Passive seismic survey is a geophysical method that utilizes a spectral frequency from seismicity data to identify subsurface reservoir fluids. Rock pores that contain hydrocarbon fluids show higher low-frequency amplitude between 2-4 Hz compared with those that contain water. This paper shows the feasibility study that has been done in S Field, South Sumatra Basin. Four wells were used to validate the result of the spectral data. This method is also considered as a prospect ranking tool in the vicinity of the S field. Eighteen measurement points were collected and grouped into 6 clusters. Four clusters are located near S-1, S-2, S-3, and S-4 wells. One cluster is located on prospect K and the other one on prospect G. Standard signal processing flows were conducted such as band-pass filter, FFT, and moving average. The result shows that the maximum amplitude low-frequency between 2-4 Hz of K and S-1 is less than 0.017. On the other hand, S-2, S-3, S-4 and G show a relatively high amplitude of more than 0.02 which indicates a greater possibility of hydrocarbon accumulation when compared with K and S-1. This result was confirmed by gas production in S-2 and oil production in S-3. S-4 has not been tested yet, but the refined well correlation it indicates that there is a limestone reservoir of about 60 feet above OWC. S-1 shows a low amplitude which indicates low potential. The completion log confirmed that the well did not penetrate the reservoir target. Prospect G which has a high amplitude of low-frequency anomaly is more interesting than prospect K. To conclude, low-frequency passive seismic method was successful in distinguishing between water or no hydrocarbons. It is feasible to employ this methodology as a tool for hydrocarbon detection and also as a tool to help in prospect ranking.

1. The Energy Company of Choice
Application of Low Frequency Passive Seismic Method
for Hydrocarbon Detection in S Field,
South Sumatra Basin
Andika Perbawa, Danar Yudhatama, M. Aidil Arham
PT. Medco E&P Indonesia

2. • Introduction
• Data and Method
• Result and Discussion
• Conclusions
Today’s Talk
Passive Seismic Method
• Case Studies
• Objectives

3. • Passive Seismic Method (PSM) is a geophysical method that utilizes a spectral frequency from seismicity data
to identify a subsurface fluid behavior/direct hydrocarbon indicator (Holzner et al., 2005; Akrawi and Bloch,
2006; Suntsov et al., 2006)
• When the seismicity is propagating through a reservoir which contains hydrocarbon, empirically it will amplify
the amplitude of low frequency between 1-6 Hz (Dangel, et al., 2003) or 1-4 Hz (Hardage, 2008) or 2-4 Hz
(Suryanto, 2008). It also called as spectral modification.
What is Passive Seismic Low Frequency Anomaly ?
Introduction
(Alwi, 2011)

4. Possible causes of spectral modifications (Suntsov, et al., 2006) :
•Attenuation phenomena in poro-elastic media
•Subsurface reflection patterns
•Resonant amplification due to oscillations
•Phase transition effects
Working Hypotheses
Introduction
Resonant Amplification
Certain frequencies of incoming waves are
amplified due to an oscillation process at the
pore scale
Resonant Scattering
Incoming waves are reflected at the
surface and the reservoir due to
heterogeneities

5. Overseas Field Cases
Case Studies
Portiguar Basin, Brazil, 2004 Voiitsdorf Area, Austria, 2005
Voiitsdorf Area, Austria, 2005
Dangel et al., 2003
Jordan Italy
Ukraine Morocco
Burgos Basin, Mexico, 2006
(Frehner, et. al., 2007)

6. • Passive seismic survey conducted over Tanggulangin oil and gas
field
• Passive Seismic method is proven to show positive relationship
between amplitude frequency and hydrocarbon accumulation
(Alwi , et.al., 2011)
Indonesia Field Case
Case Studies

7. Objectives
To test the feasibility of low frequency passive
seismic method around “S” field
To classify and rank prospect G and lead K
nearby “S” Field

8. Passive Seismic Data Point
Total data points: 18
Data and Method
0 2 Km

9. Composite Seismic Line
Data and Method
P-1 S-1 S-2 S-3 S-4 R-1GF-1K
0 2 KmTop Baturaja Limestone
Top Basement

10. • Dig a hole to around 30-50 cm
• Insert three special iron rods for placing the seismometer
• Orient the seismometer to magnetic north
• Connect the seismometer to the data logger, GPS, and laptop
• Record the seismicity data for 30 minutes
• Copy data from data logger to USB flash-disk, then copy to laptop for further analysis
Survey Acquisition
Data and Method

