cp-1a
1
Crossplots for Porosity, Lithology and Saturation 4-1 CP The neutron-density-sonic crossplot charts (Charts CP-1, CP-2 and CP-7) provide insight into lithology and permit the determi- nation of porosity. Chart selection depends on the anticipated mineralogy. Neutron-density can be used to differentiate between the common reservoir rocks [quartz sandstone, calcite (lime- stone) and dolomite] and shale and some evaporites. Sonic-neutron can be used to differentiate between the common reservoir rocks when clay content is negligible. Sonic-density can be used to differentiate between a single known reservoir rock and shale and to identify evaporate minerals. Continued on next page Porosity and Lithology Determination from Formation Density Log and SNP Sidewall Neutron Porosity Log CP-1a 0 10 20 30 40 φ SNPcor , 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 , bulk density (g/cm 3 ) φ D , density porosity (p.u.) (ρ ma = 2.71, ρ f = 1.0) 45 40 35 30 25 20 15 10 5 0 –5 –10 –15 Sulfur Salt Trona Polyhalite Langbeinite Approximate gas correction Anhydrite 0 Dolomite 0 5 10 15 20 25 30 35 Quartz sandstone Porosity 0 5 10 15 20 25 30 35 40 Calcite (limestone) 0 5 10 15 20 25 30 35 40 45 Fresh water, liquid-filled holes (ρ f = 1.0) © Schlumberger
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cp-1a
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Crossplots for Porosity, Lithology and Saturation
4-1
CP
The neutron-density-sonic crossplot charts (Charts CP-1, CP-2and CP-7) provide insight into lithology and permit the determi-nation of porosity. Chart selection depends on the anticipatedmineralogy. Neutron-density can be used to differentiate betweenthe common reservoir rocks [quartz sandstone, calcite (lime-stone) and dolomite] and shale and some evaporites.
Sonic-neutron can be used to differentiate between the commonreservoir rocks when clay content is negligible. Sonic-densitycan be used to differentiate between a single known reservoirrock and shale and to identify evaporate minerals.
Continued on next page
Porosity and Lithology Determination fromFormation Density Log and SNP Sidewall Neutron Porosity Log CP-1a
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 =
1.0
)
45
40
35
30
25
20
15
10
5
0
–5
–10
–15
Sulfur Salt
Trona
Polyhalite
Langbeinite
Approximategascorrection
Anhyd
rite
0
Dolomite
0
5
10
15
20
25
30
35
Quartz sa
ndstone
Porosity
0
5
10
15
20
25
30
35
40
Calcite (li
mestone)
0
5
10
15
20
25
30
35
40
45
Fresh water, liquid-filled holes (ρf = 1.0)
© Schlumberger
