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

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.