2007 SPE ATW on Reservoir Performance

The role of the petrophysicist in The role of the petrophysicist in reservoir characterization and reservoir characterization and the analysis of reservoir the analysis of reservoir performance.performance.What do we bring to the table?What do we bring to the table?What do we want to take home?What do we want to take home?

Bob CluffBob CluffThe Discovery Group Inc.The Discovery Group Inc.consulting geoscientists and consulting geoscientists and petrophysicistspetrophysicistsDenver, ColoradoDenver, ColoradoPresentation at SPE Applied Technology Presentation at SPE Applied Technology Workshop, Key West, Florida, 8 Feb 2007Workshop, Key West, Florida, 8 Feb 2007

The big 3 we all want to The big 3 we all want to knowknow.. PorosityPorosity PermeabilityPermeability Fluid saturationFluid saturation

But these are what we really But these are what we really measure with logsmeasure with logs.... Natural earth potentials (spontaneous potential) Natural earth potentials (spontaneous potential)

between bedsbetween beds Electrical conductivityElectrical conductivity Natural gamma ray radiationNatural gamma ray radiation Neutron slowing down lengthNeutron slowing down length Thermal neutron capture cross Thermal neutron capture cross sectonsecton Speed of soundSpeed of sound Electron density from gamma ray scatteringElectron density from gamma ray scattering Gamma ray photoelectric absorptionGamma ray photoelectric absorption Nuclear magnetic resonance relaxation timeNuclear magnetic resonance relaxation time just about any property of matter you can think of.just about any property of matter you can think of.

Role of the petrophysicistRole of the petrophysicist

Is to take the physical properties we can Is to take the physical properties we can measure measure downhole,thendownhole,then turn them into turn them into something useful.something useful.

That is, the reservoir properties of interest.That is, the reservoir properties of interest.

Two faces of PetrophysicsTwo faces of Petrophysics

Measurement scienceMeasurement science What physical properties can be measured What physical properties can be measured

that might be useful/interesting?that might be useful/interesting? Physics of the measurementPhysics of the measurement Engineering how to make the measurement Engineering how to make the measurement

in a dark, noisy, dirty in a dark, noisy, dirty downholedownhole enviromentenviroment Converting the raw measurements to Converting the raw measurements to

something closer to the property of interestsomething closer to the property of interest

Electron densityElectron density

Gamma rays are emitted by radioisotope Gamma rays are emitted by radioisotope source.source. GRGRss are scattered by the electron clouds are scattered by the electron clouds

surrounding the nearby atoms (Compton surrounding the nearby atoms (Compton scattering).scattering). GRGRss detected at 1, 2 or 3 nearby detectors are detected at 1, 2 or 3 nearby detectors are

attenuated, with the reduction directly attenuated, with the reduction directly proportional to the density of electrons proportional to the density of electrons between the source and the detectors.between the source and the detectors.

LoggingLoggingsondesonde

US Patent 3,321,625May, 1967

Electron density vs. bulk Electron density vs. bulk densitydensity

0

1

2

3

4

5

6

0 1 2 3 4 5 6

electron density (rhob x 2Z/A)

b

u

l

k

d

e

n

s

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t

y

(

g

/

c

3

)

water

quartz

dolomite

pyrite

coal

limestone

Spine and ribs plotSpine and ribs plot

The second faceThe second face..

Interpretation scienceInterpretation science Interpreting physical measurements in terms Interpreting physical measurements in terms

of rock properties of interestof rock properties of interest determine porosity from bulk densitydetermine porosity from bulk density determine hydrocarbon saturation from electrical determine hydrocarbon saturation from electrical

conductivity and porosityconductivity and porosity Interpretation model developmentInterpretation model development Integration of petrophysical properties with Integration of petrophysical properties with

engineering and geologyengineering and geology

Example: bulk density Example: bulk density interpretationinterpretation The raw tool count rates have been The raw tool count rates have been

converted to bulk density and corrected converted to bulk density and corrected for for mudcakemudcake thickness by the logging thickness by the logging service company,service company, but we want to know the porosity of the but we want to know the porosity of the

formation, not the density.formation, not the density.

