06 - Elastic properties Flashcards

1
Q

Elastic materials deform …

A

when a force is applied and return to their original shape when the force is removed

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2
Q

Young’s modulus

A

E = stress / strain

measure of the stiffness of a solid material.

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3
Q

Poisson ratio v

A

v = - (dL* / L*) / (dL/L)

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4
Q

Hooke’s law

sigma_ik

A

relationship between stress and strain

sigma_ik = C_iklm * strain_lm

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5
Q

p-wave velocity v_p

A

v_p = sqrt( (lambda+2mü)/rho )

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6
Q

s-wave velocity v_s

A

v_s = sqrt( mü/rho )

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7
Q

Correlation of Poisson ratio to Velocityratio

A

v_p/v_s = sqrt( 2* (1-v)/(1-2*v) )

the larger v the larger p and s-wave difference

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8
Q

Transmission technique

from transmitter ..

receiver..

visualizing ..
what?

A

..an ultrasonic pulse passes through sample

.. transform elastic wave into electrical signal

.. with an oscilloscope
the signal and travel time

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9
Q

shear modulus of fluids and minerals

A

fluids: 0 -> no
Minerals: yes

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10
Q

compressional modulus of fluids and minerals

A

all: yes
order: Gas, oil and water, minerals

(under specific conditions)

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11
Q

p-wave velocity

slower to fast:

oil, water, air

A

air

oil

water

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12
Q

Differences of s and p-wave velocities in Rocks

A

greater differences occur in:

Granite
Diorite
Gabbro
Ultramafic rocks
Basalt 
Eclogit
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13
Q

p-wave velocity

slower to fast:

shale, sand&gravel, sandstone, all others

A

sand&gravel

shale

sandstone

all others

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14
Q

velocity of igneous rocks

A

increases from felsic to mafic

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15
Q

velocity in methamorphic rocks

A

anisotropy (gneiss schist)

-> greater velocity parallel to schistosity

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16
Q

velocity in sedimentary/porous rocks

A

brad range

-> low velocity for porous gas bearing members

17
Q

ratio of the two wave velocities Vp/Vs or the Poisson’s ratio n is controlled mainly by …

A

rock type

pore fluid

18
Q

velocity with fracturing

A

velocity decreases
velocity show pressure dependence
anisotropic?

19
Q

Correlation of velocity with temperature

A

decreases with increasing temperature

20
Q

shear wave velocity and change of pore fluid

A

insensitive ( gas brine)

effect of clay more relevant!

21
Q

Five possible sources of seismic anisotropy

A

(1) aligned crystals,
(2) direct stress-induced anisotropy,
(3) lithological anisotropy (for example aligned grains),
(4) structural anisotropy (for example fine layering), and
(5) stress aligned crack-induced anisotropy.

22
Q

elastic properties below the critical porosity

A

rock skeleton dominated

grain contact behavior controls many effects

23
Q

elastic properties above the critical porosity

A

fluid dominated

particles are embedded in the fluid as a suspension

24
Q

Sonic logging

with ..

using ..

measure ..

A

sound wave

piezoelectric transmitter and receiver

interval transit time,
which is typically a function of lithology and rock texture but particularly porosity

25
Borehole televiewers measures .. how..
amplitude and transit time at one of two frequencies Short bursts of acoustic energy are emitted by a rotating transducer in pulse-echo mode