Lithofacies and petrophysical properties of Mesaverde ... SPE-AAPG-SEG Tight gas sand... ·...
Transcript of Lithofacies and petrophysical properties of Mesaverde ... SPE-AAPG-SEG Tight gas sand... ·...
Lithofacies and petrophysicalproperties of Mesaverde tight-gas
sandstones in Western U.S. basins
Lithofacies and Lithofacies and petrophysicalpetrophysicalproperties of Mesaverde tightproperties of Mesaverde tight--gas gas
sandstones in Western U.S. sandstones in Western U.S. basinsbasins
Robert M. Cluff The Discovery Group, IncJohn C. Webb Daniel A. Krygowski Stefani D. Whittaker
Alan P. Byrnes KGS- now Chesapeake Energy
Robert M. Cluff The Discovery Group, IncJohn C. Webb Daniel A. Krygowski Stefani D. Whittaker
Alan P. Byrnes KGS- now Chesapeake Energy
2009 SPE/AAPG/SEG Workshop: From Macro to Micro – the description and analysis of tight gas sand reservoirs29-30 June 2009, Denver, CO
Project title:Analysis of Critical Permeability,
Capillary and Electrical Properties for Mesaverde Tight Gas Sandstones
from Western U.S. Basins
US DOE # DE-FC26-05NT42660US DOE # DE-FC26-05NT42660
Center for Research
website: http://www.kgs.ku.edu/mesaverdewebsite: http://www.kgs.ku.edu/mesaverde
Project objectivesProject objectivesprovide a large database of basic provide a large database of basic petrophysicalpetrophysicalproperties for TGS (properties for TGS (““the sandboxthe sandbox””), tied to ), tied to detailed lithofacies descriptionsdetailed lithofacies descriptionsinvestigate capillary pressure as function of NCS investigate capillary pressure as function of NCS and drainage vs. imbibition behaviorand drainage vs. imbibition behaviorinvestigate critical gas saturation and residual investigate critical gas saturation and residual gas saturationgas saturationinvestigate electrical properties, FRF, m, as investigate electrical properties, FRF, m, as f f ((φ, φ, salinity)salinity)provide it all as a webprovide it all as a web--accessible database accessible database (public domain data) (public domain data)
SamplingSampling
systematic systematic characterization of characterization of KmvKmv lithofacies over lithofacies over entire Rocky entire Rocky MtnMtnregionregion44 wells/6 basins44 wells/6 basinsDescribed 7000 ft Described 7000 ft core (digital)core (digital)2200 core samples2200 core samples120120--400 advanced 400 advanced properties samplesproperties samples
Green River
Wind River
Washakie
Piceance
PowderRiver
Uinta
Wyoming
Colorado
Utah
N
WhatWhat’’s in the sandbox?s in the sandbox?
core descriptions (digital, 0.5core descriptions (digital, 0.5’’ step) with LAS log step) with LAS log data filesdata filesthin section petrography (photos, point counts)thin section petrography (photos, point counts)basic core analysis (routine & 4000 basic core analysis (routine & 4000 psipsi NCS)NCS)
porosity, permeability, PV compressibility porosity, permeability, PV compressibility
Hg capillary pressure (150 unconfined, 90 at Hg capillary pressure (150 unconfined, 90 at NCS, and 37 scanning curves)NCS, and 37 scanning curves)Formation resistivity factor at 4 salinitiesFormation resistivity factor at 4 salinitiesCritical gas saturation at percolation thresholdCritical gas saturation at percolation threshold
Digital Core Digital Core DescriptionDescription
To provide To provide lithologiclithologic input to input to equations and predict lithology equations and predict lithology from logs used 5 digit systemfrom logs used 5 digit system
1 basic type (Ss, Ls, coal)1 basic type (Ss, Ls, coal)2 grain size/sorting/texture2 grain size/sorting/texture3 consolidation3 consolidation4 sedimentary structure4 sedimentary structure5 cement mineralogy5 cement mineralogy
Property continuum Property continuum -- not not mnemonic or substitution ciphermnemonic or substitution cipherSimilar to system used in 1994 Similar to system used in 1994 and subsequent studiesand subsequent studies
Core descriptionCore description
rock typing at 0.5 ft rock typing at 0.5 ft frequency to match log frequency to match log data resolutiondata resolutionlithology, color, grain lithology, color, grain size, size, sedsed structuresstructuressample locationssample locationsimportant cementsimportant cementsdepositional depositional environmentsenvironments
Williams PA 424, 6148.8’ 152769.9% 2.66 g/cc Ka=0.0237 mD
40X
100X
PetrographyPetrography~150 advanced ~150 advanced properties properties smplssmpls were were petrographicallypetrographicallycharacterizedcharacterizedrepresentative photos at representative photos at several magnificationsseveral magnificationspoint countspoint counts
Sample QA & Sample QA & distributionsdistributions
Petrophysical property distributions Petrophysical property distributions are generally normal or logare generally normal or log--normalnormalSubSub--distributions = distributions = ff (basin, (basin, lithofacies, marine/nonlithofacies, marine/non--marine, marine, etc.)
