Successful large-scale implementation of Carbon Capture and Sequestration (CCS) requires clear demonstrations that it is possible to accurately quantify the environmental and human health risks, and the cost, of geologic carbon dioxide (CO2) storage. However, significant uncertainties exist due to limited knowledge of the interaction between CO2and geologic formations within the storage environment. These potential interactions may positively or negatively impact reservoir performance. Brookhaven researchers are developing modeling frameworks and experimental methods to identify, quantify, and manage some of the most important uncertainties.
Models of prospective geologic reservoirs are, in the best cases, constructed using geostatistical methods that combine often sparse and variable datasets to predict geologic storage formation characteristics and the performance of the caprocks that must prevent the CO2 from leaking into other subsurface resources or back into the atmosphere. These models consider structural geology, mineralogy, permeability, porosity, eventual CO2-brine chemistry, and fracture type and frequency. We are building on the extensive databases developed by the DOE Regional Carbon Sequestration Partnerships, state geological surveys (e.g., Ohio State Survey) and university geologic repositories (e.g., Western Michigan University Geological Repository) to develop methods to quantify uncertainties and heterogeneities of reservoir formations, performance criteria and pore-water geochemistry that ultimately define how well we understand these critical processes. The databases and model results will also provide boundary conditions for the experimental research described below.
Current models used to predict CO2 behavior in reservoirs only consider the hydrodynamics and physical characteristics of the geologic formations, and assume that geochemistry will not impact reservoir performance. We are developing experimental tools and methodologies to identify the conditions under which CO2-saturated brines will impact flow within migration pathways by reacting with reservoir formations, caprocks, and well cements. In order to study the origin of any flowpath changes, synchrotron-based microprobe and diffraction tomographic imaging methods are being developed at Brookhaven’s National Synchrotron Light Source (NSLS) beamline X27A. These capabilities are being used to study pore-scale precipitation and corrosion processes in core samples under pressure and temperature conditions that mimic geologic storage reservoirs. The 3-dimensional in-situ imaging capabilities will benefit greatly from improved spatial resolution and sensitivity upon completion of the NSLS II. (Figure: X-ray diffraction microtomography at beamline X27A)
Accurate risk assessments and costing models of site-specific geologic storage projects and regional capacity assessments require the development of a decision-making framework that integrates the latest scientific understanding of pore-scale flowpath geochemistry. Major collaborative efforts are required to tackle scaling issues and achieve this level of integration. We have teamed up with Princeton University and the University of Minnesota to develop an integrated decision making framework (see DOE Office of Fossil Energy NETL project factsheet).