![Page 1: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/1.jpg)
FORMATION EVALUATION
PETE 321
Summer 2010
David Schechter
DENSITY AND NEUTRON LOGS
![Page 2: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/2.jpg)
Fluorescent Intervals in 1U Sand
• Sharp transition between oil saturated pay and non-pay observed by fluorescence in core samples
![Page 3: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/3.jpg)
GEOLOGICAL AND PETROPHYSICAL DATA USED TO DEFINE FLOW UNITS
FlowUnits
Gamma RayLog
PetrophysicalData
PoreTypesLithofaciesCore
1
2
3
4
5
CorePlugs
CapillaryPressureφ vs k
Modified from Ebanks et al., 1992
![Page 4: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/4.jpg)
POROSITY TOOLS
• Sonic• Density• Neutron
![Page 5: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/5.jpg)
• Introduction to Nuclear logging• Review of basic tools
– Density Tools– Neutron Tools
• Applications/Limitations• Log examples
OVERVIEW
![Page 6: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/6.jpg)
NATURAL RADIOACTIVITY
Spontaneous emission of α and β particles and γradiation from the nucleus of a atom
• Alpha particle = 2 neutrons + 2 protons(same as helium nucleus)
• Beta particle = high velocity electrons
• Gamma rays = electromagnetic radiation(no mass or charge; energy in MeV)
![Page 7: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/7.jpg)
FAMILY OF NUCLEAR TOOLS
Density toolsGR tools Neutron tool
GasOil
GR Neutrons
Natural GR Emitted GREmittedNeutrons
ShalinessCorrelation
PorosityDensity
LithologyPorosity
Particle
Source
Application
![Page 8: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/8.jpg)
DENSITY LOGS
![Page 9: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/9.jpg)
From Halliburton (EL – 1007)
• Uses– Density– Porosity– Lithology
• Curves– Bulk density
(ρb and Δρ)– Pe
DENSITY & POROSITY MEASUREMENTS
COMPENSATED DENSITY LOG
ρcφDρe ρb
![Page 10: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/10.jpg)
Why has Sonic been displaced as phi tool
• Porosity can be determined without precise
knowledge of rock matrix
• No need for compaction correction
• Overlay of density-neutron excellent indicator of
gas
• Transitions from one rock type to another
detected
• Shale effects more evident
![Page 11: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/11.jpg)
DENSITY PRINCIPLE• Detect GR’s from the source which have been
scattered back by the formation
FormationHydraulic
sonde
Caliperarm
Skid
Detectors
Gamma rayemitting source
Gamma rays
Low DensityWindows
CesiumSource
Stabilizer
TungstenBore Liner
Far Detector
Near Detector
TungstenShield
![Page 12: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/12.jpg)
PRINCIPLE
• Gamma rays emitted from radioactive source
• Gamma rays collide with electrons in formation,
losing energy
• Detectors measure intensity of backscattered
gamma rays
– High energy GR relate to - Density
– Low energy GR relate to - Lithology
![Page 13: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/13.jpg)
GAMMA-RAY GENERATION
Chemical source- Focused- Typical properties
Cesium -137 material1.7 Curie strength33 year half-life662 keV gamma-ray energy
![Page 14: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/14.jpg)
GAMMA RAY INTERACTIONSWITH MATTER
• Pair Production
• Compton Scattering
• Photoelectric Adsorption
![Page 15: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/15.jpg)
PAIR PRODUCTION
Not of significance to density tool operation since the source strength is 0.662 MeV and it requires 1.02 MeV for pair production ( 0.51 MeV is the energy equivalent
of the mass of one electron )
![Page 16: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/16.jpg)
GAMMA RAY SCATTERINGCompton EffectMedium to High Energy GR’s
- scattered by electrons information
- each interaction loses energy- more electrons => more
scattering- Related to elect. & rock den.
