Modelling reactive transport processes in porous media

Reactive transport modelling has wide applications in geosciences. In the field of hydrogeology, it has been utilised to simulate the biogeochemical processes that disperse and degrade contaminants in the aquifer. For geotechnical applications, such as geological CO2 sequestration, the reaction of CO2 with the ambient saline aquifer determines the final success of storage. In a radioactive waste repository, scientists rely on reactive transport models to predict the mobilisation of hazardous radionuclides within space and time. In this work, the multi-component mass transport code OpenGeoSys, was coupled with two geochemical solvers, the Gibbs Energy Minimization Selektor (GEM) and the Biogeochemical Reaction Network Simulator (BRNS). Both coupled codes were verified against analytical solutions and simulation results from other numerical models. Moreover, the coupling interface was developed for parallel simulation. Test runs showed that the speed-up of reaction part had a very good linearity with number of nodes in the mesh. However, for three dimensional problems with complex geochemical reactions, the model performance was dominated by solving transport equations of mobile chemical components. OpenGeoSys-BRNS was applied to a two dimensional groundwater remediation problem. Its calculated concentration profiles fitted very well with analytical solutions and numerical results from TBC. The model revealed that natural attenuation of groundwater contaminants is mainly controlled by the mixing of carbon source and electron donor. OpenGeoSys-GEM was employed to investigate the retardation mechanism of radionuclides in the near field of a nuclear waste repository. Radium profiles in an idealised bentonite column was modelled with varying clay/water ratios. When clay content is limited, Ba-Sr-Ra sulfate solid solutions have a very strong retardation effect on the aqueous radium. Nevertheless, when clay mineral is abundant, cation exchange sites also attract Sr and Ba, thus dominates the transport of Ra

Modelling Coupled Component Based Multiphase and Reactive Transport Processes in Deep Geothermal Reservoirs using OpenGeoSys

ABSTRACT In deep geothermal reservoirs, artificial fracture networks are often stimulated and enhanced during the well construction, in order to facilitate the efficient heat transfer from the host rocks to the heat carrying fluid. However, throughout the life span of a geothermal power plant, the geochemical reactions on the fracture surfaces will gradually confine the hydraulic and mechanical behavior of the fractures, thus further affect the energy output of the reservoir. The numerical simulation of such long term behavior of the reservoir imposes several challenges to modelers. First, it is a coupled non-isothermal system that often contains multiple fluid and solid phases. In addition, depending on the pressure and temperature conditions, phase change process may happen in certain parts of the modeling domain. To further increase the non-linearity of the system, the long term fluid-rock geochemical reactions have to be included in the consideration and the model must be able to account for their feedback to the hydraulic and flow field. Within the framework OpenGeoSys software, we extended the traditional phase volume based multiphase flow module to chemical component based formulations. This allows a further coupling with geochemical processes on the fracture surface. The developed code will be verified against several benchmark cases, which involves non-isothermal multiphase flow involving phase change and mineral-water geochemical reactive transport processes. The simulation of coupled processes in fracture network dominated geothermal reservoirs will also be presented. INTRODUCTION For the performance analysis of deep geothermal reservoirs, numerical modelling tools are widely employed to simulate the flow processes in the subsurface. With high temperature and pressure in the reservoir, coupled multiphase flow processes often interact with chemical reactions and impose challenges on numerical models. In order to reproduce the phase change behavior mentioned above in the numerical simulation, there exist so far several different numerical schemes. The most popular one is the primary variable switching method proposed b

A thermo-hydro-mechanical finite element model of freezing in porous media-thermo-mechanically consistent formulation and application to ground source heat pumps

Freezing phenomena in porous media have attracted great attention in geotechnics, construction engineering and geothermal energy. For shallow geothermal applications where heat pumps are connected to borehole heat exchangers (BHEs), soil freezing around the BHEs is a potential problem due to persistent heat extraction or inappropriate design which can sig- nificantly influence the temperature distribution as well as groundwater flow patterns in the subsurface, and even lead to frost heave. A fully coupled thermo-hydro-mechanical freezing model is required for advanced system design and scenario analyses. In the framework of the Theory of Porous Media, a triphasic freezing model is derived and solved with the finite element method. Ice formation in the porous medium results from a coupled heat and mass transfer problem with phase change and is accompanied by volume expansion. The model is able to capture various coupled physical phenomena during freezing, e.g., the latent heat ef- fect, groundwater flow with porosity change and mechanical deformation. The current paper is focused primarily on the theoretical derivation of the conceptual model. Its numerical implementation is verified against analytical solutions of selected phenomena including pure phase change and thermo-hydro-mechanical process couplings

