1. Triple Detector Lithology Density
Platform Express* TLD
Triple Detector
Lithology Density

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

3. Introduction to Density Measurement
Density Tools measure two main properties:
DENSITY ==> bulk density of the formation
LITHOLOGY==> indicator of formation type
POROSITY can be derived from Density Measurement
Caliper
The tool design also allows a simultaneous caliper measurement
Density Logging Schematic

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.

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

6. TOOL Hardware: PLATFORM EXPRESS - Density
Highly Integrated Gamma Ray Neutron Sonde GR
24 in.
HGNS jN
24 in.
Electronics cartridge
HRCC
rb, Pe
18 in., 8 in., 2 in.
PE02
The initial PLATFORM EXPRESS configuration includes a new standard in formation evaluation sensors. The traditional triple-combo suite of resistivity and porosity measurements has been upgraded and expanded to include microresistivity, imaging and tool movement measurements. PLATFORM EXPRESS technology will evolve to include additional sensors in the future.
Starting at the bottom, PLATFORM EXPRESS includes a choice of resistivity measurements with either the AIT* Array Induction Imager tool or the High-Resolution Azimuthal Laterolog Sonde. Both tools include the latest advances in resistivity sensor design and specifications. The maximum vertical resolution of the resistivity measurements is 12 in.
The High-Resolution Mechanical Sonde has an integrated pad, or skid, that is pressed against the formation. The pad has two new interlaced sensors—the Three-Detector Lithology Density and the MicroCylindrically Focused Log. The TLD log is a backscatter-type density measurement with a vertical resolution of 8 in.; the new MCFL microresistivity measurement investigates the same volume of formation as the density and has a vertical resolution of 2 in.
Flex joints are built in above and below the mechanical sonde to greatly improve pad application in rough hole.
Above the mechanical sonde is a single power supply and electronics cartridge. Older-generation equipment required one electronics cartridge per tool. This made for extremely long tool combinations that required longer rig-up time and required almost a hundred feet of rathole.
We have re-engineered today's gamma ray and neutron porosity measurements into a single Highly Integrated Gamma Ray Neutron Sonde. The gamma ray and neutron porosity measurements have a standard vertical resolution of 24 in. Alpha processing is available to achieve 12-in. vertical resolution of the neutron log.
This section of the string also houses the high-speed telemetry electronics and an accelerometer that provides real-time speed correction and automatic depth-matching of the curves.
High-Resolution Mechanical Sonde
HRMS
Rxo, hmc
2 in.
Array Induction Imager Tool
High-Resolution Azimuthal Laterolog Sonde Rt
12 in.
HALS
AIT

7. High-Resolution Skid MCFL MicroCylindrically focussed log
TDD Detector Density
LS Long Spacing Detector
SS Short Spacing Detector
BS Back Scatter Detector

8. High-Resolution Skid - inside
Safety !!

9. Detectors - PM/HV/Crystal Integration
TDD Detectors
Scintillation Detectors are used
Photomultiplier and High Voltage Supply are integrated in one package
No Field Disassembly possible - only factory repair
EMR Compact PMT with integrated High Voltage Supply
Backscatter Detector shown above

10. Density GR Detectors TDD Detectors Long Spacing (LS) Detector
Scintillation Detectors are used
Long Spacing (LS) Detector
NaI (T) Sodium Iodide,Thallium doped (not colimated)
Short Spacing(SS) Detectors
NaI (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 NaI
GSO is very expensive

11. Detector Characteristics
Detector LS SS BS
Spacing(cm)
Crystals Nal Nal GSO Length (mm) Diameter (mm)
Resolution Cs 137 line 11.7% 13% 14.5%
MAX. Counts CPS outputs 40, ,000 1,200,000
Sensitivity* To density -6.3 to to to To Pe
Signal/BKG 1.2 to to to 4

12. DENSITY PHYSICS

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
Compton Scattering
Photoelectric Absorption
GR < 100 Kev
GR > 100 Kev
Pair Production
GR > 1.02 Mev

14. Interaction of Gamma-Rays
Compton scattering
Defining (electron density)
(for most elements Z/A~1/2)
Photoelectric effect
Defining (Photoelectric factor)
Pair production
(electron - positron)

15. Density Physics - Compton Scattering
Electron density index and Bulk Density
Ne = Rhob * Z * Na / A
Rhoe = Rhob * ( 2 Z / A)
## ( 2 Z / A) ~ 1
Rhoe  Rhob
## 2Z / A almost equal to 1 except for Hydrogen
Measuring Rhoe we know Rhob
(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

16. Density Physics - examples
Properties of common elements in formations

17. rbulk (actual bulk density of formation)
Density Corrections
Differences exist between
rbulk (actual bulk density of formation)
relectron (electron density of formation)
rapparent (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

18. Density Physics - Photoelectric Absorption
Reaction occurs at Low Energy à GR < 100 Kev
GR interacts with shell electrons à Absorption
Shell electrons related to à Z Atomic number
Higher Z means higher PE absorption
Count the GR reaching tool after the interactions
measure PEF à (PEF = (z/10)3.6)
Knowing ... PEF (Z) à LITHOLOGY

19. Density and PEF - common minerals and liquids
** Also see Log examples later in the presentation.

20. Density Physics - Summary
High energy GR emitted from chemical source
Source Energy 662 Kev
Compton Scattering and Photoelectric Absorption
After 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

