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PNNQI Petrophysical Interpretation Using Only PNN Data Zoran Markovic - Chombe HWLAC GmbH Wiesengasse 6 7013 Klingenbach, AUSTRIA Tel.: +43 6763166824 [email protected] www.hwlac.com 1 Petrophysical Interpretation Using Only PNN Data/ Chombe
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Page 1: Petrophysical Interpretation Using Only PNN Data · –S –Shale (Shale point) –S1–Shale 1 (Shale 1 point) 3D space means determining for each-one of them the respective values

PNNQI

Petrophysical Interpretation Using Only PNN Data

Zoran Markovic - ChombeHWLAC GmbH

Wiesengasse 6 7013 Klingenbach, AUSTRIA

Tel.: +43 [email protected]

www.hwlac.com

1

Petrophysical Interpretation Using Only PNN Data/ Chombe

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Title of the Slide

Aim of the presentation:

Show PNNQI features as New PNN Petrophysical Interpretation Software Package With Explaining Model and the Full Program Flow.

Petrophysical Interpretation Using Only PNN Data/ Chombe

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Title of the Slide- Old oil and gas fields become more interesting for development and additional production due to high oil price on the world markets.

- In the past some minor reservoirs were not taken into account at all because of not enough economic reasons.

- In existing reservoirs there were left a lot of bypassed zones or the depletion efficiency was low!

- Those fields are of are often with very limited amount of available openhole logs.

- In most cases covering basic electrical logging without any porosity logs. In some cases logs are lost or with bad quality.

- In some new oil and gas fields are trying to cut the cost by limiting number of measured logs due to different reasons weather this is expense or it is well’s technical condition.

Introduction

Petrophysical Interpretation Using Only PNN Data/ Chombe

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Title of the SlidePNN – Pulsed Neutron Neutron

• The main purpose of PNN logging in wells is to determine water saturation in measured intervals.

• PNN tool has several sensors enabling hydrocarbon saturation evaluation qualitatively or quantitatively.

• To most is less known that PNN has some more sensors used for other interpretations like volume of shale and porosity.

Introduction

Petrophysical Interpretation Using Only PNN Data/ Chombe

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Title of the SlidePulsed Neutron Neutron (PNN) measurement offers good set of curves that help us to cover the lack of data at these wells and to offer full petrophysical interpretation.

Standard PNN interpretation is based on capture-cross section (Sigma) curve which combined with independent petrophysical interpretation (porosity, lithology) gives a good present quantitative saturation evaluation.

However even in the cases when the good openholeinterpretation is unavailable PNN measurements in most of cases are giving us another curves that enables us to perform the full petrophysical interpretation (porosity and lithology as well as saturation).

Introduction

Petrophysical Interpretation Using Only PNN Data/ Chombe

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Title of the SlidePNNQI – The New Interpretation Model and Program

• The new interpretation technique as well as algorithm and program PNNQI (PNN Quick Interpretation) is developed in order to enable us full petrophysical interpretation solely based on PNN data.

• The aim of this paper is to fully describe the program and the usage with all relevant parameters as well as to show some interpretation examples.

Introduction

Petrophysical Interpretation Using Only PNN Data/ Chombe

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Title of the SlideCurves Used

• PNN tool contains several sensors which combined or independently gives us information of formation lithology, porosity and saturation.

– GRPNN – Gamma Ray

– RATIO - Ratio between Short and Long Spaced Count Rates

– SIGMA - Capture Cross-Section

• The new technique and program functionality will be in more details described in following Slides.

Input Curves

Petrophysical Interpretation Using Only PNN Data/ Chombe

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Title of the Slide• The Interpretation Model This is newly developed interpretation method based on three-dimensional (3D) space with each dimension respectively presenting:

– Sigma

– Ratio

– Gamma rayThe model is based on spacing or positioning the model points in such designed 3D space. Points that are modeled and in the same bases for the interpretation are following:

– W- Water (100% Porosity)

– HC - Hydrocarbon (100% Porosity)

– M1 – Matrix 1 (0% porosity mineral 1 point)

– M2 – Matrix 2 (0% porosity mineral 2 point)

– C – Clean (Clean point)

– S – Shale (Shale point)

– S1– Shale 1 (Shale 1 point)3D space means determining for each-one of them the respective values for above mentioned three dimensions (Sigma, Ratio and Gamma Ray).

