Crossplots for Porosity, Lithology and Saturation

4-2

CP

0 10 20 30 40

φSNPcor, neutron porosity index (p.u.) (apparent limestone porosity)

1.9

2.0

2.1

2.2

2.3

2.4

2.5

2.6

2.7

2.8

2.9

3.0

ρ b, b

ulk

dens

ity (

g/cm

3 )

φ D, d

ensi

ty p

oros

ity (

p.u.

) (ρ

ma

= 2

.71,

ρf =

1.1

)

45

40

35

30

25

20

15

10

5

0

–5

–10

–15

Sulfur Salt

Trona

Polyhalite

Dolomite

Calcite (li

mestone)

Quartz sa

ndstone

Langbeinite

Approximategascorrection

Porosity

Anhyd

rite

0

0

5

10

15

20

25

30

35

0

5

10

15

20

25

30

35

40

0

5

10

15

20

25

30

35

40

45

40

45

Salt water, liquid-filled holes (ρf = 1.1)

Porosity and Lithology Determination fromFormation Density Log and SNP Sidewall Neutron Porosity Log CP-1b

To use any of these charts, enter the abscissa and ordinatewith the required neutron, density or sonic value. The pointof intersection defines the lithology (mineralogy) and theporosity, φ.

Note that all neutron input is in apparent limestone porosity,that charts for fresh water (ρf = 1.0 g/cm3) and saline water (ρf = 1.1 g/cm3) invasion exist, and that the sonic charts containcurves assuming weighted average response (blue) and empiricalobservation response (red).

© Schlumberger