e-
Eo=hνo X ray
Eo=hνo
e-
E’=hν’
Photoelectric EffectLow Energy GR’s
- absorbed by atoms- more electrons => more absorption- Indicates the atomic number - lithology
Nucleus
![Page 17: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/17.jpg)
COMPTON SCATTERING
Measuring the number of gamma rays in the Compton Scattering energy range gives us the bulk density
![Page 18: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/18.jpg)
PHOTOELECTRIC ABSORPTION
• The number of gamma rays capable of photoelectric absorption indicates the Atomic Number and hence the Pe
• This information indicates the lithology
![Page 19: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/19.jpg)
WHAT THE DETECTOR “SEES”
Density Region(Compton scattering)
Lithology Region(Photoelectric effect)
Source
![Page 20: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/20.jpg)
EFFECT OF FORMATION DENSITY ON DETECTOR COUNT RATES
At. No. same; different density
![Page 21: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/21.jpg)
EFFECT OF FORMATION ATOMIC NUMBER ON DETECTOR COUNT RATES
Density same; At. No. different
![Page 22: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/22.jpg)
DENSITY LOGS
• Bulk density, ρb, is dependent upon:• Lithology• Formation porosity• Density and saturation of fluids in
pores
![Page 23: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/23.jpg)
GRAPI0 200
CALIXIN6 16
CALIYIN6 16
RHOBG/C32 3
DRHOG/C3-0.25 0.25
4100
4200
DENSITY LOG
Caliper
Density correction
Gamma ray Density
From NExT, 1999
![Page 24: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/24.jpg)
BULK DENSITY INTERPRETATION - 1
φρρφρ +−= )1( ma flb
• The bulk density (in g/cc) is the weighted sum of the matrix and fluid densities
• Typical values• Matrix density 2.65 SS; 2.71 LS; 2.87 Dol• Fluid density
• 0.9 – 1.0 OBM and fresh WBM• 1.1 - 1.2 salty WBM
• Density porosity curve is derived from above equation
![Page 25: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/25.jpg)
BULK DENSITY INTERPRETATION - 2
ρρρρ
φ−
−=
ma fl
ma bD
• Charts– POR-5 (S)– POR-10 (H)
• Rearranging the equation gives POROSITY
2.31 g/cc
25%
![Page 26: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/26.jpg)
BULK DENSITY INTERPRETATION - 3• The density correction (Δρ) curve is
“measurement quality”• Poor pad contact gives Δρ > 0.05• Often correlates with caliper
Δρ
-0.25 0 +0.25
CAL
If correction > 0.20 g/ccBulk density curve is invalid
![Page 27: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/27.jpg)
PHOTOELECTRIC INTERPRETATION - 1
flma
flflmama
ee
eeeee
PPP
φρρφ
φρρφ
+−
+−=
)1(
)1(
• The Pe value (in barns/electron) is the weighted sum of the matrix and fluid capture cross sections
• Typical Values• Matrix Pe: 1.8 SS; 5.1 LS; 3.1 DOL• Matrix ρePe: 4.8 SS; 13.8 LS; 9 DOL• Fluid ρePe:
• 0.1 - 0.4 OBM and fresh WBM• 0.4 – 1.0 salty WBM
![Page 28: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/28.jpg)
PHOTOELECTRIC INTERPRETATION - 2
• The logging curve is Pe• The product ρePe = U, capture cross-section/cc
flma UUU φφ +−= )1(
• This looks like the density equation• We don’t solve for φ because Ufl << Uma
• See Appendix 4 Charts for values of Pe
![Page 29: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/29.jpg)
TYPICAL FORMATIONS
Sandstone
Limestone
Dolomite
PEFRHOB
0 1032
2.65
2.87
2.715.1
3.1
1.8
Matrix values
![Page 30: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/30.jpg)
SCHLUMBERGER WIRELINE TOOL HISTORY
Three-Detector Lithology Density (TLD)
Powered Gamma Tool (PGT)
Nal(TI)Scintillation DetectorGeiger-Muller DetecterGamma Ray Source
Nal(TI) Scintillation DetectorNal(TI) Scintillation DetectorGamma Ray Source
Nal(TI) Scintillation DetectorNal(TI) Scintillation DetectorGSO(Ce) Scintillation DetectorGamma Ray Source
Litho Density Tool (LGT)
Flex Joint
FlexJoint
![Page 31: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/31.jpg)
FACTORS AFFECTING DENSITY LOG RESPONSE
• Shales and clays• May cause porosity reading to be too
high or too low• Vsh and ρsh can be obtained from log
readings in shale zones• Hydrocarbons
• In oil zones, ρhc = ρo which can be measured from fluid samples
• In gas zones, ρhc = ρg which can be measured or calculated using gas properties
• Gas will cause anomalously low density and, thus, high density porosity ρρ
ρρφ
−
−=
ma fl
ma bD
![Page 32: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/32.jpg)
DENSITY LOG COMMENTSGRAPI0 200
CALIXIN6 16
CALIYIN6 16
RHOBG/C32 3
DRHOG/C3-0.25 0.25
4100
4200
Caliper
Density correction
Gamma ray
Density
From NExT, 1999
If correction > 0.20 g/ccBulk density curve is invalid
• Very reliable tool• Used to determine
– bulk density– Porosity– lithology
• Shallow depth of investigation - 10 to 15 cm
![Page 33: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/33.jpg)
NEUTRON LOGS
![Page 34: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/34.jpg)
NEUTRON LOGSUses of neutron logs• Identify porous zones• Determine porosity• Identify gas in porous zones
Where neutron logs can be used• Any borehole
• Open or cased• Liquid- or air-filled
Depth of investigation• 6-12 inches for CN
![Page 35: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/35.jpg)
NEUTRON MEASUREMENT
• Uses• Lithology
Porosity
• Curve φN
Pe
ρb ΔρφN
![Page 36: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/36.jpg)
NEUTRON TOOL PRINCIPLE
• Detects neutrons from the source which have been scattered back by the formation
• Source AmBe 15-20Cu 5MeV
![Page 37: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/37.jpg)
•The neutron tool employs a dual detector design to compensate for mudcake, lithology, etc.