Petrophysical Interpretation Using Only PNN Data/ Chombe

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Sigma

GR

Ratio

Matrix

Shale

Shale 1

A

B

C

D

E

9

Petrophysical Interpretation Using Only PNN Data/ Chombe

Sigma-Ratio-Gamma X-Plot

Sigma-Gamma-Ratio X-Plot

Ratio-Gamma-Sigma X-Plot

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Title of the Slide

10

Title of the Slide

Petrophysical Interpretation Using Only PNN Data/ Chombe

PNNQI

FlowCalculate RATPOR

Calculate

Dual Mineral Volumes

Calculate Common Matrix

Point

Calculate Dual Volume of Shale

Calculate Water Saturation

Calculate SIGPORCalculate

Effective Porosity

Apply SWIIR Correction

Calculate Corrected Sigma

Calculate Gross/Net/Net-Pay

Save Curves

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Title of the Slide

PNNQI – Program Flow – Details → 1

11

1.) Start New Project [File → New] [ ] (Open DF)

Petrophysical Interpretation Using Only PNN Data/ Chombe

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Title of the Slide

PNNQI – Program Flow – Details → 2

12

1.) File Oppened Automatically

a) read all the relevant curves

for the interpretation,

b) populate all relevant logs

with found input and output curves

Petrophysical Interpretation Using Only PNN Data/ Chombe

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Title of the Slide

PNNQI– Program Flow – Details → 3

13

1.) File Oppened Automatically

c) create and fill all relevant X-Plots

Sigma-Ratio-Gamma X-Plot

Sigma-Gamma-Ratio X-Plot

Ratio-Gamma-Sigma X-Plot

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Title of the Slide

PNNQI – Program Flow – Details → 4

14

1.) File Oppened Automatically

d) Create interpretation charts

- Sigma Water

- Sigma Oil

- Sigma Gas

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Title of the Slide

PNNQI – Program Flow – Details → 5

15

1.) File Oppened Automatically

d) Create Whole Interpretation Zone

- Populates zone with default

interpretation parameters

Ready:

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PNNQI– Program Flow – Details → 6

16PNNQI/ Chombe

2.) Input (Output) Curves SelectionCurve Default

NameDescription

Capture Cross-Section (c.u.) SIGMA Input capture cross-section curve. Curve must exist in order to perform analysis!

Gamma Ray PNN GRPNN Input PNN natural radioactivity curve as measure from PNN in cps.

Ratio Curve from PNN RAT59 Input PNN Ratio Curve. It can be any ratio curve but preferably the best results are achieved using ratio from channels close to maximum thermalization point (5-9)

Gas/Oil Interpretation Offset Curve LSN Input Offset curve for Gas/Oil calculations. Normally this is the LSN Curve but can be as well the PNN RATPOR neutron porosity!

Gas/Oil Interpretation Base Curve SSN Input Base curve for Gas/Oil calculations. Normally this is the SSN Curve but can be as well the openhole neutron porosity!

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PNNQI – Program Flow – Details → 7

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2.) Parameters Edit/Selection

Sigma Parameters Tab

Name Abr. Min Max Default

Description

Sigma Mineral 1 (c.u.) SgM1 0 20 12 Mineral 1 capture cross-section in capture units! Typical values are from 5-10 depending of bituminous content! Typical values for sandstones are from 6-11 and even for some sandstones higher depending on high capture cross-section minerals content! Limestones

Sigma Mineral 2 (c.u.) SgM2 0 20 14 Mineral 2 capture cross-section in capture units! Typical values are from 5-20 depending of matrix composition! Typical values for sandstones are from 6-11 and even for some sandstones higher depending on high capture cross-section minerals content! Limestones

Sigma Matrix (c.u.) SgM 2 22 16 Sigma Matrix Used for Shaliness Calculation. Should be as close to clean zone capture cross-section and not to be influenced by saturation and porosity!

Sigma Shale (c.u.) SgSH 15 45 25 Shale capture cross-section in capture units! Typical values are from 16-40 depending of shale type! Look at the log in neigbouring shales for choosing correct value!

Sigma Shale 1(c.u.) SgSH1 15 45 25 Shale 1 capture cross-section in capture units! Typical values are from 16-40 depending of shale type! Look at the log in neigbouring shales for choosing correct value! Have to be different than for main shale!

Sigma Hydrocarbon (c.u.) SgH 5 25 18 Hydrocarbon capture cross-section in capture units! Typical values are from 5-17 for gasses and 17-22 for oil! Look at the available chart for choosing correct value!

Sigma Formation Water (c.u.)

SgW 22 172 39 Formation water capture cross-section in capture units! Typical values are from 22 for destiled water till 138 for oversaturated water! Look at the available chart for choosing correct value!

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PNNQI – Program Flow – Details → 8

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2.) Parameters Edit/Selection

Ratio Parameters TabName Abr. Min Max Default Description

Ratio For 100% RAT100 5 45 25 Ratio representing value of ratio for 100% porosity. This is ratio for Water and Hydrocarbon points.

Ratio For 0% RAT0 -5 15 2 Ratio representing value of ratio for 0% porosity. This is ratio value for both mineral 1 and mineral 2 in all calculations.

Ratio Matrix RATM -5 15 4 Ratio Matrix Used for Shaliness Calculation. Should be as close to clean zone ratio and not to be influenced by porosity!

Ratio Shale RATSH -5 15 9 Shale ratio. Shale 1 ratio. Should be determined according to X-plot and different from shale 1.

