In situ stress analysis in the northern Newark Basin: Implications for induced seismicity from CO_2 injection

摘要

We present detailed stress analysis in a deep well drilled in the northern Newark Rift Basin and evaluate the risk of induced seismicity for underground fluid injection at the locality. In situ stress orientation and magnitudes were estimated using quantitative analysis and modeling of borehole breakouts identified in high-resolution wellbore images. The distribution of breakouts and natural fractures in the well suggests significant variability in orientation of the principal horizontal stresses in the depth range of 450–1450 m. Evidence from surface seismic reflection imaging indicates potential presence of faults at about 800m and 1200m that bound zones of distinctly different stress orientation at this locality. Stability of natural fractures and faults under injection conditions was evaluated for a range of potential stress magnitudes and the observed stress variability with depth. Shallow crust above ~800m appears to be critically stressed under ambient conditions, and further pore pressure increase would put it at risk of frictional failure on favorably oriented fractures and faults. Deeper reservoirs, however, may allow over 10MPa increase in pore pressure without fault reactivation due to a more relaxed state of stress. Additional in situ test data are needed to more accurately constrain the magnitude of the minimum horizontal stress in the basin and to enable a more complete assessment of the induced seismic risk from potential CO_2 injection in the region.