Geologic Carbon Storage Sites Research Articles

Potential for a Process-based Monitoring Method above Geologic Carbon Storage Sites using Dissolved Gases in Freshwater Aquifers

The process-based method is a new technique for monitoring CO2 storage permanence in the vadose zone above geologic carbon storage (GCS) sites. This method uses ratios of coexisting gas species to understand geochemical processes rather than comparing CO2concentrations with large baseline data sets, thereby making monitoring more efficient. In the vadose zone, ratios among coexisting gases (CO2, O2, N2 and CH4) have been used to distinguish biologic respiration, water-rock-CO2 interaction, and methane oxidation from a leakage signal. We report the preliminary results of a feasibility test conducted in July 2012 at the Zero Emission Research and Technology Center (ZERT) controlled release site in Montana, USA to discern whether the method could be applied to dissolved gases in groundwater, thereby enhancing groundwater monitoring. Preliminary results are favorable, making the process- based approach potentially useful for monitoring shallow freshwater aquifers above GCS sites.

A model comparison initiative for a CO2 injection field test: an introduction to Sim-SEQ

Because of the complex nature of subsurface flow and transport processes at geologic carbon storage (GCS) sites, modelers often need to implement a number of simplifying choices while building their conceptual models. Such simplifications may lead to a wide range in the predictions made by different modeling teams, even when they are modeling the same injection scenario at the same GCS site. Sim-SEQ is a new model comparison initiative with the objective to understand and quantify uncertainties arising from conceptual model choices. While code verification and benchmarking efforts have been undertaken in the past with regards to GCS, Sim-SEQ is different, in that it engages in model comparison in a broader and comprehensive sense, allowing modelers the choice of interpretation of site characterization data, boundary conditions, rock and fluid properties, etc., in addition to their choice of simulator. In Sim-SEQ, 15 different modeling teams, nine of which are from outside the USA, are engaged in building their own models for one specific CO2 injection field test site located in the southwestern part of Mississippi. The complex geology of the site, its location in the water leg of a CO2-EOR field with a strong water drive, and the presence of methane in the reservoir brine make this a challenging task, requiring the modelers to make a large number of choices about how to model various processes and properties of the system. Each model team starts with the same characterization data provided to them but uses its own conceptual models and simulators to come up with model predictions, which can be iteratively refined with the observation data provided to them at later stages. Model predictions will be compared with one another and with the observation data, allowing us to understand and quantify the model uncertainties.

05/00853 No exit: thinking about leakage from geologic carbon storage sites

05/00853 No exit: thinking about leakage from geologic carbon storage sites

No exit: thinking about leakage from geologic carbon storage sites

To function as an effective method to avoid build-up of anthropogenic carbon dioxide (CO 2) in the atmosphere, storage of CO 2 in geologic repositories must be designed and operated to minimize leakage. The design objectives include the obvious requirement to avoid large sudden releases and the more challenging task of keeping long-term leak rates to de minimis levels. Long-term retention requirements are a function of both the atmospheric stabilization target for greenhouse gases and the degree of reliance on CO 2 capture and storage as a mitigation measure. A robust strategy will employ the CO 2 capture and storage method as a component of a portfolio of programs that emphasize energy efficiency and use of renewable energy. To preserve options to stabilize greenhouse gases at prudent levels, it appears we will need to rely extensively on all three components of this portfolio. In developing criteria for management of leakage from geologic repositories, the policy and technical community will need to engage with environmental groups and the public at the earliest possible point in the process.