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Dipmeter data, borehole image
logs and interpretation
Kris Vickerman
May 25, 2016
 Dipmeter refers to the bedding data (depth, dip, azimuth,
quality, etc.). The small plot on top is a dipmeter plot.
 Di...
 Data comes from the logging truck typically via satellite or
FTP transmission:
 File types such as DLIS, TIF, LIS, XTF,...
Outline
 Basics of borehole image interpretation
 Bedding and structural dip analysis
 Natural fractures
 Stress featu...
Basics of borehole image logs
 Wireline or MWD tool is positioned in the
borehole (resistivity, sonic, density, gr)
 Inc...
Basics of borehole image logs
 Wireline or MWD tool is positioned in the
borehole (resistivity, sonic, density)
 Incline...
 Typical Conductivity Image plot
is shown as an unrolled view
of the inside of the borehole
 Conductive features are dar...
Image normalization
 Image colour is statically normalized with
conductive as black and resistive as white
 To enhance l...
Image logs and core
 Conductive shale is
black, resistive
bitumen sand is
white/yellow
 We can often see
resistivity con...
Oil-Based horizontal field imager
 Horizontal field
electric images see
fractures better but
also see bit marks
 Acousti...
Borehole Image Interpretation
Step 1: Processed Image
Borehole Image Interpretation
Step 2: Beds
Borehole Image Interpretation
Step 3: Large Fractures
Borehole Image Interpretation
Step 4: Fine Fractures
Image interpretation
Dip “Tadpoles”
Hand-picked
sinusoidsLithology zoning
“Basics” products
 Plot of the interpreted image at various scales
(Paper / PDF / TIFF)
 Output of the interpreted image...
Outline
 Basics of borehole image interpretation
 Bedding and structural dip analysis
 Natural fractures
 Stress featu...
Basic Structural Dip Analysis
 Tadpole Plots
 Stereonet Plots
 Stick Plots
 True Stratigraphic Thickness Plots
Tadpole Plot
Stereonet
Stick Plot (cross-section)
Interpreted Stick Plot
True Stratigraphic Thickness Plot
True Stratigraphic Thickness Plot
Interpreted Stick Plot
Example of structural interpretaion
 Each domain is taken to
have consistent average
dip
 The boundaries between
the dom...
Interpreted Stick Plot
Simple stereonets
Uncluttered bed dips and
subtle frac. den. curve
GR and tops markers
Depth tracks...
Interpreted stick plot
Interpreted stick plot (Lithotect)
Stratigraphic beds
 Describing bedforms and lithology
 Sand count and facies plots
 Vuggy porosity analysis
Sandy IHS
 Moderate GR,
moderate resistivity
 Inclined alternating
sand/mud beds
 Consistent bedding
dip direction
towa...
Trough crossbedded sand
 Very clean GR,
high resistivity
 >10° crossbeds
 Inclined truncations
 Vsh < 10%
 Dip Downst...
Trough crossbedded sand
 Very clean GR,
high resistivity
 >10° crossbeds
 Inclined truncations
 Vsh < 10%
 Dip Downst...
Planar-tabular crossbedded sand
 Clean GR, high
resistivity
 >10° flow
crossbeds, often
alternating direction
 Flat tru...
Mud Breccia
 Moderate to high
GR, low resistivity
 Often crossbedded
 Clast supported
conductive (dark)
mud clasts
 Pe...
Sand count plot
 Sand count / facies plots can take many forms
 This one shows:
 Openhole data on the right
 High-res ...
Secondary porosity plot
 Image thresholding produces an estimate of irregular (secondary)
porosity as a percentage of the...
Bed Interpretation products
 Stereonet, Tadpole, Stick, TST, etc. (Paper / PDF)
 Lithology zonation file (LAS) and plots...
Outline
 Basics of borehole image interpretation
 Bedding and structural dip analysis
 Natural fractures
 Stress featu...
