Page 148 - Introduction to Petroleum Engineering

ACTIVITIES 135
7.7 ACTIVITIES

7.7.1 Further Reading

For more information, see Selley and Sonnenberg (2015), Tiab and Donaldson
(2011), Johnston (2010), Bjørlykke (2010), Pennington (2007), Schön (1996), and
Sheriff (1992).

7.7.2 True/False
7.1 Seismic measurements use vibrations to provide images of the subsurface.

7.2 The S‐wave is faster than a P‐wave.
7.3 A single seismic survey is sufficient to perform time‐lapse seismic analysis.
7.4 Shear modulus is the ratio of shear strain to shear stress.
7.5 Compressional impedance is the product of bulk density and compressional
velocity.
7.6 The unit of strain is length.
7.7 Seismic resolution is the ability to distinguish between two features.

7.8 A velocity model is used to transform seismic travel time to depth.
7.9 The seismic reflection coefficient RC at the interface between two formations
with equal acoustic impedances is 0.

7.10 Gassmann’s equation can be used to estimate saturated bulk modulus.

7.7.3 Exercises
7.1 A sandstone sample has bulk modulus K = 20.0 GPa, shear modulus
G = 19.9 GPa, and density ρ = 2500 kg/m . Calculate compressional wave
3
velocity V in m/s and shear wave velocity V in m/s where
P S
K +(4 G/ ) 3 G
V = ; V =
S
P
ρ ρ
To get velocity in m/s, express K and G in Pa and density in kg/m . Hint: first
3
convert GPa to Pa (1 GPa = 10 Pa and 1 Pa = 1 N/m = 1 kg/m·s ).
2
9
2
7.2 A shale sample has bulk modulus K = 20.8 GPa, shear modulus G = 13.4 GPa,
and density ρ = 2600 kg/m . Calculate compressional wave velocity V in m/s
3
P
and shear wave velocity V in m/s where
S
K +(4 G/ ) 3 G
V = ; V =
P
S
ρ ρ