Compensated Neutron(1)

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Compensated NeutronCompensated Neutron


ObjectivesCompensated NeutronObjectivesCompensated Neutron

JFE will gather sufficient knowledge to efficiently operate compensated neutron tool and explain its operational basic theory.

JEF will review standard procedures for handling the neutron sources.

JFE will be able to calibrate the compensated neutron tool.

JEF will identify different neutron log responses.


1.You will improve your skills

2.After this chapter, you be able to operate one of the most popular Open Hole tool in the Oil Industry.

3.Finally, all this represent money ($..) for you.

BenefitsCompensated NeutronBenefitsCompensated Neutron


Module 1. Introduction

Neutron Radiation

Neutron Source

Neutron Interaction.

Module 2. Compensated Neutron

Module 3 Hardware

Module 4 Calibration / Verification

Module 5 Logging Operation

AgendaCompensated NeutronAgendaCompensated Neutron


IntroductionCompensated NeutronIntroductionCompensated Neutron

Compensated Neutron instrument is a radiation logging device that indicates formation porosity in open or cased hole.

Use an induced chemical radioactive source that emits neutrons.

Two proportional counters act as detectors.


IntroductionCompensated NeutronIntroductionCompensated Neutron

Neutron logs respond to the fundamental formation property of hydrogen richness.

If all of the formation's hydrogen is contained in the form of liquids, and if these liquids completely occupy the total pore volume, hydrogen richness is an index of porosity.

Hence, a neutron log is used to determine Porosity Index.


Neutron RadiationCompensated NeutronNeutron RadiationCompensated Neutron

Neutron radiation is induced or man-made and occurs when a very excited nucleus emits a neutron in order to become more stable.

Neutrons have the following physical characteristics:

Mass of 1 No charge Varying speed varying kinetic Energy

Ek= 1/2 m v2


Neutron Radiation Compensated NeutronNeutron Radiation Compensated Neutron

Neutrons are classified by the amount of energy they possess. This energy is directly related to their speed of travel.

1. Fast neutrons > 100 KeV of energy

2. Intermediate neutrons - between 100 KeV and 100 eV of energy

3. Slow neutrons < 100 ev of energya) Epithermal neutrons - between .1 and 100 eV of energyb) Semi-epithermal neutronsc) Thermal neutrons - < 0.025 eV of energy


Neutron SourceNeutron RadiationNeutron SourceNeutron Radiation

Typically neutron logging sources are mixtures of isotopes, which when combined decay in such a manner that neutrons result.

The chemical source most commonly used contains Beryllium (Be) and Americium 241 (Am) which is an alpha emitting radioactive element.


Neutron SourceNeutron Radiation

Neutron Source

Containers(WEP)

Neutron SourceAm-241/Be - 666 GBq(18 Ci)

9 inches / 22.7 cm



As Americium spontaneously decays to neptunium, it emits sizeable quantities of alpha particles.

This decreases the atomic weight by 4 and the atomic number by 2. The alpha particle is captured by the Be which becomes C13 (Carbon

13). The carbon 13 atom is very unstable and emits a 4.5 MeV neutron,

which is a Fast neutron.

23793

42

24195 :Decay Americium NpAm +



24195 93

237 42Am Np + + 4.5 Mev



Isotopic Neutron SourcesIsotopic Neutron SourcesMixing Alpha emitter with an appropriate target material.

24

49

01 Be 612C n+ + 613C**


Features of the neutron sourceNeutron RadiationFeatures of the neutron sourceNeutron Radiation

Isotope: Americium241- Beryllium (Am241Be)

Source Type: S17S20

Activity: 666 GBq (18 Ci) activity - produces about 40 million n/sec,

Energy level 4.5 MeV.

Radioactive half life 432 years.



Am241

Compounds: Americium 241 - Beryllium (Am 241 Be)Denomination: S17S20

Activity: 18 Ci Energy: 4.5 MeVRadioactive 1/2 life: 432 years

decays

95 4 + Np2372 93Captured by Be to become

C13 (unstable)6decays FAST

NEUTRONS+ C126


Neutron InteractionNeutron Radiation

Neutron InteractionNeutron Radiation

The Neutron source emits high energy neutron radiation.

