DE-FC26-03NT15396

Project Goal
The objective of this project is to demonstrate the value of elastic-wavefield seismic stratigraphy, a new seismic interpretation science based on the principles that:

• All modes of an elastic wavefield have equal value for studying subsurface geology.
• One wave mode of a multicomponent (i.e., elastic) seismic wavefield often reveals depositional sequences and depositional facies across a stratigraphic interval that cannot be detected with the other modes of that wavefield.

Performer
Bureau of Economic Geology
University of Texas at Austin
Austin, TX

Fasken Oil and Ranch
Laredo, TX

Vecta Technology
Midland, TX

WesternGeco
Houston, TX

Project Results
Examples have been documented in which shear (S)-wave data provide geologic information that cannot be extracted from the companion compressional (P)-wave data. Examples also have been documented in which P-wave data provide information that is not present in the companion S-wave data.

Benefits
The principal benefit of this research is that it introduces a new seismic technology that will aid in the search for subtle stratigraphic trap oil reservoirs. If a subsurface structural description of major Earth layers is the only information that is needed to exploit a prospect, that information can be provided by P-wave seismic data alone. In contrast, significantly more stratigraphic information can be extracted from multicomponent (elastic wavefield) seismic data than from single-component P-wave data.

Background
Seismic stratigraphy was introduced by Exxon as a formal seismic interpretation science in 1975-77. For decades, the science was limited to single-component P-wave seismic data. This project is expanding the science to multicomponent seismic data and showing how these expanded concepts improve the detection of stratigraphic traps.

Project Summary
In Year 1, the study focused on West Texas 3-component, 3-D seismic data and demonstrated how this new science improves detection of carbonate stratigraphic traps. In Year 2, the research moved to a 3,000 square-mile area of 4-component (4-C), 2-D seismic data coverage across the northern shelf of the Gulf of Mexico and showed that new elastic-wavefield concepts allowed critical new insights into the distribution of stratigraphic traps in sand/shale sequences . In Year 3, the study concentrates on applying elastic-wavefield interpretation concepts to 9-component, 3-D seismic data across the Williston Basin. In each study area, the principal problem that is addressed is to improve the detection of stratigraphic traps.

Among the project highlights:

• 9-C, 3-D seismic data from the Williston Basin have been interpreted. The research team is now documenting distinctions and similarities between P and S seismic sequences and seismic facies observed in these data.
• The greatest differences between P and S seismic sequences and facies observed to date occur in deepwater, near-seafloor strata. Several examples are being documented.
• A numerical study of P-P, P-S, and S-S reflectivities is being done to define key petrophysical properties that cause these modes to exhibit different reflection behavior for identical geological layering.

Current Status (June 2006)
The project is on schedule and midway through its third and final year. The research team is now beginning to prepare the final project report, documenting key principles and research findings, and thinking about publications and public work-shops. Improved S-wave volumes (fast-S and slow-S) across the 9-C, 3-D Williston Basin survey will be delivered to the research team in late January. If there are significant improvements or image variations in this second processing effort compared with the volumes that have already been studied, a second interpretation will be done to develop additional comparisons of P and S seismic sequences and facies.

Project Start: August 1, 2003
Project End: July 31, 2006

Anticipated DOE Contribution: $740,573
Performer Contribution: $189,000 (20.3% of total)

Contact Information
NETL: Purna Halder (purna.halder@netl.doe.gov or 918-699-2084)
U. of Texas: Bob Hardage (bob.hardage@beg.utexas.edu or 512-471-0300

Publications
Six quarterly reports and one continuation report have been delivered to DOE.

Hardage et al., Defining P-wave and S-wave stratal surfaces with 9-C VSPs, The Leading Edge, V. 22, 2003, pp. 720-729.

Fomel et al., Multicomponent seismic data registration for subsurface characterization in the shallow Gulf of Mexico, Offshore Technology Conference, 2003, Houston, TX.

Murray et al., Interpreting multicomponent seismic data in the Gulf of Mexico, Offshore Technology Conference, 2003, Houston, TX.

DeAngelo et al., Depth registration of P and C seismic data for shallow marine sediment characterization, The Leading Edge, V. 22, pp. 96-105.

Hardage and Aluka, Elastic-wavefield seismic stratigraphy, scheduled for the January 2006 issue of AAPG Explorer.

Hardage and Aluka, Depth registration of P and S data, scheduled for the February 2006 of the AAPG Explorer.

Maps of P-P and P-SV amplitude-based seismic facies (top) across a carbonate interval of West Texas and vertical sections through these P-P and P-SV data volumes along inline 67 (bottom). A unique P-SV amplitude facies follows the trend of productive stratigraphic-trap wells (right); the P-P amplitude facies does not (left).

Comparison of deep, depth-equivalent, P-P and P-SV data windows, Gulf of Mexico. These data are a classic example of the principle of elastic-wavefield seismic stratigraphy in that the sequence geometry defined by P-SV features 1 and 2 differs from the P-P geometry.