Roadmap Tiefe Geothermie für Deutschland : Handlungsempfehlungen für Politik, Wirtschaft und Wissenschaft für eine erfolgreiche Wärmewende

Strategiepapier von sechs Einrichtungen der Fraunhofer-Gesellschaft und der Helmholtz-Gemeinschaf

IGFBP-rP1, a potential molecule associated with colon cancer differentiation

<p>Abstract</p> <p>Background</p> <p>In our previous studies, we have demonstrated that insulin-like growth factor binding protein-related protein1 (IGFBP-rP1) played its potential tumor suppressor role in colon cancer cells through apoptosis and senescence induction. In this study, we will further uncover the role of IGFBP-rP1 in colon cancer differentiation and a possible mechanism by revealing responsible genes.</p> <p>Results</p> <p>In normal colon epithelium, immunohistochemistry staining detected a gradient IGFBP-rP1 expression along the axis of the crypt. IGFBP-rP1 strongly expressed in the differentiated cells at the surface of the colon epithelium, while weakly expressed at the crypt base. In colon cancer tissues, the expression of IGFBP-rP1 correlated positively with the differentiation status. IGFBP-rP1 strongly expressed in low grade colorectal carcinoma and weakly expressed in high grade colorectal carcinoma. In vitro, transfection of PcDNA3.1(IGFBP-rP1) into RKO, SW620 and CW2 cells induced a more pronounced anterior-posterior polarity morphology, accompanied by upregulation with alkaline phosphatase (AKP) activity. Upregulation of carcino-embryonic antigen (CEA) was also observed in SW620 and CW2 transfectants. The addition of IGFBP-rP1 protein into the medium could mimic most but not all effects of IGFBP-rP1 cDNA transfection. Seventy-eight reproducibly differentially expressed genes were detected in PcDNA3.1(IGFBP-rP1)-RKO transfectants, using Affymetrix 133 plus 2.0 expression chip platform. Directed Acyclic Graph (DAG) of the enriched GO categories demonstrated that differential expression of the enzyme regulator activity genes together with cytoskeleton and actin binding genes were significant. IGFBP-rP1 could upreguate Transgelin (TAGLN), downregulate SRY (sex determining region Y)-box 9(campomelic dysplasia, autosomal sex-reversal) (SOX9), insulin receptor substrate 1(IRS1), cyclin-dependent kinase inhibitor 2B (p15, inhibits CDK4) (CDKN2B), amphiregulin(schwannoma-derived growth factor) (AREG) and immediate early response 5-like(IER5L) in RKO, SW620 and CW2 colon cancer cells, verified by Real time Reverse Transcription Polymerase Chain Reaction (rtRT-PCR). During sodium butyrate-induced Caco2 cell differentiation, IGFBP-rP1 was upregulated and the expression showed significant correlation with the AKP activity. The downregulation of IRS1 and SOX9 were also induced by sodium butyrate.</p> <p>Conclusion</p> <p>IGFBP-rP1 was a potential key molecule associated with colon cancer differentiation. Downregulation of IRS1 and SOX9 may the possible key downstream genes involved in the process.</p

First Detection of Photons with Energy Beyond 100 TeV from an Astrophysical Source

We report on the highest energy photons from the Crab Nebula observed by the Tibet air shower array with the underground water-Cherenkov-type muon detector array. Based on the criterion of muon number measured in an air shower, we successfully suppress 99.92% of the cosmic-ray background events with energies $E>100$ TeV. As a result, we observed 24 photon-like events with $E>100$ TeV against 5.5 background events, which corresponds to 5.6$\sigma$ statistical significance. This is the first detection of photons with $E>100$ TeV from an astrophysical source.Comment: April 4, 2019; Submitted to the Physical Review Letter