Triple Detector Lithology Density

transcript

Platform Express*

TLDTriple Detector

Lithology Density

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

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

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 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

GR24 in.

18 in., 8 in., 2 in.

Rxo, hmc

12 in.

HALS AIT

24 in.

Highly IntegratedGamma RayNeutronSonde

TOOL Hardware: PLATFORM EXPRESS - Density

Electronicscartridge

High-ResolutionMechanicalSonde

High-ResolutionAzimuthalLaterologSonde

ArrayInduction ImagerTool

High-Resolution Skid

MCFL MicroCylindrically focussed logTDD Detector DensityLS Long Spacing DetectorSS Short Spacing DetectorBS Back Scatter Detector

High-Resolution Skid - inside

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

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

Density

Depleted Uranium

TungstenStainless Steel

BS Integrated

SS Integrated

LS Integrated Detector

Electronics

Detector

Source

Mudcake

Formation

Density Formation

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

TLD 33

Bit Size

Caliper Reading

TLD 34

Bit Size

Apparent Bit Size

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

Sand - Hydrocarbon Bearing

Sand - Water bearing

TLD 45

Density Log Example - 2..

Sandstone

Limestone

TLD 46

Density Log Example - 3...

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

PEFZSP

Caliper

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

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

Triple Detector Lithology Density

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