Natural fracture interpretation
 Fracture types (open, closed, shear)
 Fracture properties (geometry, density, aperture)
Open Fractures
 Open fractures are filled
with conductive drilling
mud (dark on borehole
images)
 Fractures are not infi...
Open Fracture Exaggeration
50cm
 This fracture is probably on the
order of .5 mm, not 5 cm as it is
seen here
 Tool curr...
Open Fractures
 Mineralized fractures
might be filled with
calcite, quartz or
dolomite, all resistive
 Often fracture traces are
invisi...
Healed Fracture Haloing
50cm
*From Cheung, 1999
 The resistive fracture itself is
invisible, see halo instead
 Tool curr...
Healed Fractures
Shear feature in Borehole Images
 Visible as a bedding offset
 Can be healed or open
 Can be mm-scale to km-
scale in t...
Shear features
Natural fracture interpretation
 Fracture types, (open, closed, shear)
 Fracture properties (geometry, density, aperture)
Fracture Density
 Fracture density can be calculated a few ways:
 As line-density 1-D
 As tracelength density 2-D
 As ...
Fracture Density Comparison
2 metres of image
Fracture Density Comparison
9 m2/m3 5 m2/m3
2 metres of image
Fracture Density Plot
 Gives an at-a-glance
curve to tell fracture
intensity but no indication
of aperture, permeability
...
Fracture aperture estimation
50cm
 Open fractures are invaded by conductive
drilling mud
 The amount of invaded mud is s...
MUD
Fracture aperture estimation
*U.S. Patent No: 52435211
Aperture = A * Rt 0.1505 * Rm 0.8495
A = Excess conductance
Rt ...
Fracture aperture plot
 Apertures are calculated two
ways:
 As an average for each
fracture
(red dots, second to right)
...
Fracture Interpretation products
 Fracture types on tadpole, image and stereonet
plots and in LAS / ASCII
 Fracture dens...
Outline
 Basics of borehole image interpretation
 Bedding and structural dip analysis
 Natural fractures
 Stress featu...
Un-natural fractures
 Stress direction from borehole breakout
 Stress direction from induced fractures
Stress direction from breakout
 Measure shmin by
observing where
breakouts occur in
the wellbore
 Vertical and oriented
...
Stress direction from breakout
shmax
shmin
 Breakout visible as
paired vertical
conductive smears
 Can pick the centre
o...
Stress direction from breakout
shmax
shmin
 Breakout visible as
paired vertical
conductive smears
 Can pick the centre
o...
Stress Magnitude from breakout
 Width of the breakout
is proportional to the
magnitude of shmin
 Width of the breakout
i...
Un-natural fractures
 Stress direction from borehole breakout
 Stress direction from induced fractures
Stress direction - Induced fractures
 Measure shmax by
observing where
drilling induced
fractures occur
 Vertical and or...
Stress direction – Induced fractures
 Induced fracs. visible
as paired thin vertical
conductive cracks
 Can pick the cen...
Stress direction – Induced fractures
 Induced fracs. visible
as paired thin vertical
conductive cracks
 Can pick the cen...
Stress direction – Both types
shminshmaxshmax shmin
Stress direction – Both types
shminshmaxshmax shmin
Stress Interpretation products
 Horizontal maximum stress direction on stereonet
 Stress features on tadpole plots and i...
 Interpreted borehole image data should always be
distributed as digital files (Downloaded via FTP/website or
on DVD)
 C...
 The words Dipmeter and Borehole image log are pretty
loaded and can mean a lot of things
 Depending on the questions, t...
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Dipmeter Data, Borehole Image Logs and Interpretation

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Introduction to Borehole Image Logs presented to Geoscience Data Managers in 2016 by Kris Vickerman of HEF Petrophysical Consulting Inc.