Immediately upon entering the borehole-formation environment, neutrons start undergoing a continuous de-energizing process.

This energy reduction occurs when the neutron collides with nucleus of borehole and formation elements.

A neutron loses some of its total kinetic energy each time it is involved in either an elastic or inelastic collision.

Neutrons with low energy can be absorbed or capture by the target nucleus become a excited stated.


Elastic CollisionNeutron InteractionElastic CollisionNeutron Interaction

Remember your last billiard gameRemember your last billiard game

11

2

211

1vmEE kk ==

BeforeBefore

V1 1122

V1

V2

22''

'2

222

11

2

vmvmE

EEE

k

kkk

+=+=

AfterAfter=



NNV1

HHV1 = V2

The neutron transfer 100 % of its Energy to the Hydrogen

The neutron transfer 100 % of its Energy to the Hydrogen

Head-on collision between particles of the same masse: neutron and hydrogen



Conservation of the kinetic Energy.

The best transfer appears with a particle of same masse: HYDROGEN.

Hydrogen is primarily responsible for the reduction of the neutron energy.

The matrix has a significant effect.


2

211

1vmEE kk ==

BeforeBefore

Inelastic CollisionNeutron InteractionInelastic CollisionNeutron Interaction

11V1 11

22

V1

V2

emitting -rayemitting -ray

Atom 2 is in an excited stateAtom 2 is in an excited state

21' kkk EEE +=

AfterAfter


Inelastic CollisionNeutron InteractionInelastic CollisionNeutron Interaction

No conservation of the kinetic energy.

The struck nucleus is left in an excited state.

Emission of -ray so the excited nucleus comes back to its ground state.


Neutron CaptureNeutron InteractionNeutron CaptureNeutron Interaction

NNV1

22V2 = 0

The neutron is absorbed by the target nucleus, and this nucleus, emits instantaneously a gamma

ray

The neutron is absorbed by the target nucleus, and this nucleus, emits instantaneously a gamma

ray

The Neutron incident has low energy


Neutron InteractionCompensated NeutronNeutron InteractionCompensated Neutron

Since hydrogen atoms are both relatively abundant and nearly equal in mass to the neutron, they are primarily responsible for reducing high energy neutrons to their thermal state.


Compensated Neutron Module 2

Detecting Hydrogen and relation sheet with Porosity

Reading with high porosity and low porosity conditions.

Position of detectors

Ratio SSN/LSN

Eccentricity

Lithology Effects

Gas Effects



The two thermal neutron detectors are positioned at different spacing from an 18 Curie Americium 241 Beryllium neutron source.

- The near detector is referred to as the "short-spaced" (SS) detector.

- The far detector is referred to as the "long-spaced" (LS) detector.



The neutron source continuously emits fast neutrons.

When fast neutrons collide with the various nuclei in the formation they lose energy, slowing to an epithermal energy level, then to a thermal energy level.



Therefore a decreasing detector count indicates an increasing amount of hydrogenous material between the source and the detectors.

This in turn indicates a higher formation porosity.

The count rates from the long-spaced detector and the short-spaced detector are each processed in the instrument and transmitted to the surface.



Whether the detector type used is responsive to capture gamma rays or to slow neutrons

the measurement is indicative of the relative amount of hydrogen in the formation.

When formation liquids are the primary source of formation hydrogen

neutron measurements are correlative to the quantity of liquid existing in the pore space.



In high porosity, liquid-filled formations, the neutron flux is thermalised close to the source, so that relatively few neutrons or capture gamma rays are detected.

Thus high porosity is indicated by a low neutron counting rate.

The reverse reasoning will relate low porosity to a high count rate.


