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GCPrevious HitPhaseNext Hit Residules Can Reveal Stratigraphic Features*

 

Oswaldo Davogustto1

 

Search and Discovery Article #41141 (2013)

Posted June 30, 2013

 

*Adapted from the Geophysical Corner column, prepared by the author, in AAPG Explorer, April, 2013, and entitled “It’s Just a Previous HitPhaseNext Hit (Residue)”.
Editor of Geophysical Corner is Satinder Chopra ([email protected]). Managing Editor of AAPG Explorer is Vern Stefanic

 

1University of Oklahoma, Norman, Oklahoma ([email protected])

 

General Statement

In the March AAPG Explorer Geophysical Corner (Search and Discovery Article #41140) my colleagues Marcilio Matos and AAPG member Kurt Marfurt discussed the concept of Previous HitphaseNext Hit unwrapping and the computation of Previous HitphaseNext Hit residues. Here, we go deeper: I elaborate on the application of Previous HitphaseNext Hit residues to Previous HitseismicNext Hit data – and the resulting subsequent interpretation of geological features.

Some geologically induced spatial discontinuities, such as channels and faults, easily can be identified as Previous HitseismicNext Hit Previous HitphaseNext Hit shifts or amplitude anomalies when they are above Previous HitseismicNext Hit resolution – but Previous HitphaseNext Hit shifts from condensed sections and erosional unconformities can be subtle and not as easily detected. Spectral decomposition is a proven, powerful means of identifying such discontinuities at specific frequencies that are otherwise buried in the Previous HitseismicNext Hit broadband response.

Although Previous HitseismicNext Hit acquisition and processing preserve Previous HitseismicNext Hit Previous HitphaseNext Hit very well, little has been published about interpreting the Previous HitphaseNext Hit components resulting from spectral decomposition. Morlet complex wavelet transform Previous HitphaseNext Hit residues can improve Previous HitseismicNext Hit spectral decomposition interpretation by detecting the Previous HitphaseNext Hit discontinuities in the joint time-frequency spectral Previous HitphaseNext Hit component – by evaluating the Previous HitphaseNext Hit shifts that are derived from thickness changes in a wedge model.

We unwrap Previous HitphaseNext Hit the Previous HitphaseNext Hit traversing a rectangular contour about each time-frequency sample. In almost all incidents, the contour closes. However, in some cases we have a +180 or -180 degree Previous HitphaseNext Hit anomaly. We display the location of these Previous HitphaseNext Hit residue anomalies and correlate them to stratigraphic discontinuities and inconsistencies in Previous HitseismicNext Hit data quality.

General statement

Figures

Example

Conclusion

Acknowledgment

 

 

 

 

 

 

 

 

 

General statement

Figures

Example

Conclusion

Acknowledgment

 

 

 

 

 

 

 

 

General statement

Figures

Example

Conclusion

Acknowledgment

 

 

 

 

 

 

 

 

Figure Captions

Figure 1. Well to Previous HitseismicNext Hit calibration for wells A and B. Correlation coefficient for both wells is 75 percent.

Figure 2. (a) Previous HitSeismicNext Hit data; (b) the Previous HitphaseNext Hit residues response of a representative time section; (c) and time slice through Previous HitseismicNext Hit amplitude at 1.8 s.

Figure 2c. (a) Previous HitSeismicNext Hit data; (b) the Previous HitphaseNext Hit residues response of a representative time section; (c) and time slice through Previous HitseismicNext Hit amplitude at 1.8 s.

Figure 3. Chair diagram of the Previous HitseismicNext Hit data with a time slice at 1.8 s (a) and a 3-D view of the geo-cellular grid constructed from the combined well log and Previous HitphaseNext Hit residues interpretation (b).

Example

We are able to map interference patterns between the wavelets that occur below Previous HitseismicNext Hit resolution. For example, here we apply the Previous HitphaseNext Hit residues to a Previous HitseismicNext Hit dataset that served as one of the first published applications of spectral decomposition. The geology consists of an incised valley system in the Red Fork Formation of the Anadarko Basin that had at least five stages of incision and fill. Previous works described that the fill of the mentioned incised valley as comprising lag deposits, shales, coals, muddy sands and sands. This dataset also is known for the occurrence of invisible channels – channels that can be detected and correlated through logs, but that are below the resolution of the Previous HitseismicNext Hit data.

Based on the response of the Previous HitphaseNext Hit residues and the tops interpreted from the logs, we identified the incision stages in the Previous HitphaseNext Hit residues attribute. We interpreted each stage as a Previous HitseismicNext Hit horizon and constructed a geological model that honors the well, Previous HitseismicNext Hit and attribute data. This geological model can be further used in reservoir modeling for reservoir properties, such as net-to-gross, porosity and permeability, with the versatility that these properties can change as the depositional environment changed from stage to stage.

Figure 1 shows our well-to-Previous HitseismicNext Hit calibration for two wells, A and B. Locations of wells A and B are shown in Figure 2c. The correlation coefficient is 75 percent for both wells. We identify very distinctive patterns in the log response for each well – well A is located in the regional Red Fork facies and shows faster P-wave velocity, whereas well B is located in the incised valley system facies and displays lower P-wave velocities from the sonic log.

In Figure 2 we display the Previous HitseismicNext Hit data (a), the Previous HitphaseNext Hit residues response of a representative time section (b), and a time slice through Previous HitseismicNext Hit amplitude at 1.8 s (c). Previous HitSeismicNext Hit data (a) are able to resolve only one of the incision stages identified on the time slice of the data (c). This is a common problem in midcontinent datasets, where channels are identified in time slices but not on vertical sections. Using Previous HitphaseNext Hit residues (b) we identify three anomaly responses that correlate with the channel-like features interpreted as incised valleys in the time slice data (c). Using the well and the Previous HitphaseNext Hit residues data, we interpreted the incision stages.

In Figure 3 we show a chair diagram of the Previous HitseismicNext Hit data with a time slice at 1.8 s (a) and a 3-D view of the geo-cellular grid constructed from the combined well log and Previous HitphaseNext Hit residues interpretation (b). This detailed geo-cellular grid allows us to model the properties of each incision stage and the regional Red Fork as a separate event with their on-reservoir properties and modeling technique.

Conclusion

In conclusion, we demonstrated how the use of Previous HitphaseNext Hit residues can be effectively applied to reveal and enhance important stratigraphic features not otherwise revealed by conventional Previous HitseismicNext Hit amplitude. We have developed a workflow that combines well data with Previous HitphaseNext Hit attributes in order to produce a well-to-Previous HitseismicTop consistent stratigraphic model.

Acknowledgment

I would like to thank Mark Falk and Al Warner for their support and advice in this project. I also would like to thank Chesapeake Energy Corporation and CGG-Veritas for donating the data for this project, and to Schlumberger and CGGVeritas for facilitating the software used in these displays.

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