The Charlton 30/31 field, located in the northern reef trend of the Michigan Basin was developed within the stratigraphie unit historically referred to as the Niagaran Brown. The field covers 300 acres with a structural closure of approximately 300 feet and produced 2.6 million Bbl. of oil during its primary production. A total of 6 wells were drilled during the 1970′s to produce the field. This reservoir is a low porosity, low permeability limestone matrix with irregular dolomitized intervals of higher porosity and permeability. Core Energy selected this field for enhanced oil recovery (EOR) using CO2. The source of the CO2 is a nearby natural gas processing plant which removes the CO2 from the produced gas stream of local Antrim Shale formation production in order to meet pipeline quality specifications.

To monitor the flooding of this reef a full field study is being conducted which includes earth model construction, reservoir simulation with history matching and the acquisition of a 4D seismic survey. This study is being funded by the US Department of Energy and the first 3D survey has been acquired. Basic and advanced geophysical analyses were performed on this initial 3D survey. These included wavelet extraction, well to seismic tie generation, horizon interpretation, seismic variance analysis and investigations into a number of other seismic attributes. The results of this interpretation along with the well data were used in static model construction.

Reservoir simulation was performed using this static model and a 25-year production history. During preparation of the field for injection, it was discovered that the reservoir had been an inadvertent dump-flood with water from the overlying Dundee formation, entering the reef through corroded well casings. This significantly complicated the forward reservoir simulation that was used to predict how the CO2 would flood through this reservoir.

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