Sonic -2000

7/31/2019 Sonic -2000

http://slidepdf.com/reader/full/sonic-2000 1/60

SONIC THEORY

7/31/2019 Sonic -2000


Sonic energy is generated and detected by devices called

transducers. By definition, a transducer is a “device thatis actuated by power from one system to supply power

in any other form to a second system” ; i.e. , a

transducer converts energy from one form to another. In

sonic logging, the conversion is electrical to acousticenergy (transmitters) or acoustic to electrical energy (

receivers).

Two types of transducers are typically used for logging: 1.

2.

7/31/2019 Sonic -2000


CREST

TROUGH

SINUSOIDAL WAVE TRAIN

A

B

C A M

P L I T U D

E

TIMEE

F

G

HD

T

T

T

T=PERIOD OF THE WAVE

7/31/2019 Sonic -2000


THE WAVELENGTH

A

B

C A M

P L I T U D

E

DISPLACEMENT (POSITION)E

F

G

HD

SINUSOIDAL WAVE TRAIN

7/31/2019 Sonic -2000


PROPERTIES OF WAVES

•

••

attenuation

7/31/2019 Sonic -2000


ACOUSTIC WAVES

•

•

•

7/31/2019 Sonic -2000


SONIC MONOPOLE THEORY

7/31/2019 Sonic -2000


COMPRESSIONAL WAVE

DIRECTION OFPROPAGATION

DIRECTION OF

PARTICLE

DISPLACEMENT

RAREFACTION

COMPRESSION

COMPRESSION

RAREFACTION

7/31/2019 Sonic -2000


SHEAR WAVE

DIRECTION OF

PROPAGATION

DIRECTION OF

PARTICLE

DISPLACEMENT

7/31/2019 Sonic -2000


THE COMPRESSIONAL AND SHEARVELOCITIES

vK

v

K BULK MODULUS

SHEAR MODULUS

BULK DENSITY

p

s

( / )4 31/ 2

1/ 2

7/31/2019 Sonic -2000


A

F Modulus

Angleor Volume Length

Strain

Parameter Parameter inChangeStrain

Area

ForceStress

Strain

Stress Modulus

,,

ELASTIC MODULI

7/31/2019 Sonic -2000


FORCE =F

FORCE FORCE

VOLUMETRIC DEFORMATION

V A

FV MODULUS BULK K

7/31/2019 Sonic -2000


FORCE = F

FORCE = F

l

l

SHEARING DEFORMATION

l A

Fl

ll

AF

Tan

AF MODULUSSHEAR

/

/ /

7/31/2019 Sonic -2000


Rock/

Fluid

Mineral Density

(gm/cc)

Young’s

Modulus

Bulk

Modulus

Shear

Modulus

Poisson’s

Ratio

Sandstone Quartz 2.65 0.92 (Mbars) 0.370 (Mbars) 0.424 (Mbars) 0.09

Limestone Calcite 2.71 0.89 0.732 0.342 0.30

Dolomite CaMg

(CO3)2

2.87 1.66 0.820 0.500 0.25

Oil n( CH2) 0.85 - 0.014 0.0 -

Water H2O 1.00 - 0.023 0.0 -Gas - 0.001 - 1.5x10

-60.0 -

MECHANICAL PROPERTIES OF

DIFFERENT MATERIALS

SHEAR WAVE

7/31/2019 Sonic -2000


SHEAR WAVE

PROPAGATION

7/31/2019 Sonic -2000


CYLINDRICAL DEFORMATION

and POISSON’S RATIO

FORCE

l

r

l

FORCE

r

strainallongitudin

strainlateral

7/31/2019 Sonic -2000


SONIC VELOCITIES AND

POISSON’S RATIO

RatiosPoisson

t

t

v

v

p

s

s

p

'

)2 / 1(

12 / 1

Velocity Ratio

7/31/2019 Sonic -2000


SNELL’S LAW ANALYSIS

normal

angle of

incident

angle ofrefraction

r

i

BOREHOLE

FORMATIONi

v

vr

f

bsinsin

7/31/2019 Sonic -2000


SNELL’S LAW REPRESENTATION OF

SONIC WAVE PROPAGATION

M1 M2

C

r s

is

r s

M1 M2

A

r Pi

M1 M2

B

r pr s

ip

7/31/2019 Sonic -2000


SNELL’S LAW ANALYSIS

For wave propagation down the

borehole wall, =90 degress ( sin =1)

so that we now obtain:

sini

v

vcritical

f

b

angle ofincidenti

BOREHOLE

FORMATION

angle of

refraction


7/31/2019 Sonic -2000



T

R1

R2

ipis

st pt

S wave

P wave

ip =CRITICAL

COMPRESSIONAL

ANGLE

Is=CRITICAL

SHEAR

ANGLE

CRITICALLY

REFRACTED

COMPRESSIONAL

AND SHEAR

WAVES

7/31/2019 Sonic -2000


QUESTION:

CAN Vf BE GREATER

THAN Vb ?