Compensated NeutronCompensated NeutronCan be divided in 3 zonesCan be divided in 3 zones

Higher porosity,More Hydrogen

around the source,

Neutrons thermalized

closer from the source,

Detector is closed to the

source Higher count rate

More porosity, more hydrogen

COUNTS DECREASE QUICKER

Further away from the source LESS

COUNTS

Reading INCREASE

when porosity DECREASE

SAME READING whatever value is

the porosity

High reading,Reading decrease

when porosity decrease



The far spacing zone provides:

1. Increased depth of investigation formation porosity is emphasized over borehole effects.

2. Improved porosity resolution fractional change in count rate per unit porosity change.



The Compensated Neutron tool is the standard used for open hole logging.

A fast neutron source is located near the bottom of the tool,

and two thermal neutron detectors are spaced ~1 and ~1.5 ft above it, both are in the far field.

The ratio of the count rates from the near and far detectors, SSN/LSN is related to formation porosity



The ECLIPS acquisition system uses the ratio of the short-spaced (SS) count rate to the long-spaced (LS) count rate to compute an apparent limestone porosity curve.

The computed curve may be further corrected for environmental and formation effects.


2435 CN Porosity ResponseCompensated Neutron2435 CN Porosity ResponseCompensated Neutron

SSN / LSN is presented on the X-axis.

THE RATIO INCREASES WITH POROSITY.

Remember : both SSN and LSN decrease with porosity but LSN decreases more.

Need to be link to porosity


Tool EccentricityCompensated NeutronTool EccentricityCompensated Neutron

Neutron count rates increase as the tool approaches contact with the borehole wall from a center hole position.

To aid in this the tool is normally run with a decentralizer in place.


Lithology EffectsCompensated NeutronLithology EffectsCompensated Neutron

While the SSN/LSN ratio depends primarily on porosity, there is also a significant dependence on lithology because the matrix contributes some to the slow down and capture of the neutrons.

Therefore to derive porosity from the count ratio with any accuracy the lithology must be known.



The ratio-porosity relationship used to derive CN is normally limestone matrix, and is referred to as:

Apparent Limestone Porosity For different lithology such as

sandstone and dolomite correction charts have been derived.


Gas EffectCompensated NeutronGas EffectCompensated Neutron

The measurement of porosity is only valid in rocks filled with oil or water

both fluids have the same volumetric hydrogen contents.

Gas filled formations will show too low a value for porosity

the number of hydrogen atoms per unit volume in gas is much lower than that of water or liquid hydrocarbons.


Hardware Module 3Compensated NeutronHardware Module 3Compensated Neutron

Detectors SSN and LSN Electronic

Main components Data transmission Subset Sample rate Computed Curves General parameters

Compensated Neutron Logs presentations


LS and SS detectorsCompensated Neutron - HardwareLS and SS detectorsCompensated Neutron - Hardware

The detectors are proportional counters encased in nylon moderator sleeves.

The counters consist of two electrodes mounted in a metal cylinder and pressurised with active helium gas (He3).


Proportional CounterCompensated Neutron - Hardware

Similar to ionization chamber. The operating voltage between theanode (center wire) and cathode (cylinder) is more than 1000 volts.

Primarily used as epithermal and thermal neutron detectors. The cylinder is filled with an active gas (He ) pressurized to 10

atmospheres. The cylinder is encased in a nylon sleeve which acts as a

moderator and has a cadmium shield. Detection begins with the absorption of neutrons by the atoms of

He .


Proportional CounterCompensated Neutron - Hardware

Advantages Fairly rugged and temperatures to 400 F tolerated Signal pulses large enough to be easily counted Pulse strength proportional to the energy level of the radiation particles

detected by the counter.

Disadvantage Dead Time

Application 2418, 2435, 2438, 2446 Compensated Neutron


Deadtime of detectorsCompensated Neutron - Hardware

Its defined simply as the amount of time that must elapse before another event can be detected.

Any events that occur during the deadtime of a detector are missed. The deadtime for 2446XAs detectors is 20 microseconds for the

short space and 24 microseconds for the long space. Deadtime correction is applied to 2446XAs detectors using the next

formula:count rate raw/(1-count rate raw*t)= count rate deadtime corrected

where t is the deadtime known for each detector.


