Presentation to the Denver Geophysical Society 2011 Modern seismic data acquisition continues the decades-long trend for more: more flexibility, more speed, higher channel counts, more accurate recordings, better safety. An example of this evolution was showcased at the Durham Ranch 3D acquisition near Craig, Colorado. A shallow fractured shale play in the Niobrara formation, acquisition had to overcome extreme time constraints and deliver high-quality, spatially dense data from a ruggedly mountainous terrain. In this talk I will present the techniques we used to solve the challenge, as well as some of the 3D and CW results obtained from the data.

1. [ 1 ]
Durham Ranch Seismic Acquisition
Colorado USA, Using ION FireFly

2. Organization - Chronological
0. Overview
1. Scouting / Permitting
2. Designing / Surveying
3. Shothole Drilling
4. Seismometer Deployment
5. Shooting / Recording
6. Processing

3. [ 3 ]
Durham Ranch
Moffat County, Northwestern Colorado
Sand Wash Basin
CO

4. [ 4 ]
Durham Ranch
A Closer View
• 31 square miles. Elevation
ranges from 7500 to 9000
feet above sea level
• Breached anticline:
Sandstone over shale.
• Significantly varying
topography, ranging from
irrigated farmland to exposed
cliffs to high mountain
meadows.
• Livestock and wildlife are
prevalent. Prime hunting
location in Colorado.
• The BLM has numerous
restrictions in place to protect
native species, including
birds-of-prey, deer, and black
bear.Satellite image courtesy of Google Earth

5. [ 5 ]
Durham Ranch - Producing Wells
• The Durham Ranch
area contains a
number of oil wells that
average between 50-
100 barrels per day.
• However, multiple dry
holes have also been
drilled since the field
was discovered in the
1950’s. No 3D seismic
had ever been shot
here.

6. [ 6 ]
Durham Ranch: The Reservoir Target
Fractured Carbonates in the Niobrara Formation
• An outcrop of the target
Niobrara reservoir alongside
the Green Mountain
Reservoir, just north of
Silverthorne, CO.
• Left: thin laminations of a
section of the carbonate
reservoir that is not highly
fractured.
• Middle/right: fracturing
becomes more intense.
• Expected Niobrara levels
from ~ 1200ft-3000ft in
project area

7. Organization - Chronological
0. Overview
1. Scouting / Permitting
2. Designing / Surveying
3. Shothole Drilling
4. Seismometer Deployment
5. Shooting / Recording
6. Processing

8. [ 8 ]
Acquisition Timeline
FireFly Survey at Durham Ranch
FEB MAR APR MAY JUN JUL AUG SEP
Permitting
Shot-hole
drilling
Crew
mobilization
System
deployment
Shooting
System
retrieval
Processing
• Significant time
constraints.
– Hunting season starts
September 1.
– All seismic acquisition
operations must be
completed by this date.
• East Resources invited
several seismic
contractors to bid on the
project, with many
submitting ‘no-bids’

9. [ 9 ]
Planning: Winter Scouting

10. Organization - Chronological
0. Overview
1. Scouting / Permitting
2. Designing / Surveying
3. Shothole Drilling
4. Seismometer Deployment
5. Shooting / Recording
6. Processing

11. [ 11 ]
LIDAR Basics
Reflection Points
from surface features
from ground features
•Lidar collects elevation points of surface features
(full feature model).
•Lidar can also image the surface beneath the canopy
(bare earth model).
As long as light can penetrate the canopy, the laser
will also penetrate the canopy and you will get hits off
the ground surface underneath.
•Lidar is independent of sun angle and can be
collected day or night.