Ratio Shale 1 RATSH1 -5 15 8 Shale 1 ratio. Should be determined according to X-plot and different from shale.

Porosity Alpha Factor ALPHA 1 5 1 Alpha factor to determine the rate of porosity reduction with increase of volume of shale!

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PNNQI – Program Flow – Details → 9

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2.) Parameters Edit/Selection

GR Parameters TabName Abr. Min Max Default Description

GR Mineral 1 GRM1 5 45 25 Mineral 1 Gamma Ray value. Used for recalculation of shaliness and volumetrics of minerals!

GR Mineral 2 GRM2 -5 15 2 Mineral 1 Gamma Ray value. Used for recalculation of shaliness and volumetrics of minerals!

GR Matrix GRM -5 15 4 GR Matrix Used for Shaliness Calculation. Should be as close to clean zone gamma ray!

GR Shale RATSH -5 15 9 Shale GR. Should be determined according to X-plot and different from shale 1.

GR Shale 1 RATSH1 -5 15 8 Shale 1 GR. Should be determined according to X-plot and different from shale.

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PNNQI – Program Flow – Details → 10

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2.) Parameters Edit/Selection

Shale Parameters TabName Abr. Mi

nMa

xDefault Description

VSH Larionov Exponent Ex 0 10 3.7 Larionov Factor For Shaliness correction for compensation for rocks age in shaliness calculation!

Max. VSH For Correction (%)

ShCUT 0 100 30 Maximal shaliness value for which Porosity will be calculated. Shaliness higher than this parameter vill have porosity of 0.1%.

VSH GR Factor MULGR 0 2 1 GR multiplicative factor used to increase or decrease influence of Gamma Ray curve for overall calculation of shaliness.

VSH Sigma Factor MULSIG 0 2 1 Sigma multiplicative factor used to increase or decrease influence of Sigma curve for overall calculation of shaliness.

VSH Ratio Factor MULRAT 0 2 1 Ratio multiplicative factor used to increase or decrease influence of Ratio curve for overall calculation of shaliness.

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PNNQI – Program Flow – Details → 11

21 HWQuantNET/ Chombe

2.) Parameters Edit/Selection

Irreducible Water/Hydrocarbon Tab

Name Abr. Min Max Default Description

Check if you want to use SHIrr correction.

UseSHIRR

0 1 1 Specifies to use SHH Irr Correction.

Check if you want to use SWIrr correction.

UseSWIRR

0 1 1 Specifies to use Sigma matrix curve rather than the specified parameters foor matrix Sigma.

SH Irreducible Factor ShIRRF 0.01 0.11 0.03 Enter SHIrreducible factor for recalculation of SWIRR from porosity/SWIrr Chart.

SW Irreducible Factor SwIRRF 0.01 0.11 0.04 Enter SWIrreducible factor for recalculation of SWIRR from porosity/SWIrr Chart.

SH Irreducible (%) SHhIRR 5 55 25 Enter SH Irreducible values in percentages.

SW Irreducible (%) SwIRR 5 55 25 Enter SWIrreducible values in percentages.

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PNNQI – Program Flow – Details → 12

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2.) Parameters Edit/Selection

Cut-Off Tab

Name Abr. Min Max

Default Description

Maximum SIGMA For Saturation Calculation (%).

SgMAX 20 40 29 Enter maximal SIGMA that will be used for Water saturation calculation. If SIGMA is higher than this value then used SIGMA will be this value.

Minimum SIGMA For Saturation Calculation (%).

SgMIN 0 20 9 Enter Enter minimal SIGMA that will be used for Water saturation calculation. If SIGMA is lower than this value then used SIGMA will be this value.

SWPNN Cut-off (%). NetSWPNNCUT

20 80 55 PNN Water Saturation cut of for NET PAY zone calculation. SW lower and same as this parameter will be taken as Net-Pay zone.

SW Cut-off (%). NetSWCUT 20 80 55 Water Saturation cut of for NET PAY zone calculation. SW lower and same as this parameter will be taken as Net-Pay zone.

Porosity Cut-Off (%). NetPORCUT

0 25 12 Porosity cut of for NET zone calculation. Porosity higher and same as this parameter will be taken as Net zone.

VSH Cut-Off (%). NetSHCUT 0 100

50 Shale cut-off for Gross calculation!

Minimum Porosity For Saturation Calculation(%).

PorMIN 0 20 2 Enter minimal porosity for which water saturation will be calculated. If porosity is lower than this value then water saturation will be 100%.

Maximum Porosity For Porosity Calculation(%).

PorMAX 0 20 2 Enter minimal porosity for which water saturation will be calculated. If porosity is lower than this value then water saturation will be 100%.

