1. 4D Seismic - A Technology for Future Oil and Gas Exploration

2. Outline of my Project What is Dimension (dot, 1D, 2D, 3D and 4D)?
What is Seismic?
What is 4D seismic (Time Lapse Seismic) and parameters for Time Lapse Seismic?
Four basic stages in E&P life Cycle (Oil and Gas Fields)
Example of Time Lapse Seismic
Study Area – Norne Basin, North Sea
Analysis
Summary
References
Acknowledgement

3. 4rth dimension here is Time and thus
Dimensions
X axis
Y axis
X axis
Z axis
X axis
Y axis
4rth dimension here is Time and thus
Time Lapse
Y axis
X axis
Z axis

4. Concept of Seismic Exploration
Survey ship
Source of shock waves (air gun)
hydrophone
Sea Bed
Sedimentary Rock layers
Path of Reflected waves
Unconformity
Porous Reservoir Rock
water
Oil
Gas
Send some vibrations to the earth and listen them once they are reflected back from various reflectors i.e. record the sound waves

5. Air Guns Generate a Disturbance Hydrophones Detect Pressure
Marine Operations
Air Guns Generate a Disturbance
Hydrophones Detect Pressure
Land Operations
Vibrators Generate a Disturbance
Geophones Detect Motion
Device #1
Device #2
0.0
0.3
0.4
0.5
0.6
0.7
0.8
0.1
0.2
Listening device
#1 records a reflection starting at 0.4 seconds
#2 records a reflection starting at 0.8 seconds
Time
Listening Devices
0 s 
An Explosion!
Energy
Source
.1 s
.2 s
.3 s
Some Energy is Reflected
Most Energy is Transmitted
.4 s
.5 s
.6 s
.7 s
.8 s
To Image the Subsurface, We Use Many Shots (explosions)
and Many Receivers (listening devices)
Arranged in Lines either on Land or Offshore

6. Seismic Data Processing of Field Record
Stream
SLIDE 6
Here is a display of raw seismic data – what would be recorded for one shot/explosion (marine example)
The horizontal scale is receiver number which can be translated into ft/miles or meters/km
The vertical scale is two-way travel time
The receiver nearest the boat is on the left; receiver furthest away on the right
Notice the hyperbolic shape of the reflections
This is because near the boat the energy travels almost straight down and up – very little lateral distance (red arrow on right figure)
For receivers far from the boat (perhaps 4 km) the energy not only has a vertical component but also a horizontal component (blue arrows on right figure)
Thus the distance traveled by the blue rays is longer than the red rays – and takes more time
Based on the hyperbolic shape of the reflections, we can calculate the average velocity along the ray paths
Field Record
Subsurface ‘Image’

7. Number of 2D images combined together form a 3D image
2D seismic and 3D seismic Cube
2D Images
3D Image
Number of 2D images combined together form a 3D image

8. Time is the 4th dimension
What is Time Lapse Seismic?
Number of 3D seismic surveys repeated over a period of time in order to observe reservoir.
Time is the 4th dimension
Solution for reservoir monitoring and may act a partial substitute to the drilling
Image the fluid flow in the subsurface spatially in the region not sampled by wells
To monitor and predict the changes in reservoir properties as a result of production
Improved understanding of drainage and helps to increase ultimate recovery rate
It provides Cheap and reliable solution for reservoir monitoring and may act a partial substitute to the drilling
It provides An opportunity to image the fluid flow in the subsurface spatially in the region not sampled by wells.
It helps to monitor and predict the changes in reservoir properties as a result of production (Saturation and pressure changes, reservoir ambiguity, compartmentalization, undrained reserves etc.)

9. Principles of Time-Lapse Reservoir Imaging
Base 3D seismic survey
“4D” time-lapse seismic measures changes in time (changes in fluids, pressures, temperatures)
Monitor 3D seismic survey

10. Parameters of Time lapse Study
Repeatability
Similarity between two seismic surveys
Acquisition Geometry, Processing similarity, S/N ratio
Detectability
Magnitude of the seismic response to production changes
Rock properties, fluid properties
Interpretability
Integration with available geoscience data
Map based, Model based, Volume based

11. Why we do 4D seismic? Reduce subsurface Uncertainty -
Drainage patterns
Connectivity
Compartmentalization
Scenario choice
Improved static & dynamic model -
Better forecasts
Better plans
Improve Field performance -
Better well positions (producers and injectors)
Control existing wells to:
increase rates/UR,
Avoid water breakthrough
Reduce water/gas production

