4-D High-Resolution Seismic Reflection Monitoring of Miscible CO2 Injected into a Carbonate Reservoir Page: 7 of 12
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Weak-anomaly enhancement of selected non-inversion, 4-D seismic attribute data represented a
significant interpretation development and proved key to seismic monitoring of CO2 movement.
Also noteworthy was the improved definition of heterogeneities affecting the expanding flood
bank. Among other findings, this time-lapse seismic feasibility study demonstrated that miscible
CO2 injected into a shallow, thin carbonate reservoir could be monitored, even below the classic
temporal seismic resolution limits.
Seismic Activities During Funding Year 3 (September 1, 2005 to August 31, 2006)
Technical Progress
Seismic data acquisition and preliminary processing on the nine 3-D reflection surveys (one
baseline and eight monitor) proposed for budget periods 1, 2, and 3 has been completed or is
proceeding as planned. Consistent with the proposed time line, evaluation of various interpreta-
tion approaches continues and has produced images with strong agreement to production models,
volumetrics, and observations that provide the essential ground truth for this study. Data
acquisition continues on schedule with the utmost care taken to insure the highest possible data
quality, repeatability, and field efficiency. Preliminary data processing on eight of the nine
seismic volumes is complete with secondary processing underway to enhance data resolution and
interpretation potential beyond any documented studies at these depths and for beds this thin.
Interpretations are still very crude and working with processed data that is still being optimized
for consistency, resolution, and signal-to-noise. Several unique approaches to data equalization
have allowed differencing and interpretation consistent with our previous work, enhancing
confidence in the image and growth pattern suggested from preliminary processing. A variety of
unexpected data and reservoir characteristics have been identified and explained, providing
engineers with detailed scenarios of fluid movement unlike any reservoir study in the literature.
As part of the ongoing evaluation task, unique and consistent anomalies in both amplitude and
frequency data suggest the presence of CO2 in the rock can be imaged at these depths and reser-
voir characteristics and as key aspects of the data are identified and enhanced with specialized
processing flows images of the CO2 plume should become vivid. After extensive equalization of
reflection data to minimize and eliminate noise and balance data signal characteristics with
properties inconsistent from survey to survey and not related to fluid changes in the reservoir,
time slices from the reservoir interval were differenced, resulting in interpretable patterns con-
sistent with previous analysis. Tasks ten, eleven, and twelve were completed during budget year
3 as proposed.
Project Results
The efficiency of enhanced oil recovery (EOR) programs relies heavily on accurate reservoir
models. Movement of miscible carbon dioxide (CO2) injected into a thin (~5 m), shallow-shelf,
oomoldic carbonate reservoir around 900 m deep in Russell County, Kansas, was successfully
monitored using high-resolution 4D/time-lapse seismic techniques. High-resolution seismic
methods showed great potential for incorporation into CO2-flood management, highlighting the
necessity of frequently updated reservoir-simulation models, especially for carbonates. Use of an
unconventional approach to acquisition and interpretation of the high-resolution time-lapse/4D
seismic data was key to the success of this monitoring project.
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Miller, Richard D.; Raef, Abdelmoneam E.; Byrnes, Alan P. & Harrison, William E. 4-D High-Resolution Seismic Reflection Monitoring of Miscible CO2 Injected into a Carbonate Reservoir, report, August 31, 2006; United States. (https://digital.library.unt.edu/ark:/67531/metadc881705/m1/7/: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.