10.5061/DRYAD.37PVMCVG9
An, Mengke
0000-0002-4998-6259
Tongji University
Zhang, Fengshou
Tongji University
Elsworth, Derek
Pennsylvania State University
Xu, Zhengyu
PetroChina Hangzhou Institute of Geology
Chen, Zhaowei
China National Petroleum Corporation (China)
Zhang, Lianyang
University of Arizona
Data from: Friction of Longmaxi shale gouges and implications for
seismicity during hydraulic fracturing
Dryad
dataset
2020
hydraulic fracturing
seismicity
Shale
2020-04-10T00:00:00Z
2020-04-10T00:00:00Z
en
97127706 bytes
6
CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
Longmaxi formation shales are the major target reservoir for shale gas
extraction in the Sichuan Basin, southwest China. Swarms of earthquakes
accompanying hydraulic fracturing are observed at depths typified by the
Longmaxi formation. Mineral composition varies broadly through the
stratigraphic section due to different depositional environments. The
section is generally tectosilicate-poor and phyllosilicate-rich with a
minor portion (~5 wt.%) the converse. We measure the frictional and
stability properties of shale gouges taken from the full stratigraphic
section at hydrothermal conditions. Velocity-stepping experiments were
performed on representative shale gouges at σc = 60 MPa, Pf = 30 MPa and T
=150 ℃. Results show that the gouges are generally frictionally strong
with friction coefficients spanning a range of 0.50-0.75. Two
phyllosilicate+TOC-poor gouges exhibited higher frictional strength and
velocity weakening behavior, capable of potentially unstable fault slips,
while only velocity strengthening behavior was observed for the remaining
phyllosilicate+TOC-rich gouges. These results confirm that the frictional
and stability properties are mainly controlled by phyllosilicate+TOC
content. Elevating the temperature further weakens the gouges and drives
it towards velocity weakening. The presence of observed seismicity in
majority velocity strengthening materials suggest the importance of the
minority velocity weakening materials. We suggest a model where seismicity
is triggered when high pore fluid pressures drive aseismic slip in the
near-field and triggers seismic slip on adjacent faults. Our results have
important implications in understanding the physics of earthquakes in
Sichuan Basin and highlights the importance of identifying the location
and characteristics of faults prior to hydraulic fracturing.
Experiment details, recorded data during each shear experiment, and
friction data used to reflect the frictional properties of Longmaxi shale
gouges in Sichuan Basin, southwest China.