123906

NEUTRON PREAMP

LSDETECTOR

SSDETECTOR

133906

NEUTRON

PREAMP

1

5

5

0

1

1

8

M

I

C

R

O

C

O

N

T

R

O

L

E

R

HH

L

E

C

B

A

M

133913NEUTRON

SIGNAL PROCESSOR

B00

BZ0

UDI

+ 5

+24V

GND

LSCNT

SSCNT

L

S

C

N

T

S

S

C

N

T

G

N

D

+

H

V

+

2

4

V

Boost the pulsesBoost the pulses Detectorslow output signalDetectors

low output signal

Signal Processing board1. Buffer2. Voltage reference3. Discriminator4. Scaler ( SS/16 LS/4)5. Pulse shaping

Signal Processing board1. Buffer2. Voltage reference3. Discriminator4. Scaler ( SS/16 LS/4)5. Pulse shaping

Micro-Controller

WTS M2 comms Voltage monitorFrequency counter

Micro-Controller

WTS M2 comms Voltage monitorFrequency counter

DIAGRAM OF THE CIRCUIT Compensated Neutron - Hardware


Neutron CurvesCompensated Neutron - HardwareNeutron CurvesCompensated Neutron - Hardware

Raw curves

Computed curves

ssnr : raw short space countlsnr : raw long space countssnr : raw short space countlsnr : raw long space count

CN : compensated neutron porosityCNC : borehole size corrected CNCNCF : Field normalized CNC (made

to look like Schlumberger curve for high porosity)



PresentedPresented


Data TransmissionCompensated Neutron - HardwareData TransmissionCompensated Neutron - Hardware

All data is transmitted to surface via the 3514 using the WTS telemetry scheme.

The total long space/short space counts and diagnostic curves are sent to surface via M2.

The tool commands are sent from surface to the tool via M2.


SubsetCompensated Neutron - HardwareSubsetCompensated Neutron - Hardware

The tool can acquire only one subset:

Subset #0: LSN (Long space counts), SSN (Short space counts), W0AF (flask temperature) and W0AP (+24V power supply).

M2 telemetry only.


Sample RateCompensated Neutron - HardwareSample RateCompensated Neutron - Hardware

Data is typically acquired at

4 samples/foot (13.12 samples/meter), which is a finer resolution than the vertical bed resolution of the instrument.

Other sample rates are available as defined by the ACTs available within the OCT being used, these are normally 2/ft or 8/ft.


General Parameters in EclipsCompensated NeutronGeneral Parameters in EclipsCompensated Neutron


Limestone MatrixLimestone Matrix


Sandstone MatrixSandstone Matrix


Calibration and Verification Module 4Compensated Neutron

API neutron calibration pit 2437XB Calibrator Tank 2446XA Rod Moderators used in the calibrator tank. Normalized Ratio for 2446XA Normalized Ratio for 2438XA Primary Calibration, Primary Verification Safety Procedures handling Neutron source. Inserting the Radioactive Source Extracting the Source Emergency Removal Procedure



The standard unit of measurement for neutron logs is the API Porosity Unit.

Test pit in Houston university.

3 references: 1.9%, 19%, 26%.


2437XB CN Calibrator2437XB CN Calibrator

We use a calibrator and moderator rod.

It is filled with water/propylene glycol.


2446XA Compensated Neutron2446XA Compensated Neutron



C arrangement. Reading depends of tool

series. Ratio SSN / LSN is 8.31

(2438XA). Tolerance is +/- 0.15. Corresponds to a porosity of

25.738 % API.


2435XA Compensated Neutron2435XA Compensated NeutronREAD THE TOOL ANSWER

Read a value for SSN/LSN with the Rods in the C arrangement.

