Page 86 - Reservoir Geomechanics

a. 10

DYNAMIC MODULI
8 (ULTRASONIC)

Bulk modulus (GPa) 6 4

2

STATIC MODULI
0
5 10 15 20 25 30
Hydrostatic pressure (MPa)

b.
5000

100 cp

V p
10 cp
4000
1cp
Velocity (m/s)

3000
Log Lab

V s
2000
4 5
Log frequency (Hz)
Figure 3.6. (a) Comparison between static bulk modulus measurements and dynamic (ultrasonic)
measurements for a dry, uncemented sand as a function of pressure. (b) Comparison between P-
and S-wave velocity measurements in a water saturated at frequencies corresponding to
geophysical logs (several kilohertz) and laboratory measurements (∼ one megahertz). Note the
significant difference for P-wave velocity. The curves correspond to SQRT theory (Dvorkin, Mavko
et al. 1995). Note that the theory explains the increase in velocity with frequency between log and
lab measurements for water in the pores of the rock.