a petrophysical comparison of the barnett and woodford shales jeff kane bureau of economic geology...

A Petrophysical Comparison of the A Petrophysical Comparison of the Barnett and Woodford ShalesBarnett and Woodford Shales

Jeff KaneJeff Kane

Bureau of Economic GeologyBureau of Economic Geology

PBGSP Annual MeetingPBGSP Annual Meeting

February 26-27, 2007February 26-27, 2007

Jeffrey A. Kane, Bureau of Economic Geology ,Jeffrey A. Kane, Bureau of Economic Geology , PBGSP Annual Meeting, February 26-27, 2007PBGSP Annual Meeting, February 26-27, 2007

OverviewOverview

• Modeling the Barnett mineralogy – Modeling the Barnett mineralogy – problems and solutionsproblems and solutions

• A look at the Woodford – a compare and A look at the Woodford – a compare and contrast approachcontrast approach

• Finish up – possible ramifications of the Finish up – possible ramifications of the differencesdifferences


Constituents of the Barnett – XRD data (weight %)Constituents of the Barnett – XRD data (weight %)

Data from 64 samples with the exception of 35 samples for siderite and 325 samples for Kerogen/TOC.


Constituents of the Barnett – Kerogen weight fraction estimationConstituents of the Barnett – Kerogen weight fraction estimation

k

Sk C

CSTOCW

)(11

(from Guidry and Olszewski, 1990) where:Wk is the weight fraction of kerogen in the sampleTOC is the weight fraction of total organic carbon in the sampleS1 is the weight fraction of free oil in the rock sampleCS1

is the weight fraction of carbon in the free oil

and Ck is the weight fraction of carbon in the kerogen

Guidry and Olszewski (1990) suggest 0.87 and 0.75 for CS1 and Ck

respectively. Jarvie (1999) recommends a value of 0.83 for CS1.


Log response – Log models work in volume fractionsLog response – Log models work in volume fractions

where:Vi is the volume fraction of constituent iWi is the weight fraction of constituent i B is the bulk densityi is the density of constituent i

i

Bii

WV


Constituents of the Barnett – XRD data (weight %)Constituents of the Barnett – XRD data (weight %)



Constituents of the Barnett – XRD data (volume %)Constituents of the Barnett – XRD data (volume %)



Log response – KerogenLog response – Kerogen

• KerogenKerogen• Density about 1 to 1.2 gm/cc; however Density about 1 to 1.2 gm/cc; however

probably more variable than this range probably more variable than this range suggests (suggests (Guidry and Olszewski, 1990; Jarvie, personal communication; Mendelson and Toksöz, 1985)

• Modeling work suggests that 1 gm/cc works reasonably well


Log response – KerogenLog response – Kerogen

• KerogenKerogen• Has a hydrogen index of 0.65 to 0.8 (with Has a hydrogen index of 0.65 to 0.8 (with

water having a hydrogen index of 1.0) water having a hydrogen index of 1.0) ((Mendelson and Toksöz, 1985)

• Again modeling work shows a value of 0.8 Again modeling work shows a value of 0.8 works reasonably wellworks reasonably well

• Does not conduct electricityDoes not conduct electricity• The organic material responsible for kerogen The organic material responsible for kerogen

also tends to fix uranium during depositionalso tends to fix uranium during deposition


Estimation of Kerogen from log data (uranium) – Blakely #1Estimation of Kerogen from log data (uranium) – Blakely #1

0.0

3.0

6.0

9.0

12.0

15.0

0.0

4.0

8.0

12.0

16.0

20.0

Ker

ogen

(vo

l. %

)

Uranium (PPM)


Blakely #1Blakely #1

Total gamma RayGAPI0 300

7100

7200

7300

7400

Depthfeet

Thorium - Potassium Ratio (smoothed)0.5 50


Estimation of Kerogen from log data (total gamma ray) – Blakely #1Estimation of Kerogen from log data (total gamma ray) – Blakely #1

0

50

100

150

200

250

0.0

4.0

8.0

12.0

16.0

20.0

Ker

ogen

(vo

l. %

)

Gamma Ray (GAPI)


