A Petrophysical Comparison of the Barnett and Woodford Shales Jeff Kane Bureau of Economic Geology PBGSP Annual Meeting February 26-27, 2007

Jeffrey A. Kane, Bureau of Economic Geology, PBGSP Annual Meeting, February 26-27, 2007 Overview Modeling the Barnett mineralogy – problems and solutionsModeling the Barnett mineralogy – problems and solutions A look at the Woodford – a compare and contrast approachA look at the Woodford – a compare and contrast approach Finish up – possible ramifications of the differencesFinish up – possible ramifications of the differences

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

Jeffrey A. Kane, Bureau of Economic Geology, PBGSP Annual Meeting, February 26-27, 2007 Constituents of the Barnett – Kerogen weight fraction estimation (from Guidry and Olszewski, 1990) where: W k is the weight fraction of kerogen in the sample TOC is the weight fraction of total organic carbon in the sample S 1 is the weight fraction of free oil in the rock sample C S 1 is the weight fraction of carbon in the free oil andC k is the weight fraction of carbon in the kerogen Guidry and Olszewski (1990) suggest 0.87 and 0.75 for C S 1 and C k respectively. Jarvie (1999) recommends a value of 0.83 for C S 1.

Jeffrey A. Kane, Bureau of Economic Geology, PBGSP Annual Meeting, February 26-27, 2007 Log response – Log models work in volume fractions where: V i is the volume fraction of constituent i W i is the weight fraction of constituent i  B is the bulk density  i is the density of constituent i

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

Jeffrey A. Kane, Bureau of Economic Geology, PBGSP Annual Meeting, February 26-27, 2007 Constituents of the Barnett – XRD data (volume %) Data from 64 samples with the exception of 35 samples for siderite and 325 samples for Kerogen/TOC.

Jeffrey A. Kane, Bureau of Economic Geology, PBGSP Annual Meeting, February 26-27, 2007 Log response – Kerogen KerogenKerogen Density about 1 to 1.2 gm/cc; however probably more variable than this range suggests (Density about 1 to 1.2 gm/cc; however probably more variable than this range suggests (Guidry and Olszewski, 1990; Jarvie, personal communication; Mendelson and Toksöz, 1985) Modeling work suggests that 1 gm/cc works reasonably well

Jeffrey A. Kane, Bureau of Economic Geology, PBGSP Annual Meeting, February 26-27, 2007 Log response – Kerogen KerogenKerogen Has a hydrogen index of 0.65 to 0.8 (with water having a hydrogen index of 1.0) (Has a hydrogen index of 0.65 to 0.8 (with water having a hydrogen index of 1.0) (Mendelson and Toksöz, 1985) Again modeling work shows a value of 0.8 works reasonably wellAgain modeling work shows a value of 0.8 works reasonably well Does not conduct electricityDoes not conduct electricity The organic material responsible for kerogen also tends to fix uranium during depositionThe organic material responsible for kerogen also tends to fix uranium during deposition

Jeffrey A. Kane, Bureau of Economic Geology, PBGSP Annual Meeting, February 26-27, 2007 Estimation of Kerogen from log data (uranium) – Blakely #1

Jeffrey A. Kane, Bureau of Economic Geology, PBGSP Annual Meeting, February 26-27, 2007 Blakely #1

Jeffrey A. Kane, Bureau of Economic Geology, PBGSP Annual Meeting, February 26-27, 2007 Estimation of Kerogen from log data (total gamma ray) – Blakely #1

Jeffrey A. Kane, Bureau of Economic Geology, PBGSP Annual Meeting, February 26-27, 2007 Log response – Pyrite PyritePyrite Density (RHOB) reads 5.0 gm/ccDensity (RHOB) reads 5.0 gm/cc 1% pyrite shifts density log by about gm/cc (Clavier and others, 1976)1% pyrite shifts density log by about gm/cc (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.) reads -2% in pure pyriteThe thermal neutron log (NPHI, CNC, etc.) reads -2% in pure pyrite Appears to vary with porosity (Clavier and others, 1976)Appears to vary with porosity (Clavier and others, 1976)

Jeffrey A. Kane, Bureau of Economic Geology, PBGSP Annual Meeting, February 26-27, 2007 Log response – Pyrite PyritePyrite The resistivity of pyrite ranges from ohmmThe resistivity of pyrite ranges from ohmm The affect on logs varies with measurement frequency (induction logs are more affected than laterologs) and distribution in the rockThe affect on logs varies with measurement frequency (induction logs are more affected than laterologs) and distribution in the rock As little as 3% pyrite by volume can cause a reduction of 50% in the measured resistivity for an induction log (Clavier and others, 1976)As little as 3% pyrite by volume can cause a reduction of 50% in the measured resistivity for an induction log (Clavier and others, 1976) Fortunately it doesn’t affect the gamma rayFortunately it doesn’t affect the gamma ray

Jeffrey A. Kane, Bureau of Economic Geology, PBGSP Annual Meeting, February 26-27, 2007 Log response – Pyrite (T.P. Sims #2)

Jeffrey A. Kane, Bureau of Economic Geology, PBGSP Annual Meeting, February 26-27, 2007 Constituents of the Barnett – XRD data (volume %) Data from 64 samples with the exception of 35 samples for siderite and 325 samples for Kerogen/TOC.

