基于核磁共振和恒速压汞的致密砂岩孔喉结构表征新方法

doi:10.3969/j.issn.1006-6535.2025.01.016

摘要/Abstract

摘要： 致密砂岩孔喉细小、孔隙结构复杂、非均质性严重。为准确表征致密砂岩储层的孔喉结构特征,以松辽盆地长岭断陷营城组营3储层致密砂岩为例,采用场发射扫描电镜、铸体薄片、恒速压汞和核磁共振方法对致密砂岩孔隙结构进行了多尺度研究,通过将NMR与CMP实验相联合,有效识别了孔隙与喉道半径分布,明确了可动流体孔喉半径下限。实验表明:经过NMR与CMP联合识别,目标储层的平均喉道半径为0.331～0.824 μm,平均孔隙半径为17.600～24.290 μm,平均孔喉连通比为27.62～53.17;可动流体孔喉半径下限是一个范围,下界限r₁和上界限r₂可将赋存流体划分为束缚区、过渡区和可动区;随着渗透率降低,r₁逐渐增大,r₂逐渐降低,束缚区范围变大,过渡区和可动区范围变小;r₁增大会导致吸附孔孔隙度增大,渗流孔孔隙度降低,储层质量变差;r₁可作为评价储层流动能力界限的指标。该研究成果可为优选致密砂岩优质储层提供依据。

关键词: 致密砂岩, 孔隙结构, 喉道, 恒速压汞, 核磁共振

Abstract: Tight sandstone features small pore throats,a complex pore structure and severe heterogeneity.To accurately characterize the pore throat structure characteristics of tight sandstone reservoirs,taking the tight sandstone of the third member of Yingcheng Formation in Changling Fault Depression,Songliao Basin as an example,the pore structure of tight sandstone was investigated by means of field emission scanning,casting thin section,constant-rate mercury injection and nuclear magnetic resonance method.Through the combination of NMR with CMP experiment,the distribution of pore and throat radius was effectively identified,and the lower limit of pore throat radius of movable fluid was defined.The experimental results indicate that the average throat radius of the target reservoir ranges from 0.331 to 0.824 μm,the average pore radius ranges from 17.600 to 24.290 μm,and the average pore-throat connectivity ratio ranges from 27.62 to 53.17.The lower limit of the pore throat radius of movable fluid is within a range.The lower limit r₁ and the upper limit r₂ can divide the fluid into the bound zone,the transition zone and the movable zone.As the permeability decreases,r₁ gradually increases,r₂ gradually decreases,the range of the bound zone becomes larger,and the range of the transition zone and the movable zone becomes smaller.The increase of r₁ will lead to the increase of adsorption pore porosity,the decrease of seepage pore porosity and the deterioration of reservoir quality.r₁ can be used as an index to evaluate the boundary of reservoir flow capacity.The research results can provide a basis for optimizing high-quality tight sandstone reservoirs.

Key words: tight sandstone, pore structure, throat, constant-rate mercury injection, nuclear magnetic resonance

中图分类号:

TE349

刘客. 基于核磁共振和恒速压汞的致密砂岩孔喉结构表征新方法[J]. 特种油气藏, 2025, 32(1): 135-143.

LIU Ke. A new method for characterizing the pore-throat structure of tight sandstone based on nuclear magnetic resonance and constant-rate mercury intrusion[J]. Special Oil & Gas Reservoirs, 2025, 32(1): 135-143.

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