12. [ 12 ]
LiDAR – “Bare Earth”
Sagebrush
& Vegetation
Steep Gully
Drill Site
(1mi x 1mi - Wyoming)

13. [ 13 ]
LiDAR – “Full Feature”
Sagebrush
& Vegetation
Drill Site
Steep Gully
(1mi x 1mi - Wyoming)

14. [ 14 ]
LiDAR – “Slope Analysis”
LEGEND: % slope
grey 0-5%
R 5-10%
O 10-15%
Y 15-20%
G 20-25%
B 25-30%
I 30-35%
V >35%
(1mi x 1mi - Wyoming)

15. [ 15 ]
LIDAR Canopy = Full Feature – Bare Earth

16. [ 16 ]
LiDAR 3D Visualization ‘Fly Through’

17. [ 17 ]
21st Century Imaging Challenges

18. [ 18 ]
Seismic Data: Wavelength > 30m

19. [ 19 ]
Traditional geometry
600 m
station interval: 25 m
line interval: 400 m
recording template:
8 lines x 100 stations
Challenge: Shot/Receiver Density

20. [ 20 ]
Challenge: Shot/Receiver Density
station interval: 25 m
line interval: 125 m
recording template:
20 lines x 100 stations
Densely sampled geometry
600 m

21. [ 21 ]
Challenge: Shot/Receiver Density
station interval: 25 m
line interval: 25 m
recording template:
100 lines x 100 stations
Fully sampled geometry
600 m

22. [ 22 ]
Survey Parameters
Densely Sampled, Full-wave Multi-client Survey
BLM controlled area is shown in yellow.
• Geophones: 6,100
• Receivers: 10,597 (327 “miles”)
• Sources: 7,271 (223 “miles”)
• Traces: about 10 million
• Receiver Density: 346/ square
mile
• Nominal fold: 240
• Area: 31 square miles
• Surface relief: 2000 feet

23. [ 23 ]
Staking – Lets not!
Survey Supplies –
Daily
Induced Receiver Location Error Induced Source Location Error

24. Organization - Chronological
0. Overview
1. Scouting / Permitting
2. Designing / Surveying
3. Shothole Drilling
4. Seismometer Deployment
5. Shooting / Recording
6. Processing

25. [ 25 ]
Shotpoint Planting: Stakeless Drilling
• Dynamite Sources
• No surveying & staking
• Faster, Cheaper
• Less HSE risk
• More Accurate

26. Organization - Chronological
0. Overview
1. Scouting / Permitting
2. Designing / Surveying
3. Shothole Drilling
4. Seismometer Deployment
5. Shooting / Recording
6. Processing

27. [ 27 ]
Wireless Field Station Unit
Full-wave, multi-
component MEMS
digital sensors
FireFly recording unit with
Bluetooth, VHF, processor
and flash memory
No wires for communication and power, anyway….

28. FSU Deployment - Navtool
Crew 3
Coordinates and elevation
of actual receiver position
are entered into trace
headers
Also:
Digital
Compass
Orientation
Pole

29. [ 29 ]
Easy Operational Environment

30. [ 30 ]
Not as easy as it seems…

31. [ 31 ]
Not as easy as it seems

32. [ 32 ]
Not as easy as it seems

33. [ 33 ]
FSU Deployment: VSI training and crew

34. [ 34 ]
FSU Deployment : Mini-me
• Miniaturized NavTool deployment
pole for climbing crews
– Allows climbers to carry pole
on their backs

35. FSU Deployment: Horizontal Deployment
Bonded with drywall paste
Weighted by Sandbag
Vertical Buried Sensor not
shown in picture
All three sensors have nearly identical response
Good that
Vectorseis is
insensitive to
angle…

36. FSU Deployment
Field crews deploy gear where it is safe. Trace
headers will contain actual coordinates and
elevations where the gear is deployed.

37. [ 37 ]
Deployment
GPS and LiDAR DEM for positioning
Shooting
System: Ethernet, VHF, Bluetooth, GPS
Doghouse
Accurate
SEGY headers
in real time

38. [ 38 ]
FSU Deployment: River Crossing

39. [ 39 ]
Communication: Heliportable Towers

40. Organization - Chronological
0. Overview
• Scouting / Permitting
• Designing / Surveying
• Shothole Drilling
• FSU Deployment
• Shooting / Recording
• Processing

41. [ 41 ]
Conventional Source Control
• Voice communications make it difficult to manage large number of
shooting crews
“Hey Shooter2, sorry to
keep asking, but are you
guys finally ready yet?
You’ve been working on
that hole for the past 10
minutes.”
“We’re almost ready –
the leads were buried
in the ice. Give us
about 10 more minutes
and maybe we’ll be
ready to go.”