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PNNQI – Program Flow – Details → 13

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2.) Parameters Edit/Selection

Gas/Oil TabName Abr. M

inMax Default Description

Perfor Gas Interpretation

UseGASINT

0 2 0 Select which type of hydrocarbon interpretation is used:OilGasGas/oilIf Gas/Oil is used than following parameters are relevant!

Base Left ScaleBLeft

0 Base curve left compatible scale. Will be used for normalization of base curve!

Base Right ScaleBRight

1000 Base curve lright compatible scale. Will be used for normalization of base curve!

Offset Left ScaleOLeft

0 Offset curve left compatible scale. Will be used for normalization of base curve!

Offset Right ScaleORight

200 Offset curve lright compatible scale. Will be used for normalization of base curve!

Gas Index Alpha Coefficient

Alpha 1 5 1 Gas Calculation GAS Alpha coefficient!

Gas Index Exponent Exp 0 10 1 Gas Calculation GAS Index Exponent!

Normalized Difference Oil

NOil -1 1 -0.01 Normalized difference value for Oil point!

Normalized Difference Gas

NGas -1 1 -0.25 Normalized difference value for Gas point!

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PNNQI – Program Flow – Details → 17

24 HWQuantNET/ Chombe

3.) Parameters Edit Interactivity

parameters changes are automatic which means if some parameter is changed it is interactively connected to log, x-plot, zone management and the processing of currently selected zone is done immediately and results may be seen on the logs and on the x-plots.

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PNNQI – Program Flow – Details → 15

25 HWQuantNET/ Chombe

3.) GROSS, NET, NET-PAY Autoprocesssing

In the same time it is made automatic recognition of GROSS, NET and NET-PAY zones with zones selection and statistical evaluation.

4.) Perforations and Special Interest Zones

Same calculation and statistical evaluation was done for perforation zones and also special interest zones (as specified by customer) may be added and evaluated.

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PNNQI – Program Flow – Details → 16

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5.) Result Export ( LAS, WDB ... )

At any moment after our satisfaction we may export immediately resulting curves and send to customer. .(File→Save Result LAS File)

6.) Automatic reporting

Automatic reporting option enables fast and accurate creation of written reports toward customer

7.) Project Saving/Opening

Project may be saved(File→Save QA Project) and later reopened(File→Open QA Project) for additional interpretation or just reporting.

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PNNQI – Parameters Editing Details

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Parameters may be changed from several locations:

1.) Parameters Tab Page

2.) Interactive X-Plot

3.) Zone Management Control

4.) Log

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PNNQI – Parameters Editing Details

28 HWQuantNET/ Chombe

Parameters Tab Page Editing

- by entering or sliding the values. Each parameter has the help description hidden under the sign. All program parameters may be changed from there

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PNNQI – Parameters Editing Details

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X-Plot Parameters Editing

- by interactively moving points at any X-Plot.

Only selected and specific parameters may be changed.

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PNNQI – Parameters Editing Details

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Zone Management Parameters Editing

- double clicking on the zone opens Parameter Edit Dialog

- From this dialog it is possible to change any parameter.

-it is also possible to group parameters into groups and then it is possible to change parameter for all zones belonging to one group. After that ii is necessary to run all the zones in order to apply made changes and this is done by clicking on Run All Zones button ( ) in Menu Bar.

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PNNQI – Parameters Editing Details

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Log Parameters Editing

- it is possible to edit some selected parameters(SgW, SgH, SgM and SgSH).

- parameters are presented as lines and these lines may be moved for each zone.

- Just by clicking inside another zone changes this zone to be Active and ready to run.

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PNNQI – Oil/Gas Interpretation

32 HWQuantNET/ Chombe

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PNNQI – Gross/Net/Net-Pay Processing

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PNNQI enables automatic

recognition/selection of gross net and net-pay zones.

This is done immediately after main saturation calculation.

The results of this calculation is that we have automatically selected list of GROSS, NET and NET-PAY zones. These zones are shown at the main interpretation log

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PNNQI – Gross/Net/Net-Pay Processing

34 HWQuantNET/ Chombe

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Summary

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This presentation presented PNNQI, new program for full petrophysical interpretation using only data from pulsed neutron measurements.

New program offers possibility of crating 3D model from PNN Curves GRPNN, RATIO and SIGMA (SRG3D Model). SRG3D model enables modelling and calculation of lithology as well as porosity curves using Dual Mineral → Dual Shale Interpretation.

The program calculates also two porosity curves from PNN RATPOR and SIGPOR as well as corrected Sigma curve in washout zones.There is full statistical Gross/NET/Net-Pay evaluation as well as gas\oil interpretation!

The program is presented with detailed listing of parameters used and detail explanation of program.

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Title of the Slide

Thanks ????????????

End

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Title of the SlideGRPNN – Gamma Ray• There is a lot written about natural radioactivity curve written in vast amount of

petrophysical literature of any kind. In here will just notify the some aspects.

• The natural radioactivity comes from radioactive minerals or elements composing minerals contained in the rocks.

