Bayesian source mechanism inversion of induced seismicity in oil/gas fields and pico-seismicity (acoustic emission) in the laboratory

Chen Gu, German A. Prieto, Ulrich Mok, Youssef M. Marzouk, Brian Evans, & Nafi Toksöz

Published August 16, 2017, SCEC Contribution #7890, 2017 SCEC Annual Meeting Poster #049

We studied the source mechanisms of earthquakes occurred in multi-scales, from induced seismicity in oil/gas fields to pico-seismicity in the laboratory. A Bayesian source mechanism inversion method was demonstrated using data from field to laboratory. The seismicity that occurred in the oil/gas fields is probably induced by fluid injection and extraction in oil/gas fields, resulting in the reactivation of the pre-existing fault network. Double-couple dominant source mechanisms were obtained for the field data and the importance of the regional stress field and local fault networks in generating that micro-seismicity was observed.

Laboratory generated acoustic emissions (AEs) can be used to study different rupture processes (e.g., hydraulic fracturing, stick-slip) in a controllable way. In a loading experiment of intact cylindrical Berea sandstone sample, the sample was subjected to conventional triaxial loading with a constant confining pressure of 10 MPa. The axial load was then increased at a constant rate of 0.16 MPa/s to failure at 70 MPa. We used AE event locations to reveal a pico-seismicity nucleation process during fracturing. After the eventual fracture plane was formed in the sample, the location of the pico-events delineated the topography of the irregular fracture plane. The double-couple dominant source mechanism of these events indicated the dip-slip fracture with the maximum differential stress in the vertical direction.

Key Words
source mechanisms, oil/gas fields, induced seismicity, laboratory, pico-seismicity/acoustic emission

Citation
Gu, C., Prieto, G. A., Mok, U., Marzouk, Y. M., Evans, B., & Toksöz, N. (2017, 08). Bayesian source mechanism inversion of induced seismicity in oil/gas fields and pico-seismicity (acoustic emission) in the laboratory. Poster Presentation at 2017 SCEC Annual Meeting.

Related Projects & Working Groups
Seismology