Log response – PyriteLog response – Pyrite

• PyritePyrite• Density (RHOB) reads 5.0 gm/ccDensity (RHOB) reads 5.0 gm/cc

• 1% pyrite shifts density log by about 0.023 gm/cc 1% pyrite shifts density log by about 0.023 gm/cc (Clavier and others, 1976)(Clavier and others, 1976)

• The photoelectric factor (PEF) reads 17 b/eThe photoelectric factor (PEF) reads 17 b/e• The thermal neutron log (NPHI, CNC, etc.) The thermal neutron log (NPHI, CNC, etc.)

reads -2% in pure pyritereads -2% in pure pyrite• Appears to vary with porosity (Clavier and others, Appears to vary with porosity (Clavier and others,

1976) 1976)


Log response – PyriteLog response – Pyrite

• PyritePyrite• The resistivity of pyrite ranges from 0.00001 - The resistivity of pyrite ranges from 0.00001 -

0.8 ohmm0.8 ohmm• The affect on logs varies with measurement The affect on logs varies with measurement

frequency (induction logs are more affected than frequency (induction logs are more affected than laterologs) and distribution in the rocklaterologs) and distribution in the rock

• As little as 3% pyrite by volume can cause a As little as 3% pyrite by volume can cause a reduction of 50% in the measured resistivity for an reduction of 50% in the measured resistivity for an induction log (Clavier and others, 1976)induction log (Clavier and others, 1976)

• Fortunately it doesn’t affect the gamma ray Fortunately it doesn’t affect the gamma ray


Log response – Pyrite (T.P. Sims #2)Log response – Pyrite (T.P. Sims #2)

CaliperIN6 16

Gamma rayGAPI0 300

7900

DEPTHFEET

Neutron porosityV/V0.3 -0.1

Bulk densityG/C32 3

PEFB/E0 10

Spherically focussed logOHMM0.2 2000

Medium inductionOHMM0.2 2000

Deep inductionOHMM0.2 2000


Constituents of the Barnett – XRD data (model volume %)Constituents of the Barnett – XRD data (model volume %)



Petrophysical modeling - T. P. Sims #2Petrophysical modeling - T. P. Sims #2

7400

7500

7600

7700

7800

DEPTHFEET

CaliperIN6 16

Gamma rayGAPI0 200

Bulk densityG/C32 3


Delta transit timeUS/F100 40

PEFB/E0 10

Deep inductionOHMM0.2 2000

Medium inductionOHMM0.2 2000

Spherically focussed logOHMM0.2 2000

Quartz

Calcite

Clay

Pyrite

Clay BoundWater

Kerogen


Constituents of the Barnett – XRD data (model volume %)Constituents of the Barnett – XRD data (model volume %)

XRD data from 64 samples with the exception of 35 samples for siderite and 325 samples for Kerogen/TOC.

Constituents of the Barnett – XRD and log derived data (model volume %)Constituents of the Barnett – XRD and log derived data (model volume %)

XRD data from 64 samples with the exception of 35 samples for siderite and 325 samples for Kerogen/TOC.Log data from entire Barnett interval of T. P. Sims #2


To reviewTo review

• A reasonable compositional model is available A reasonable compositional model is available for the Barnett accounting for the presence of for the Barnett accounting for the presence of kerogen, pyrite, non-clay silicates, carbonate kerogen, pyrite, non-clay silicates, carbonate material and clay.material and clay.

• It requires at a minimum, gamma ray, It requires at a minimum, gamma ray, compressional sonic, neutron, density, PEF, and compressional sonic, neutron, density, PEF, and resistivity logs.resistivity logs.• Sufficient information to derive a direct relationship Sufficient information to derive a direct relationship

between kerogen volume and log data (i.e. GR) is between kerogen volume and log data (i.e. GR) is necessary for model stabilitynecessary for model stability

• The analysis can be enhanced with the inclusion The analysis can be enhanced with the inclusion of a spectral gamma rayof a spectral gamma ray




Comparison of the Barnet and Woodford – XRD data (volume %)Comparison of the Barnet and Woodford – XRD data (volume %)

