CCS and Power Systems
Carbon Storage - Geologic Storage Technologies and Simulation and Risk Assessment
Nature and Dynamics of the Reservoir/Caprock Contact and Implications for Carbon Storage Performance
Performer: New Mexico Institute of Mining and Technology
Project No: FE0004844
The purpose of this study is to analyze and assess the zone comprised of the top of the storage formation rock and bottom of the overlying confining zones (known as the confining zone/formation interface, Figure 1) surrounding CO2 injection wells. Effective confining zones are typically low-permeability rock units that are relatively thick and serve as a seal above the storage formation rock that prevents any injected CO2 from migrating upwards out of the storage formation. The study is using information obtained from rock outcropings and core samples of proposed CO2 clastic formations and overlying mudstone confining zones to determine the characteristics of this interface zone, and is using these data to develop conceptual models of the behavior of formation-confining zone interfaces and, in particular, sandstone/mudstone contacts.
The New Mexico Institute of Mining and Technology (NMIMT), in collaboration with Utah State University and Sandia National Laboratories, is examining the primary depositional texture of the sediment at the interface, the structural characteristics of the rock within this zone, and the changes that the sediment underwent as it transformed into rock and following rock formation (diagenesis). These elements affect how the rock responds physically and chemically to CO2 injection. Of concern is the possibility that mesoscale (centimeters to several meters) features at the interface—such as zones where the rock interfaces are preferentially cemented (diagenetic), or is deformed (e.g., fractures)—may greatly influence the degree that the formation and confining zone are connected (Figure 2). High connectivity may in some cases provide leakage pathways into the confining zone, compromising its ability to provide a long-term seal for stored CO2.