Log Analysis Using Microsoft Excel

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Log AnalysisUsing Microsoft ExcelFocus on the
Marcellus

• Tim Carr
• West Virginia University

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My Observations
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Background

• Costs Are Becoming More Significant
• High Land Costs
• More Moderate Commodity Price
• High Capital Costs
• Horizontal Wells Large Multi-Stage Fracture
  Stimulations
• Key Reservoir Parameters
• Thickness
• Unit Definitions (Formation ? Bed)
• Lithology
• Thermal Maturity
• Total Organic Carbon (TOC)
• Gas Fraction (Adsorbed and Free)
• Permeability

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AVERAGE WELL HEAD PRICE

• 2.95 per MMBtu 2002
• 6.25 per MMBtu 2007
• 7.96 per MMBtu 2008
• 3.71 per MMBtu 2009
• 4.33 per MMBtu 2010
• 4.04 per MM Btu on 11/16/2010
• EIA (http//www.eia.gov )

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Recent Growth in Natural Gas Production, Lower 48
States, Attributed Largely to Unconventional Gas
(EIA, 2010)
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Natural Gas Supply by source, 1990-2030
(trillion cubic feet)
History
Projection
Unconventional
Alaska
Net imports
Non-associated offshore
Associated-dissolved
Non-associated conventional
Source Energy Information Administration, Annual
Energy Outlook 2009
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Marcellus Shale Resource
Marcellus Resource
U.S. Resources1 2,080 Tcf
U.S. Proved Reserves2 244 Tcf
Marcellus Shale Resource3 256 Tcf
Annual U.S. Consumption 23 Tcf
1 Potential Gas Committee, June 18, 2009 2 U.S.
Energy Information Administration 3 Marcellus
Proved Reserves lt 1 Tcf
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Marcellus Shale Production Forecasts
Sources An Emerging Giant Prospects and
Economic Impacts of Developing the Marcellus
Shale Natural Gas Play. T. Considine, R. Watson,
R. Entler, J. Sparks, The Pennsylvania State
University, College of Earth Mineral Sciences,
Department of Energy and Mineral Engineering.
July 24, 2009. Integrated Resource Plan for
Connecticut. The Brattle Group. January 1, 2010.
(Wood Mackenzie)
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Marcellus Shale Production Outlook
Source Williams Partners L.P.
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Unconventional Resource Production Technology,
Economies of Scale, Integration
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Unconventional Resource Production Technology,
Economies of Scale, Integration
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Gas Shale Characteristics

• Very High Gamma Ray Activity (Kerogen Content)
• High Uranium
• High Resistivity Low Water Saturation
• Relatively Low Clay Content
• Smectite to Illite Transition
• Low Bulk Density (Kerogen Content)
• Kerogen - Petrophysical Characteristics
• Bulk Density 1.0 to 1.2 g/cm3
• U 0.18 to 0.24
• Neutron Porosity 50 to 65 p.u.
• Gamma Ray Activity 500 to 4000 API
• Sonic Slowness 160 µs/ft

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Three Approaches

• Logs to be used
• Bulk Density g/cm3
• Density Porosity Percent or Decimal
• Neutron Porosity Percent or Decimal
• Photo-Electric Barns
• Gamma Ray API Units
• Clay Typing Related to Deposition Diagensis
• Spectral Gamma Ray Logs
• Uranium (PPM), Thorium (PPM) and Potassium
  (Percent)
• Compositional Lithology Logs
• Rhomaa-Umaa
• Computational Analysis (Linear)

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Spreadsheets

• Ubiquitous and Low Cost
• Provide Some Hands-On Understanding of the
  Process
• Allow Easy Export to Higher End Packages
• Use Basic Logs
• Clay Typing
• Estimate Uranium Content from Full Spectrum
  Gamma-Ray Logs
• Compositional Lithology Logs
• Rhomaa-Umaa
• Computational Analysis (Linear)
• Organic Content (Next Time)
• Saturation (Next Time)
• Heavily Modified Archie

