A Comparative Study on Fracture Characteristics of the Red Sandstone under Water and Nitrogen Gas Fracturing

Table 4

Calculation parameters.

Physical quantity	Unit	Value
Drilling radius	m	0.005
Sample radius	m	0.025
Young’s modulus	GPa	5.6
Poisson ratio		0.1
Biot’s coefficient		0.9
Compressive volumetric modulus of skeleton	GPa	200
Compressed volumetric modulus of water	GPa	2.2
Initial porosity		0.1
Initial permeability	m^2	1e − 16
Initial pore pressure	MPa	0.101
Crack length	m	0.013
Fracture toughness	MPa m^1/2	0.99
Viscosity of water	Pa s	1e − 3
Viscosity of nitrogen	Pa s	0.178e − 4
Loading rates of the water fracturing	MPa/s	0.09552 (W1), 0.07328 (W2), 0.06368(W3)
Loading rates of the nitrogen gas fracturing	MPa/s	0.03259 (G1), 0.02254 (G2), 0.01237 (G3)