•Still, corrections are required for the NPHI values
•NOTE : The tool is pressed against the borehole wall to minimize mud effects
![Page 38: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/38.jpg)
LIFE OF A NEUTRON - 1
• Neutrons emitted from source• Neutrons interact with Hydrogen in formation• Neutrons lose energy• Neutrons are absorbed or reflected back to
detectors– High counts = Low porosity– Low counts = High porosity
![Page 39: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/39.jpg)
LIFE OF A NEUTRON - 2
• Source AmBe 15-20Cu 5MeV neutrons
• Collisions cause neutrons to lose energy
• Energy loss due mainly to hydrogen
• Therefore tool measures amount of hydrogen in formation, ie., water, oil
![Page 40: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/40.jpg)
Thermal Neutrons
• The neutron tool responds primarily to the presence of hydrogen
• The more hydrogen, more neutrons slowed to the thermal level and captured by the formation
• Other minerals also have a small effect on the neutron tool, which requires compensation
![Page 41: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/41.jpg)
NEUTRON TOOL DESIGN• Both detectors placed in
long spacing zone
• Count rates at the detectors are inversely proportional to formation porosity and distance from source
• Near/Far Ratio proportional to porosity
• Ratio compensates for mudcake
![Page 42: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/42.jpg)
ENVIRONMENTAL EFFECTS ON NPHI
Lithology Effects
• The tool responds mostly to the presence of hydrogen, but different minerals will slow neutrons to different degrees
• Therefore, the Neutron tool reads different values for NPHI in different formations of the same porosity
• This must be taken into account for the NPHI curve
![Page 43: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/43.jpg)
NEUTRON LOG INTERPRETATION - 1• Ratio converted to
apparent porosity, φN• Many environmental
effects• Assumes
• Matrix• Usually LS• Sometimes SS
• Water-filled• Charts POR-12--16
• Chart varies with tool
![Page 44: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/44.jpg)
Question:
On a limestone scale, the NPHI is 20%. However the formation is a sandstone. What is the true porosity?
Answer : 25%.
![Page 45: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/45.jpg)
GAS EFFECTS ON NPHI• Gas has a lower hydrogen concentration
than oil or water due to it’s lower density
• A neutron tool interprets gas to be water
occupying a smaller volume; a smaller
volume means a smaller porosity
• Hence in gas zones, the neutron tool reads
anomalously low porosity
![Page 46: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/46.jpg)
NEUTRON LOG INTERPRETATION - 2• Reads deeper than density
• More affected by virgin zone fluid• Gas effect
• Gas lowers H concentration, lowers apparent porosity
Gas effect
-3+9+15+21φ N
![Page 47: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/47.jpg)
Notice the NPHI reading is less in a gas zone than in an oil zone in the same lithology
In a gas zone, NPHI reads too low and DPHI reads too high
The 2 curves track closely in oil-saturated zone
GASEFFECT
![Page 48: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/48.jpg)
SHALE EFFECTS ON NPHI
• Shaliness affects neutron porosity• Shale has bound water in lattice structure• This water is immobile and does not represent
EFFECTIVE porosity• However, the neutron tool responds to the presence
of hydrogen in the bound water of shales, and the neutron tool reads anomalously high NPHI
![Page 49: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/49.jpg)
NEUTRON LOG INTERPRETATION - 3• Shale effect
• Responds to bound water
Shale effect
Por. = 39%
0
Each PHIN division = 3%
![Page 50: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/50.jpg)
NEUTRON SHALE EFFECT
PEF• Sand – Clean ~ 1.8• Sand – Dirty ~ 2.7• Average Shale ~3.4
![Page 51: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/51.jpg)
NPHI SCALES• NPHI is usually plotted on a limestone scale
or a sandstone scale • If on a limestone scale, in a 100% water
bearing limestone, the neutron reads the correct porosity; in a 100% sandstone, the porosity is wrong and must be corrected for lithology
• If on a sandstone scale, in a 100% water bearing sandstone, the neutron tool is reads the correct porosity; in a limestone, readings must be corrected for the lithology
![Page 52: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/52.jpg)
High NPHI across shales
On a limestone scale, it reads actual porosity in limes
In sands, it reads a different porosity from the actual
SHALEEFFECT
![Page 53: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/53.jpg)
NEUTRON LOGSUses of neutron logs• Identify porous zones• Determine porosity• Identify gas in porous zones
Where neutron logs can be used• Any borehole
• Open or cased• Liquid- or air-filled
Depth of investigation• 6-12 inches for CN
![Page 54: FORMATION EVALUATION PETE 321 - College of · PDF fileFORMATION EVALUATION PETE 321 Summer 2010 David Schechter. DENSITY AND NEUTRON LOGS. ... SCHLUMBERGER WIRELINE TOOL HISTORY Three-Detector](https://reader031.vdocuments.net/reader031/viewer/2022021419/5a9c212c7f8b9aba4a8e1c0c/html5/thumbnails/54.jpg)
SUMMARY• Nuclear porosity tools
• Source• Detectors
• Density• Bulk density• Photoelectric effect• Quality curve• Flushed zone measurements
• Neutron• Apparent porosity• May respond to virgin zone