0
5
10
15
20
25
30
35
40
45
50
1E-7
- 1E
-6
1E-6
- 1E
-5
1E-5
- 1E
-4
0.00
01-0
.001
0.00
1-0.
01
0.01
-0.1
0.1-
1
1-10
10-1
00
100-
1,00
0
In situ Klinkenberg Permeability (mD)
Perc
ent o
f Pop
ulat
ion
(%)
AllGreen RiverPiceancePowder RiverSand WashUintahWind RiverWashakie
etc.)
0
10
20
30
40
50
60
2.58-2.60
2.60-2.62
2.62-2.64
2.64-2.66
2.66-2.68
2.68-2.70
2.70-2.72
2.72-2.74
Grain Density (g/cc)
Perc
ent o
f Bas
in P
opul
atio
n
Green RiverPiceancePowder RiverUintahWind RiverWashakieSand Wash
0
5
10
15
20
25
30
35
40
45
0-2
2-4
4-6
6-8
8-10
10-1
2
12-1
4
14-1
6
16-1
8
18-2
0
20-2
2
22-2
4
In situ Porosity (%)
Perc
ent o
f Pop
ulat
ion
(%)
AllGreen RiverPiceancePowder RiverSand WashUintahWind RiverWashakie
Permeability Permeability vsvs PorosityPorosityOverall trend allows prediction of Overall trend allows prediction of KKikik from porosity with 10X errorfrom porosity with 10X errorBreaking into two Breaking into two subtrendssubtrends at at φφ~12% improves to 5X error~12% improves to 5X errorDifferent Different kk--φφ trends among basins trends among basins Beyond common kBeyond common k↑↑ with grain sizewith grain size↑↑, , lithologiclithologic influence changes are influence changes are complex and nonlinearcomplex and nonlinear
0.0000001
0.000001
0.00001
0.0001
0.001
0.01
0.1
1
10
100
1000
0 2 4 6 8 10 12 14 16 18 20 22 24In situ calc Porosity (%)
Klin
kenb
erg
Perm
eabi
lity
(4,0
00 p
si, m
D)
Green RiverPiceancePowder RiverUintahWashakieWind RiverlogK=0.3Phi-3.7logK=0.3Phi-5.7
Pore Volume Pore Volume CompressibilityCompressibility
0.70
0.75
0.80
0.85
0.90
0.95
1.00
100 1000 10000
Confining Pressure (psi)
Frac
tion
ofPo
rosi
tyat
200
psi
y = 0.0060x + 0.03R2 = 0.59
0.00
0.05
0.10
0.15
0.20
0.25
0 2 4 6 8 10 12 14 16 18 20 22 24
Routine Helium Porosity (%)
Por
eVo
lum
eC
hang
eSl
ope
(-1/p
si)
y = 0.013x + 1.08R2 = 0.51
1.0
1.1
1.2
1.3
1.4
1.5
0 2 4 6 8 10 12 14 16 18 20 22 24
Routine Helium Porosity (%)Po
re V
olum
e C
hang
e In
terc
ept
(1/p
si)
Previously documented in literatureno large datasets in public domain113 SamplesLog-linear pore volume change seen in EVERY sample, avg. R2 = 0.99 characteristic of cracks/sheet-poresSlope and intercept increase with increasing porosity
Previously documented in literaturePreviously documented in literatureno large datasets in public domainno large datasets in public domain113 Samples113 SamplesLogLog--linear pore volume change seen in linear pore volume change seen in EVERY sample, avg. REVERY sample, avg. R22 = 0.99 = 0.99 characteristic of cracks/sheetcharacteristic of cracks/sheet--poresporesSlope and intercept increase with Slope and intercept increase with increasing porosity increasing porosity
Stress dependence of Stress dependence of permeabilitypermeability