Barnett data from 64 samples with the exception of 35 samples for siderite and 325 samples for Kerogen/TOC.Woodford data from 49 samples with the exception of 106 samples for Kerogen/TOC


Uranium content – Barnett and WoodfordUranium content – Barnett and Woodford

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0

10 20 30 40 50 60

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0

10 20 30 40 50 60

Uranium (ppm) distributionin Barnett (Blakely #1)

Uranium (ppm) distributionin Woodford (CBP)


Uranium distribution – Barnett - Pervasive (more or less) – Blakely #1Uranium distribution – Barnett - Pervasive (more or less) – Blakely #1

U-free gamma rayGAPI0 600

Total gamma rayGAPI0 600

7100

7200

7300

7400

DEPTHFEET

UraniumPPM0 60


Bulk densityG/C32 3

PEFB/E0 10

Shallow resistivityOHMM0.2 2000

Medium resistivityOHMM0.2 2000

Deep resistivityOHMM0.2 2000


Uranium distribution – Woodford – Stratigraphic controls? - CBPUranium distribution – Woodford – Stratigraphic controls? - CBP

U-free gamma rayGAPI0 600

Total gamma rayGAPI0 600

7800

7900

8000

8100

8200

DEPTHFEET

UraniumPPM0 60


Bulk densityG/C32 3

PEFB/E0 10

Shallow resistivityOHMM0.2 2000

Medium resistivityOHMM0.2 2000

Deep resistivityOHMM0.2 2000


To concludeTo conclude

• A reasonable compositional model is available for the A reasonable compositional model is available for the Barnett accounting for the presence of kerogen, pyrite, Barnett accounting for the presence of kerogen, pyrite, non-clay silicates, carbonate material and clay.non-clay silicates, carbonate material and clay.• This model appears to also work in the Woodford with differing This model appears to also work in the Woodford with differing

clay parameters (illite-corensite vs. illite-smectite).clay parameters (illite-corensite vs. illite-smectite).

• It requires at a minimum, gamma ray, compressional It requires at a minimum, gamma ray, compressional sonic, neutron, density, PEF, and resistivity logs.sonic, neutron, density, PEF, and resistivity logs.• Sufficient information to derive a direct relationship between Sufficient information to derive a direct relationship between

kerogen volume and log data (i.e. GR) is necessary for model kerogen volume and log data (i.e. GR) is necessary for model stability. Such a relationship exists in the Barnett and can be stability. Such a relationship exists in the Barnett and can be assumed to exist in the Woodford.assumed to exist in the Woodford.

• The analysis can be enhanced with the inclusion of a The analysis can be enhanced with the inclusion of a spectral gamma ray in the log suite.spectral gamma ray in the log suite.• Better kerogen estimation and better stratigraphic correlationBetter kerogen estimation and better stratigraphic correlation


To concludeTo conclude

• The Woodford has about 50% more clay per unit volume The Woodford has about 50% more clay per unit volume than the Barnett. This will affect the mechanical than the Barnett. This will affect the mechanical properties and probably means that frac jobs will be less properties and probably means that frac jobs will be less efficient in the Woodford with respect to the Barnettefficient in the Woodford with respect to the Barnett• This invites an area of investigation involving mechanical This invites an area of investigation involving mechanical

properties in the two formations (subtle hint for shear sonic data)properties in the two formations (subtle hint for shear sonic data)

• The Woodford also has about half the kerogen per unit The Woodford also has about half the kerogen per unit volume than the Barnett. Pressure and temperature volume than the Barnett. Pressure and temperature arguments aside, this will lower the gas in place numbers arguments aside, this will lower the gas in place numbers with respect to the Barnett.with respect to the Barnett.• The kerogen distribution in the Woodford appears to have The kerogen distribution in the Woodford appears to have

stronger stratigraphic controls on it than in the Barnettstronger stratigraphic controls on it than in the Barnett

a petrophysical comparison of the barnett and woodford shales jeff kane bureau of economic geology...

Documents

rnett constituents

barnett vol

barnett xrd data weight

rnett wt

barnett mineralogy problems

possible ramifications

contrast approachfinish

petrophysical comparison