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Dipmeter Data, Borehole Image Logs and Interpretation

  1. 1. Dipmeter data, borehole image logs and interpretation Kris Vickerman May 25, 2016
  2. 2.  Dipmeter refers to the bedding data (depth, dip, azimuth, quality, etc.). The small plot on top is a dipmeter plot.  Dipmeter also refers to an older tool with 4, 6 or 8 buttons  Borehole image logs refer to any tool that samples an array of measurements in the borehole:  Resistivity – FMI, CMI, XRMI, etc.  Ultrasonic images – UBI, CBIL, CAST  LWD images – (GR, Density, Resistivity and so on.) Introduction
  3. 3.  Data comes from the logging truck typically via satellite or FTP transmission:  File types such as DLIS, TIF, LIS, XTF, AFF, LAS, CSV  Large files, often 100’s of MB  Data is also found in digital archives:  Corporate archives as digital or paper well files  Government archives (BCOGC), as scans, paper logs, and digital  Service company archives (HEF for example has more than 10,000 wells in our Recall Database dating back to the early 90’s)  Log data vendor archives as rasters, etc.  Digitized data such as ASCII bed dip files from above sources  Data can also be sourced from physical media:  Magnetic tapes, CD/DVD, scanning old paper prints and so on… Introduction – input data sources
  4. 4. Outline  Basics of borehole image interpretation  Bedding and structural dip analysis  Natural fractures  Stress features
  5. 5. Basics of borehole image logs  Wireline or MWD tool is positioned in the borehole (resistivity, sonic, density, gr)  Inclined surfaces intersect the measurement buttons at different depths, unrolling to a sinusoid in the standard display
  6. 6. Basics of borehole image logs  Wireline or MWD tool is positioned in the borehole (resistivity, sonic, density)  Inclined surfaces intersect the measurement buttons at different depths, unrolling to a sinusoid in the standard display
  7. 7.  Typical Conductivity Image plot is shown as an unrolled view of the inside of the borehole  Conductive features are dark; resistive are light  Planes that intersect the borehole become sine waves in this view  Bedding (orange-yellow) and fractures (black) visible in this section Borehole Image Example (FMI)
  8. 8. Image normalization  Image colour is statically normalized with conductive as black and resistive as white  To enhance local contrast, colours are renormalized in a sliding 1m window making a “Dynamically Normalized” image Dynamically NormalizedStatic
  9. 9. Image logs and core  Conductive shale is black, resistive bitumen sand is white/yellow  We can often see resistivity contrast features that are hard to see in core DynamicStatic
  10. 10. Oil-Based horizontal field imager  Horizontal field electric images see fractures better but also see bit marks  Acoustic images are lower resolution  Bedding is clear  Some fracturing is visible  Some induced features are visible
  11. 11. Borehole Image Interpretation Step 1: Processed Image
  12. 12. Borehole Image Interpretation Step 2: Beds
  13. 13. Borehole Image Interpretation Step 3: Large Fractures
  14. 14. Borehole Image Interpretation Step 4: Fine Fractures
  15. 15. Image interpretation Dip “Tadpoles” Hand-picked sinusoidsLithology zoning
  16. 16. “Basics” products  Plot of the interpreted image at various scales (Paper / PDF / TIFF)  Output of the interpreted image in DLIS  Output/backup of the interpreted image in DB format like Recall or Geoframe, etc.  Output of the interpreted features (Beds, fractures, etc.) in LAS
  17. 17. Outline  Basics of borehole image interpretation  Bedding and structural dip analysis  Natural fractures  Stress features
  18. 18. Basic Structural Dip Analysis  Tadpole Plots  Stereonet Plots  Stick Plots  True Stratigraphic Thickness Plots
  19. 19. Tadpole Plot
  20. 20. Stereonet
  21. 21. Stick Plot (cross-section)
  22. 22. Interpreted Stick Plot
  23. 23. True Stratigraphic Thickness Plot
  24. 24. True Stratigraphic Thickness Plot
  25. 25. Interpreted Stick Plot
