1. Detection of Mobile Fluids
Kandiah Balachandran
Pacific Coast Section - SEG, September 9, 2015

2. The Main Points
Common receiver gathers are “always” more coherent than common shot gathers (field records)
Cause: Scattering close to receivers is more important than those close to the source
Anomalous event on horizontal component seismograms suggests the possibility of direct detection
Scattering is analogous to “coupling”, impedance matching, etc. and involves conversion from P to S

3. Anomalous Event: P- to SV- wave Conversion at Near Normal Incidence May Be An Indicator Of Mobile Fluids
Fractures and heterogeneities may be associated with guided waves – the strength and persistence may help in estimating properties of reservoirs especially in marine surveys (large offsets).

6. Typical good record
Refractions
Ground Roll
Reflections
Multiples
P-S converted reflections

7. Typical NG Record
Refraction
???
Scattered noise
Elastic Scattering converts P- waves to S- waves partially

8. Hammer Blow Experiment Powder River Basin
X X … X O O O … O
R1 … R24 S1 S S3 S8
R1 – R 24: 6 in. (15 cm) spacing
S1 – S8: 12 ft (3.66 m) spacing
S – R offset: 6 in. to 96 ft (29.3 m)

10. Common Receiver Gathers from Hammer Blow Experiment

14. VSP – Eastern Saudi Arabia
Elevation view Plan View
Shots up the hole nearest four seismometers
590 ft to 10 ft at 10ft 10 ft from hole

15. Reversed VSP Signals recorded at one surface seismometer for shots at depths ranging from 590 feet to 10 feet at 10-foot intervals

16. Another reversed VSP

17. Comparison of signals from the deepest 4 shots at the four surface seismometers surrounding the Borehole

18. Mounds Test Site

20. Velocity Profile-Amoco Ennis

21. Field Layout – Sapulpa, OK

22. Normal Wave Tests

23. Transposed Wave Test Each panel is a collection of signals recorded at one particular receiver station from weight drops at the 2-ft spaced source locations

29. CONCLUSIONS
P- to SV- wave Conversion at Near Normal Incidence may be an Indicator of MOBILE FLUIDS
FRACTURES other heterogeneties may be the cause of guided waves

30. Selected References
Balachandran, K., Horizontal Component Seismograms: SPE preprint 7437, 1978
Balachandran, K., Seismic problems in clinker areas,
Balachandran, K., Noninterchangeability of sources and receivers, Geophysics, 39,73-80, 1974
Frankel, A., and Clayton, R.W., 1986, Finite difference simulations of seismic scattering, JGR, 91,
Hudson,J.A., The Attenuation of surface waves by scattering: Proc. Camb. Phil. Soc., 67, ,1970

31. References (continued)
Levander, A.R. and Hill, N.R., 1985, P – SV resonances in irregular low-velocity surface layers, Bull. Seis. Soc. Am., 75, 847 – 64
Can we use dynamic elastic nonlinearity measurements of rocks to map reservoir properties? Tawassul Khan, Sofia McGuire, OGJ Sept.10, 2001
In situ seismic shockwaves, Sergei Kostrov, William Wooden, Peter Roberts: OGJ Sept.3, 2001