1. Borehole Seismic Introduction

2. Overview Introduction Seismic Signals in the borehole
Borehole Environment
Borehole survey types
Borehole seismic deployment

3. What is a VSP?
A VSP or Vertical Seismic Profile is the process of recording seismic data in a wellbore environment. The geophones are vertical in the earth versus horizontal along it as in surface seismic.

4. Borehole Seismic Surveys
Checkshot
Vertical Incidence
Walkaway
3D-VSP
DBSeis
Offset VSP
Salt Proximity
Zero Offset
LWD Tool
SeismicMWD
Integrated Seismic Surveys
GECO LONGVA
OSLO
Pressure &
Temperature
Flow &
Phase
4C Sensors
Borehole seismic surveys : the past, the present and the future
Checkshot surveys - The time taken for seismic energy generated from an explosive source to propagate downwards is measured at receivers positioned at key formation tops. From this information it is possible to calculate the formation interval velocities.
Zero Offset VSPs - Geophones are evenly distribution along the well bore. As well as providing travel-time and velocity information from a single source positioned at the well-head, it is possible to measure the reflectivity of each horizon and build up a single trace seismic image at the wellbore.
Moving Source VSPs or Walkaway VSPs - Here the geophone is stationary, with the sources moving, firing every 25 metres along a 6km line. As the boat traverses, a profile of reflected seismic energy for each horizon is built up, and is shown by the green and blue lines. This generates a 2D image of the sub surface underneath the path of the source line.
This technique can be extended to 3D, by acquiring many 2D profiles at different offsets.
Although acquiring 3D-VSP data-sets has been around since the late 1980s, until now positioning the data correctly both spatially and in depth (known as migration) has been done strictly using 2D techniques.
Schlumberger over the past few years have improved their depth migration algorithm from 2D to 2.5D (used for the Brent survey acquired by Shell, and featured in a recent First Break) and now have a full 3D migration algorithm.
Integrated Reservoir Technology The future challenge will be the application of integrated reservoir evaluation and monitoring technology in which 4D-4C borehole seismic surveys will be one of the key components for the complete reservoir monitoring
NEXT SLIDE : Rationale for 3D VSP

5. Introduction
Seismic Signals in the borehole
Borehole Environment
Borehole survey types
Borehole seismic deployment

6. Seismic Signal in the Borehole
Time
Downgoing direct arrival
Reflected upgoing primary
Downgoing multiple
Reflected upgoing multiple
Depth

7. Vertical Seismic Profile
Time-Depth
Seismic Reflections
Time
Time-Depth
Depth

8. One-Way Time vs. Two Way Time
Surface Seismic
VSP
TWT = OWT + TT
Time
Reflection
TWT
Transit
Time (TT) TT
Reflection
Time (OWT)
OWT TT
Depth

9. Borehole Multiples
Upgoing Multiples

10. Borehole Multiples
Downgoing Multiple

11. Borehole Multiples
All Multiples

12. Tube Wave Energy Source
Tube waves are generated when surface waves from the source come in contact with the borehole fluid and become a guided wave traveling up and down the borehole.
As the tube wave travels vertically in the borehole it pushes the wall horizontally.
When the geophones are properly clamped to the borehole wall most of the tube wave energy will be seen in the horizontal geophones.
At changes in the borehole dimensions some of the tube wave energy will be reflected back to the surface. This will also occur when the energy reaches the bottom of the hole.

13. Tube Waves Raw Data One-Way Time Depth Vertical Channel Tube wave
Horizontal Channel
Vertical Channel
Tube wave Y X
HODOGM

14. Surface Seismic Comparison
VSP Data
Offset
Depth
One-Way Time
Two-Way Time

15. Introduction
Seismic Signals in the borehole
Borehole Environment
Borehole survey types
Borehole seismic deployment

16. Resonance types & effects
Resonance generates signal distortion
Coupling resonance effect
Modal resonance effect

17. Resonance Attenuation
Reduce tool dimension & mass
Increase tool application force
Optimize contact geometry
Combined tools
Shaker
Coupling contacts
Geophones
Isolating
springs
Versatile Seismic Imager - VSI
Isolated geophone package: 3.5 lbs
Positive mechanical anchoring
Combinable Seismic Imager - CSI
Isolated geophone package: 20 lbs
Positive mechanical anchoring
Array Seismic Imager - ASI
Isolated geophone package: 9 lbs
Magnetic clamping

