triple detector lithology density
DESCRIPTION
Outline Introduction to Density Measurement Hardware Description Physics of Measurement Gamma Ray Interactions, Detector response Nuclear Spectrum, Gain stabilization Measurement Analysis Response model, Inversion algorithm, Examples Operations Parameters, Corrections, Calibration Safety LQC Log Examples, Products Sonde Mechanics - OverviewTRANSCRIPT
TLD 1
Platform Express*
TLDTriple Detector
Lithology Density
TLD 2
Outline
• Introduction to Density Measurement
• Hardware Description
• Physics of Measurement– Gamma Ray Interactions, Detector response
– Nuclear Spectrum, Gain stabilization
• Measurement Analysis– Response model, Inversion algorithm, Examples
• Operations– Parameters, Corrections, Calibration– Safety
• LQC
• Log Examples, Products
• Sonde Mechanics - Overview
TLD 3
Introduction to Density MeasurementDensity Tools measure two main properties:DENSITY ==> bulk density of the formationLITHOLOGY==> indicator of formation type
POROSITY can be derived from Density Measurement
Density Logging Schematic
CaliperThe tool design also allows a simultaneous caliper measurement
TLD 4
Density Tools History • PGT - Powered Gamma Tool• LDT - Litho Density Tool• TLD - Triple Detector Litho-Density
Fundamental Difference in Tool Physics and Detectors have been implemented with each evolution of tool.
TLD 5
TLD Measurement Objectives The main objectives of the Platform Express density measurement are:• Give a high resolution estimate of density when pad
application is good and mudcake thickness small (<.5”)
• Provide a robust formation density measurement in bad borehole conditions (rugosity, standoff)
• Improve the Pe measurement with regard to precision (statistical error) and mudcake effect compensation
• Reproduce the LDT density estimation when this tool performs well
TLD 6
GR24 in.
b, Pe
18 in., 8 in., 2 in.
Rxo, hmc
2 in.
Rt
12 in.
HGNS
HRMS
HALS AIT
N
24 in.
Highly IntegratedGamma RayNeutronSonde
TOOL Hardware: PLATFORM EXPRESS - Density
Electronicscartridge
High-ResolutionMechanicalSonde
High-ResolutionAzimuthalLaterologSonde
ArrayInduction ImagerTool
HRCC
TLD 7
High-Resolution Skid
MCFL MicroCylindrically focussed logTDD Detector DensityLS Long Spacing DetectorSS Short Spacing DetectorBS Back Scatter Detector
TLD 8
High-Resolution Skid - inside
LS
BSSSMCFLLSXtal/PMT
Flex cable to sonde Electronics Xtal/PMT Xtal/PMT
Depleted Uranium
TungstenStainless Steel
MCFL SS BS SOURCE
Safety !!
TLD 10
Density GR Detectors
Long Spacing (LS) DetectorNaI (T) Sodium Iodide,Thallium doped (not colimated)
Short Spacing(SS) DetectorsNaI (T) Sodium Iodide,Thallium doped (not collimated)
Backscatter (BS) Detector GSO - Gadolinium Orthosilicate, Cerium doped, (collimated0
NaI is rated to 350 degf.GSO has lesser temp rating than NaI
GSO is more efficient than NaIGSO is very expensive
TDD Detectors
Scintillation Detectors are used
TLD 12
DENSITY PHYSICS
TLD 13
Gamma Ray Interactions - Review• High Energy GR emitted from chemical source• Reacts with matter in formation• Type of interaction dependent on GR energy level• Source used is Cesium-137, 662 Kev• Hence Compton Scattering and P.E. Absorption occur
Photoelectric Absorption Compton Scattering
Pair ProductionGR < 100 Kev GR > 100 Kev
GR > 1.02 Mev
TLD 15
Density Physics - Compton Scattering
## 2Z / A almost equal to 1 except for Hydrogen
Measuring Rhoe we know Rhob
Ne = Rhob * Z * Na / A
Rhoe = Rhob * ( 2 Z / A)
## ( 2 Z / A) ~ 1
Rhoe Rhob
Electron density index and Bulk Density
(Ne) Number of electrons in one gram(A) Atomic weight - the mass of an atom (grams/gram-atom).(Z) Atomic number (Z) - the number of electrons in a neutral atom (electrons/atom).(Na) Avogadro's number (Na ) - the number of atoms in a gram-atom
(6.02 x 1023 ).(Rhob) Bulk density(Rhoe) Electron density index
TLD 16
Density Physics - examplesProperties of common elements in formations
TLD 17
Density Corrections
• Differences exist between bulk (actual bulk density of formation)
electron (electron density of formation)
apparent (what the tool measures)
• Most times the corrections are negligible
• Correction charts are available
• Tool is calibrated for water filled LIMESTONE
• Hence zero correction for Limestone
TLD 18
Density Physics - Photoelectric Absorption• Reaction occurs at Low Energy GR < 100 Kev
• GR interacts with shell electrons Absorption
• Shell electrons related to Z Atomic number
• Higher Z means higher PE absorption
• Count the GR reaching tool after the interactions
measure PEF (PEF = (z/10)3.6)