7/31/2019 Sonic -2000


7/31/2019 Sonic -2000


SONIC DIPOLE THEORY

HALLIBURTON

7/31/2019 Sonic -2000


12 in

12 in

MONO TRANS

DIPOLE TRANS

MONO

RECVSDIPOLE

RECVS

12 in

LFDT

ISOLATOR

7/31/2019 Sonic -2000


FLEXURAL WAVE

7/31/2019 Sonic -2000


DISPERSION PLOT IN A

SLOW SANDSTONE

0 5 10 15291

265

241

222

I n v e r s e d

p h a s e d v

e l o c i t y

s/ft

Frequency (khz)

tflexuralvs frequency

tshear

ts

7/31/2019 Sonic -2000


p

f pV V criticali )(sin

For critically refracted

compressional waves:

SONIC WAVE PROPAGATIONAL

7/31/2019 Sonic -2000


SONIC WAVE PROPAGATIONAL

PATHS

T

R1

R2

TOOL BODY

BOREHOLE

FLUID

ALTERED

(DAMAGED ZONE)

UNALTERED

(UNDAMAGED)

ZONE

7/31/2019 Sonic -2000


GUIDED WAVES

•

•

•

7/31/2019 Sonic -2000


THE LEAKY AND NORMAL MODES

Both the Leaky and Normal

modes are produced by

constructive interferencebetween reflected waves at

the borehole wall and body

waves traveling down the

formation

7/31/2019 Sonic -2000


Stoneley waves are generatedalong the borehole wall, essentially

by flexing of the wall caused byinteraction of the formation and theborehole fluid

7/31/2019 Sonic -2000


STONELEY

WAVE

PROPAGATION

PORE FLUID COMPRESSED

7/31/2019 Sonic -2000


BOREHOLE

MUDCAKE

STONELEY WAVE PROPAGATIONPORE FLUID COMPRESSED

WHICH CAUSES MOVEMENT

INTO FORMATION

7/31/2019 Sonic -2000


b

smud mud tubestoneley

t t t t

t OF TERMS IN

22

STONELEY WAVE VELOCITY

AT LOW FREQUENCY

7/31/2019 Sonic -2000


TOTAL ACOUSTIC WAVEFORM

P wave

Leaky mode

S wave Stoneley

wave

Normal Mode

time

7/31/2019 Sonic -2000


7/31/2019 Sonic -2000


Time(microseconds)

A

B

C

CENTRALIZED TOOL WITH NO WASHOUT

http://fwst.ppt/

http://fwst.ppt/

http://fwst.ppt/

http://fwst.ppt/

7/31/2019 Sonic -2000


T

R1

R2

tR1

tR2

A

B

C

D

E

tR2= A+B+D+E

tR1

=A+B+C

A,B,C,D,E,=TRAVEL TIMES

tR2 - tR1 = A+B+D+E -(A+B+C)

tR2 - tR1 = D+(E-C)

ASSUME

E=C

tR2 - tR1 = D

t 2

D

s acin

t t Δt

R1 R2

TIME TRANSIT

CENTRALIZED TOOL WITH NO WASHOUT

SLOWNESS

INVERSE

PHASE

VELOCITY

ACOUTIC SIGNAL AT TWO RECEIVERS

pacing

7/31/2019 Sonic -2000


ACOUTIC SIGNAL AT TWO RECEIVERS

THE ZERO CROSSING THRESHOLD TECHNIQUE

pacing

7/31/2019 Sonic -2000


TR

R1

R2

B

A

CD

E

A

B

CD

E

REASONS FOR

BOREHOLE

COMPENSATIONS

CAVED HOLE

(WASHOUT)

TOOL TILT

BOREHOLE COMPENSATION SONIC

7/31/2019 Sonic -2000


BOREHOLE COMPENSATION SONIC

(BCDT)