• These minerals tends mostly to concentrate in clays and shales. Clean formations usually contains minor amount of radioactive minerals. This fact enables good shaliness interpretation in most cases.

• It have to be stated that the clean formations (non-shaly) can sometimes have higher amount of radioactive minerals (potassium feldspars, mica, some radioactive salts, volcanic ash) and on these cases the alternative models for interpretation of shaliness should be used..

• The good fact of gamma ray curve that is equally effective in measurements in open and cased hole making it good for correlation but also for lithology (shaliness) evaluation in cased hole measurement (in this case using PNN tool).

• Gamma ray shale content interpretation is well known technique standardly and is relatively straight-forward interpreted using some algorithms/formulas. Most famous is Larionov formula or Larionov model which enables the age of the rocks to be compensated during the shaliness interpretation by application of different LarionovExponent (E).

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Title of the SlideGRPNN – Shaliness Interpretation - Larionov

CleanShale

CleanLog

GRGRGR

GRGRI

−= 𝑉𝑆𝐻 =

2𝐸𝑥−𝐼𝐺𝑅 − 1

2𝐸𝑥 − 1

Older rocks

Tertiary rocks

Linear

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Title of the SlideRATIO – PNN SSN/LSN Ratio• Ratio is general expression for the ratio between PNN short and long spacing detector

count-rates. These ratios can be from all channels on both detectors but also from count-rates from specially selected channels. There are several papers from PNN conference describing ratio.

. Highest energy loss will happen when neutron

hits nucleus of similar mass to the mass of

neutron. This is hydrogen nuclei. Therefore the

rate at which neutron will be slowed to thermal

energy level depends on hydrogen index (HI) of

all components of the formation and formation

fluids that contain a significant fraction of

hydrogen. In clean formations that mean that

neutron curve responses on hydrogen which is

inside water or oil in pore space. By measuring

“hydrogen index” neutron tools are measuring

porosity of the clean formation. However there

are some hydrogen in clay minerals as bound

water and OH groups and neutron porosity

needs to be corrected for shaliness.

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Title of the SlidePNN Porosity Measurement Theory

Among other sensors PNN tool has electrical neutron generator and two neutron detectors. Theory of

measurement is same but with one difference. Both detectors are measuring thermal neutrons in 60 time

channels, each 36 microseconds wide.

RATPOR

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Title of the SlideSigma – Capture Cross-Section

• PNN tool is measuring the capture cross section (Sigma, S ) of certain volume of rock. A mineral's ability to absorb thermal neutrons is defined as its capture cross section, sigma.

• Sigma is measured in capture units (c.u.). The higher the value of sigma, the greater its ability to capture thermal neutrons. By measuring the rate at which thermal neutrons are absorbed into the formation (either by measuring the thermal neutrons themselves or by measuring the prompt gamma rays given off during thermal neutron absorption), the capture cross section of the formation and formation fluids can be predicted.

• The capture cross section tables list many of the elements and compounds found throughout the world.

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Title of the SlideSigma – Capture Cross-Section Table

Formations, and even more importantly, formation fluids

containing chlorine atoms are the most effective

capturers of thermal neutrons.

This is because high thermal neutron absorbers such as

cadmium are rarely found in oilfield geology (Boron is

more commonly encountered, but is still just a drop in the

bucket when compared to salt water).

From the table, it can be seen that rock salt has a high

sigma value due to its chlorine content.

Salt water values may range from 25,000 ppm (30 c.u.)

to 275,000 ppm (130 c.u.) equivalent chlorides.

Material (Pure) Computed Sigma @20°C

Quartz (SiO2) 4.26

Calcite (CaCO3) 7.07

Dolomite (CaCO3 · MgCO3) 4.70

Anhydrite (CaCO4) 12.5

Gypsum (CaSO4 · 2H2O) 18.4

Magnesite (MgCO3) 1.44

Iron 193

Rock salt (NaCl) 753

Boron (B) 99,405

Cadmium (Cd) 113,315

Fresh water (H2O) 22

Salt water 22-138

Oil 17-22

Gas 5-17

Sandstone 7-16

Limestone 7-11

Dolomite 6-10

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43

Title of the SlideInterpretation Technique – Sigma-Ratio-Gamma X-Plot

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44

Title of the SlideInterpretation Technique – Sigma-Gamma-Ratio X-Plot

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45

Title of the SlideInterpretation Technique –Ratio-Gamma-Sigma X-Plot

Page 46: Petrophysical Interpretation Using Only PNN Data · –S –Shale (Shale point) –S1–Shale 1 (Shale 1 point) 3D space means determining for each-one of them the respective values

46

Title of the SlideRATPOR Calculation

RATPOR is compensated neutron porosity curve from PNN and it is calculated

either by linear or nonlinear (Polynomial) calculation from defined values for Matrix

Ratio and for 100% porosity Ratio.

