This project is being conducted in two phases. The objective of the first phase is to characterize the reservoir using advanced evaluation methods in order to assess the potential of a CO2 flood of the target reservoir. This reservoir characterization includes advanced petrophysical, geophysical, geological, reservoir engineering, and reservoir simulation technologies. The objective of the second project phase is to demonstrate the benefits of using advanced seismic methods for the monitoring of the CO2 flood fronts.

Schlumberger Data & Consulting Services - Pittsburgh, PA
New Horizon Energy - Traverse City, MI

During the 1970s and 1980s, a number of Silurian Reef oil fields were discovered in the northern and southern flanks of the Michigan Basin. These fields have produced over 1 billion barrels of oil to date and are in the late stage of their primary productive life. EOR projects in these fields using CO₂ injection guided by 4-D seismic monitoring will ensure that the maximum remaining reserves are recovered. This technology also will apply to monitoring CO₂ sequestration projects in the future.

Project Results
The project has established a mappable correlation between low instantaneous frequency and high porosity. This relationship has been supported by the wavenumber study conducted with the depthed volume. This relationship will be tested in the near future when a new borehole will be drilled into the reef. Once its location has been determined the porosity the borehole will encounter will be predicted with this technique. Should this relationship be proved, it will allow the porosity distribution through these reefs to be mapped accurately. Reservoir simulations needed to optimize the field’s CO₂ injection parameters then can incorporate seismically detected porosity volumes to predict CO₂ migration in carbonates. The final report will discuss the details of the project work.

Benefits
If it is confirmed that instantaneous frequency can be used to accurately predict the distribution of >5% porosity through-out these reefs, this will allow for highly accurate reservoir simulations and greater reserve recoveries, thereby resulting in the most optimized enhanced oil recovery (EOR) projects possible. Monitoring of CO₂ floods will result in the ability to modify the injection parameters to recover more oil and sequester more CO₂.

Summary
Project milestones include the following:

• Researchers chose for this project a Silurian-age reef in the Northern Reef trend of the Michigan Basin that was selected for a CO₂ flood.
• Existing geological information was used to develop a rock property volume that then was used to model and optimize the seismic acquisition parameters.
• The base 3-D seismic survey was acquired over the Silurian reef.
• The research team performed basic seismic processing on the acquired 3-D data and interpreted the data volume.
• Seismic-attribute analysis was performed, and a potential relationship was noted between lower instantaneous frequency and porosity over 5%.
• Project researchers, using the initial porosity volume, conducted a preliminary reservoir simulation and production history matching.
• A number of existing wellbores in the reef were worked over in preparation for the commencement of CO₂injection operations.
• Researchers completed azimuthal processing on the 3-D seismic data and performed an azimuthal velocity analysis on this data set.
• A depth volume also was generated and interpreted.
• Small volumes of CO₂ were injected in the upper section of the northern end of the reef.
• The research team conducted wavenumber analysis using depthed volume, which appears to support the instantaneous-frequency study.
• It was discovered that the reef has been inadvertently “dump flooded” through shallow casing leaks since the primary production was concluded.
• A more detailed porosity distribution throughout the reef has been generated.
• The new porosity distribution is currently being used for a new reservoir simulation that will attempt to better model the field performance.
• The simulation is in the process of major updating to include recent pressure data, CO₂ injection history, addition of the A-1 Carbonate formation as a productive interval, and an improved PVT description.

(February 2009)
This project has been completed. Due to its size (57MB), the final report is available upon request. See contact information below.

$1,971,240

$7,085,519 (78% of total)

NETL - Chandra Nautiyal (Chandra.Nautiyal@NETl.doe.gov or 918-699-2021)
Schlumberger - Joseph Frantz (frantz@pittsburgh.oilfield.slb.com or 412-787-5403)

Due to the size of the PDF file (57MB), the final report is available upon request.