7.9 in this case7.9 in this case

Ratio SSN/LSNRatio SSN/LSN

P

o

r

o

s

i

t

y

P

o

r

o

s

i

t

y


2435XA Compensated Neutron2435XA Compensated NeutronCHECKS THE RATIO IS IN TOLERANCE

Acceptable Ratio Range : 7.63 to 9.09

7.9 in this case7.9 in this case

P

o

r

o

s

i

t

y

P

o

r

o

s

i

t

y



SHIFT THE POINT Determination of the multiplicative

calibration factor MCF = Nominal Ratio

Normalized ratio = tool reading * MCF

NORMALIZES THE ANSWER


P

o

r

o

s

i

t

y

P

o

r

o

s

i

t

y

Normalized ratioNormalized ratioSSN / LSNSSN / LSN



Primary CalibrationPrimary Calibration


Primary VerificationPrimary Verification


Compensated Neutron (Source Insertion)Compensated Neutron (Source Insertion)


Compensated Neutron (Source Extraction)Compensated Neutron (Source Extraction)


Compensated Neutron source sub side door screwsCompensated Neutron source sub side door screws

P/N f091715000


P/N F097409000.

Compensated Neutron source sub side door screwsCompensated Neutron source sub side door screws


Screw damaged and can not be released?

Do not pry on source door !!!Do not pry on source door !!!Use source-sub punch and hammer to shear screws!

Order material# f091715000!

Compensated Neutron (Emergency Removal Procedure)Compensated Neutron (Emergency Removal Procedure)


Logging Operation Module 5Compensated Neutron

Main Factors Matrix Mud Salinity Hole Diameter Mud Density Mud Cake Thickness Gas Casing.CurvesMatching Neutron and Density ScalesNeutron Density curves response


OPERATION

Factor affecting the log Solution

Tool position :

Any gaps between the formation and tool housing will cause reading error. (Higher values of porosity).

A neutron Decentraliser must be used.

Exists in different sizes.

It has a SPECIFIC position.


Attach it where you installthe tool clamp (Hex head)

Attach it where you installthe tool clamp (Hex head)


Neutron DecentralizerCompensated NeutronNeutron DecentralizerCompensated Neutron

The decentralizer must be below or above of neutron tool, and when run with z-density, the decentralizer must be aligned with the arm of z-density tool, not confuse with the pad !!!


THE MATRIX :

the matrix contribute to the slowdown and capture of the neutron.

Parameter : select the matrix (limestone, sandstone, dolomite).

Curve is recorded in the APPARENT MATRIX POROSITY

Depending of the formation the reading need to be corrected

OPERATION



CorrectionCorrection

For a 15 % readingFor a 15 % reading

If the matrix is Limestonethe porosity of the formation is

15 %

If the matrix is Limestonethe porosity of the formation is

15 %If the matrix is Sandstone

the porosity of the formation is19 %

If the matrix is Sandstonethe porosity of the formation is

19 %If the matrix is Dolomitethe porosity of the formation is

8 %

If the matrix is Dolomitethe porosity of the formation is

8 %


MUD SALINITY

Cl- capture thermal neutron very well.

There could be a high content in the mud.

PARAMETER section :

found the value of NaCl in the mud report.

Enter Cl- concentration calculated from chart.

OPERATION



HOLE DIAMETER :

Large borehole will show a false high porosity.

CN tool is calibrated in a 7-7/8 in hole.

PARAMETER section :

use CALIPER for correction if available

Use FIXED Size if not caliper is run in combination or failed.

FIXED Size = BIT SIZE.

OPERATION



MUD DENSITY

High density mud will show a slightly lower porosity.

POST PROCESSING :

use environmental correction menu.

Most of the time negligible.

OPERATION



Software touse

Software touse


MUD CAKE THICKNESS

Thick mud cake might show a slightly lower porosity.

Most of the time negligible

OPERATION



GAS

Neutron will read very low.

None, sign of a gas zone.

If plotted with ZDEN , this separation is known as Negative Separation

OPERATION



CASING :

Iron is a good neutron absorber.

Cement behind casing affecting counts.

PARAMETER section :

Select casing correction ON and casing parameter.

Select Bit Size behind casing.

Set the expected casing thickness.

OPERATION



Where To Enter The Correction?Where To Enter The Correction?