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Gamma-Ray Log Analysis
U
Th
K
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Gamma-Ray Spectrum
Uranium
Thorium
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Gamma-Ray Spectrum
Schlumberger Log Interpretation Principles 1989,
Page 3-7
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Geochemists concept of typical shale and black
shale
North American Shale Composite (NASC) Gromet et
al. (1984) Th 12.3 ppm, U 2.66 ppm, K 3.2
GR 121.7 API units
Black Shale Composite (BSC) Quinby-Hunt et al.
(1989) Th 11.6 ppm, U 15.2 ppm, K 2.99
GR 215.8 API units
API unit multipliers Th ppm 4 U ppm 8 K
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Typical Spectral Gamma-Ray Log Presentation
Format
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Potassium-Thorium Crossplot with Generalized
Mineral Fields (after Schlumberger)
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Potassium-Thorium Crossplot with Generalized
Mineral Fields (after Schlumberger)
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Thorium and Uranium ConcentrationandRedox
Potential
Adams and Weaver (1958)
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Gamma-Ray and Spectral Ratio LogsPermian
Cretaceous Central Kansas
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Photo-Electric and Spectral Gamma Ray
Schlumberger, Log Interpretation Principles 1989,
Page 6-4
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Photo-Electric and Spectral Gamma Ray
Schlumberger, Log Interpretation Principles 1989,
Page 6-4
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Idealized Kansas Pennsylvanian Cyclothem
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Spectral Gamma-Ray Log Lansing Group, Wabaunsee
County, Kansas
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Chestnut Drive Section Spectral Gamma Ray Response
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Devonian Shale Analysis
Harrell
Tully
Mahantango
Marcellus
Onondaga
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Devonian Shale Oxidizing and Reducing Conditions

• Reducing Vs. Oxidizing conditions determined by
  Th/U

Oxidizing
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Devonian Shale Clay Type

• Clay type can be determined from Th/K
• Illite-Pink
• Smectite-Green
• Illite can increase porosity by 4

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Wells 1 3
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Wells 1 3
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Well 2
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Project 1
http//www.geo.wvu.edu/tcarr/PTTC_11_2010

• Make sure you open an LAS File with Notepad
• Import a LAS File to EXCEL
• Well 3.LAS
• Open Spectral Gamma Ray Template
• Well 1.LAS
• Marcellus (7375-7562)
• Well 2.LAS
• Marcellus (7359-7501)
• Create Examine Plots
• What is the difference in the two wells

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Open with Notepad
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Importing a LAS File to EXCEL
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Importing a LAS File to EXCEL
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Importing a LAS File to EXCEL
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Introduction to Porosity Logs

• Porosity Logs DO NOT Directly Measure Porosity
• Acoustic (Sonic) Logs Measure Wave Travel Time
• Density Logs Measure Formation Bulk Density
• Neutron Logs Measure Formation Hydrogen Content

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Neutron Log Applications

• Porosity
• Lithology with Density and/or Sonic
• Gas Indicator
• Clay Content
• Correlation
• Cased Hole

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Neutron Tool Background

• Outgrowth of Work by Italian Physicists (1935)
• Slowing down and stopping of neutrons by a
  hydrogen rich material (e.g., water).
• Radioactive Source of High Energy Neutrons
• Americium and Beryllium
• Fairly Shallow Zone of Investigation
• 6 inches (Flushed Zone (Rxo) in most cases)
• Neutrons lose energy each time they collide with
  nuclei as they travel through the formation
• Greatest loss in energy when neutrons collide
  with nuclei of a similar mass
• Hydrogen atoms
• As the neutrons slow they can be captured and
  emit a gamma ray.
• Reduction in Neutron Flux (Increased Gamma Rays)
  is largely controlled by concentration of
  hydrogen in the formation.
• Water (Oil) Filled Porosity in Flushed Zone of
  Clean Units
• Clays
• Lithology Effect
• Hydrocarbon Gas Effect
• Depress apparent neutron porosity

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The Neutron Porosity Tool
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Historical Development of Neutron Logging

• Common Curve Mnemonics
• FN, PHIN, NPHI
• Usually Tracks 2 or 3 and dashed line.
• Units
• Counts
• , Decimal Fraction

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Neutron Energy Loses
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Density Log Applications

• Porosity
• Lithology with PE, Neutron and/or Sonic
• Gas Indicator
• Synthetic Seismograms with Sonic
• Rock Properties with Sonic
• Poissons Ratio, Youngs Modulus
• Clay Content
• Borehole Conditions (Size and Rugosity)

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Density Tool Background

• Source of High Energy Gamma Rays
• Cesium 137
• Shallow Zone of Investigation
• lt2 inches
• Gamma rays interact with the electron clouds of
  the atoms they encounter, with a reduction in the
  gamma ray flux, which is measured by both a near
  and far detector.
• Higher Energy Range Affected by Compton
  Scattering
• Reduction is a function of the electron density
  of the formation
• Number of Electrons Matched by the Number of
  Protons
• In Most Cases Z/A 0.5
• Z - Atomic Number
• A Atomic Mass
• Two Density Values
• Bulk Density (RhoB or ?b) Measured by Logging
  Tool Solid Fluid
• DEN, ZDEN
• Matrix Density (?ma) Density of the Rock that
  has no Porosity
• Hydrocarbon Gas Effect
• Enhances apparent density porosity