18. Shaker Response

19. Introduction
Seismic Signals in the borehole
Borehole Environment
Borehole survey types
Borehole seismic deployment

20. Borehole Seismic History
Checkshot
Single Trace
2-D Lateral Coverage

21. Checkshot Surveys Formation Travel Times Formation Velocities
Source
Depth Model
Surface
Seismic
Depth (m)
Acoustic
Impedance
Formation
Velocities
Synthetic
Seismogram
Geophones
Depth-Velocity
Model Inputs
Surface Seismic
Correlation
Time (s)
Wavelet
Processing

22. Zero Offset VSP Surface Seismic Correlation
Source
Depth Model
Surface
Seismic
Depth (m)
Over-pressure Zone Prediction
Corridor
Stack
Geophones
Multiple Pattern
Identification
Wavelet
Processing
Time (s)
Formation
Velocities

23. Vertical Incident VSP Surface Seismic Correlation
WALKABOVE
Vertical Incident VSP
Surface Seismic
Correlation
Sources
Depth Model
Surface
Seismic
Depth (m)
Lateral Coverage Beneath Well
VSP
Image
Geophones
Multiple Pattern
Identification
Fault and Dip
Identification
Time (s)
Formation
Velocities

24. Offset VSP Surface Seismic Correlation Fault and Dip Identification
Source
Depth Model
Surface
Seismic
Depth (m)
Fault and Dip
Identification
VSP
Image
Geophones
Salt Proximity
Identification
Shear Wave
Analysis
Time (s)
Surface Seismic
Survey Design

25. Imaging Walkaway Surface Seismic Correlation Fault and Dip
Source
WALKAWAY
Surface
Seismic
Depth (m)
Geophones
Fault and Dip
Identification
Shear Wave
Analysis
Depth Model
VSP
Image
Surface Seismic
Survey Design

26. True Seismic Amplitude
AVO WALKAWAY
AVO Walkaway
Source Positions
True Seismic Amplitude
With Changing Offset
P-Wave
S-Wave
P-P and P-SV Analysis
Anisotropy velocity model
Q factor analysis
Reflector

27. Salt Proximity Survey Provides Accurate Salt Face Image
2D, 2.5D and 3D Imaging Solutions

28. 3D VSP Very High Sub-Surface Imaging Resolution
Well 1
Well 2
Exploration and Development Applications
Surface seismic 3D PSDM
Well 1
Well 2
Detailed Preplanning and 3D Modeling Required
3D-VSP Depth Migration

29. Introduction
Seismic Signals in the borehole
Borehole Environment
Borehole survey types
Borehole seismic deployment

30. Borehole seismic on Wireline
Downhole
Geophones
Source
Reference
Sensors
Recording
Unit
Downgoing Wavefront
Pit
Applications
All seismic applications
Operations - Max deviation
dependant of well liquid type & well geometry (example: so far, ASI ran in 77 deg deviation, in Brine)

31. Pipe Conveyed Acquisition
Applications
All seismic applications
Operations
Max deviation: no limit (113o exp)
Ex : 3 * CSI / MDT / Pex / DSI
Extendable CSI sub isolates geophones from tool body & pipes
Wet connect
CSI
Pressure sampling
Sonic
Neutron
Gamma density
Tension sub
Resistivity
Gamma spectroscopy
Compression sub

32. Conventional VSP source
Through Drill Seismic TDS
Conventional VSP source
GAC sensor
Drill bit
TDS Thru-Drill Seis
Applications
All seismic applications, & particularly...
… Position of the drill bit:
on the surface seismic
from the target
... Imaging beside the well
... Prediction ahead of the bit
Operations
Data acquisition
... Tool Pumped down
… Reciprocate between levels
… No circulation
… Acquisition 10 min max
Min deviation so far = 7 deg
Max deviation so far = 90 deg
Saving rig time
Taking effective and fast decisions

33. Logging While Drilling
Drill Bit Seismics
seismic reflector
LWD Tool
sea floor
MWD telemetry
SeismicMWD
Sensor
Surface System
Source
Applications
Real Time checkshots...
… Position of the drill bit:
on the surface seismic
from the target
… Along with ISONIC:
Calibration of ISONIC data & RT Synthetic seismogram
Operations
Saving rig time
Taking effective and fast decisions
Sensors
Weights
sea floor
Drill Bit
seismic reflector

34. Through Tubing Seismic
VSP source
Applications
All seismic applications, & particularly...
... Imaging beside the well (coil tubing drilling, well redevelopment, etc)
Operations
Data acquisition - Stop production
Geophones (GAC)

35. Simultaneous Acquisition
Applications
All seismic applications, & particularly...
… Acquiring borehole seismic data before surface processing starts: Velocity anisotropy, Q attenuation, AVO, VSP-guided processing, shear model
Operation
Tool stays stationary in the well
Platform
Joint acquisitions with GP