Developing correlations for velocity models in vertical transverse isotropic media: Bakken case study

Finally, the correlations have been applied to well log data from a vertical well in the Bakken Formation, and compared to the stiffness coefficients obtained using the M-ANNIE assumptions. Moreover, minimum horizontal stress is calculated and compared using ANNIE, M-ANNIE, and the proposed correlations, these last ones determined from Bakken Formation velocity measured data. Generally, the new correlations provide results for the minimum horizontal stress a little bit lower than the M-ANNIE model, but greater than the ANNIE model. It is also shown that C13 M-ANNIE assumption works really well for shales, however, C12 M-ANNIE assumption does not work for shales. Furthermore, C66 calculated and used for the ANNIE and M-ANNIE models, is based on the Stoneley wave velocity which has been indicated not to be a reliable measurement. For these setbacks, the proposed correlations provide an alternative and practical solution for the in-situ stress estimation.