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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..
PorosityPorosityPermeabilityPermeabilityFluid 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 bedsElectrical conductivityElectrical conductivityNatural gamma ray radiationNatural gamma ray radiationNeutron slowing down lengthNeutron slowing down lengthThermal neutron capture cross Thermal neutron capture cross sectonsectonSpeed of soundSpeed of soundElectron density from gamma ray scatteringElectron density from gamma ray scatteringGamma ray photoelectric absorptionGamma ray photoelectric absorptionNuclear magnetic resonance relaxation timeNuclear magnetic resonance relaxation timejust 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 scienceWhat 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 measurementEngineering how to make the measurement Engineering how to make the measurement in a dark, noisy, dirty in a dark, noisy, dirty downholedownhole enviromentenviromentConverting 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)
bulk
den
sity
(g/c
3)
water
quartz
dolomite
pyrite
coal
limestone
Spine and ribs plotSpine and ribs plot
The second faceThe second face..
Interpretation scienceInterpretation scienceInterpreting 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 densitydetermine hydrocarbon saturation from electrical determine hydrocarbon saturation from electrical conductivity and porosityconductivity and porosity
Interpretation model developmentInterpretation model developmentIntegration 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 densityRhoBRhoB = measured bulk density= measured bulk densityRhoFlRhoFl = 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
3.0
2.9
2.8
2.7
2.6
2.5
2.4
2.3
2.2
2.1
2.0
1.9
Den
sity
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
15
20
25
30
35
40
Limest
one
0
5
10
15
20
25
30
35
40
45
Sandst
one
0
5
10
15
20
25
30
35
40
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
32.
92.
82.
72.
62.
52.
42.
32.
22.
12
1.9
Den
sity
Schlumberger Chartbook (1991) p.38
Dolom
ite
0
5
10
15
20
25
30
35
Limest
one
0
5
1015
2025
3035
4045
Sandst
one
0
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)
32.
92.
82.
72.
62.
52.
42.
32.
22.
12
1.9
1.8
Den
sity
Schlumberger Chartbook (1991) p.44
Time Average
Dolom
ite
0
10
20
30
40
Sand
stone
0
10
20
30
40
Limest
one
0
10
20
30
40
Sulfer
Sylvite
SaltTrona
Gypsum
Polyhalite
Anhydrite
Schlumberger Chartbook (1991) p.44
Field Observation
Dolom
ite
0
10
20
40
Sand
stone0
10
2030
Limest
one
0
10
20
30
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
4050
6070
8090
100
110
Soni
c Tr
ansi
t Tim
e (u
s/ft)
Schlumberger Chartbook (1991) p.42
Time Average
Dolom
ite
0
5
10
15
20
25
30
35
Limest
one
0
5
10
15
20
25
30
35
40
Sand
stone
0
5
10
15
20
25
30
35
40
Salt
Anhy
drite
Schlumberger Chartbook (1991) p.42
Field Observation
Dolom
ite
05
10
15
20
25
30
35
Limest
one
05
10
15
20
25
30
35
Sand
stone
0
5
10
15
20
25
30
Salt
Anhy
drite
Shale Point
0 1 2 3 4 5 6Pe [N/A]
32.
92.
82.
72.
62.
52.
42.
32.
22.
12
1.9
Den
sity
Schlumberger Chartbook (1991) p.64
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 samplesMud log observationsMud log observationsAll 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 environmentExpect 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.
ChallengesChallenges
#3 is permeability#3 is permeabilityPerm 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 toolsDynamic properties are difficult to determine from Dynamic properties are difficult to determine from static measurementsstatic measurementsInherently vector quantity when we mostly take Inherently vector quantity when we mostly take scalar, scalar, omniomni--directional directional measurmentsmeasurmentsPerm itself is poorly understood at the rock levelPerm itself is poorly understood at the rock levelWe 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
ChallengesChallenges
#4 is the evaluation of unconventional #4 is the evaluation of unconventional reservoirsreservoirs
TodaysTodays seals, tomorrows reservoirsseals, tomorrows reservoirsWeWere 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 fieldsTight 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 materialsAbility 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?