致密砂岩孔喉结构分析与渗透率预测方法——以川中地区侏罗系沙溪庙组为例

Pore throat structure analysis and permeability prediction method of tight sandstone: a case study of Jurassic Shaximiao Formation in central Sichuan Basin

陈少云 杨勇强 邱隆伟 王小娟 杨保良 叶热杰普·哈布腊什木

CHEN Shaoyun YANG Yongqiang QIU Longwei WANG Xiaojuan YANG Baoliang Erejep HABILAXIM

1. 中国石油大学(华东) 地球科学与技术学院, 山东 青岛 266580; 2. 深层油气全国重点实验室, 山东 青岛 266580; 3. 中国石油 西南油气田公司 勘探开发研究院, 成都 610041

1. School of Geosciences, China University of Petroleum (East China), Qingdao, Shandong 266580, China; 2. National Key Laboratory of Deep Oil and Gas, Qingdao, Shandong 266580, China; 3. Research Institute of Exploration and Development, PetroChina Southwest Oil & Gas Field Company, Chengdu, Sichuan 610041, China

致密砂岩储层孔喉结构精细表征和渗透性预测是优质储层评价和开发的关键。以川中地区侏罗系沙溪庙组为例，利用高压压汞实验和分形理论，对孔喉结构进行静态表征，探讨孔喉结构、分形维数、储层物性之间的关系，进而分析孔喉结构对渗透率的贡献，建立渗透率预测模型。沙溪庙组样品可分为4种类型：Ⅰ类样品排驱压力低、物性好、孔隙连通性好、平均分形维数为2.11，孔隙以半径大于0.1 μm的大孔和中孔为主，半径大于1 μm的孔喉贡献了90%以上的渗透率；Ⅱ类样品排驱压力在0.4～1.0 MPa之间，平均孔渗分别为9.72%、0.375×10-3 μm2，分形维数为2.20，半径大于0.1 μm的中孔含量上升，并贡献了大部分渗透率；Ⅲ、Ⅳ类样品排驱压力与分形维数明显高于Ⅰ、Ⅱ类样品，孔隙度低且缺乏大孔导致渗透率较低。半径大于0.1 μm的大孔和中孔贡献了沙溪庙组98%以上的渗透率。分形维数是指示孔喉结构的良好标志，分形维数与孔喉半径、最大进汞饱和度、渗透率均呈现明显的负相关关系，而与排驱压力、孔喉相对分选系数呈正相关关系。分形维数与孔喉组成有着强相关性，基于分形维数、孔隙度、最大孔喉半径建立了“孔隙型”储层渗透率定量预测模型。

Subtle characterization of pore throat structure and permeability prediction of tight sandstone reservoir are the key for quality reservoir evaluation and development. Taking Jurassic Shaximiao Formation in central Sichuan Basin as an example, the pore throat structure is statically characterized by HPMI and fractal theory. The relations among pore throat structure, fractal dimension and reservoir physical property are discussed, the contribution of pore throat structure to permeability is analyzed, and a permeability prediction model is established. The samples of Shaximiao Formation can be divided into four types: type Ⅰ samples have low displacement pressure, favorable physical properties and good pore connectivity; the average fractal dimension is 2.11, the pores are mainly macropores and mesopores with radius >0.1 μm, and the pore throat with radius >1 μm contributes more than 90% of the permeability. As for type Ⅱ samples, the displacement pressure are 0.4-1.0 MPa, the average porosity and permeability are 9.72% and 0.375×10-3 μm2, respectively, and the fractal dimension is 2.20; the mesopore content increases and mesopores contribute most of the permeability. The displacement pressure and fractal dimension of type Ⅲ and Ⅳ samples are significantly higher than those of type Ⅰ and Ⅱ samples, and the low porosity and lack of macropore lead to low permeability. The macropores and mesopores with radius > 0.1 μm contribute more than 98% of the permeability of Shaximiao Formation. Fractal dimension is a good indicator of pore throat structure. Fractal dimension is significantly negatively correlated with pore throat radius, maximum mercury saturation and permeability, and is positively correlated with displacement pressure and relative separation coefficient of pore throat. There is a strong correlation between fractal dimension and pore throat composition, and a permeability quantitative prediction model based on fractal dimension, porosity and maximum pore throat radius is established.

国家自然科学基金项目“咸化湖盆细粒物质的成因及其混合沉积作用”(41972099)和“基于现代沉积和沉积模拟的湖相滩坝沉积模式与精细表征研究”(4217020246)联合资助。

https://doi.org/10.11781/sysydz202401202