Hydraulic Fracturing Behavior in Shale with Water and Supercritical CO₂ under Triaxial Compression

Table 4

Reduction proportion of shale breakdown pressure under different deviator stresses.

No.	Bedding plane angle	Fracturing fluid	Deviator stress (MPa)	Breakdown pressure (MPa)	Reduction proportion; ()
W1	0°	Water	5	70.37	19%
W9	0°		15	57.02
W7	90°		5	42.45	19%
W11	90°		15	34.53
S1	0°	SC-CO2	5	52.15	21%
S9	0°		15	41.31
S7	90°		5	38.04	24%
S11	90°		15	28.88

denotes the breakdown pressure of shale under the deviator stress of 5 MPa in hydraulic fracturing using water or SC-CO₂. denotes the breakdown pressure of shale under the deviator stress of 15 MPa in hydraulic fracturing using water or SC-CO₂.