Dissolution-Precipitation in Porous Media: Experiments and Modelling

The evolution of porosity due to dissolution/precipitation processes of minerals and the associated change of transport parameters are of major interest for natural geological environments and engineered underground structures. We designed a reproducible and fast to conduct 2D experiment, which is flexible enough to investigate several process couplings implemented in the numerical code OpenGeosys-GEM (OGS-GEM). We investigated advective-diffusive transport of solutes, effect of liquid phase density on advective transport, and kinetically controlled dissolution/precipitation reactions causing porosity changes. In addition, the system allowed to investigate the influence of microscopic (pore scale) processes on macroscopic (continuum scale) transport. A Plexiglas tank of dimension 10 × 10 cm was filled with a 1 cm thick reactive layer consisting of a bimodal grain size distribution of celestite (SrSO4) crystals, sandwiched between two layers of sand. A barium chloride solution was injected into the tank causing an asymmetric flow field to develop. As the barium chloride reached the celestite region, dissolution of celestite was initiated and barite precipitated. Due to the higher molar volume of barite, its precipitation caused a porosity decrease and thus also a decrease in the permeability of the porous medium. The change of flow in space and time was observed via injection of conservative tracers and analysis of effluents. In addition, an extensive post-mortem analysis of the reacted medium was conducted. We could successfully model the flow (with and without fluid density effects) and the transport of conservative tracers with a (continuum scale) reactive transport model. The prediction of the reactive experiments initially failed. Only the inclusion of information from post-mortem analysis gave a satisfactory match for the case where the flow field changed due to dissolution/precipitation reactions. We concentrated on the refinement of post-mortem analysis and the investigation of the dissolution/precipitation mechanisms at the pore scale. Our analytical techniques combined scanning electron microscopy (SEM) and synchrotron X-ray micro-diffraction/micro-fluorescence performed at the XAS beamline (Swiss Light Source). The newly formed phases include an epitaxial growth of barite micro-crystals on large celestite crystals (epitaxial growth) and a nano-crystalline barite phase (resulting from the dissolution of small celestite crystals) with residues of celestite crystals in the pore interstices. Classical nucleation theory, using well-established and estimated parameters describing barite precipitation, was applied to explain the mineralogical changes occurring in our system. Our pore scale investigation showed limits of the continuum scale reactive transport model. Although kinetic effects were implemented by fixing two distinct rates for the dissolution of large and small celestite crystals, instantaneous precipitation of barite was assumed as soon as oversaturation occurred. Precipitation kinetics, passivation of large celestite crystals and metastability of supersaturated solutions, i.e. the conditions under which nucleation cannot occur despite high supersaturation, were neglected. These results will be used to develop a pore scale model that describes precipitation and dissolution of crystals at the pore scale for various transport and chemical conditions. Pore scale modelling can be used to parameterize constitutive equations to introduce pore-scale corrections into macroscopic (continuum) reactive transport models. Microscopic understanding of the system is fundamental for modelling from the pore to the continuum scale.

Process to develop a State Model Law to reduce prescription drug trafficking while protecting pain management

This paper will discuss the intersection of pill mills and the under-treatment of pain, while addressing the unintended consequence that cracking down on pill mills actually has on medical professionals' treatment of legitimate pain in clinical settings. Moreover, the impact each issue has on the spectrum of related policy, regulatory issues and legislation will be analyzed while addressing the national impact on medical care. Lastly, this paper will outline a process to develop a State Model Law on this subject. This process will include suggestions for the future and how we can move forward to adequately address public safety needs and how we can attempt to mitigate the unintended impact prescription drug trafficking has had on a patient's right to appropriate pain management. This balance is achievable and this paper will address ways we can find this elusive balancing point through the development of a State Model Law. ^

Modelling of the TICS Catalyse : Realization of a project

An action of modelling of the Territorial Intelligence Community Systems or TICS began in 2009 at the end of the CaEnti project. It has several objectives: - Establish a set of documents understandable by computer specialists who are in charge of software developments, and by territorial intelligence specialists. - Lay the foundation of a vocabulary describing the main notions of TICS domain. - Ensure the evolution and sustainability of tools and systems, in a highly scalable research context. The definition of models representing the data manipulated by the tools of the suitcase Catalyse is not sufficient to describe in a complete way the TICS domain. We established a correspondence between this computer vocabulary and vocabulary related to the theme to allow communication between computer scientists and territorial intelligence specialists. Furthermore it is necessary to describe the roles of TICS. For that it is interesting to use other kinds of computing models. In this communication we present the modelling of TICS project with business process

Modelling of the TICS Catalyse : Realization of a project

An action of modelling of the Territorial Intelligence Community Systems or TICS began in 2009 at the end of the CaEnti project. It has several objectives: - Establish a set of documents understandable by computer specialists who are in charge of software developments, and by territorial intelligence specialists. - Lay the foundation of a vocabulary describing the main notions of TICS domain. - Ensure the evolution and sustainability of tools and systems, in a highly scalable research context. The definition of models representing the data manipulated by the tools of the suitcase Catalyse is not sufficient to describe in a complete way the TICS domain. We established a correspondence between this computer vocabulary and vocabulary related to the theme to allow communication between computer scientists and territorial intelligence specialists. Furthermore it is necessary to describe the roles of TICS. For that it is interesting to use other kinds of computing models. In this communication we present the modelling of TICS project with business process