WeWe’’ve known for many years ve known for many years that lowthat low--K sandstones are K sandstones are stress sensitivestress sensitive1997 Byrnes equation:1997 Byrnes equation:log log kkikik = 1.34 (log = 1.34 (log kkairair) ) -- 0.60.6this dataset n = 2062this dataset n = 2062Statistically similar except for Statistically similar except for k > 1 k > 1 mDmDno meaningful stress no meaningful stress dependence over 10 dependence over 10 mDmD
y = -0.0088x3 - 0.0716x2 + 1.3661x - 0.4574R2 = 0.9262
-7
-6
-5
-4
-3
-2
-1
0
1
2
3
-7 -6 -5 -4 -3 -2 -1 0 1 2 3log Routine Air Permeability Ppore = 100 psi (mD)
log
In s
itu K
linke
nber
g Pe
rmea
bilit
y (m
D)
This study:This study:log log kkikik = = --0.0088 (log k0.0088 (log kairair))33 -- 0.072 (log k0.072 (log kairair))2 2 + 1.37 log + 1.37 log kkairair -- 0.460.46
Capillary pressureCapillary pressureinvestigated Pc as investigated Pc as ff (lithology, (lithology, φφ, K), K)
120 high120 high--low pairslow pairssampled across basins, permeability range, & lithologysampled across basins, permeability range, & lithology
stress sensitivity of Pcstress sensitivity of Pcmost MICP curves are run under laboratory conditions, but given most MICP curves are run under laboratory conditions, but given stress dependence of permeability we expect Pc to also be stress dependence of permeability we expect Pc to also be stress sensitivestress sensitive
relationship between initial and residual nonrelationship between initial and residual non--wetting wetting phase saturations (phase saturations (““scanning curvesscanning curves””))
only published data are for conventional reservoir rocksonly published data are for conventional reservoir rocks
CapilaryCapilary Pressure MeasurementPressure Measurement
Three different airThree different air--Hg measurementsHg measurements
Unconfined (n=150)Unconfined (n=150)InIn--situ drainage only situ drainage only (n=90)(n=90)InIn--situ drainage situ drainage ––imbibition (n=37)imbibition (n=37)
•• NES = 4000 NES = 4000 psipsi
Res
ista
nce
Ref
eren
ceC
ell
high -Pcore holder
Cor
e P
lug
high-P fluid
mercury in
electricinsulator
Pressuretransducer
In situ Mercury Intrusion
high -Pcore holder
Cor
e Pl
ug
mercury in
Pressuretransducer
Unconfined (routine) Mercury Intrusion
Unconfined Unconfined Capillary Capillary Pressure
0 10 20 30 40 50 60 70 80 90 100
01000
20003000
40005000
60007000
80009000
10000
Air-Hg Capillary Pressure (psia)
Wetting Phase Saturation (%)
PressureCapillary pressure Capillary pressure varies with varies with lithofacies and lithofacies and associated pore size associated pore size distribution and distribution and permeabilitypermeability
Normalization:Normalization: LeverettLeverett J J FunctionFunction
J function works J function works poorly for mixed poorly for mixed lithofacies and lithofacies and between basinsbetween basinsDoes work OK Does work OK for single for single lithofacies in a lithofacies in a small areasmall areaWorks very well Works very well for a single for a single sample, stressed sample, stressed vs. unstressedvs. unstressed
0
1
2