𝑅𝐴𝑇𝑃𝑂𝑅 =𝑅𝐴𝑇𝐿𝑜𝑔−𝑅𝐴𝑇0

𝑅𝐴𝑇100−𝑅𝐴𝑇0× 100 (3)

Where:

𝑅𝐴𝑇𝑃𝑂𝑅 - PNN Neutron Porosity

𝑅𝐴𝑇𝐿𝑜𝑔 - Measured Ratio

𝑅𝐴𝑇100 - 100% Porosity Ratio

𝑅𝐴𝑇0 - 0% Porosity Ratio

RATPOR is output curve from the program and in the same time serves as the

base for effective porosity calculation in combination with other curves (volume of

shale, volume of minerals) calculated through calculation method.

Page 47: Petrophysical Interpretation Using Only PNN Data · –S –Shale (Shale point) –S1–Shale 1 (Shale 1 point) 3D space means determining for each-one of them the respective values

The program is calculating dual mineral volumetric based on the fact that two active

minerals may show different radioactivity. This is very often the case and may be

good method in some cases for differentiation of two or more minerals. This kind of

calculation will of course be effected with shaliness radioactivity. However in certain

cases and especially in case of carbonates it may be very effective way of evaluating

different matrix mineralogy. This is very important because such different two

minerals may have highly different matrix capture cross-section and therefore high

influence on saturation calculation from sigma curve.

𝑉2𝐹 =𝐺𝑅𝐿𝑜𝑔−𝐺𝑅𝑀1

𝐺𝑅𝑀2−𝐺𝑅𝑀1

𝑉1𝐹 = 1 − 𝑉2𝐹Where:

𝑉1𝐹 - Fractional Volume of Mineral 1

𝑉3𝐹 - Fractional Volume of Mineral 2

𝐺𝑅𝐿𝑜𝑔 - Measured Gamma Ray

𝐺𝑅𝑀1 - Mineral 1 Gamma ray

𝐺𝑅𝑀2 - Mineral 2 Gamma Ray

These fractional mineral volumes are then recalculated to normalize for the volume of

Matrix which will be shown below.47

Title of the SlideDual Mineral Volume Calculation

Page 48: Petrophysical Interpretation Using Only PNN Data · –S –Shale (Shale point) –S1–Shale 1 (Shale 1 point) 3D space means determining for each-one of them the respective values

Common matrix point in Sigma-Ratio-Gamma 3D (SRG3D) space is calculated in

order to be one of the anchors for dual shale vs. matrix interpretation.

𝑀𝑆𝑅𝐺3𝐷 =𝑆𝐼𝐺𝑀1+𝑆𝐼𝐺𝑀2

2

𝑅𝐴𝑇𝑀1+𝑅𝐴𝑇𝑀2

2

𝐺𝑅𝑀1+𝐺𝑅𝑀2

2

Where:

𝑀𝑆𝑅𝐺3𝐷 - Common Matrix Point in SRG3D

𝑆𝐼𝐺𝑀1 - Mineral 1 Sigma

𝑆𝐼𝐺𝑀2 - Mineral 2 Sigma

𝑅𝐴𝑇𝑀1 - Mineral 1 Ratio

𝑅𝐴𝑇𝑀2 - Mineral 2 Ratio

𝐺𝑅𝑀1 - Mineral 1 Gamma ray

𝐺𝑅𝑀2 - Mineral 2 Gamma Ray

This SRG3D point together with two below defined shale SRG3D points makes

triangle in the SRG3D plane.

48

Title of the SlideCommon Matrix Point Calculation

Page 49: Petrophysical Interpretation Using Only PNN Data · –S –Shale (Shale point) –S1–Shale 1 (Shale 1 point) 3D space means determining for each-one of them the respective values

Through program parameters and through interactive moving of points on x-plots two

SRG3D shale points are defined. These are the points for the main shale (𝑆𝑆𝑅𝐺3𝐷)and second shale (𝑆1𝑆𝑅𝐺3𝐷).

𝑆𝑆𝑅𝐺3𝐷 = 𝑆𝐼𝐺𝑆 𝑅𝐴𝑇𝑆 𝐺𝑅𝑆𝑆1𝑆𝑅𝐺3𝐷 = 𝑆𝐼𝐺𝑆1 𝑅𝐴𝑇𝑆1 𝐺𝑅𝑆1𝐶𝑆𝑅𝐺3𝐷 = 𝑆𝐼𝐺𝐶 𝑅𝐴𝑇𝐶 𝐺𝑅𝐶

Where:

𝑆𝑆𝑅𝐺3𝐷 - Main Shale Point in SRG3D

𝑆1𝑆𝑅𝐺3𝐷 - Second Shale Point in SRG3D

𝑆𝐼𝐺𝑆 - Main Shale Sigma

𝑅𝐴𝑇𝑆 - Main Shale Ratio

𝐺𝑅𝑆 - Main Shale GR

𝑆𝐼𝐺𝑆 - Second Shale Sigma

𝑅𝐴𝑇𝑆 - Second Shale Ratio

𝐺𝑅𝑆 - Second Shale GR

The three SRG3D points define the plane (CSS1) in SRG3D space and in the same

time they form triangle in the same plane Figure-9.49

Title of the SlideDual Volume of Shale Calculation

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Title of the Slide

50

Title of the Slide

Petrophysical Interpretation Using Only PNN Data/ Chombe

Sigma

GR

Ratio

Matrix

Shale

Shale 1

A

B

C

D

E

A – Represents point inside triangle and mostly in the MSS1 plane. It is closest to Matrix

point and with low volume of shale.