Knowing ... PEF (Z) LITHOLOGY
TLD 19
Density and PEF - common minerals and liquids
** Also see Log examples later in the presentation.
TLD 20
Density Physics - SummaryHigh energy GR emitted from chemical sourceSource Energy 662 KevCompton Scattering and Photoelectric AbsorptionAfter interactions, GR reaches the Scintillation detectors
Density tool measures Electron Density
Electron density is related to Bulk Density
2Z/A is almost equal to 1 for common formation
Electron density almost equal Bulk Density
Heavier the matter higher the Z atomic number
Higher Z means higher Photoelectric absorption
Tool also measures the absorption factor
Knowing PEF (Z) gives indication of formation
TLD 21
Density Nuclear Spectrum
Energy
Count Rate
GR Detector Electronics Spectrum
After interaction with the formation, GR reaches crystalIncident GR have different energy levelsBoth .. Energy and Counts of the GR are of interest Detector pulse height proportional to GR energy The pulses are then sorted and counted by electronicsThe count rate vs energy distribution is called SpectrumThe Spectrum will vary with formation - (GR interactions)
TLD 22
Nuclear Spectrum - Regions
Count/Sec
Region of Photoelectric Effect( & Z Information)
Region of Compton Scattering( Information Only)
Source Energy662 keV
Lithology Window
Energy keV
Density Window
TLD 23
Spectrum Change with Lithology
Count/Sec
Region of Photoelectric Effect( & Z Information)
Region of Compton Scattering( Information Only)(Low Z)(Med Z)
(High Z)Source Energy662 keV
Energy keV
= constant
TLD 24
Spectrum Change with Density
Count/Sec/keVRegion of Photoelectric Effect
(Low )(Med )
(High )
Source Energy662 keV
Region of Compton Scattering
Z = constant
TLD 25
Spectrum Stabilisation
Reference R/A source 1 cu, 662 Kev is usedThis has a small spectrum centered at 662 KevTherefore Photomultiplier High Voltage is adjusted.
CONTINUOUS FEEDBACK LOOP
GR Detector
Energy
Count Rate
Spectrum
Detector level/gain (e.g. temperature) can shift the spectrum
Energy
Count Rate
PM High Voltage
662 KevReference Source
TLD 26
Spectra Comparison - LS
WATER
LIMESTONE
DIABASE
Attenuative - decreasing count rates with density. This also applies to SS.
Two orders of magnitude between counts in water and diabase.
TLD 27
BS Spectrum - behaves differently
Positive - increasing count rates with density.
Factor of two between counts in water and diabase.
