The Anisotropic Horizontal Stress Estimated Using Well Logs Sonic Data In Deep Longmaxi Shales

ABSTRACT: A series of velocity measurements and static triaxial tests are performed in this paper to estimate the anisotropic horizontal stresses of deep Longmaxi shales with consideration of poroelastic effect and temperature. The results show that the static stiffness coefficients are smaller than their corresponding dynamic results but the static Biot's coefficient is higher than dynamic value. And there are good linear regression correlations between above dynamic and static parameters. In the evaluation of log-based models, the ANNIE model is inapplicable here because ratio of νv/νh is not always greater than 1 while the M-ANNIE model improves the prediction of C13, which demonstrate that M-ANNIE model is applicable to deep Longmaxi shale. In the prediction of horizontal stresses, one hand the relative error significantly decreases after using static parameters, on the other hand the isotropic model underestimates the horizontal stresses compared with VTI model. The Biot's coefficient has a significant impact on predicting horizontal stresses while the effect of thermal stress on horizontal stress is extremely small.