Common questions

What is Vp in geology?

What is Vp in geology?

The ratio of Vp-waves velocity to Vs-waves velocity (Vp/Vs) is used in engineering seismology and engineering geology (Slavina et al. In engineering geology, the velocity ratios Vs/Vp and Vp/Vs аre used for definition of physical-technical characteristics of rocks.

What is VP and VS?

The use of the ratio of compressional wave velocity to shear wave velocity, Vp/Vs, is a good tool in identifying fluid type. The increase of compressional travel time (decrease of compressional wave velocity) is due to the decrease of bulk modulus of reservoir rocks which compensates the decrease of rock density.

What is seismic velocity?

1. n. [Geophysics] The rate at which a seismic wave travels through a medium, that is, distance divided by traveltime. Seismic velocity can be determined from vertical seismic profiles or from velocity analysis of seismic data.

What means VP?

vice president
1 : an officer next in rank to a president and usually empowered to serve as president in that officer’s absence or disability. 2 : any of several officers serving as a president’s deputies in charge of particular locations or functions.

What is velocity ratio?

: the ratio of a distance through which any part of a machine moves to that which the driving part moves during the same time.

Where do P and S waves originate?

Both P and S waves travel outward from an earthquake focus inside the earth. The waves are often seen as separate arrivals recorded on seismographs at large distances from the earthquake. The direct P wave arrives first because its path is through the higher speed, dense rocks deeper in the earth.

Which material would have the highest seismic velocity?

Of the common rocks of the crust, velocities are greatest in basalt and granite. S-waves are slower than P-waves, with velocities between 0.1 km/s and 0.8 km/s in soft sediments, and between 1.5 km/s and 3.8 km/s in solid rocks.

What controls seismic velocity?

Ultimately, seismic velocity depends on the density and elastic properties of the material, whatever its composition. Specifically, Compressional-wave velocity depends on the “incompressibility” of the material, as embodied in the bulk modulus.

Why is it called shear waves?

S-Waves. Secondary , or S waves, travel slower than P waves and are also called “shear” waves because they don’t change the volume of the material through which they propagate, they shear it. As a transverse wave passes the ground perpendicular to the direction that the wave is propagating. S-waves are transverse waves …

Is sound a shear wave?

Longitudinal waves: In a longitudinal wave, particle motion in the medium is parallel to the direction of the wave front. Audible sound waves are longitudinal waves. Shear waves can exist in solids only, not in liquids or gasses. They can convert to longitudinal waves through reflection or refraction at a boundary.

Is the VP / VS ratio an absolute indicator of lithology?

The ratio of compressional to shear velocity, Vp / Vs, is an effective lithology indicator because each lithology exhibits a defined trend that is independent of porosity and depth ( Fig. 2 ). However, because the Vp / Vs ratio is affected by formation anisotropy, the ratio values may not be absolute indicators of a particular lithology.

How are rock physics parameters used in lithology?

The rock physics parameters such as velocity ratio, Lamé parameters and Poisson’s ratio were estimated from the logs using Goodway et al.’s (1997) [18], and the calculated P-wave and S-wave logs.

What’s the difference between lithology and rock type?

Lithology focuses on grains, while rock type focuses on pores. The list of rock types contains more than 250 classifications. [Personal communication with R.M. Sneider, R.M. Sneider Exploration Inc., Houston (1990).] Another term used in the literature is the Greek equivalent “petrofacies.”

How are gas sand and shale related to lithology?

Gas sand, oil sand, brine and shale were all discriminated using the various rock physics cross plots. Sand is the predominant lithology in the near-surface while the percentage of shale increases with depth to a point where the percentage of shale exceeds that of sand.