42. [ 42 ]
Automated Source Control
• Shooting efficiency increased by eliminating non-emergency voice
communications
• Simplifies management of large shooting crews
“Shooter2
Ready?”
“Yes”
“No.”

43. [ 43 ]
Shooting
• Average 318 shots / day
• Maximum 723 shots / day
• Shooting completed in 20 days

44. [ 44 ]
Shots Recorded by Day
Daily Average = 318
Battery Swap Day

45. [ 45 ]
August 25: 723 Shots

46. This was Firefly v2.0, 2.1 now in production
• FireFly v2.1:
– Power reduced by 20%-35%
– RF bandwidth increased by 150%-230%
– Trace attributes
– Analog sensor via Geophone Digitizing Unit
– RTK GPS
– Continuing massive software development
• V2.2 currently in testing…

47. Organization - Chronological
0. Overview
1. Scouting / Permitting
2. Designing / Surveying
3. Shothole Drilling
4. FSU Deployment
5. Shooting / Recording
6. Processing

48. Processing: Anisotropy and Converted Wave
• HTI and migrations - Scott Schapper and Rob Jefferson
• VTI, HTI and migrations - Ed Jenner
• Converted wave – Mike Stewart and Alex Calvert

49. OVT PSTM, TLE Publication
“Anisotropic Velocities and Offset
Vector Tile Pre-stack Migration
Processing of the Durham Ranch 3D,
Northwest Colorado”
The Leading Edge; November 2009; v. 28;
no. 11
Scott Schapper1, Robert Jefferson1, Alexander Calvert1,
and Marty Williams2
1Ion Geophysical, GXT Imaging Solutions, Denver, CO,
USA
2East Resources, Broomfield, CO, USA
( Waddle Creek oil field = subset of Durham Ranch )

50. NW SE NW SEWaddle Creek FieldWaddle Creek Field
The isotropic migration on the left does not fully image the buried focus at 1.5 sec. The
VTI anisotropic migration (η=0.1) on the right properly images the buried focus,
revealing what appears to be sediments folded atop faulted basement.
OVT PSTM: Isotropic versus VTI
Basement Basement

51. [ 51 ]
Processing Flow: Migration ↔ AZIM
Geometry (pre-processing)
and Refraction Statics
First pass Velocities and
Residual Statics
Signal Processing
Second Pass Velocities and
Residual Statics
AZIM™, 3rd Pass Res. StaticsTest PSTM
Trim Statics
FXY Decon
Stack & Post-Stack TM
Post-Migration Enhancements
OVT Pre-Stack TM eta=0.1
AZIM™ Analysis and Correction
Post-Migration Enhancements
• 9,220,050 traces
• 8776 receivers
• 6683 sources

52. [ 52 ]
Fold – all offsets (color scale set to 1 – 168)
CMP fold map – full fold

53. OVT: Sectoring by Azimuth and Offset

54. NW NWSE SEWaddle Creek FieldWaddle Creek Field
Anisotropic PSTM: Common Offset versus OVT
Both migrations account for VTI anisotropy with η= 0.1. The two
images are comparable in the deep section, but the OVT image
appears to suffer more from shallow sampling deficiencies.
Niobrara
Entrada
Basement
Niobrara
Entrada
Basement

55. Vf-Vs(ft/s)
0
2500
Anisotropy analysis after OVT PSTM
The OVT migrated attribute appears to be better positioned relative to interpreted faulting (magenta
arrow), and fault influence on this attribute is also more apparent. The deeper high Vfast-Vslow anomaly
(yellow arrow) has decreased in magnitude and moved closer to the lateral ramp deformation zone,
suggesting that the dip effect has been removed, but the possible influence of lateral velocity variation
may remain.
Basement Basement
EntradaEntrada
Niobrara Niobrara