  26. 26. Example of structural interpretaion  Each domain is taken to have consistent average dip  The boundaries between the domains are oriented on the bisectors of the dip domains
  27. 27. Interpreted Stick Plot Simple stereonets Uncluttered bed dips and subtle frac. den. curve GR and tops markers Depth tracks visible but not in the way Projected bedding Anything else you might like to add FDEN, tadpoles, openhole data
  28. 28. Interpreted stick plot
  29. 29. Interpreted stick plot (Lithotect)
  30. 30. Stratigraphic beds  Describing bedforms and lithology  Sand count and facies plots  Vuggy porosity analysis
  31. 31. Sandy IHS  Moderate GR, moderate resistivity  Inclined alternating sand/mud beds  Consistent bedding dip direction towards channel centre  Vsh 10-40%
  32. 32. Trough crossbedded sand  Very clean GR, high resistivity  >10° crossbeds  Inclined truncations  Vsh < 10%  Dip Downstream
  33. 33. Trough crossbedded sand  Very clean GR, high resistivity  >10° crossbeds  Inclined truncations  Vsh < 10%  Dip Downstream
  34. 34. Planar-tabular crossbedded sand  Clean GR, high resistivity  >10° flow crossbeds, often alternating direction  Flat truncations  Vsh < 10%  Dip down-current
  35. 35. Mud Breccia  Moderate to high GR, low resistivity  Often crossbedded  Clast supported conductive (dark) mud clasts  Petrophysically indistinguishable from laminated mud beds below  Vsh > 10%
  36. 36. Sand count plot  Sand count / facies plots can take many forms  This one shows:  Openhole data on the right  High-res resistivity curve for thin bed petrophysics (red, on the right)  Facies track (Green/yellow/black)  Sand count track (brown and yellow to the right of image)  Sand bed thickness and percentage curves (yellow and grey to the right of image)
  37. 37. Secondary porosity plot  Image thresholding produces an estimate of irregular (secondary) porosity as a percentage of the whole  Plot shows limestone / dolostone flag on left, thresholded black and white image on right followed by secondary porosity curves in red, green and grey
  38. 38. Bed Interpretation products  Stereonet, Tadpole, Stick, TST, etc. (Paper / PDF)  Lithology zonation file (LAS) and plots  Bed dip types on plots and in LAS / ASCII
  39. 39. Outline  Basics of borehole image interpretation  Bedding and structural dip analysis  Natural fractures  Stress features
  40. 40. Natural fracture interpretation  Fracture types (open, closed, shear)  Fracture properties (geometry, density, aperture)
  41. 41. Open Fractures  Open fractures are filled with conductive drilling mud (dark on borehole images)  Fractures are not infinite in length so partial intersections are common  Direct measurements include dip, azimuth, trace length, minimum radius, type (LAS)
  42. 42. Open Fracture Exaggeration 50cm  This fracture is probably on the order of .5 mm, not 5 cm as it is seen here  Tool current “seeks” the conductive fracture before and after it, making it appear much larger *From Cheung, 1999
  43. 43. Open Fractures
  44. 44.  Mineralized fractures might be filled with calcite, quartz or dolomite, all resistive  Often fracture traces are invisible  See artificial halo inside fracture plane Healed Fractures
  45. 45. Healed Fracture Haloing 50cm *From Cheung, 1999  The resistive fracture itself is invisible, see halo instead  Tool current “piles up” inside of resistive fracture plane and is dispersed outside of it
  46. 46. Healed Fractures
  47. 47. Shear feature in Borehole Images  Visible as a bedding offset  Can be healed or open  Can be mm-scale to km- scale in throw  Geologists would call these faults but some managers might not be so keen
  48. 48. Shear features
  49. 49. Natural fracture interpretation  Fracture types, (open, closed, shear)  Fracture properties (geometry, density, aperture)
  50. 50. Fracture Density  Fracture density can be calculated a few ways:  As line-density 1-D  As tracelength density 2-D  As a modelled volumetric density 3D
  51. 51. Fracture Density Comparison 2 metres of image
  52. 52. Fracture Density Comparison 9 m2/m3 5 m2/m3 2 metres of image