3
4
5
6
7
8
9
0 10 20 30 40 50 60 70 80 90 100
Wetting Phase Saturation (%)
Leve
rett
J Fu
nctio
n
0.00025md0.00049md0.0012md0.0017md0.0018md0.0030md0.0040md0.0057md0.0085md0.012md0.013md0.032md0.046md0.085md0.25md0.41md0.56md0.84md2.24md
Stress effect on PcStress effect on Pc
1
10
100
1000
10000
0 10 20 30 40 50 60 70 80 90 100Wetting Phase Saturation (%)
Air
-Hg
Cap
illar
yPr
essu
re(p
sia)
R091255.9 ftk = 113 mD
= 24.5%φ
1
10
100
1000
10000
0 10 20 30 40 50 60 70 80 90 100Wetting Phase Saturation (%)
Air-
Hg
Cap
illar
yPr
essu
re(p
sia)
LD43C4013.25 ftk = 0.190 mD
= 12.9%φ
1
10
100
1000
10000
0 10 20 30 40 50 60 70 80 90 100Wetting Phase Saturation (%)
Air
-Hg
Capi
llary
Pres
sure
(psi
a)
PA4244606.5 ftk = 0.00107 mD
= 12.7%φ
1
10
100
1000
10000
0 10 20 30 40 50 60 70 80 90 100Wetting Phase Saturation (%)
Air-
Hg
Cap
illar
yP
ress
ure
(psi
a)R7802729.9 ftk = 7.96 mD
= 19.2%φ
1
10
100
1000
10000
0 10 20 30 40 50 60 70 80 90 100Wetting Phase Saturation (%)
Air
-Hg
Capi
llary
Pres
sure
(psi
a)
B02913672.5 ftk = 0.000065 mD
= 2.6%φ
1
10
100
1000
10000
0 10 20 30 40 50 60 70 80 90 100Wetting Phase Saturation (%)
Air
-Hg
Cap
illar
yPr
essu
re(p
sia)
B02911460.6 ftk = 0.0255 mD
= 4.4%φ
1
10
100
1000
10000
0 10 20 30 40 50 60 70 80 90 100Wetting Phase Saturation (%)
Air-
Hg
Cap
illar
yP
ress
ure
(psi
a)
E9466530.3 ftk = 0.0416 mD
= 9.5%φ
1
10
100
1000
10000
0 10 20 30 40 50 60 70 80 90 100Wetting Phase Saturation (%)
Air
-Hg
Cap
illar
yPr
essu
re(p
sia)
E9466486.4 ftk = 0.637 mD
= 12.2%φ
113 mD 8 mD
0.6 mD 0.2 mD
0.04 mD 0.02 mD
0.001 mD 0.00007 mD
no significant difference in no significant difference in highhigh--low pairs at high Klow pairs at high Kincreasing increasing PcePce separation separation with decreasing Kwith decreasing Kmerging of curves at 35merging of curves at 35--50% 50% SwSwusers of users of WinlandWinland R35 need R35 need to adjust for confining stressto adjust for confining stress
y = 11.77x0.50
R2 = 0.77
y = 11.28x0.50
R2 = 0.93
0.01
0.1
1
10
100
1E-06 0.00001 0.0001 0.001 0.01 0.1 1 10 100
Klinkenberg Permeability/Porosity (mD/%)
Thre
shol
dEn
try
Pore
Dia
met
er( µ
m)
A
y = 6.48x-0.50
R2 = 0.77
y = 6.75x-0.50
R2 = 0.93
1
10
100
1000
10000
1E-06 1E-05 0.0001 0.001 0.01 0.1 1 10 100
Klinkenberg Permeability/Porosity (mD/%)
Thre
shol
dEn
try
Gas
Col
umn
Hei
ght(
ft)
C
threshold entry threshold entry pressure is pressure is predictable from predictable from √√K/K/φφ at any at any confining pressureconfining pressurecorrect unconfined correct unconfined PcePce to to insituinsitu PcePcebased on perm based on perm change with change with stressstress
DrainageDrainage--Imbibition PcImbibition Pcwhat is the residual trapped gas when a reservoir what is the residual trapped gas when a reservoir leaks or is along a gas migration path?leaks or is along a gas migration path?
0.1
1
10
100
1000
10000
0 10 20 30 40 50 60 70 80 90 100
Wetting Phase Saturation (%)
App
rox.