56. 7500 ft7500 ft
7500 ft7500 ft
Azimuthal attributes at Entrada Horizon
Unmigrated OVT PSTM
IntervalVfast-Vslow
Anisotropydirection
andcoherency

57. VTI, HTI and migration; TLE article
“Combining VTI and HTI anisotropy
in prestack time migration: Workflow
and data examples”
The Leading Edge; July 2011; v. 30;
no. 7
Edward Jenner1
1Ion Geophysical, GXT Imaging
Solutions, Denver, CO, USA

58. Workflow
Input gathers for PSTM
Possibly Common-Offset PSTM
VTI parameter estimation
VTI OVT PSTM
HTI velocity analysis (AZIM)
Residual VTI analysis
HTI velocity analysis (AZIM)
VTI+HTI OVT PSTM
Residual HTI velocity analysis
Current VTI Workflow VTI+HTI Workflow

59. Combined VTI and HTI migration
Portion of OVT prestack time migrations migrated with a) VTI velocity field, b)
VTI velocity field with residual VTI and HTI corrections and c) combined
VTI+HTI velocity field followed by residual HTI correction.

60. [ 60 ]
Converted Waves
S R
P to S conversion pointMid point
Vp:Vs
6
4.5
3
2.5
2
Asymptotic conversion zone
Conversion point
closer to receiver when
higher Vp:Vs ratio
PW SW

61. C-Wave Scoping Workflow
• Receiver Gather Analysis/Comparison (Z, H1, H2, Radial, Transverse)
– Radial/Transverse QC
– check for p-wave leakage or mode conversions, or valid c-wave energy
• Signal processing (noise attenuation, decon, bandpass)
• Receiver gather velocity analysis (determine if Vc is too similar to Vp)
• Receiver stacks (initial look at structure, receiver statics)
• Sectored receiver stacks (investigate structure, splitting)

62. C-Wave scoping
What we would like to see for radial and transverse...
... if splitting were present.
(Not from Durham Ranch)

63. [ 63 ]
0 90 180 270 360
FAST direction (peaks)
SLOW direction (troughs)
Radial: azimuth sectored gathers

64. [ 64 ]
0 90 180 270 360 Polarity reversal.
These correspond to
FAST & SLOW
azimuth directions
Transverse: azimuth sectored gathers

65. Raw Radial Receiver Gather ( Azimuth Sect. )
• Not sinusoidal, but azimuthally varying due to structure
0 90 180 270 360

66. Raw Transverse Receiver Gather ( Azimuth Sect. )
• No Polarity Flips, but azimuthally varying due to structure

67. C-Wave Scoping: Conclusions
• C-Wave signal is most likely upcoming P converting on shallow
interface or free surface effect
• Ground roll disturbs C-Wave signal at interesting offsets & depths
• Can not determine a useful Vc due to p-wave leakage
• Azimuth sorted Radial and Transverse receiver gathers show
significant azimuthal effects due to structure and possibly anisotropy.
But derivation of fracture direction is not possible.
• Radial component azimuth sectored common receiver stacks using
the derived 1D velocity function from the supergather, shows poor
stack quality and holes. Could make derivation of receiver statics
challenging.

68. [ 68 ]

69. 15001000500Time(ms)
a b c
a) raw gathers with spherical
divergence correction
b) with noise attenuation c) with deconvolution
Representative shot gather signal processing
progression

70. [ 70 ]
Processing Comments
• The PSTM volumes improve imaging around deeper fault-areas in a
manner that appears to be geologically-reasonable.
• The inclusion of Eta within the PSTM appears to produce further
improvements around these deeper faults.
• AZIM™ attributes determined post OVT-PSTM appear to be more
consistent with structure and faulting. These volume appear to be
improved relative to AZIM™ volumes produced from unmigrated data.