Bulk densityBulk density--density density porosity plotporosity plot

Schlumberger, 2005

Porosity computationPorosity computation

PhiDPhiD = (= (RhoMaRhoMa RhoB)/(RhoMaRhoB)/(RhoMa RhoFlRhoFl))Where: Where: RhoMaRhoMa = the matrix density= the matrix density RhoBRhoB = measured bulk density= measured bulk density RhoFlRhoFl = fluid density= fluid density

Problem for the interpretation petrophysicist is:Problem for the interpretation petrophysicist is: What is the matrix density? What is the matrix density? Rocks are rarely pure end member mineralsRocks are rarely pure end member minerals-- they are usually they are usually

mixtures so the matrix density will not be a constant value.mixtures so the matrix density will not be a constant value. What is the fluid density? Water, oil, gas, or a combination What is the fluid density? Water, oil, gas, or a combination

thereof? thereof? At formation conditions. At formation conditions. Do we need to know Do we need to know saturation to solve for porosity??saturation to solve for porosity??

Density porosity solutionDensity porosity solution

-0.05 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45OCNL

3

.

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.

9

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9

D

e

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GRCORR0 300[N/A]

GRCORR0 300[N/A]

Density1.95 2.95G/C3

Neutron0.45 -0.15V/V

Sonic140 40US/F

Pe0 20[N/A]

Density1.95 2.95G/C3

Neutron0.45 -0.15V/V

Sonic140 40US/F

Pe0 20[N/A]

7950

8000

8050

8100

8150

82008200

LESA 6.1, 1992-2006 Digital Formation, Inc.File: LA-LIME.LAS Well Name: LOUISIANA LIMESTONEPlot: C-DN-S46.PLT Plot Name: Density vs. Comp. Neutron (S-1991, p.46)Gross Interval: 7950 to 8170 by 1 FRanges: 7950-8170Time: 05:59 PM Date: Sat, Feb 03, 2007

Schlumberger Chartbook (1991) p.46

Dolom

ite

0

510

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Limest

one

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Sandst

one

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Anhy

drite

0

SulfurSalt

Plagioclase

Kspar

Chlorite

Illite

Kaolinite

Is this a change inmatrix density (lithology)or a change in fluids??

Log Log exampleexample

-0.05 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45Neutron

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Dolom

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35

Limest

one

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1015

2025

3035

4045

Sandst

one

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5

10

1520

25

3035

40

SaltSulfur

Anhydrite

K-spar

Plagioclase Chlorite

Illite

Kaolinite

Shale Point

40 50 60 70 80 90 100 110 120 130Sonic Transit Time (us/ft)

3

2

.

9

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8

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Time Average

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Sand

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Limest

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Sulfer

Sylvite

SaltTrona

Gypsum

Polyhalite

Anhydrite


Field Observation

Dolom

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40

Sand

stone0

10

2030

Limest

one

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20

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40Sulfer

Sylvite

SaltTrona

Gypsum

Polyhalite

Anhydrite

Shale Point

-0.05 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45Neutron

4

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S

o

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/

f

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)


Time Average

Dolom

ite

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35

Limest

one

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Sand

stone

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Salt

Anhy

drite


Field Observation

Dolom

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Limest

one

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Sand

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drite

Shale Point

0 1 2 3 4 5 6Pe [N/A]

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Sand

ston

e

010

2030

40

Dol

omite

010

2030

40

Lim

esto

ne

010

2030

40 Sal

t

0A

nhyd

rite

0

Illite

Chlorite

Kaolinite

Montmorillonite

Shale Point

LESA 6.1, 1992-2006 Digital Formation, Inc.File: 2508321080_Daniels 1.las Well Name: DANIELSPlot: Interactive Shale Point - English.plt Plot Name: Density vs. Pe (S-1991, p. 64)Gross Interval: 11000 to 12532 by 0.5 FRanges: 11000-12532Time: 06:13 PM Date: Sat, Feb 03, 2007

Density in Shale = 2.514

Neutron in Shale = 0.299

Dt in Shale = 65

Pe in Shale = 3.5

So what is it we do?So what is it we do?

