Predicting the azimuth of natural fractures and in situ horizontal stress: A case study from the Sichuan Basin, China

Abstract

The azimuth of fractures and in situ horizontal stress are important factors in planning horizontal wells and hydraulic fracturing for unconventional resource plays. The azimuth of natural fractures can be directly obtained by analyzing image logs. The azimuth of the maximum horizontal stress [Formula: see text] can be predicted by analyzing the induced fractures on image logs. The clustering of microseismic events also can be used to predict the azimuth of in situ maximum horizontal stress. However, the azimuth of natural fractures and the in situ maximum horizontal stress obtained from image logs and microseismic events are limited to the wellbore locations. Wide-azimuth seismic data provide an alternative way to predict the azimuth of natural fractures and maximum in situ horizontal stress if the seismic attributes are properly calibrated with interpretations from well logs and microseismic data. To predict the azimuth of natural fractures and in situ maximum horizontal stress, we have focused our analysis on correlating the seismic attributes computed from pre- and poststack seismic data with the interpreted azimuth obtained from image logs and microseismic data. The application indicates that the strike of the most-positive principal curvature [Formula: see text] can be used as an indicator for the azimuth of natural fractures within our study area. The azimuthal anisotropy of the dominant frequency component of offset vector title seismic data can be used to predict the azimuth of maximum in situ horizontal stress within our study area that is located in the southern region of the Sichuan Basin, China. The predicted azimuths provide important information for the subsequent well planning and hydraulic fracturing.