12. Four basic stages in E&P life Cycle (Oil and Gas Fields)
Exploration
Appraisal
Development
Production
Reservoir and hydrocarbon production is optimized using innovative seismic processing and interpretation techniques , thereby enhancing the value of an asset at every stage
Objective changes as fields mature with a strong impact on expenditures and development and production strategies

13. Two Complementary 4D Analysis Techniques

14. Example of Time Lapse Seismic
Old 3D
New 3D
Top Reservoir
Cap Rock
Oil
Water-flushed
Water-
flushed
Water
OWC
Oil Water Contact shifted upward
OWC
Repeated 2D/3D Seismic Data acquired under similar conditions at different time intervals (4rth dimension is the calendar time).
The difference between two seismic vintages acquired at different time intervals give information on changes in seismic amplitude due to hydrocarbon production.

15. Time Lapse Seismic

16. Norne Basin – North Sea
Norne Field lies in blocks 6608/10 and 6608/11.
85 kilometres from Heidrun, water depth ~ 380 metres.
operated by Statoil (December 1991)
Located on a horst block in the south eastern part of Nordland II in the norwegian sea.
Consists  of two separate  oil compartments, the Norne main structure and the North-east segment.
Total hydrocarbon column is 135 m in which 110 m oil and 25m gas (Statoil, 2001). Reservoir - rocks of lower and middle Jurassic age
~ 80 percent of oil - in Ile and Tofte formations and Gas in Garn formation
Reservoir depth ~ 2,500 metres below sea level.

17. Horst and Graben Structure of Norne basin
North-East / G Segment
Saddle Area
C, D and E Segment
Main Structure

18. Depth Contours laid on Tectonic Setup of Reservoir
Main Structure
North-East
Segment

19. Schematic Diagram – Reservoir System Norne
Garn Formation
Not Formation
U. And L. Ile Formation
Tofte Formation
Tilje Formation
Gas ~ 25 m
Oil ~ 110m
Water

20. Representative Seismic Section Passing Through Wells
Seismic section going through the C- and G-segment. Exploration wells –
6608/10-2,
6608/10-4,
Production well –
6608/10-E-4
Injection well –
6608/10-F-4
Top Springar Fm,
Top Garn Fm,
Top Not Fm,
Top Åre Fm.
Top Garn Fm
Top Not Fm
Top Are Fm

21. Difference Seismic Section 2003 Vintage - 2001 Vintage
PEAK
TROUGH

22. Difference Seismic Section 2004 Vintage - 2001 Vintage
PEAK
TROUGH

23. Difference Seismic Section 2006 Vintage - 2001 Vintage
PEAK
TROUGH

24. Summary Measure changes in seismic response as a result of production
Repeatability is a major concern
Minimize changes between survey acquisition designs
Baseline survey needs to be designed with 4D in mind
Must integrate all information
Four monitor surveys – Each adding information and value

25. References
Vedanti, N., et al. "Time lapse (4D) seismic: Some case studies." Earth Science India 2 (2009):
Aronsen, Hans Andreas, et al. "Time will tell: New insights from time-lapse seismic data." Oilfield Review 14.2 (2002):
Aschjem, Gunnar. "Mapping Reservoir Changes Using 4D Seismic on the Norne G-segment, Norwegian Sea." (2013).
Landrø, Martin. "4D Seismic." Petroleum Geoscience. Springer Berlin Heidelberg,
Osdal, B., and T. Alsos. "Norne 4D and Reservoir Management–The keys to success." 72nd EAGE Conference and Exhibition incorporating SPE EUROPEC
Aarre, Victor. "Estimating 4D velocity changes and contact movement on the Norne field." 2006 SEG Annual Meeting. Society of Exploration Geophysicists, 2006.
Koster, Klaas, et al. "Time-lapse seismic surveys in the North Sea and their business impact." The Leading Edge 19.3 (2000):
Landrø, Martin, et al. "The Gullfaks 4D seismic study." Petroleum Geoscience 5.3 (1999):
Landrø, Martin. "Discrimination between pressure and fluid saturation changes from time-lapse seismic data." Geophysics 66.3 (2001):

26. Acknowledgement
The authors would like to thank NTNU for providing Norne data.
Thank you to RIL for their continuous support and guidance
Thank you to IWSA for giving this platform to present our work