关键词: 鄂尔多斯盆地, 特低渗透砂岩储层, 可动流体孔隙度, 核磁共振技术, 可动流体, 分布特征, 微观孔隙结构

Abstract: The sandstone samples of the ultra-low permeability reservoir in Yanchang Formation of Ordos Basin were tested with the nuclear magnetic resonance technique.The porosity parameter was defined to analyze the characteristics and the influencing factors of movable fluid.The existing characteristics of movable fluid include the following aspects: The amplitude of T₂ spectrum is relatively low,and the content of movable fluid is also low.The parameters of movable fluid is expanse and the heterogeneity is intense.The relation between the movable fluid parameter and the permeability gets better with the increase of permeability.The movable fluid parameter gets higher attenuation velocity with decrease of permeability and has more sensitivity to the changes of permeability.The micro-pore structure determines the existing state of fluid.The main influencing factors of the movable fluid include micro-fracture,filling degree of clay mineral in pores,secondary porosity and recrystallization.

Key words: Ordos Basin, ultra-low permeability sandstone reservoir, movable fluid porosity, nuclear magnetic resonance technique (NMR), movable fluid, distribution feature, micro-pore structure