TR

R2

TR

R1

3 FT

2 FT

3 FT

7/31/2019 Sonic -2000


t3

TR

R2

TR

R1

t1

t4

t2

BOREHOLE

COMPENSATION

CAVED HOLE

)2

7/31/2019 Sonic -2000


BOREHOLE

COMPENSATION

TOOL TILT

t1

t3

t2

t4

ft

t t t t

t c 2

)(

2 / 1

2143

TR

DEPTH DERIVED BOREHOLE

7/31/2019 Sonic -2000


Z=1 ft

10 ft

TR

R1

R2

t4

B

TR

R1

R2

t1

t2

C


COMPENSATION

DTRCVR = (t2-t1)/z

TR

R1

R2

t3

A

TR

R1

R2DTXMIT = (t4-t3 )/z

DT(BHC) = (DTXMIT+DTRCVR)/2

TR


7/31/2019 Sonic -2000


Z=1 ft

10 ft

TR

R1

R2

t1

t2

C


COMPENSATION

TR

R1

R2

A,B

TR

R1

R2

t3

t4

TR


7/31/2019 Sonic -2000


TR

R1

R2

t1

t2

C


COMPENSATION

TR

R1

R2

t3

A,B

TR

R1

R2

t4

7/31/2019 Sonic -2000


TR

R2

TR

R1

BOREHOLE

COMPENSATION

CAVED HOLE

THE WYLLIE TIME -AVERAGE

7/31/2019 Sonic -2000


THE WYLLIE TIME -AVERAGE

EQUATION

1- f f

1MATRIX FLUID

THE WYLLIE TIME-AVERAGE

7/31/2019 Sonic -2000


THE WYLLIE TIME-AVERAGE

EQUATION

t t t

s o lv in g fo r p o r o sity

t t

t t

f m a

sm a

f m a

lo g

lo g

( )

f f

f f

1

The fluid in the zone of interest is

typically mud filtrate

is usually considered 189 u sec/ft f t

7/31/2019 Sonic -2000


The presence of gas in the pore space of a

rock will increase the sonic transit time over

its value in the same liquid-saturated rock.Because of the increase in tlog (cycle

skipping may also add to this effect), the

sonic porosity is optimistic if gas is present inthe flushed zone (using the Wyllie equation,

the input value for tf will be too low).

CYCLE SKIPPING

7/31/2019 Sonic -2000


THRESHOLD LEVEL

E4

E1

E2

E3

E3

E1

E2 E4

E1

E2

CYCLE SKIPPING

7/31/2019 Sonic -2000


GAS EFFECT ON SONIC TOOL RESPONSE

As has already been stated,the presence of gas in the pore spaceof a rock will increase the sonic transit time over its value in the

same liquid-saturated rock. Gas is very compressible; when it

replaces pore liquid, it lower the rock rigidity more than its

density and decreases Sonic velocity.

The decrease in velocity is almost negligible in deeper low-

porosity formations where pore volume is low and compaction

pressure is high, which means that pore fluid contributes little

to rock rigidity. However, it can be as high as 40 % in shallow,

high -porosity formations where pore volume is large and

compaction pressure is minimum-in which case pore fluid has a

much larger contribution to formation rigidity.

7/31/2019 Sonic -2000


COMPACTION CORRECTION

p

s

C

1

tt

tt

mafluid

malog

f

100

Shale p t C

EFFECTIVE POROSITY

7/31/2019 Sonic -2000


EFFECTIVE POROSITY

When shale is present in the formation,

the effective porosity can be calculated

from

ma fl

mashsh

shma fl

maeff

t t

t t V t t t

t t 100logf

Here t sh is from the adjacent (nearby)shale

7/31/2019 Sonic -2000


Lithology

Sandstone 55.6

Limestone 47.5Dolomites 43.5

) / ( ft st ma

TYPICAL DELTA-t MATRIX VALUES

f

7/31/2019 Sonic -2000


Primary

porositySecondary

porosity(Vugs,or

fractures)

PRIMARY and

SECONDARY POROSITY

D

f

f

sec

7/31/2019 Sonic -2000


OFFSET 8 FEET = LONG SPACED TOOL

Potential for deeper investigation

LONG SPACED VS SHORT SPACED TOOLS

OFFSET < 8 FEET = SHORT SPACED TOOL

TRANS

REC

OFFSET

Can make measurements in larg

LARGE BOREHOLE EFFECT

7/31/2019 Sonic -2000


LARGE BOREHOLE EFFECT

TR

R1

A

B

A

B

TR

R1

TR

R1

TR

R1

TR

R1

TR

R1

A

B

A

B

7/31/2019 Sonic -2000


Documents

Sonic -2000