Preliminary assessment of the scaling relationships of in-situ stress orientation variations indicated by wellbore failure data

Borehole failure data provides a unique insight in the characteristics of the stress field because in deep boreholes it tends to be pervasive, providing the opportunity to study variability of the stress compo-nents. This variability might follow self-affine scaling and could be related to scaling characteristics of the natural fractures network and earthquake magnitude-frequency statistic. If this were the case, then the meas-urable variations in stress orientation could be used to constrain statistical attributes of the fracture network and to anticipate the seismic response of a rock mass. In this paper, we evaluate seven techniques to deter-mine the fractal dimension, D, of stress orientation variations indicated by wellbore failure data by applying them first to synthetic data of known fractal dimension. Particular attention was given to assess the biases in-troduced by the presence of gaps and noise in the data. Finally, the evaluation techniques were applied to real borehole failure data from Soultz-sous-Forêts and Basel. Preliminary results indicate that significantly differ-ent estimates of D were found for different methods applied to the same dataset which are best explained as reflecting the impact of gaps in the data.

, 2014