Default valuesDefault values


Other CorrectionsOther Corrections

Default valuesDefault values

Affect the neutron processing

Affect the neutron processing


Neutrons CurvesCompensated NeutronNeutrons CurvesCompensated Neutron

Raw curves

Computed curves

ssnr : raw short space countlsnr : raw long space countssnr : raw short space countlsnr : raw long space count





PresentedPresented


Ratio ss/ls

P

o

r

o

s

i

t

y

cncnplm

cncfnphi

+/- 25 %

Neutron CurvesCompensated Neutron


No MagicHow to match neutron and density scale?No MagicHow to match neutron and density scale?

Formula of porosity =Formula of porosity = ma - fluidma - fluidma - bulkma - bulk

For limestone, Density curve is presented from 1.95 to 2.95 g/cc We want the neutron curve to stack with the density one in water. For limestone, Density curve is presented from 1.95 to 2.95 g/cc We want the neutron curve to stack with the density one in water.

= =2.71 - 12.71 - 1

2.71 - 1.952.71 - 1.95= 0.4444 very close to 45 % = 0.4444 very close to 45 % = =

2.71 - 12.71 - 1

2.71 - 2.952.71 - 2.95= - 0.1403 very close to - 15 %= - 0.1403 very close to - 15 %


Few Value To RememberFew Value To Remember

Sandstone read - 4 pu lower dolomite read + 7 pu higher anhydride read - 2 pu Salt read - 3 pu

Recorded in limestone matrix and presented on limestone scaleRecorded in limestone matrix and presented on limestone scale


Neutron / Density Curve ResponseNeutron / Density Curve Response


MOST LOGS ARE RECORDEDON LIMESTONE SCALES WITH

A LIMESTONE MATRIX

Because a the CN toolis calibrated for waterfilled limestone, the CNC curve will readthe porosity of limestone correctly


MOST LOGS ARE RECORDEDON LIMESTONE SCALES WITH

A LIMESTONE MATRIX

For example:

10% porosity water filled limestone reads 10 p.u.s

25% porosity water filled limestone reads 25 p.u.s


HOW DOES THIS LOOK ON A LOG?HOW DOES THIS LOOK ON A LOG?

LETS LOOK AT THE CNC SCALE

45 pu

30 pu 15 pu0 pu -15 pu

EACH CHART DIVISION IS 3 PUS



REMEMBER THE SCALES ARE SUCH THAT THE ZDEN AND CNC CURVES OVERLAY IN A WATER FILLED LIMESTONE

Limestone 10%Water Filled




HOW DOES HYDROCARBON LOOK?HOW DOES HYDROCARBON LOOK?

HYDROCARBON WILL AFFECT BOTH THE CNC AND ZDEN

RESPONSESLETS LOOK AT A 10% POROSITY

LIMESTONE FORMATION

Limestone 10%Gas Filled

Limestone 10%Oil Filled



HOW DOES HYDROCARBON LOOK?HOW DOES HYDROCARBON LOOK?




This is known as negative separation

This is largenegative separation

and indicates gas


WHY DOES IT BEHAVE IN THIS WAY?WHY DOES IT BEHAVE IN THIS WAY?




= (0.9 x 2.71) + (0.1 x 0.8)

= 2.52 g/cc

= (0.9 x 2.71) + (0.1 x 0)

= 2.44 g/cc

Here, pore space is filled with gas CNC tends

towards zero p.u.

Limestone MatrixLimestone ScalesZDEN overlays CNC at 10 pu

LETS HAVE A LOOK AT THE ZDEN RESPONSE FIRSTNOW LETS LOOK AT THE

CNC RESPONSE

Oil in the pore space reduces the CN porosity


WHAT ABOUT INCREASED POROSITY?WHAT ABOUT INCREASED POROSITY?




AN INCREASE IN POROSITY INCREASES THE

SEPERATION CAUSED BY H-C





HOW DOES A SANDSTONE LOOK?HOW DOES A SANDSTONE LOOK?

Sandstone 15%Gas Filled

Sandstone 15%Oil Filled

Sandstone 15%Water Filled

LETS BRING UP THE CORRECTION CHART FOR

LITHOLOGY






15 % WATER FILLED SANDSTONE READS 10 P.U.

