47th Annual AAPG-SPE Eastern Section Joint Meeting

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Preliminary Assessment of the CO2 Storage Capacity in the Lower Copper Ridge Dolomite (Upper Cambrian), Northeastern Kentucky


The Kentucky Geological Survey drilled its 1 Hanson Aggregates stratigraphic research well, Carter County, northeast Kentucky, to identify potential CO2 storage reservoirs in the Knox Group and deeper strata, identify potential confining intervals, and test reservoir rock properties in the southern Appalachian Basin. The lower Copper Ridge Dolomite of the Knox (3313 - 4170 ft) was evaluated to determine porosity and permeability as a standalone CO2 storage reservoir. The interval is composed almost exclusively of dolomite with occasional thin sandstone and shale interbeds. Average porosity calculated in the entire lower Copper Ridge is 5.8% and permeability measured in core plugs ranges from less than 0.001 mD to 34 mD. A step-rate test was conducted in the Copper Ridge from 3695–3945 ft, an interval that showed substantial vugular porosity in cores. The interval was isolated at its base by a cast iron bridge plug and cement plug at 3945–3963 ft to prevent pressure communication and fluids loss to underlying strata during testing, effectively abandoning the wellbore below 3963 ft. The interval with swabbed through tubing in 19 runs prior to the step-rate test to recover formation water, recovering 43 barrels of water. Analysis of the water sample showed 114,900 mg/l residue total dissolved solids. A static bottomhole pressure was obtained followed by the step-rate test. The test featured stable pumping rates from 0.25 to 5.5 BPM in 5-minute steps, but was terminated when the supply of fresh drinking water test-fluid was exhausted. After completion of the final step the well was shut-in and pressure falloff monitored for about 12 hrs. The lower Copper Ridge test interval fractured at a pressure of 1979 psi, or a fracture gradient of 0.60 psi/ft. Average permeability of the test interval calculated from the falloff pressure was 15.3 mD. Porosity and net reservoir thickness for calculating potential CO2 storage volume in the lower Copper Ridge were determined using an industry-standard 7% porosity cutoff. Average reservoir thickness in the study area at the cutoff is 71 ft and porosity is 9.0%. Net lower Copper Ridge reservoir pore volume in the 615,450-acre potential storage area is about 4.0 million acre-feet. CO2 storage volume was determined using the methodology of the U.S. DOE, Office of Fossil Energy, National Energy Technology Laboratory. Estimated P50 CO2 lower Copper Ridge storage volume is about 1320 metric tons/acre and 811 million metric tons in the study region. Thus, about 760 surface acres would be required to store 1 million metric tons of CO2, the average annual CO2 released by a coal- fired power plant in the Ohio River industrial corridor.