21. Density Nuclear SpectrumGR
Detector
Electronics
Spectrum
Energy
Count Rate
After interaction with the formation, GR reaches crystal
Incident GR have different energy levels
Both .. Energy and Counts of the GR are of interest
Detector pulse height proportional to GR energy
The pulses are then sorted and counted by electronics
The count rate vs energy distribution is called Spectrum
The Spectrum will vary with formation - (GR interactions)

22. Nuclear Spectrum - Regions
Lithology Window
Region of Photoelectric Effect ( r
& Z Information)
Density Window
Region of Compton Scattering
Count/Sec ( r
Information Only)
Source Energy
662 keV
Energy keV

23. Spectrum Change with Lithology
Region of Photoelectric Effect ( r
& Z Information)
Count/Sec
Region of Compton Scattering
(Low Z) ( r
Information Only)
(Med Z)
(High Z)
r = constant
Source Energy
662 keV
Energy keV

24. Spectrum Change with Density
Count/Sec/keV
Region of Photoelectric Effect
Region of Compton Scattering
(Low r)
(Med r)
Z = constant
(High r)
Source Energy
662 keV

25. Spectrum StabilisationGR
Detector
Energy
Count Rate
Spectrum
Detector level/gain (e.g. temperature) can shift the spectrum
Energy
Count Rate
PM High Voltage
662 Kev
Reference Source
Reference R/A source 1 mcu, 662 Kev is used
This has a small spectrum centered at 662 Kev
Therefore Photomultiplier High Voltage is adjusted.
CONTINUOUS FEEDBACK LOOP

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.

27. BS Spectrum - behaves differently
Positive - increasing count rates with density.
Factor of two between counts in water and diabase.

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

29. Processing Outputs Standard resolution High resolution (main)
Resolution of 18”
Output sampling rate: 2”
LDT like output
RHOZ, PEZ, UZ, ROMZ, PEMZ, DSOZ
High resolution (main)
Resolution of 8”
RHO8, PE8, U8, ROM8, PEM8, DSO8
Very high resolution
Resolution of 2”
Output sampling rate: 0.5”
RHOI, PEI, UI, DSOI

30. Density Hole Correction
Bit Size
Apparent Bit Size

31. Density Hole Correction
Bit Size

32. Density Hole Correction
Bit Size
Apparent Bit Size

33. Density Hole Correction
Bit Size
Caliper Reading

34. Density Hole Correction
Bit Size
Apparent Bit Size

35. SAFETY

36. TDD - Safety HRMS 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 cover
Be careful during Q-check
Detector Reference source is CS-137
9 mCi for BS and LS, 0.6mCi for LS
Cs-137 is toxic, Use tweezers while handling
Thallium doped NaI crystal - handle with care. Mildly poisonous
Dessicant in electronics causes irritation
Use gloves for handling, Wash hands, Do not ingest, or contact with eyes
High voltages present in the tool
250V head voltage
3000 V (max) for PM tube.
GSR-J source used for logging
All R/A precautions and rules to be followed

37. SAFETY - GSR-J Source
2 mrem/hr
17 metres
The GSR-J source is collimated - Do not Stand in front
2 mrem/hr distance is 17 metres in front of skid
Source Handling Tool and Safety Clip must be used
Radiation Badge must be worn
Only the Engineer is allowed to transfer a Radioactive Source

38. LOG QUALITY CONTROL

39. Quality Indicators Hardware quality flags
Tau loop error /Offsets /Crystal resolution /Low
energy noise /Total count rate /P.M high voltage/
Form Factor
Density Detector Quality Flag
Processing quality indicators
Density Computation Quality Flag
Pe computation Quality Flag
Based on reconstruction errors (W - W )/W
and database limits
Cal
Rec
Density correction curve (r - r )
LOW LS

40. Hardware - LQC

41. Processing - LQC

42. DENSITY LOG RESPONSE
and
EXAMPLES

43. Density - Porosity Calculation
Density response model rf
rma
1-f f
Volumetric Contribution
rb = rma (1-f ) + rf f
f = (rma- rb)
(rma- rf)
Bulk Density is measured.
Matrix Type and the Fluid Type from Lithology identification
Porosity can be derived from Bulk Density if matrix known

44. Density Log Example - 1... Lithology Identification
Shale
Sand - Hydrocarbon Bearing
Sand
- Water bearing
X800

45. Density Log Example - 2..
Sandstone
Shale
Limestone
Shale

46. Density Log Example
SALT
Shale
Sand- shaly

47. Density Log Example
Dolomite
Limestone

48. Density Log Example
Anhydrite

49. Answer Product - example ... (unreleased example)
LITHOCOLUMN
Carbonate Reservoir
AIT Resistivity Image
Resistivity Logs
Nuclear Logs
RHOZ
NPHI
PEFZ SP
Caliper GR
PEX ANSWER Product with Lithology Analysis from TDD measurements is shown above.
Correct PEF reading is crucial
The TDD provides formation PEF measurement corrected for heavy mudcake (barite) effects , previously not available.

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

51. HRMS Overview - Mechanical Design

52. Flex Joint Advantage - Rugosity
Hinge Joints
Good Pad Contact in Rugose Holes

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: metres
Max Build Rate: deg/30m
average 72 deg/30m
Bit Size: 6 1/4” - 8 1/2”
Depths: m
Need to convey on Drill Pipe
30 metres measured depth
Build Angle