  53. 53. Fracture Density Plot  Gives an at-a-glance curve to tell fracture intensity but no indication of aperture, permeability or connection to porosity  If drilling induced fractures or foliation is included, it gives false results
  54. 54. Fracture aperture estimation 50cm  Open fractures are invaded by conductive drilling mud  The amount of invaded mud is somehow proportional to aperture
  55. 55. MUD Fracture aperture estimation *U.S. Patent No: 52435211 Aperture = A * Rt 0.1505 * Rm 0.8495 A = Excess conductance Rt = Formation resistivity Rm = Mud resistivity
  56. 56. Fracture aperture plot  Apertures are calculated two ways:  As an average for each fracture (red dots, second to right)  …And as a rolling mean (blue-red cuve on right)
  57. 57. Fracture Interpretation products  Fracture types on tadpole, image and stereonet plots and in LAS / ASCII  Fracture density plot and LAS file  Fracture aperture plot and LAS file  Fracture statistics like trace length, minimum radius, height and so on in LAS file
  58. 58. Outline  Basics of borehole image interpretation  Bedding and structural dip analysis  Natural fractures  Stress features
  59. 59. Un-natural fractures  Stress direction from borehole breakout  Stress direction from induced fractures
  60. 60. Stress direction from breakout  Measure shmin by observing where breakouts occur in the wellbore  Vertical and oriented in the plane of shmin  Borehole sloughs in when the drilling fluid pressure is less than formation pressure shmax shmin After: Mossop, Shetsen, 1994 Low Pf
  61. 61. Stress direction from breakout shmax shmin  Breakout visible as paired vertical conductive smears  Can pick the centre of the breakouts to get shmin
  62. 62. Stress direction from breakout shmax shmin  Breakout visible as paired vertical conductive smears  Can pick the centre of the breakouts to get shmin shmin shmin
  63. 63. Stress Magnitude from breakout  Width of the breakout is proportional to the magnitude of shmin  Width of the breakout is also proportional to the rock strength  Need a database of the strengths of various formations to measure shmin Width
  64. 64. Un-natural fractures  Stress direction from borehole breakout  Stress direction from induced fractures
  65. 65. Stress direction - Induced fractures  Measure shmax by observing where drilling induced fractures occur  Vertical and oriented in the plane of shmax  Borehole wall cracks when drilling fluid pressure is more than formation pressure shmax shmin High Pf
  66. 66. Stress direction – Induced fractures  Induced fracs. visible as paired thin vertical conductive cracks  Can pick the centre of the induced fractures to get shmax shmax shmin
  67. 67. Stress direction – Induced fractures  Induced fracs. visible as paired thin vertical conductive cracks  Can pick the centre of the induced fractures to get shmax shmax shmin shmaxshmax
  68. 68. Stress direction – Both types shminshmaxshmax shmin
  69. 69. Stress direction – Both types shminshmaxshmax shmin
  70. 70. Stress Interpretation products  Horizontal maximum stress direction on stereonet  Stress features on tadpole plots and in LAS files  Further analysis can be done for more in depth geomechanical understanding
  71. 71.  Interpreted borehole image data should always be distributed as digital files (Downloaded via FTP/website or on DVD)  Can be printed on paper  Can be supplied in a format that can be loaded into other software packages (a DLIS array of the processed image)  Should be stored by the interpreter and logging contractor (if different) in some permanent database (Recall, etc.)  Ideally should become part of government databases once off confidential Outtroduction – data outputs
  72. 72.  The words Dipmeter and Borehole image log are pretty loaded and can mean a lot of things  Depending on the questions, these logs can provide a large suite of answers about the nature and textures of bedding and fracturing in the subsurface  The products come in a wide and challenging variety of plots, files and media Conclusion

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