Hoek-Brown准则在致密砂岩弹性参数测井解释中的应用

Application of Hoek-Brown Criterion for Tight Sandstone Elastic Parameters in Log Interpretation

  • 摘要: 为了解决深层-频繁互层型致密砂岩、泥页岩地层弹性参数测井解释结果可靠性难以保证的问题,以致密砂岩和泥页岩试样为研究对象,分析了岩石应力-应变各阶段的特征及地层应力状态;基于Hoek-Brown准则提出了一种岩石弹性参数测井解释新方法,对该准则中GSI,a,s和mb进行了合理取值;对岩石弹性模量和泊松比进行了最终解释。研究发现,利用波速自洽确定的GSI值与岩石三轴强度具有较好的对应关系;mb和s与岩石三轴强度正相关,a与其负相关,可以利用s对mb进行定量表征(相关系数为0.884);岩石弹性模量及泊松比解释结果的平均相对误差分别为6.50%和5.55%,优于常规解释方法的平均相对误差8.44%和5.78%。研究表明,新方法不需要横波测井资料,岩石弹性模量与Hoek-Brown准则参数间具有指数相关性,岩石泊松比与弹性模量间具有线性相关性;同时,岩石纵波波速与Hoek-Brown准则的定义参数间亦具有较好的线性关系,可以利用纵波波速对弹性模量进行定量表征。

     

    Abstract: In order to solve the problem of unreliable elastic parameters in log interpretation results, and for determining the deep-frequent alternating layers of dense sandstone and shale formations, the stress-strain characteristics and formation stress status were researched with the samples of tight sandstone and muddy shale at different stages.A new approach with rock elastic parameters for logging interpretation was established based on H-B criterion, it took a reasonable value of GSI, a, s and mb, and obtained the final interpretation of brittleness by using Young’s Modulus and Poisson’s Ratio.The results showed that GSI and rock triaxial strength were good correlation, there was a positive relation of both mbb and s with rock triaxial strength, and negative relation with a and the triaxial strength.s can be used to quantitatively characterize mb(correlation coefficient R=0.884);the average error of Em and Poisson’s Ratio was 6.4 % and 5.59 % respectively, the result was better than that obtained by conventional method(8.44 % and 5.78 %).The research suggested that the new method did not need shear wave data, and that there was an index correlation of Em and H-B Citerion parameters, and a linear correlation of Poisson’s Ratio and Em.At the same time, there was also a good linear relation of longitudinal wave velocity of rock and H-B criterion parameters, Em can be quantitatively characterized by longitudinal wave velocity.

     

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