Relationships between compressional‐wave and shear‐wave velocities in clastic silicate rocks

Abstract

New velocity data in addition to literature data derived from sonic log, seismic, and laboratory measurements are analyzed for elastic silicate rocks. These data demonstrate simple systematic relationships between compressional and shear wave velocities. For water-saturated elastic silicate rocks, shear wave velocity is approximately linearly related to compressional wave velocity and the compressional-to-shear velocity ratio decreases with increasing compressional velocity. Laboratory data for dry sandstones indicate a nearly constant compressional-to-shear velocity ratio with rigidity approximately equal to bulk modulus. Ideal models for regular packings of spheres and cracked solids exhibit behavior similar to the observed watersaturated and dry trends. For dry rigidity equal to dry bulk modulus, Gassmann' s equations predict velocities in close agreement with data from the water-saturated rock.

Monitoring of environmental influences on seismic velocity at the geological storage site for CO2 in Ketzin (Germany) with ambient seismic noise

“…However, we showed in Section 3.2 that the coherence between horizontal and vertical ground motion is in accordance with the propagation of Rayleigh waves and a velocity of 300 m s −1 is in agreement with shear wave energy propagating in unconsolidated saturated sediments ( Castagna et al 1985;Vernon et al 1998). At the Ketzin site Xu et al (2012) found shear wave velocities of 303.6 m s −1 in the shallowest 5 m.…”

Petrophysical Characteristics of Coastal Swamp Depobelt Reservoir in the Niger Delta Using Well-Log Data

“…This work shows that there is a linear relationship between P-wave velocity and S-wave velocity for brine saturation. In the Gulf of Mexico, Castagna [18] established the Mudrock Line to be Vp = 1.16Vs + 1.36 for velocity in km/s. From Figure 19 Mudrock Line for the study area is here established to be: V p = 0.807V s + 1.600 (14) where velocity is in km/s.…”

Amplitude versus offset analyses of the deep sedimentary structures at the northern flank of the Porcupine Basin, SW of Ireland

“…9) amplitude-dependent section. The S-wave velocity section is calculated with the formula of Castagna et al (1985). The pseudo-Poisson reflectivity shows the normalised change in pseudo-Poisson ratio.…”

“…Amplitude versus offset inversions using the Aki and Richards linearised approximation of the Zoeppritz equation yield the following attribute sections: Pwave reflectivity section (DV P /V P ), S-wave reflectivity section (DV S /V S ), as a lithology indicator of their linear combinations being the pseudo Poisson reflectivity (Dh/ h = DV P /V P -D V S /V S ), and the Fluid Factor. The Fluid Factor, a hydrocarbon indicator, is a deviation from the ''mudrock line'' of Castagna et al (1985) that gives a relation of P-wave velocity to S-wave velocity for water-saturated clastic silicate rocks. The Fluid Factor is given as…”

“…For water-saturated clastic silicates, the Fluid Factor should be zero everywhere except where gas has displaced part of the water. On the basis of in situ sonic and field measurements done by Castagna et al (1985), we estimated the Vp/Vs ratio for mudrocks in the Connemara Field to be…”