B – Represents point inside triangle and mostly in the MSS1 plane. It is closest to Shale

point and with low volume of Shale 1 and Matrix.

C – Represents point which is above MSS1 plane. It has to be projected to the plane.

D – Represents point inside triangle and mostly in the MSS1 plane. It is deep inside

triangle and consists of all components, Shale, Shale 1 and Matrix.

E – Represents point which is below MSS1 plane. It has to be projected to the plane.

vector mathematics

analytical geometry in space

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Title of the Presntation / Author 51

Ratio

SigmaGR

Matrix Shale

Shale 1

A

B

C

D

E

Now we can see that all the points have the new rotated SRG3D

coordinates where the rotation removed the effect of GR dimension and

only recalculated rotated Ratio and Sigma coordinated may be used for

calculation of 3-component volumetric. It can be seen that now the C

and E points are clearly inside triangle with it’s rotated and recalculated

coordinates which may be used for calculation.

2D Triangle Calculation

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Title of the Presntation / Author 52

Now we can see that all the points have the new rotated SRG3D

coordinates where the rotation removed the effect of GR dimension and

only recalculated rotated Ratio and Sigma coordinated may be used for

calculation of 3-component volumetric. It can be seen that now the C

and E points are clearly inside triangle with it’s rotated and recalculated

coordinates which may be used for calculation.

3D Triangle Calculation

A

a

b

V1 = b/(a+b) * 100V2= d/(c+d) * 100V3 = f/(e+f) * 100

c

d

f

e

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Water Saturation is graphically and using analytical geometry calculated from the

cross Plot. First the common matrix point 𝑀𝑆𝑅𝐺3𝐷 is calculated for above calculated

volumes of matrix 1 and matrix 2. Together with water point (𝑊𝑆𝑅𝐺3𝐷) and

hydrocarbon point (𝐻𝐶𝑆𝑅𝐺3𝐷) two lines are created.

𝑀𝑆𝑅𝐺3𝐷 = 𝑆𝐼𝐺𝑀 𝑅𝐴𝑇𝑀 𝐺𝑅𝑀𝑊𝑆𝑅𝐺3𝐷 = 𝑆𝐼𝐺𝑊 𝑅𝐴𝑇𝑊 𝐺𝑅𝑊

𝐻𝐶𝑆𝑅𝐺3𝐷 = 𝑆𝐼𝐺𝐻𝐶 𝑅𝐴𝑇𝐻𝐶 𝐺𝑅𝐻𝐶Where:

𝑀𝑆𝑅𝐺3𝐷 - Matrix Point in SRG3D

𝑊𝑆𝑅𝐺3𝐷 - Water Point in SRG3D

𝐻𝐶𝑆𝑅𝐺3𝐷 - Hydrocarbon Shale Point in SRG3D

𝑆𝐼𝐺𝑀 - Main Shale Sigma

𝑅𝐴𝑇𝑀 - Main Shale Ratio

𝐺𝑅𝑀 - Main Shale GR

𝑆𝐼𝐺𝑊 - Water Sigma

𝑅𝐴𝑇𝑊 - Water Ratio

𝐺𝑅𝑊 - Water GR

𝑆𝐼𝐺𝐻𝐶 - Hydrocarbon Sigma

𝑅𝐴𝑇𝐻𝐶 - Hydrocarbon Ratio

𝐺𝑅𝐻𝐶 - Hydrocarbon GR

Obviously for the need of saturation calculation the GR component of 3D space is

disregarded. The interpretation is done only in Sigma-Ratio axis plane!53

Title of the SlideSaturation Calculation

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Two lines are created:

100% Water Saturated Zone (Water Line) between points 𝑀𝑆𝑅𝐺3𝐷 and 𝑊𝑆𝑅𝐺3𝐷.

0% Water Saturated Zone (Hydrocarbon Line) between points 𝑀𝑆𝑅𝐺3𝐷 and 𝐻𝐶𝑆𝑅𝐺3𝐷.

For each point in our calculation the theoretical 100% water Sigma value is

calculated:

𝑆𝐼𝐺100 =(𝑅𝐴𝑇𝐿𝑜𝑔−𝑏𝑤)

𝑎𝑤(14)

Where:

𝑆𝐼𝐺100 - Sigma Value for 100% Water Saturation (c.u).

