Tenth Year Annual Report:
Carbon Storage: 2000-2010 Accomplishments
Completion of Cement Durability Studies
One major aspect of the group's work has been completed by George Scherer and colleagues - characterization of cement durability under CO2 injection conditions. Flow-through and batch experiments, coupled with time-lapse photography, have yielded an equation for cement dissolution rate as a function of temperature and pH. This information, complemented by diffusivity data from fresh cement and field samples, will now be used to inform and verify simulations of CO2-well interactions.
Development of a Multi-Physics Simulator for Deep-Aquifer Injection
Another major goal of the group was to build on an existing geomechanical model, dynaflow, to create a simulator capable of predicting the fate of CO2 and geochemical changes in an injection aquifer. Jean H. Prévost and collaborators have now developed a multiphase, multi-component model that is exceptional in coupling geomechanics (including fracture) with geochemistry. With the addition of new modules that can also be used in other simulators such as Eclipse, dynaflow is able to simulate reaction and degradation of well cements in the presence of carbonated brine solutions, resolve small-scale behavior in the vicinity of wells, and, uniquely, describe the phase behavior of fluid phases, including boiling of CO2.
Creation of Fast Models for Basin-Scale Leakage Estimates
A third goal was to create modeling tools that can make predictions of field-scale CO2 leakage useful for risk assessment. Early research by the Celia Group focused on creating on simplified analytical and semi-analytical models of CO2 plume migration, brine movement, and pressure buildup, which can now be accessed on the web. More recently, the group has created a hierachical modeling system which can incorporate fast analytical and semi-analytical solutions for small-scale features within a coarse-scale numerical simulation. The resulting hybrid models are faster than complex numerical simulators and can be used in making probabilistic assessments of CO2 leakage risk.
New Technique for Estimating Effective Well Permeability
In collaboration with colleagues at BP and Los Alamos National Laboratory, Michael Celia and colleagues have applied and analyzed vertical interference tests to estimate in situ permeability of the area immediately outside the casing of a wellbore, including the cement sheath. The results of the testing are complemented by log data and core samples. These measurements provide an innovative way to obtain the kind of data on leaky wells critical to large-scale numerical simulations of CO2 leakage.
Completion of Molecular-Based CO2-Water Phase Behavior Study
The Debenedetti group, in collaboration with Thanos Panagiotopoulos of Chemical and Biological Engineering, has completed a comprehensive assessment of the performance of several CO2/H2O models for the prediction of phase behavior across a broad range of temperatures and pressures.