Pore-Fluid Composition Oriented 4-D Seismic Data Processing and Interpretation: Implications for Monitoring EOR and/or Sequestration CO₂

Raef, Abdelmoneam E. ¹, Richard D. Miller¹, Alan P. Byrnes¹, William E. Harrison¹ (1) Kansas Geological Survey, Lawrence, KS

High-resolution 4D-seismic data used for monitoring small (15% or less) carbonate reservoir fluid changes in carbonates can be very important in an EOR and/or carbon sequestration endeavor. The high-resolution required for successful monitoring necessitates a seismic data-processing flow that balances two competing attributesevent coherency and high-frequency content-in the data undergoing processing for monitoring/mapping pore-fluid changes. In many situations the ability to steer the processing flow toward superb event continuity comes at the expense of preserving invaluable 4D-seismimc signatures related to subtle pore-fluid changes.

We advocate tolerating less than perfect event continuity (structural imaging) in pursuit of maintaining a more representative poststack seismic wavelet that, to a great extent, honors pre-stack wavelet characteristics and preserves subtle 4D-seismic signatures. Proper understanding of the interplay among high-resolution data sensitivity to time and phase-shifts, the event continuity-bandwidth trade-off, and the modeled 4D-seismic signature of injected CO₂ is crucial to selecting seismic attributes that are responsive to pore fluid. The pore-fluid oriented data processing flow of a pilot timelapse seismic monitoring of injected tertiary EOR-CO₂ project at the Hall-Gurney Field in Kansas resulted in successful and enhanced CO₂-imaging despite the challenging geological and geophysical setting of the targeted thin (6 m) carbonates composed of an ooid shoal complex that encompasses two to three stacked, shallowing-upward cycles of the Lansing-Kansas City Group. The improvement in CO₂- imaging came as a result of adopting a processing flow that emphasizes preserving pre-stack wavelet characteristics, thus enhancing and preserving the reservoir 4D-seismic signature.

AAPG Search and Discovery Article #90055©2006 AAPG Rocky Mountain Section Meeting, Billings, Montana