11. Processing Workflow
Data and Method

12. Data Processing
Data and Method

13. CWT
Data and Method: Data Processing
0 1 2 3 4 5 6 7 8 9 10
0
0.01
0.02
0.03
0.04
0.05
0.06
Amplitude Spectrum of U-D(t)
Frequency (Hz)
|Z(f)|
0 1 2 3 4 5 6 7 8 9 10
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Amplitude Spectrum of U-D(t)
Frequency (Hz)
|Z(f)|
Window1Window2Window3
NormalizedamplitudeNormalizedamplitudeNormalizedamplitude
FFT
Smoothing
FFT
Smoothing
FFT
Smoothing
Frequency Spectrum Up-Down (UD) Frequency Spectrum Up-Down (UD)
Frequency Spectrum Up-Down (UD) Frequency Spectrum Up-Down (UD)
Frequency Spectrum Up-Down (UD) Frequency Spectrum Up-Down (UD)

14. Bubble Map of Amplitude Frequency 2-4 Hz for
Vertical component (UD) for all data points
Result
Result and Discussion
Window 1
Window 3
Window 2

15. Result and Discussion
Average Amplitude of Frequency Between 2-4 Hz (UD)
0 2 Km

16. Result and Discussion
Average Amplitude of Frequency 2-4 Hz
0.017 0.021 0.031 0.038
Gas Zone
Oil Zone
?
Gas Zone
Oil Zone

17. Result and Discussion
Average Amplitude of Frequency 2-4 Hz
0.017 0.021 0.031 0.038
Basement

18. Well to Amplitude Correlation Analysis
Result and Discussion
Point
Vertical
Amplitude
Well Status
S-1 0.017 Dry Hole
S-2 0.021 Gas
S-3 0.031 Oil
S-4 0.038
P&A well with no testing
but possible oil
accumulation
G 0.041 Prospect
K 0.010 Lead
Average Amplitude of Frequency Between 2-4 Hz

19. Prospect and Lead Ranking
Result and Discussion

20. 1. Four locations have a relatively higher amplitude (>0.021) frequency between 2-4 Hz: S-2, S-3, S-4
and prospect G while S-1 and lead K shows a relatively small amplitude frequency (<0.017)
2. Passive seismic confirms that low amplitude frequency in S-1 corresponds with no hydrocarbon
accumulation while a high amplitude frequency in S-2 and S-3 corresponds with hydrocarbon
accumulation in S field
3. S-4 shows a high amplitude of low frequency which is justified by 60 feet of limestone reservoir
above oil-water contact. It is possible that the zone is filled with oil
4. Prospect G shows a high amplitude frequency similar with S-3 which indicates high possibility of
hydrocarbon accumulation in Prospect G
5. Lead K shows a low amplitude frequency similar with S-1, which indicates low possibility of
hydrocarbon accumulation in Lead K
6. Passive seismic method is successfully applicable for identifying hydrocarbon accumulation in the
subsurface
Conclusions

21. Alwi, M., Praptono, S.H., Murtadho., 2011, Low Frequency Passive Seismic Study In Brantas Block,
East Java, Indonesia. IPA Proceeding. Jakarta
Bloch, G. and Akrawi, K., 2006, Application of Low Frequency Passive Seismic Surveys in ADCO, UAE.
EAGE Workshop Passive Seismic, December 10-13, Dubai, Uni Arab Emirates
Dangel, S., M. E. Schaepman, E. P. Stoll, R. Carniel, O. Barzandji, E.-D. Rode, and J. M. Singer, 2003,
Phenomenology of tremor-like signals ob-served over hydrocarbon reservoirs. Journal of
Volcanology and Geother-mal Research,128, 135–158.
Frehner, M., Schmalholz, S., Podladchikov, Y., Holzner, R., 2007, Low Frequency Modification of
Seismic Background Noise Due to Interaction With Oscillationg fluids in Prorous Rocks. EAGE.
Hardrage, B., 2008, Passive Seismic Techniques, Search and Discovery Articles #40319.
Holzner, R., Eschle, P., Zurcher, H., Lambert, M., Graf, R., Dangel, S. and Meier, P. F., 2005, Applying
microtremor analysis to identify hydrocarbon reservoirs. first break, 23, 41-46
Suntsov, A.E., Aroutunov, S.L., Mekhin, A.M. and Meltchouk, B.Y., 2006, Passive Infra-Frequency
Microseismic Technology-Experience and Problems of Practical Use: EAGE Workshop
Passive Seismic, December 10-13, Dubai, United Arab Emirates
Suryanto, W., Wahyudi., 2008, Monitoring Mikroseismik Untuk Deteksi Langsung Keberadaan
Hidrokarbon. PIT HAGI 2008. Bandung.
References

22. The Energy Company of Choice
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