(147c) Chemical Impacts of CO2 Intrusion into Heterogeneous Caprock

Authors: 
Xiao, T., University of Utah
McPherson, B., University of Utah
Moodie, N., University of Utah
Irons, T., University of Utah
Jia, W., University of Utah
Esser, R., University of Utah
Carbon capture, utilization, and storage (CCUS) is considered one of the most practical options for reducing CO2 emissions from stationary sources. Particularly, CO2-enhanced oil recovery (CO2-EOR) with CO2 injected into oil reservoirs is a well-established and relatively mature technology that offers potential economic benefits of increasing oil production and reducing costs of CO2 storage. Sealing formation (caprock) integrity is considered as a key risk factor, because of the potential for leaked CO2 or brine to migrate into shallow groundwater formations. The purpose of this work is to evaluate the long-term caprock sealing capacity and effects of caprock hydrological heterogeneities on CO2 migration. The Farnsworth Unit (FWU), an oilfield in the northern Anadarko Basin in Texas undergoing active CO2 enhanced oil recovery (EOR) is selected as a case study. A two-dimensional reactive transport model of the caprock (Morrow Shale and Thirteen Fingers) of the FWU was developed based on the site geological model. Specific objectives of this study include: (1) to understand how CO2 is likely to influence the caprock integrity; and (2) to analyze the effects of caprock heterogeneity that control CO2 migration and CO2-water-rock interactions.

Heterogeneities in permeability and porosity could significantly affect containment of intruded CO2 within the caprock. Key results of analysis include forecasted spatial and temporal CO2 distribution in caprock near injection wells, because the pressure and CO2 saturation tend to be the highest over the reservoir. The risk of CO2 leakage through the caprock is evaluated, and mineral alteration of the caprock and self-sealing effects are assessed.

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