Jeffrey A. Kane, Bureau of Economic Geology, PBGSP Annual Meeting, February 26-27, 2007 Constituents of the Barnett – XRD data (model volume %) Data from 64 samples with the exception of 35 samples for siderite and 325 samples for Kerogen/TOC.

Jeffrey A. Kane, Bureau of Economic Geology, PBGSP Annual Meeting, February 26-27, 2007 Petrophysical modeling - T. P. Sims #2

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

Jeffrey A. Kane, Bureau of Economic Geology, PBGSP Annual Meeting, February 26-27, 2007 To review A reasonable compositional model is available for the Barnett accounting for the presence of kerogen, pyrite, non-clay silicates, carbonate material and clay.A reasonable compositional model is available for the Barnett accounting for the presence of kerogen, pyrite, non-clay silicates, carbonate material and clay. It requires at a minimum, gamma ray, compressional sonic, neutron, density, PEF, and resistivity logs.It requires at a minimum, gamma ray, compressional sonic, neutron, density, PEF, and resistivity logs. Sufficient information to derive a direct relationship between kerogen volume and log data (i.e. GR) is necessary for model stabilitySufficient information to derive a direct relationship between kerogen volume and log data (i.e. GR) is necessary for model stability The analysis can be enhanced with the inclusion of a spectral gamma rayThe analysis can be enhanced with the inclusion of a spectral gamma ray

Jeffrey A. Kane, Bureau of Economic Geology, PBGSP Annual Meeting, February 26-27, 2007 Constituents of the Barnett – XRD data (volume %) Data from 64 samples with the exception of 35 samples for siderite and 325 samples for Kerogen/TOC. 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

Jeffrey A. Kane, Bureau of Economic Geology, PBGSP Annual Meeting, February 26-27, 2007 Uranium content – Barnett and Woodford Uranium (ppm) distribution in Barnett (Blakely #1) Uranium (ppm) distribution in Woodford (CBP)

Jeffrey A. Kane, Bureau of Economic Geology, PBGSP Annual Meeting, February 26-27, 2007 Uranium distribution – Barnett - Pervasive (more or less) – Blakely #1

Jeffrey A. Kane, Bureau of Economic Geology, PBGSP Annual Meeting, February 26-27, 2007 Uranium distribution – Woodford – Stratigraphic controls? - CBP

Jeffrey A. Kane, Bureau of Economic Geology, PBGSP Annual Meeting, February 26-27, 2007 To conclude A reasonable compositional model is available for the Barnett accounting for the presence of kerogen, pyrite, non-clay silicates, carbonate material and clay.A reasonable compositional model is available for the Barnett accounting for the presence of kerogen, pyrite, non-clay silicates, carbonate material and clay. This model appears to also work in the Woodford with differing clay parameters (illite-corensite vs. illite-smectite).This model appears to also work in the Woodford with differing clay parameters (illite-corensite vs. illite-smectite). It requires at a minimum, gamma ray, compressional sonic, neutron, density, PEF, and resistivity logs.It requires at a minimum, gamma ray, compressional sonic, neutron, density, PEF, and resistivity logs. Sufficient information to derive a direct relationship between kerogen volume and log data (i.e. GR) is necessary for model stability. Such a relationship exists in the Barnett and can be assumed to exist in the Woodford.Sufficient information to derive a direct relationship between kerogen volume and log data (i.e. GR) is necessary for model stability. Such a relationship exists in the Barnett and can be assumed to exist in the Woodford. The analysis can be enhanced with the inclusion of a spectral gamma ray in the log suite.The analysis can be enhanced with the inclusion of a spectral gamma ray in the log suite. Better kerogen estimation and better stratigraphic correlationBetter kerogen estimation and better stratigraphic correlation

Jeffrey A. Kane, Bureau of Economic Geology, PBGSP Annual Meeting, February 26-27, 2007 To conclude The Woodford has about 50% more clay per unit volume than the Barnett. This will affect the mechanical properties and probably means that frac jobs will be less efficient in the Woodford with respect to the BarnettThe Woodford has about 50% more clay per unit volume than the Barnett. This will affect the mechanical properties and probably means that frac jobs will be less efficient in the Woodford with respect to the Barnett This invites an area of investigation involving mechanical properties in the two formations (subtle hint for shear sonic data)This invites an area of investigation involving mechanical properties in the two formations (subtle hint for shear sonic data) The Woodford also has about half the kerogen per unit volume than the Barnett. Pressure and temperature arguments aside, this will lower the gas in place numbers with respect to the Barnett.The Woodford also has about half the kerogen per unit volume than the Barnett. Pressure and temperature arguments aside, this will lower the gas in place numbers with respect to the Barnett. The kerogen distribution in the Woodford appears to have stronger stratigraphic controls on it than in the BarnettThe kerogen distribution in the Woodford appears to have stronger stratigraphic controls on it than in the Barnett