Hei
ght a
bove
Fre
e W
ater
Le
vel (
ft)
Primary DrainageFirst ImbibitionSecondary DrainageSecond ImbibitionTertiary DrainageThird Imbibition
Trapping increases with Trapping increases with increasing initial saturationincreasing initial saturation
(after Lake 2005)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Initial Nonwetting Phase Saturation (Snwi)
Res
idua
l Non
wet
ting
Phas
e Sa
tura
tion
(Snw
r)
unconfinedconfinedLand C=0.66, Swi=0Land C =0.54, Swi=0
Residual Gas Residual Gas SaturationSaturation
1
10
100
1000
10000
0 10 20 30 40 50 60 70 80 90 100
Wetting Phase Saturation (%)
Air-
Hg
Cap
illar
yP
ress
ure
(psi
a)Primary DrainageFirst ImbibitionSecondary DrainageSecond ImbibitionTertiary DrainageThird Imbibition
E393 7001.1ft = 17.4% = 28.9 mD
φ
kik
1
10
100
1000
10000
0 10 20 30 40 50 60 70 80 90 100Wetting Phase Saturation (%)
Air-
Hg
Cap
illar
yP
ress
ure
(psi
a)
Primary DrainagePrimary ImbibitionSecond DrainageSecond ImbibitionThird DrainageThird Imbibition
B049 9072.1 ft (A) = 12.3% = 6.74 mD
φ
kik
1
10
100
1000
10000
0 10 20 30 40 50 60 70 80 90 100Wetting Phase Saturation (%)
Air-
Hg
Cap
illar
yPr
essu
re(p
sia)
Primary DrainagePrimary ImbibitionSecond DrainageSecond ImbibitionThird DrainageThird Imbibition
E393 7027.2 ft = 15.0% = 1.93 mD
φ
kik
1
10
100
1000
10000
0 10 20 30 40 50 60 70 80 90 100Wetting Phase Saturation (%)
Air
-Hg
Cap
illar
yP
ress
ure
(psi
a)
Primary DrainagePrimary ImbibitionSecond DrainageSecond ImbibitionThird DrainageThird Imbibition
R829 5618.3 ft (B) = 9.2% = 0.287 mD
φ
kik
1
10
100
1000
10000
0 10 20 30 40 50 60 70 80 90 100Wetting Phase Saturation (%)
Air
-Hg
Cap
illar
yP
ress
ure
(psi
a)
Primary DrainagePrimary ImbibitionSecond DrainageSecond ImbibitionThird DrainageThird Imbibition
B646 8294.4 ft (B) = 7.6% = 0.022 mD
φ
kik
1
10
100
1000
10000
0 10 20 30 40 50 60 70 80 90 100Wetting Phase Saturation (%)
Air
-Hg
Cap
illar
yP
ress
ure
(psi
a)
Primary DrainagePrimary ImbibitionSecond DrainageSecond ImbibitionThird DrainageThird Imbibition
S685 6991.2 ft (B) = 8.6% = 0.0063 mD
φ
kik
1
10
100
1000
10000
0 10 20 30 40 50 60 70 80 90 100Wetting Phase Saturation (%)
Air-
Hg
Cap
illar
yPr
essu
re(p
sia)
Primary DrainagePrimary ImbibitionSecond DrainageSecond ImbibitionThird DrainageThird Imbibition
E458 6404.8 ft (A) = 9.5% = 0.0019 mD
φ
kik
1
10
100
1000
10000
0 10 20 30 40 50 60 70 80 90 100Wetting Phase Saturation (%)
Air
-Hg
Cap
illar
yPr
essu
re(p
sia)
Primary DrainagePrimary ImbibitionSecond DrainageSecond ImbibitionThird DrainageThird Imbibition
KM360 8185.7 ft (B) = 5.9% = 0.00070 mD
φ
kik
•Land equation:C = 1/[(Snwr-Swi)-1/(Snwi-Swi)]Snwr = 1/[C + 1/Snwi]
• C ~ 0.54 to 0.66
•Land equation:C = 1/[(Snwr-Swi)-1/(Snwi-Swi)]Snwr = 1/[C + 1/Snwi]
• C ~ 0.54 to 0.66
DrainageDrainage--Imbibition PcImbibition Pcis this the answer to the is this the answer to the ““Pinedale problemPinedale problem”” we saw we saw earlier?earlier?
