Effect of gas saturation on P-wave velocity in tight sandstone  

气体饱和度对致密砂岩中P波速度影响的实验研究

作　　者：Pan Bao-Zhi Zhou Wei-Yi Guo Yu-Hang Fang Chun-Hui Zhang Li-Hua 潘保芝;周伟一;郭宇航;房春慧;张丽华(地球探测科学与技术学院,吉林大学,长春130026)

机构地区：[1]College of Geo-exploration Science and Technology,Jilin University,Changchun 130026,China

出　　处：《Applied Geophysics》2024年第3期487-495,617,共10页应用地球物理（英文版）

基　　金：supported by NSFC(42072323 and 42204122).

摘　　要：By measuring the variation of the P-and S-wave velocities of tight sandstone samples under water saturation,it was confirmed that with the decrease in water saturation,the P-wave velocity first decreased and then increased.The variation in velocity was influenced by the sandstone’s porosity.The commonly used Gassmann equation based on fluid substitution theory was studied.Comparing the calculated results with the measured data,it was found that the Gassmann equation agreed well with the measured data at high water saturation,but it could not explain the bending phenomenon of P-wave velocity at low saturation.This indicated that these equations could not accurately describe the relationship between fluid content and rock acoustic velocity.The reasons for this phenomenon were discussed through Taylor’s expansion.The coefficients of the fitting formula were calculated and verified by fitting the measured acoustic velocity changes of the cores.The relationship between P-wave velocity and saturation was discussed,which provides experimental support for calculating saturation using seismic and acoustic logging data.通过测量致密砂岩样品的P波和S波速度随水饱和度的变化,证实了随着水饱和度的降低,P波速度先降后升,速度的变化受到孔隙度的影响。本文还研究了基于流体置换理论的常用Gassmann方程。将计算结果与实测数据相比较,我们发现Gassmann方程在高水饱和度时与实测数据吻合良好,但不能解释低饱和度时P波速度的弯曲现象,说明这些方程不能准确描述流体含量与岩石声速的关系。通过Taylor展开法,我们讨论了这种现象产生的原因。本文计算了拟合公式的系数,并通过拟合测得的岩心声速变化进行了验证。P波速度和饱和度之间的关系的讨论和分析,将为利用地震和声波测井数据计算饱和度提供实验支持。

关 键 词：Tight sandstone Saturation model Reservoir parameters Acoustic wave measurement 

分 类 号：P631[天文地球—地质矿产勘探]