We integrate the observed tool response We integrate the observed tool response with with Our geologic understanding of the formation Our geologic understanding of the formation

of interest. of interest. Core and ditch cutting samplesCore and ditch cutting samples Mud log observationsMud log observations All the other log measurements that respond All the other log measurements that respond

to lithology and porosity to obtain a to lithology and porosity to obtain a consistent & logical interpretationconsistent & logical interpretation

Biggest challenges facing Biggest challenges facing petrophysics in this decadepetrophysics in this decade #1 is people, people, people!#1 is people, people, people! Look around you. WeLook around you. Were not getting younger.re not getting younger. Largest potential pool of petrophysical talent will be Largest potential pool of petrophysical talent will be

the people retiring from big companies.the people retiring from big companies. Retirees donRetirees dont want to work in a traditional office or t want to work in a traditional office or

cubicle, 8cubicle, 8--5, commuting environment5, commuting environment Expect to see Expect to see micromicro--consultanciesconsultancies pop up in odd pop up in odd

places like Key West, Maui, places like Key West, Maui, TusconTuscon, etc., etc. We are working towards a virtual office concept We are working towards a virtual office concept

where our employees can be scattered around the where our employees can be scattered around the world, weworld, well provide the infrastructurell provide the infrastructure

ChallengesChallenges

#2 is also people!#2 is also people! Frankly, we donFrankly, we dont work together very well.t work together very well. Still an inherent tension in this industry Still an inherent tension in this industry

between engineers and geoscientists.between engineers and geoscientists. CrossCross--disciplinary training and even disciplinary training and even

understanding of what the other people are understanding of what the other people are doing remains weak.doing remains weak. There are HUGE gains to be made in how There are HUGE gains to be made in how

we interact and work together.we interact and work together.


#3 is permeability#3 is permeability Perm is the farthest property of interest from what Perm is the farthest property of interest from what

we can measure with wireline or LWD toolswe can measure with wireline or LWD tools Dynamic properties are difficult to determine from Dynamic properties are difficult to determine from

static measurementsstatic measurements Inherently vector quantity when we mostly take Inherently vector quantity when we mostly take

scalar, scalar, omniomni--directional directional measurmentsmeasurments Perm itself is poorly understood at the rock levelPerm itself is poorly understood at the rock level We donWe dont do too bad a job in sandstone reservoirs, t do too bad a job in sandstone reservoirs,

but carbonates and tight formations are toughbut carbonates and tight formations are tough


#4 is the evaluation of unconventional #4 is the evaluation of unconventional reservoirsreservoirs TodaysTodays seals, tomorrows reservoirsseals, tomorrows reservoirs WeWere producing re producing TCFTCFss of gas from rocks of gas from rocks

that are tighter than the seals over most that are tighter than the seals over most offshore fieldsoffshore fields Tight gas sands are difficult, but gas shales Tight gas sands are difficult, but gas shales

are a whole different ballgameare a whole different ballgame

What do we bring to the What do we bring to the party?party? Understanding of the underlying Understanding of the underlying

measurements & physicsmeasurements & physics wewere putting the physics back into re putting the physics back into PetrophysicsPetrophysics

Geologic expertise and our understanding of Geologic expertise and our understanding of the behavior of earth materialsthe behavior of earth materials Ability to work with diverse data collected over Ability to work with diverse data collected over

many years, bringing it together into as many years, bringing it together into as coherent a package as possiblecoherent a package as possible

What do we need What do we need back back fromfrom you?you? Ground truth.Ground truth. Integration of the static data with the Integration of the static data with the

dynamic data.dynamic data. Feedback to improve our models and Feedback to improve our models and

representations if they are not providing a representations if they are not providing a plausible reservoir description.plausible reservoir description. Help us sort out nonHelp us sort out non--unique answers.unique answers.

The role of the petrophysicist in reservoir characterization and the analysis of reservoir performance.What do we bring to thThe big 3 we all want to know.But these are what we really measure with logs..Role of the petrophysicistTwo faces of PetrophysicsElectron densityLoggingsondeElectron density vs. bulk densitySpine and ribs plotThe second face.Example: bulk density interpretationBulk density-density porosity plotPorosity computationDensity porosity solutionLog exampleSo what is it we do?Biggest challenges facing petrophysics in this decadeChallengesChallengesChallengesWhat do we bring to the party?What do we need back from you?

2007 SPE ATW on Reservoir Performance

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