0.1
1
10
100
1000
10000
0 10 20 30 40 50 60 70 80 90 100
Wetting Phase Saturation (%)
App
rox.
Hei
ght a
bove
Fre
e W
ater
Le
vel (
ft)
Primary DrainageFirst ImbibitionSecondary DrainageSecond ImbibitionTertiary DrainageThird Imbibition
Mesaverde
U Lance
M-L Lance high NTG
Critical Gas SaturationCritical Gas SaturationExperimental work indicates Experimental work indicates Sgc < 10%, often < 5%Sgc < 10%, often < 5%butbut KrgKrg curves extrapolate curves extrapolate to 35% < Sgc < 10%to 35% < Sgc < 10%IssuesIssues
little krg data at Sw > 65%little krg data at Sw > 65%two different ways to model two different ways to model the data, which is better?the data, which is better?
0.00001
0.0001
0.001
0.01
0.1
1
0 10 20 30 40 50 60 70 80 90 100Water Saturation
Gas
Rel
ativ
e Pe
rmea
bilit
y
Critical Nonwetting Critical Nonwetting Phase SaturationPhase Saturation
Electrical conductivity and Pc inflection Electrical conductivity and Pc inflection indicate 0% < Sgc < 22%indicate 0% < Sgc < 22%Higher Sgc as bedding complexity increasesHigher Sgc as bedding complexity increases
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
0.22
0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000
In situ Klinkenberg Permeability (mD)
Crit
ical
Non
-wet
ting
Phas
e Sa
tura
tion
MICP-inflectionElectrical Resistance High Pressure Vessel
Oil Hgpositive
displacementpump
Hg
Highpressure
oilpump
Core
316 SSend caps
Rubbersleeve
VoltmeterV∆
Vacuum
Sgc and Sgc and percolation theorypercolation theory
experimental results can be experimental results can be explained using four explained using four -- pore pore network architecture modelsnetwork architecture models
critical gas saturation strongly critical gas saturation strongly controlled by sedimentary controlled by sedimentary structures/rock fabricstructures/rock fabricanyany bedding parallel bedding parallel laminations result in low Sgclaminations result in low Sgc
1) Percolation Network N ( ) - Macroscopically homogeneous, random distribution of bond sizes, e.g., Simple Cubic Network (z=6)
p
2) Parallel Network N
N
( ) preferential orientation of pore sizes or beds of different
networks parallel to the invasion direction.
II
p
Invasion direction
3) Series network N
N
( ) - preferential sample-spanning orientation of pore sizes or beds of different networks perpendicular to the invasion direction.
p
4) Discontinuous series network N
Np
N N
( ) - preferential non-sample-spanning orientation of pore sizes or beds of different networks perpendicular to the invasion direction. Represents continuum between and
d
p.
