. In this paper, 10 shale core samples from the 7th member of Triassic Yanchang Formation (Chang 7 member) in Huachi area, Ordos Basin were selected to carry out scanning electron microscope (SEM) observation and low-temperature nitrogen adsorption experiment, and the fractal dimension was calculated to quantitatively characterize the pore structure of shale in the research area combined with fractal FHH model. On this basis, the relationship between fractal dimension and pore structure parameters and oil-bearing parameters was discussed, and the main influencing factors of pore development of shale in the Chang 7 member were determined. The results show that the shale of the Chang 7 member in Huachi area has high organic matter abundance, which are good-to-excellent source rocks mainly composed of quartz and clay minerals, with good oil-bearing property (up to the middle oil-bearing level) and mobility. The reservoir space is dominated by intergranular pores, intragranular pores and a small amount of organic pores. There are two types of pore morphology, namely, parallel plate-shaped slit+unilateral slit and ink bottle-shaped + parallel plate-shaped slit. The pores are mainly micropores and mesopores, with macropores less developed. Most samples have fractal characteristics. The fractal dimension D1 of small pores is between 2.264 7 and 2.714 9, and the fractal dimension D2 of large pores is between 2.373 3 and 2.77 7. Among them, D2 has a good correlation with surface area, pore volume, average pore diameter and S1, which can characterize the development characteristics of pore structure and oil-bearing property of shale, while D1 can only characterize the mobility of shale oil. The pore development of shale is mainly controlled by TOC and quartz content, and has a certain relationship with feldspar content, while clay mineral content is not the main influencing factor.

中国石油天然气集团有限公司—中国石油大学(北京)战略合作科技专项 ZLZX2020-02

https://doi.org/10.11781/sysydz202303576