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The Formation Density Tool
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Density Porosity

• FD (?ma ?b) / (?ma ?fluid)
• DPHI, PHID, DPOR
• Sandstone 2.644 gm/cm3
• Limestone 2.710 gm/cm3
• Dolomite 2.877 gm/cm3
• Anhydrite 2.960 gm/cm3
• Halite 2.040 gm/cm3
• Freshwater 1.0 gm/cm3
• Saltwater 1.15 gm/cm3

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Question Why does FN read much higher Than FD
in the red boxed area? What are the general
lithologies in this well?
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Photo Electric Pe Tool

• Lithology with Density, Neutron and/or Sonic
• Supplementary Measurement of the Density Tool
• 1970s Onward
• Lower Energy Range Gamma Rays Affected by
  Photoelectric Effect
• Logged Value is a function of Z - Atomic Number
• Pe (Z/10)3.6
• Barns per electron
• Only mild affect of Pore Volume and Fluid/Gas
  Content
• Quartz 1.81 Barns
• Dolomite 3.14 Barns
• Calcite 5.08 Barns
• Pe, PE, PEF

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Photoelectric factor log
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Compositional Analysis

• Combing More Than Two Logs

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Compositional Analysis

• Determine Lithology
• Graphic Plots
• Computation
• Identification and Semi-Quantitative Estimates

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Porosity Log Combinations

• Single Porosity Measurement
• Lithology is Specified for Correct Porosity
• Choice of Matrix Value
• Two Porosity Measurements
• Two Lithologies can be Predicted along with
  Porosity
• Three Porosity Measurements
• Three Lithologies can be Predicted along with
  Porosity
• Greater the number of Measurements the Greater
  the Complexity of the Lithology that can be
  Estimated

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2 Logs 2 Minerals
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Dolomitic-Limestone System
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Three-Measurement Cross-Plot

• Three Mineral Matrix Can Be Determined
• Usually Reduce From 3-D to 2-D
• Collapse the 3 measurements to two axes with
  common denominator
• M-N Plots
• Axis 1 Sonic and Density
• Axis 2 Neutron and Density
• Problem of Density and Sonic being Correlated
• Addition of Pe in Newer Methods

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M-N Cross Plot
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M N Crossplot

• Remove the effect of pore fluid
• Usually drilling fluid
• Combine Sonic and Density Logs (M)
• M (?tfluid ?tmatrix) / (?matrix ?fluid)
• Combine Neutron and Density
• N (Fnfluid Fn matrix) / (?matrix ?fluid)

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M-N Cross Plot
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RHOmaa Umaa Crossplot

• Mineral Identification (MID) Plots
• Apparent Matrix Density RHOmaa
• Density and Neutron
• Apparent Matrix Photoelectric Cross Section Umaa
• Density, Neutron and Photoelectric Effect

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Apparent Matrix Density RHOmaa

•  

 
 
 
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Photoelectric (PE) Factor
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Volumetric Photoelectric Absorption U/cm3

• The photoelectric absorption index (Pe) is
  measured in units of barns per electron. In order
  to linearize its relation with composition, the
  variable must be converted to a volumetric
  photoelectric absorption index (U) with units of
  barns per cc
• and is approximated by

 
 
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Volumetric Photoelectric Absorption U of the
matrix

• This is the volumetric photoelectric absorption
  coefficient of the zone (matrix plus fluid). The
  hypothetical volumetric photoelectric absorption
  coefficient of the matrix is UMAA.

 
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Umaa Values (Apparent ??)
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RHOmaa Umaa Plot
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Shale Characterization
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2 Logs 2 Minerals
Computational Analysis
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Computational Analysis
C - matrix of the log responses of the components
V - vector of the component proportions L -
vector of the log readings To Solve for V need
the inverse of the component matrix
CVL V C-1L
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Log response equations
Rewritten as matrices
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The compositional solution vector is then given
by pre-multiplying the log response vector by the
inverse of the coefficient matrix
We are Saved - Easily computed in Excel
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Compositional Analysis
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Project 2
http//www.geo.wvu.edu/tcarr/PTTC_11_2010

• Use Parameters From Appendix B
• Open Compositional Template
• Load in Separate Template Well 1.LAS
• Marcellus (7375-7562)
• Onondaga (7562.5 7578)
• Why are data points outside the Rhomaa-Umaa
  Triangle
• Load in Separate Template Well 2.LAS
• Marcellus (7359-7501)
• Onondaga (7501.5 7516)
• Why are data points outside the Rhomaa-Umaa
  Triangle
• Create Computational Plots
• What is the difference in the two wells

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My Observations
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Tim Carr Phone [phone] Email
tim.carr_at_mail.wvu.edu