0
100
200
300
400
500
600
700
800
900
1000
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0Water Saturation
Gas
-Wat
erC
apill
ary
Pres
sure
(kPa
)
0.001 md0.1 md
AB
ArchieArchie’’s equations equation
Swn = (a / φ m) * (Rw / Rt )
completely empirical completely empirical –– no theoretical basisno theoretical basis““mm”” is the porosity or cementation exponentis the porosity or cementation exponent
generally considered related to generally considered related to ““tortuositytortuosity”” or length of the or length of the current flow path; better thought of as electrical efficiency ofcurrent flow path; better thought of as electrical efficiency of the the pathpath
““nn”” is the saturation exponentis the saturation exponentrelated to change in conductivity path with changing saturationrelated to change in conductivity path with changing saturation
Archie porosity exponentArchie porosity exponentfor a simple bundle of capillary tubes oriented for a simple bundle of capillary tubes oriented parallel to current flow direction: m parallel to current flow direction: m →→ 11
insensitive to cross section shape, so fractures will insensitive to cross section shape, so fractures will act like capillary tubesact like capillary tubes
as porosity increases there is more dead space as porosity increases there is more dead space outside the conductive path, so m outside the conductive path, so m ↑↑for an for an ““averageaverage”” sandstone comprised of sandstone comprised of spherical grains, m spherical grains, m →→ 22
Capillary tube model for mCapillary tube model for mm 1.0
> 1
~2
>> 2
m = 1
after Herrick & Kennedy, 1993, SPWLA Paper HH
When F and When F and φφ are plotted logare plotted log--loglog
1
10
100
1000
0.01 0.1 1
φ
m= 3m= 2
m= 1
log F = -m log φ
F
FRF vs. FRF vs. φφ for Mesaverdefor Mesaverde
1.0
10.0
100.0
1000.0
10000.0
0.10 1.00 10.00 100.00
porosity (%)
form
atio
n re
sist
ivity
fact
or
m = 2
m = 1
40K ppm dataset, n=310
Porosity dependence of mPorosity dependence of m
Empirical: Empirical: m = 0.676 log m = 0.676 log φφ + 1.22 + 1.22
RR22 = 0.63 (RMA)= 0.63 (RMA)limit m = 1.95 limit m = 1.95
no significant no significant increase above12% increase above12% porosityporosity
40K ppm brine data
1.0
1.2
1.4
1.6
1.8
2.0
2.2
0 4 8 12 16 20 24
In situ Porosity (%)
In s
itu A
rchi
e C
emen
taito
n Ex
pone
nt
behavior is contrary to behavior is contrary to expectations.....expectations.....
but only because we call it the but only because we call it the ““cementation cementation exponentexponent””
Shell equation for m
0.0
1.0
2.0
3.0
4.0
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35
porosity
"cem
entation
expon
ent"
m
after Neustaedter, 1968, SPE 2071
Dual porosity modelDual porosity modelm = log[m = log[φφ11
m1m1 + + φφ22m2m2]/log ]/log φφtt
φφ expressed as expressed as v/vv/vφφ22 = 0.0035, m1=2, m2=1; SE both = 0.11= 0.0035, m1=2, m2=1; SE both = 0.11rock behaves like a mixture of matrix porosity and cracks, rock behaves like a mixture of matrix porosity and cracks, with cracks dominating low porosity sampleswith cracks dominating low porosity samples
cap at m = 1.95 (cap at m = 1.95 (φφ ~ 16%)~ 16%)both models fit databoth models fit data
φφtt = total porosity, (= total porosity, (φφ11 + + φφ22))φφ11 = matrix porosity= matrix porositymm11 = matrix cementation = matrix cementation
exponentexponentφφ22 = fracture porosity= fracture porositymm22 = fracture cementation = fracture cementation
exponentexponent
40K ppm brine data
1.0
1.2
1.4
1.6
1.8
2.0
2.2
0 4 8 12 16 20 24
In situ Porosity (%)
In s
itu A
rchi
e C
emen
taito
n Ex
pone
nt
Archie porosity (cementation) exponentArchie porosity (cementation) exponentNearly all cores exhibit some salinity dependenceNearly all cores exhibit some salinity dependencetested plugs with 20K, 40K, 80K, and 200K tested plugs with 20K, 40K, 80K, and 200K ppmppm brinesbrines
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.1
2.2
2.3
0.01 0.1 1
Brine Resistivity (ohm-m)
In s
itu A
rchi
e C
emen
tatio
n Ex
pone
nt,
(m, A
=1)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0 2 4 6 8 10 12 14 16 18 20 22
Brine Conductivity (mho/m)
Cor
e C
ondu
ctiv
ity (m
ho/m
)
n=335
All data, all salinities All data, all salinities
0.80
1.00
1.20
1.40
1.60
1.80
2.00
2.20
2.40
0 2 4 6 8 10 12 14 16 18 20 22
In situ Porosity (%)
Arc
hie
Cem
enta
iton
Expo
nent
(m, a
=1)
200K
80K
40K
20K
Data, presentations and reports are Data, presentations and reports are on our project website:on our project website:
http://www.kgs.ku.edu/mesaverdehttp://www.kgs.ku.edu/mesaverde
also accessible viaalso accessible viahttp://www.discoveryhttp://www.discovery--group.comgroup.com
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