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Page 37
Volume 3
Journal of Environmental Chemistry and Toxicology
oil and gas
August 05-06, 2019 | Singapore
International Conference on
Oil Gas 2019
August 05-06, 2019
J Environ Chem Toxicol, Volume 3
A study on dynamic hydraulic fracture: the relation between crack tip and fluid front
Jingnan Dong
CNPC Engineering Technology R&D Company Limited, China
W
e present direct observation and theoretical analysis on the relation between the crack tip and the fluid front in dynamic hydraulic
fracturing of impermeable material. A laboratory-scale hydraulic fracturing device is built to induce dynamic mode I hydraulic
fracture in PMMAspecimen. The derived analytic solution of stress intensity factor for this configuration is in good agreement with the
existing numerical results and the experimental result obtained using the combination of the digital image correlation and theWilliams’
series. Taking the horizontal component of crack-flank resistance into consideration, the force-balance equation of the fracturing fluid
under constant fracturing pressure accounting for the dynamic relation between the crack tip and the fluid front is established. Results
show that the theoretical predictions conform well to the directly observed results of these two fronts. The analysis on energy terms
show that the kinetic energy of the fluid occupies over half of the total input energy before the fluid front approaches the crack tip.
When the crack slows down or arrest, this ratio further increases. Then we explore the existence of equilibrium state in this dynamic
system, which indicates that if the hydraulic fracture propagates at a constant speed V
C
, the fluid front will also travel at a constant
velocity P
E
V
C
(0<P
E
<1) after a certain period of time, and will not catch up with the running crack tip. The separation criterion of the
crack tip and the fluid front is established and found to conform well to the experimental data. The dynamic relation between the two
fronts in different crack profile proposed by recent experimental research are investigated. Results show that the crack profile and the
crack opening level only exert very limited influence. This study provides a better understanding on the dynamic relation between the
crack tip and the fluid front in hydraulic fracture.