TLD 28
BS Spectrum
The BackScatter Spectrum differs from LS and SS
Count rates are much higher
Therefore GSO crystal is used
Increasing density results in increasing counts
This is mainly due to detector design
The Backscatter detector is COLLIMATED
Formation
Mudcake
Mud
Density
Hmc
Depleted Uranium
TungstenStainless Steel
BS Integrated
SS Integrated
MCFL
LS Integrated Detector
Electronics
Detector
Detector
Source
Mudcake
Formation
HRGD
Density Formation
Model
Formation
TLD 29
Processing Outputs
• Standard resolutionResolution of 18”Output sampling rate: 2”LDT like outputRHOZ, PEZ, UZ, ROMZ, PEMZ, DSOZ
• High resolution (main)Resolution of 8”Output sampling rate: 2” RHO8, PE8, U8, ROM8, PEM8, DSO8
• Very high resolutionResolution of 2”Output sampling rate: 0.5” RHOI, PEI, UI, DSOI
TLD 30
Bit Size
Apparent Bit Size
Density Hole Correction
TLD 31
Bit SizeDensity Hole Correction
TLD 32
Bit Size
Apparent Bit Size
Density Hole Correction
TLD 33
Bit Size
Caliper Reading
Density Hole Correction
TLD 34
Bit Size
Apparent Bit Size
Density Hole Correction
TLD 35
SAFETY
TLD 36
TDD - SafetyHRMS is heavy - back injury hazard - Plan the lifting
HRGD skid is heavy- When caliper is open look out for finger crushing
Depleted Uranium Shield in the HRGD- do not dismantle the HRGD skid
Beryllium Window is highly poisonous - do not scratch /puncture the BS or SS coverBe careful during Q-check
Detector Reference source is CS-1379 Ci for BS and LS, 0.6Ci for LSCs-137 is toxic, Use tweezers while handling
Thallium doped NaI crystal - handle with care. Mildly poisonous
Dessicant in electronics causes irritationUse gloves for handling, Wash hands, Do not ingest, or contact with eyes
High voltages present in the tool250V head voltage3000 V (max) for PM tube.
GSR-J source used for loggingAll R/A precautions and rules to be followed
TLD 37
SAFETY - GSR-J Source
2 mrem/hr
17 metres
The GSR-J source is collimated - Do not Stand in front2 mrem/hr distance is 17 metres17 metres in front of skidSource Handling Tool and Safety Clip must be usedRadiation Badge must be wornOnly the Engineer is allowed to transfer a Radioactive Source
TLD 38
LOG QUALITY CONTROL
TLD 39
Quality Indicators
Tau loop error /Offsets /Crystal resolution /Low energy noise /Total count rate /P.M high voltage/Form Factor
Density Detector Quality Flag
Density Computation Quality FlagPe computation Quality Flag
Density correction curve (LOW LS
Based on reconstruction errors (W - W )/Wand database limits
Cal CalRec
• Hardware quality flags
• Processing quality indicators
TLD 40
Hardware - LQC
TLD 41
Processing - LQC
TLD 42
DENSITY LOG RESPONSE
andEXAMPLES
TLD 44
Density Log Example - 1... Lithology Identification
Shale
Sand - Hydrocarbon Bearing
Sand - Water bearing
Shale
X800
TLD 45
Density Log Example - 2..
Sandstone
Limestone
Shale
Shale
TLD 46
Density Log Example - 3...
SALT
Shale
Sand- shaly
TLD 47
Density Log Example - 4...
Dolomite
Limestone
TLD 49
Answer Product - example ... (unreleased example)
LITHOCOLUMN
Carbonate ReservoirAIT Resistivity Image
Resistivity Logs Nuclear Logs
RHOZ
NPHI
PEFZSP
Caliper
GR
PEX ANSWER Product with Lithology Analysis from TDD measurements is shown above.Correct PEF reading is crucialThe TDD provides formation PEF measurement corrected for heavy mudcake (barite) effects , previously not available.
TLD 50
Summary - TDD Measurement
• High resolution density measurement (BS-SS)
• Formation Pe compensated for mudcake effect (non-barite environment)
• Good statistics in hard formations
• Mudcake thickness estimation
• Co-located Rxo measurement
TLD 51
HRMS Overview - Mechanical Design
TLD 52
Flex Joint Advantage - Rugosity
Hinge Joints
Hinge Joints
Good Pad Contact in Rugose Holes
TLD 53
HRMS - Short Radius Logging
• PEX is useful for deviated wells with short radius, due to the high flexibility of HRMS
• Good Field examples• No tools stuck or seriously damaged
– Minimum Dogleg Radius: 20 - 45 metres– Max Build Rate: 39 - 86 deg/30m
• average 72 deg/30m– Bit Size: 6 1/4” - 8 1/2” – Depths: 800 - 2500 m
• Need to convey on Drill Pipe
30 metres measured depth
Build Angle