Simulation of the Impact of Annex Gases (SOx, NyOx, O2 co-injected with CO2 during its geological storage) on the Reservoir-Rocks Reactivity – SIGARRR

Advances in numerical modeling tools must enable to simulate the long term behavior of co-injected gases in CO2 storage sites. For this purpose, we recommend expanding the thermodynamic databases through the acquisition of missing experimental data that will help to calibrate and to validate the equations of state adapted to these systems. A series of experiments investigating reservoir-rock and gas mixtures systems and achieved in realistic pressure and temperature conditions will be compared with the results of numerical simulations to validate the newly implemented codes.
Our research program will focus on some impurities (SO2 , NO, O2) and we will evaluate their impact on reservoir rocks (silicates + clay minerals) believed to provide specific reactivity (i.e. iron containing minerals) to possible inferences on the environment in case of leakage .

The numerical simulation (geochemistry and molecular) and experimental combined approach is a real plus for the project.
The acquisition of new unpublished experimental data and pseudo- experimental, especially for NO, gas mixtures and complete gas-brine-rock systems is and will be an important result.
The development of reactive-transport codes (Chess/Hytec and perhaps Tough2 as part of the project or PhreeQc3 elsewhere) allows a better representation of gases and of their non-ideal behavior in high pressure/high temperature conditions with prospects not only for the geological storage of CO2 but also for other applications. Similarly, the development of the thermodynamic database Thermoddem notably concerning the properties of gases, also opens interesting perspectives for modelers.
Among the participants of the consortium, two proposals emerged and were submitted to ANR in their last calls for projects ANR. One of this proposal, FluidStory carried by BRGM and accepted for funding this year, is about the valorization of CO2 for the storage of wind energy.

A first interesting perspective lies in the expected formulation of first recommendations in terms of environmentally acceptable concentrations of impurities, potentially co-injected with the CO2. These results could affect the retained capture techniques and their associated costs and thus contribute to the deployment of the whole technology.
Various developments are expected: experimental procedures, thermodynamic models or computer codes, the Thermoddem database open to the relevant research teams several application prospects in the field of the capture/storage CO2 but also in other areas.
As mentioned above, a project of CO2 valorization within the context of energy storage, FluidStory, has notably been selected for funding by ANR and will start in 2016. The BRGM, as coordinator, and ARMINES / MINES ParisTech among others will participate in this project.

The acquisition of experimental data, molecular simulations (pseudo- experimental data), the development of geochemical and thermodynamic models and the associated numerical simulations follow their parallel course at the moment. In each area, the different experimental and pseudo- experimental teams shall exchange their approaches/problems/solutions ... Modeling teams have already started to compare their results to verify and validate the various selected modeling options.
Several teams presented their work related to the project at international conferences, notably at the most important conference on the subject of capture, storage, valorization of CO2, GHGT.
The LRGP wrote a paper on thermodynamic models that has already been accepted by the journal Industrial & Engineering Chemistry Research . While part of the experimental work of GéoRessources will soon be submitted for publication in the journal Fluid Phase Equilibria.

Most of the industrialized countries have started to significantly reduce their greenhouse gases emissions. CO2 capture and geological storage processes entered an operational phase with the emergence of several pilot-sites where different technologies are tested.
The major part of the total induced cost occurs during the capture, in the separation step, where CO2 is dissociated from other gas components. The gas mixture composition can vary considerably both qualitatively and quantitatively, based on the origin of CO2, the chosen process of capture and the concerned industrial sector. Indeed, in addition to CO2, several components can be present at various concentration levels, including O2, N2, SOx, H2S, NyOx, H2, CO, and Ar that are a concern to the energy industry. These impurities can have an impact on the chemical reactivity with water, reservoir or cap-rock forming minerals, and the materials constituting injection or monitoring wells installed in a repository site. Moreover, some impurities (SOx, H2S, NyOx, CO) are toxic for human health and the environment, even at low concentrations.

The role of these gas impurities on the geochemical behavior of the storage sites is presently not well documented (a few experimental results on the CO2-H2S mixture and some geochemical simulations on CO2-H2S/SO2). In 2006, two projects funded by the ANR, “Puits-CO2” and “Gaz Annexes”, have been initiated and were mainly focused on the experimental characterization of the impact of gas mixture on the reactivity of minerals and materials present within geological repositories. The Institut National Polytechnique de Lorraine (INPL) directed the second project, which finished in May 2011 and led to important experimental/modeling results on individual gases and even to first investigations on the water-gas mixture-rock system.

Based on the technical experience gained and the laboratory equipment acquired from these previous research efforts, it is appropriate to propose a new project to study the behavior of co-injected gases mixtures under storage conditions. In this investigation, our research team will focus efforts on numerical modeling of the water-gas-rock system. The main thrust of purpose of this proposal is to conduct geochemical simulations to model the long-term behavior of co-injected gases within CO2 storage sites. We will then focus on the:
- Impact of CO2 and co-injected gases on the minerals and reservoir geochemistry,
- Possible inferences on the environment in case of leak.
Besides, we recommend extending thermodynamic databases by acquiring essential experimental data, which will allow fitting and validating the appropriate equations of state for all these systems. A series of experiments achieved in realistic pressure and temperature conditions and investigating reservoir-rock and gas mixtures systems will enable us to compare results of numerical simulations with the results of experiments to validate the newly implemented codes. We will focus the research program on some impurities (SO2, NO, O2) and evaluate their influence on the reservoir-rocks (silicates + clay minerals) expected to provide specific reactivity (e.g. iron containing minerals). For such reservoir rocks, the learning acquired about the fate of impurities in reservoir will lead to some conclusions about the possible composition of unexpected leakages and their impacts on environment and health.
Finally, integrating the results of the whole project, some first recommendations about the composition of injected CO2 stream will be formulated in order to minimize environmental risks.