BY THE CNC CURVE

15%

CNC=10 pu






HERES THE 15 PU LINE

15 % WATER FILLED SANDSTONE READS 10 P.U.

BY THE CNC CURVE

zden = (0.85 x 2.65)+ (0.15 x 1)= 2.4 g/cc






THE 2.5 CHART DIVISION SEPERATION IS A TYPICAL

WATER FILLED SANDSTONE RESPONSE ON LIMESTONE

MATRIX/SCALES






2.25 g/cc

2.37 g/cc

2.4 g/cc


WHAT ABOUT OTHER FORMATIONS?WHAT ABOUT OTHER FORMATIONS?

SHALE

Dolomite 15%Water Filled

Anhydrite

Salt

Coal

Salt:Zden = 2.08 g/ccCnc = -3 pu

2.08 g/cc -3 pu



SHALE


Anhydrite

Salt

Coal

Shale:Zden = 2.3 -2.7 g/ccCnc = High

2.08 g/cc -3 pu

2.3-2.7 g/ccHigh



SHALE


Anhydrite

Salt

Coal

2.08 g/cc -3 pu

2.3-2.7 g/ccHigh

Positive separationHigh water content



SHALE


Anhydrite

Salt

Coal

Anhydrite:Zden = 2.98 g/ccCnc = -2 p.u.

2.08 g/cc -3 pu

2.3-2.7 g/ccHigh

2.98 g/cc -2 pu



SHALE


Anhydrite

Salt

Coal

Type of evaporiteHence very dense

2.08 g/cc -3 pu

2.3-2.7 g/ccHigh

2.98 g/cc -2 pu



SHALE


Anhydrite

Salt

Coal

2.08 g/cc -3 pu

2.3-2.7 g/ccHigh

2.98 g/cc -2 pu

FOR DOLOMITE LETS BRING UP THE CORRECTION CHART

FOR LITHOLOGY AGAIN



SHALE


Anhydrite

Salt

Coal

2.08 g/cc -3 pu

2.3-2.7 g/ccHigh

2.98 g/cc -2 pu

15 % WATER FILLED DOLOMITE READS 22 P.U. BY

THE CNC CURVE

15%

CNC=22 pu



SHALE


Anhydrite

Salt

Coal

2.08 g/cc -3 pu

2.3-2.7 g/ccHigh

2.98 g/cc -2 pu

15% Dolomite:Zden = 2.58 g/ccCnc = 22 p.u.

2.58 g/cc22 pu



SHALE


Anhydrite

Salt

Coal

2.08 g/cc -3 pu

2.3-2.7 g/ccHigh

2.98 g/cc -2 pu

Coal (Anthracite):Zden = 1.6 g/ccCnc = 46 p.u.

2.58 g/cc22 pu

46 pu1.6 g/cc



LETS LOOK AT THE CNC SCALE

60 pu

45 pu 30 pu15 pu

0 pu

EACH CHART DIVISION IS 3 PUS


OTHER LITHOLOGIES?OTHER LITHOLOGIES?




SHALEUsing the Lithology Correction Chart


OTHER LITHOLOGIES?OTHER LITHOLOGIES?




SHALE

2.5 cds+ve separation

8 cds+ve separation


Cnc-zden CrossplotsCnc-zden Crossplots

Cnc-Zden crossplots are used to determine two important factors:

1. Lithology2. Porosity

They can also give an indication to how much shale is in the formation



For Lithology, three lines are drawn on the crossplot relating to:

Sandstone

Limestone

Dolomite

Sandstone

Limestone

Dolomite



For Lithology, three lines are drawn on the crossplot relating to:

Sandstone

Limestone

Dolomite

Where the CN vs ZDEN points plot indicates the type of lithology, or combination of lithologies



Shale pulls the points down:

Sandstone

Limestone

Dolomite

Gas or light hydrocarbon pushes the points up

Shale effect

H-C effect



Sandstone

Limestone

Dolomite

To determine an accurate porosity, the lithology lines have the porosities marked on them.

These can just be read straight off the cross plot

Porosities

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Compensated Neutron(1)

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