Reactive Transport Modeling of the Injection and CO2 Fate in the Mt. Simon Sandstone Formation
Faye (Yifei) Liu1, Peng Lu1, Chen Zhu1, and Yitian Xiao2
1Indiana University, Department of Geological Sciences, Bloomington, IN 47408, [email protected], [email protected], [email protected]
2Exxon Mobil Upstream Research Company, Houston, TX 77027, [email protected]
Reactive transport modeling is an effective tool for monitoring, verification and accounting of CO2 sequestration in deep geological formations. In the current study, reactive transport modeling is performed for CO2 injection into Mt. Simon sandstone formation, a major regional deep saline reservoir in the Midwest, USA at a depth of 2 km and 75 °C. The simulated injection rate is one million tons for 100 years, and modeling continues for 10,000 years to monitor long term fate of injected CO2 and rock-fluid interactions. The results indicate that most of the injected CO2 remains in a radius of 0 – 2500 m lateral distribution within the injection well. A strongly acidified zone (pH < 5) forms in the areas affected by the injected CO2 (0 – 2500 m), and consequently, causing aggressive mineral precipitation and dissolution reactions. Part of the injected CO2 is trapped as secondary carbonate minerals, including calcite, magnesite, ankerite and dawsonite. In association with the extensive dissolution of K-feldspar as a primary mineral, kaolinite, illite and smectite form as secondary minerals in three zones at 0-100 m, 100-2000 m, and 800-2000 m from the injection well, respectively. These three zoning profiles correspond to acidic, weak acidic, and slightly alkaline pH zones. The mineral alteration induced by CO2 injection results in changes in porosity due to these complex mineral dissolution and precipitation reactions. Significant increases in porosity occur in the low-pH zones due to the acidic dissolution of minerals. A zone of decrease in porosity occurs between 200 m and 2500 m due to the precipitation of carbonate minerals.
AAPG Search and Discovery Article #90095©2009 AAPG Eastern Section Meeting, Evansville, Indiana, September 20-22, 2009