fluid identification using neutron porosity and bulk ... · the porosity equivalence curve for...
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Fluid Identification Using Neutron
Porosity and Bulk Density Logs
Neutron and Density Logs on Compatible Scales
• The neutron porosity and bulk density logs are used to identify reservoir fluid type in addition to computing the formation porosity, shale volume, etc.
• In order to correctly identify the reservoir fluid type, the neutron porosity and bulk density logs must be plotted and displayed on what is known as compatible scales.
• As an industry standard the Neutron Porosity log is recorded in Limestone Porosity Units and displayed in either V/V units, P.U. (Porosity Units), % (percentage) or decimal units (dec.).
• The Bulk Density log is displayed in gm/cc (oilfield units) or kg/m3 (kg/cubic meter) in SI units.
• The neutron porosity logging tool is calibrated in limestone porosity units and the bulk density logging tool is calibrated in density units.
• The following slides explain about how the neutron porosity and density logs should be plotted and displayed on compatible scales to facilitate in identification of reservoir fluid type.
Thermal Neutron Porosity Equivalence Curves
The porosity equivalence curve for Limestone is a straight line.
It has a one-to-one relationship, between the apparent measured
limestone porosity and the true porosity for the indicated matrix.
The equivalence curves for Sandstone and Dolomite have non-
linear relationships. They are curved lines.
Courtesy of Schlumberger
Matrix point for limestone: RHOB = 2.71 gm/cc and NPHI = 0 P.U.Matrix point for sandstone: RHOB = 2.65 gm/cc and NPHI = -3 P.U.
Courtesy of Schlumberger
Courtesy of Schlumberger
Tight Rocks
Location of Neutron Porosity and Bulk Density data points
Gas: Low Density, Low Neutron porosity - North West quadrant
Tight Rocks: High Density, Low Neutron porosity - South West quadrant
Shales: High Density, High Neutron porosity – South East quadrant
Coals: Low Density, High Neutron porosity – North East quadrant
Bad Hole: Low density, High Neutron porosity – North East quadrant
Sandstone compatible scales
Note: When RHOB = 2.65 gm/cc, NPHI = -3 P.U.
NPHI must be in Limestone Porosity Units.
Note: When RHOB = 2.71 gm/cc, NPHI = 0 P.U.
NPHI must be in Limestone Porosity Units.
Courtesy of Baker Hughes
Shifting of logs by changing presentation scales can result
in the separation between neutron and density logs to be
increased, reduced or totally disappear depending on how
the scales are changed
Gas bearing sandstone reservoir
Neutron and Density logs plotted on sandstone compatible scale.
FDC and CNL are trademarks of Schlumberger
FDC: Formation Density Compensated log (Bulk density log)
CNL: Compensated Neutron Log (Neutron porosity log)
Gas Bearing Sandstone
Gas
Oil Bearing Sandstone
Water Bearing Shaly Sandstone
COAL
Coal Beds
CARBONACEAOUS
SHALE
COAL
Carbonaceous Shale
Gas Bearing Limestone
Gas
Water Bearing Limestone
Dolomitic Limestone
Ha Long-1X
TNPH / RHOZ
Interval : 1675. : 1905.
3.
2.8
2.6
2.4
2.2
2.
RH
OZ
-0.05 0.07 0.19 0.31 0.43 0.55
TNPH
0.
15.
30.
45.
60.
75.
90.
105.
120.
135.
150.
DSOZ
SS 0
10
20
30
40
LS 0
10
20
30
40
DOL 0
10
20
30
40
(SWS) Density Neutron(NPHI) Overlay, Rhofluid = 1.0 (CP-1c 1989)
1510 points plotted out of 1510
Well Depths
Ha Long-1X 1675.M - 1905.M
Tight Carbonate Reservoir
Jacaranda-1
NPHI / RHOB
Interval : 1490. : 1650.
3.
2.8
2.6
2.4
2.2
2.
RH
OB
-0.05 0.05 0.15 0.25 0.35 0.45
NPHI
0.
15.
30.
45.
60.
75.
90.
105.
120.
135.
150.
GR
SS 0
10
20
30
40
LS 0
10
20
30
40
DOL 0
10
20
30
40
(SWS) Density Neutron(NPHI) Overlay, Rhofluid = 1.0 (CP-1c 1989)
1014 points plotted out of 1051
Well Depths
Jacaranda-1 1490.M - 1650.M
Basalt Beds
Jade-2X
TNPH / RHOZ
Interval : 2960. : 3220.
3.
2.8
2.6
2.4
2.2
2.
RH
OZ
-0.05 0.05 0.15 0.25 0.35 0.45
TNPH
50.
70.
90.
110.
130.
150.
170.
190.
210.
230.
250.
ECGR
SS 0
10
20
30
40
LS 0
10
20
30
40
DOL 0
10
20
30
40
(SWS) Density Neutron(NPHI) Overlay, Rhofluid = 1.0 (CP-1c 1989)
1519 points plotted out of 1707
Well Depths
Jade-2X 2960.M - 3220.M
Intrusive Volcanic Bed
Kamia-1
CN / ZDEN
Interval : 1130. : 1215.
3.
2.8
2.6
2.4
2.2
2.
ZD
EN
-0.05 0.05 0.15 0.25 0.35 0.45
CN
0.
15.
30.
45.
60.
75.
90.
105.
120.
135.
150.
GR
SS 0
10
20
30
40
LS 0
10
20
30
40
DOL 0
10
20
30
40
(WA) Neutron Density Overlay, Rhofluid = 1.0 (Ch.6-42 1985)
674 points plotted out of 1117
Well Depths
Kamia-1 1130.M - 1215.M
Conglomerate Bed
Courtesy of Schlumberger
The End