𝑅𝐴𝑇𝐿𝑜𝑔 - Measured Ratio Value

𝑏𝑤 - Water Line b Factor

𝑎𝑤 - Water Line a Factor (Slope)

For each point in our calculation the theoretical 0% water Sigma value is calculated:

𝑆𝐼𝐺0 =(𝑅𝐴𝑇𝐿𝑜𝑔−𝑏ℎ𝑐)

𝑎ℎ𝑐(15)

Where:

𝑆𝐼𝐺0 - Sigma Value for 0% Water Saturation (c.u).

𝑅𝐴𝑇𝐿𝑜𝑔 - Measured Ratio Value

𝑏ℎ𝑐 - Hydrocarbon Line b Factor

𝑎ℎ𝑐 - Hydrocarbon Line a Factor (Slope)54

Title of the SlideSaturation Calculation

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Title of the Slide

55

Title of the SlideThen water saturation is calculated:

𝑆𝑊𝑃𝑁𝑁 =(𝑆𝐼𝐺𝐿𝑜𝑔−𝑆𝐼𝐺0)

(𝑆𝐼𝐺100−𝑆𝐼𝐺0)∗ 100 (16)

Where:

𝑆𝑊𝑃𝑁𝑁 - PNN Water Saturation (%).

𝑆𝐼𝐺𝐿𝑜𝑔 - Measured Sigma Value

𝑆𝐼𝐺100 - Sigma Value for 100% Water Saturation (c.u).

𝑆𝐼𝐺0 - Sigma Value for 0% Water Saturation (c.u).

Page 56: Petrophysical Interpretation Using Only PNN Data · –S –Shale (Shale point) –S1–Shale 1 (Shale 1 point) 3D space means determining for each-one of them the respective values

SIGPOR is Sigma derived porosity curve from PNN and it is calculated by linear

calculation from defined values for Matrix Sigma and for 100% porosity (Water)

Sigma.

𝑆𝐼𝐺𝑃𝑂𝑅 =𝑆𝐼𝐺𝐿𝑜𝑔−𝑆𝐼𝐺0

𝑆𝐼𝐺100−𝑆𝐼𝐺0× 100 (17)

Where:

𝑆𝐼𝐺𝑃𝑂𝑅 - PNN Sigma Porosity

𝑆𝐼𝐺𝐿𝑜𝑔 - Measured Sigma (c.u.)

𝑆𝐼𝐺100 - 100% Porosity Sigma. Water Sigma (c.u.).

𝑆𝐼𝐺0 - 0% Porosity Sigma. Matrix Sigma (c.u.).

SIGPOR is output curve from the program and is used for comparison with RATPOR

curve where there will be expressed separation in direction of lower porosity between

RATPOR and SIGPOR curves.

56

Title of the SlideSIGPOR Calculation

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Title of the Slide

57

Title of the Slide

Page 58: Petrophysical Interpretation Using Only PNN Data · –S –Shale (Shale point) –S1–Shale 1 (Shale 1 point) 3D space means determining for each-one of them the respective values

Effective porosity is calculated from RATPOR taking into account volume of shale

value:

𝑃𝑂𝑅 = 𝑅𝐴𝑇𝑃𝑂𝑅 ∗ (1 −𝑉𝑆𝐻

100)𝐴𝐿𝑃𝐻𝐴

Where:

𝑃𝑂𝑅 - Effective Porosity (%)

𝑅𝐴𝑇𝑃𝑂𝑅 - PNN Ratio Porosity (%)

𝑉𝑆𝐻 - Volume of Shale (%)

𝐴𝐿𝑃𝐻𝐴 - Factor Influencing Reduction Of Porosity with shaliness

POR is output effective porosity curve from the program.

58

Title of the SlideEffective Porosity Calculation

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If requested from the program by selection of parameters the correction for irreducible

water saturation is made. The first the irreducible water saturation value for certain

porosity is calculated:

𝑆𝑊𝐼𝑟𝑟 =𝐶

𝑃𝑂𝑅

100

∗ 100

Where:

𝑆𝑊𝐼𝑟𝑟 - Irreducible Water Saturation (%)

𝑃𝑂𝑅 - Effective Porosity (%)

𝑐 - Factor Linking Porosity and Permeability

If Water saturation is lower than irreducible water saturation then the water saturation

is set to be irreducible water saturation.

59

Title of the SlideSaturation Correction Calculation

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Sigma corrected for water saturation is calculated for the usage of correction in zones

where there is too high influence of some chemical treatments on the reservoir to

processed Sigma curve. Too high influenced zones may be replaced by corrected

Sigma value.

60

Title of the SlideSigma Correction Calculation

Gross/Net/Net-Pay zones are automatically extracted from the program and

complete statistical evaluation is tabled.

Calculate Gross/Net/Net-Pay Zones


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