Dynamic Simulation of Pilot Scale CO2 Injection in the Arbuckle Saline Aquifer at Wellington Field in Southern Kansas

Holubnyak, Yevhen; Watney, Willard L.; Rush, Jason; Birdie, Tiraz; Doveton, John; Fazelalavi, Mina

The Arbuckle Group saline aquifer is a thick (>800 ft) and deeply buried (>3,500 ft) siliceous dolomite with interbedded shales. This aquifer is part of the Paleozoic-age Ozark Plateau Aquifer System (OPAS) in southern Kansas. It is identified as an excellent candidate for geological CO2 storage due to its location and proximity to major CO2 emission sources, high storage capacity potential, and multiple overlying sealing units, which can ensure safe CO2 storage for the long term. A DOE sponsored pilot-scale project has been funded in which 40,000 metric tons of CO2 from a nearby biofuel plant will be injected in the lower part of the Arbuckle reservoir over a period of 9 months at Wellington field in Sumner County, KS.

This work focuses on development of various dynamic simulation scenarios in order to assess potential risks in support of the EPA class VI (CO2 sequestration) well permit application. The key objective is to estimate the resulting rise in pore fluid pressure, the extent of CO2 plume migration, and geomechanical and geochemical stability of the formation rock and any structural features that may be present. The over arching goal for the EPA is to ensure that the injected CO2 does not negatively impact the underground sources of drinking water in the area.

A detailed geocellular model of the Arbuckle reservoir was produced based on the existing well-logs, seismic data, drill stem tests, step rate test, core analysis, and geochemical evaluations. The data from this modeled was upscaled to the CMG-based dual-permeability compositional model. Base case and alternative dynamic model simulations were conducted by varying key reservoir properties of the formation fluids, rock, and structural features. The simulation results indicate that the injection pressure within the Arbuckle will not exceed the 300 psi threshold limit which can cause the Arbuckle brine to migrate into the overlying freshwater aquifers via improperly abandoned wells or faults. The CO2 plume is projected to be primarily vertical; spreading less than 750 feet laterally. The low permeability units within the Arbuckle will effectively contain the free phase CO2, which eventually dissolves in the brine within a period of 30 years. The spatial distribution of mechanical stresses is also presented from which it is clear that the simulated reservoir pressures are not large enough to compromise sealing unit and wellbore integrity.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013