油气地质与采收率2024，Vol.31Issue(6)：45-56,12.DOI:10.13673/j.pgre.202309024
鄂尔多斯盆地长7段致密砂岩二元孔隙结构及分形特征
Binary pore structure and fractal characteristics of tight sandstone:A case study of Chang 7 Member of Triassic Yanchang Formation in Ordos Basin
摘要
Abstract
The pore structure characteristics of tight sandstone are of significance for the exploration and development of tight oil reservoirs.However,little attention is paid to the flow characteristics and influencing factors of different types of pores.This re-stricts the understanding of the flow and storage capacity of tight sandstone and affects the evaluation and prediction of favorable ar-eas for tight oil reservoirs.Therefore,this paper focuses on the tight sandstone in the Chang 7 member of the Triassic Yanchang For-mation in Ordos Basin,and casting thin sections,scanning electron microscopy,nuclear magnetic resonance,and the fractal method are adopted to research the pore structure characteristics of tight sandstone.The results indicate that the pore structure of tight sandstone is a binary pore system composed of bound pores and movable pores.The morphological characteristics and connec-tivity of different types of pores vary greatly.Bound pores are mainly composed of intergranular pores,and the pore model is the en-velope surface of clay accumulation.The pore radius is small,the connectivity is poor,and the fluid flow is poor.The pore features a regular shape,weak heterogeneity,low fractal dimension,and an average value of 1.306 3.The movable pores are mainly com-bined pores with a spiky-spherical shape.This type of pore has a large radius and multiple connecting channels formed by dissolu-tion,resulting in strong connectivity.The shape of movable pores is irregular,with strong heterogeneity,a large fractal dimension,and an average value of 3.241 6.The influence of different types of pores on physical properties is also different.The average contri-bution of bound pores to porosity is 47.7%,and that of movable pores to porosity is 52.3%.The two types of pores have similar con-tent but are affected by differences in connectivity.The average contribution of bound pores to permeability is 0.2%,while that of movable pores to permeability is 99.8%.Movable pores are the main factor affecting the permeability of tight sandstone.The fractal dimension can characterize the pore structure of tight sandstone.Sandstone is mainly composed of composite pores and located near the source rocks is a favorable area for exploration and development of tight sandstone.关键词
核磁共振/分形维数/致密砂岩/孔隙结构/鄂尔多斯盆地Key words
nuclear magnetic resonance/fractal dimension/tight sandstone/pore structure/Ordos Basin分类
能源科技引用本文复制引用
吴小斌,杜支文,强小龙,雷甜,蒋婷婷,王伟,朱玉双..鄂尔多斯盆地长7段致密砂岩二元孔隙结构及分形特征[J].油气地质与采收率,2024,31(6):45-56,12.基金项目
国家地区科学基金项目"深水相致密砂岩CO2溶蚀机理及其强化封存机制"(42062011)和"异常低压盆地压力场演化对页岩气富集的影响机理研究"(42362023),陕西省教育厅一般项目"榆林地区CCUS地质封存中致密砂岩CO2-水-岩反应机理及其对物性影响评价"(22JK0630),陕西省科技厅青年项目"鄂尔多斯盆地低渗透油藏封存CO2的储层微观孔隙特征及主控因素研究"(2023-JC-QN-0347). （42062011）
