Reactive Transport Modeling of the Injection and CO₂ Fate in the Mt. Simon Sandstone Formation

Faye (Yifei) Liu¹, Peng Lu¹, Chen Zhu¹, and Yitian Xiao^2
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