1. Methods  Two codes were coupled together to establish a robust simulator for thermo-hydro-mechanic-chemical coupling issue raised in CCS projects, as shown in Fig. 3.  FLAC3D (ITASCA) addresses the mechanical response, while TOUGHREACT (Berkeley) solves multiphase reactive solute transport problem.  Besides these programming efforts, new elasto-plastic damage model was developed for sedimentary rocks that are prone to “fracking”.  Variables and parameters are constantly computed and updated amongst simulator components, as shown in Fig. 4.  Programs, subroutines, simulator components were integrated, compiled and thoroughly tested with a variety of verifications. A Coupled Simulator for Stability and Geochemical Analysis of Deep Geological Carbon Sequestration Zhenze Li (Postdoc); Mamadou Fall (Professor) Department of Civil Engineering, University of Ottawa; Email: lazyhero@live.cnlazyhero@live.cn Introduction  Carbon capture and sequestration (CCS) is one of the most promising and ambitious project for carbon management.  Ideal conditions for the storage of captured CO 2 can be found in deep geological repository, i.e. highly permeable sandstone, oil/gas field or saline water etc. overlain with thick layers of good seals.  Pioneering CO 2 injection into deep saline aquifers has been carried out in Alberta since 1990s. Ongoing CCS projects in the praires continue to explore the scientific and engineering cutting-edge boundaries.  Injection of CO 2 into underground involves thermo-mechanical-hydro-chemical (THMC) couplings, which requires comprehensive theoretical studies with respect to its long-term stability and environmental risks.  CO 2 can react with rock and minerals either by dissolving out excessive porosity or by producing secondary precipitations. Sharp reduction in pH is ubiquitous, along with remobilization of concentrated toxicants.  Large scale CO 2 injection tests have been conducted in Canada, US and EU. However, theoretical research provides an alternative with minimum demands for financing and time.  This study first developed a numerical simulator with THMC coupling capacity; then verify the simulator with lab test results; and finally applied the new model and simulator into a field study. Verification of simulator 1. Hydrogeological behaviors  A series of shear tests (Zhang & Rothfuchs 2008) and gas injection tests (Hildenbrand et al. 2004) on clayrock samples were simulated and compared with experimental results to verify the proposed coupling approach and codes.Zhang & Rothfuchs 2008Hildenbrand et al. 2004  The cell sample is sized as 2.0*2.85 cm 2 (L*D), pre-saturated by water at 50 o C before permeated with CO 2 (P i =6 MPa).  Both mechanical and hydrological behaviors can be satisfactorily predicted and interpreted by the coupled models and simulator. 2. Reactive transport behaviors  A detailed experimental study (Yu et al. 2012) about CO 2 permeation through oil field sandstone sample.Yu et al. 2012  The sample is sized as 2*17 cm 2 (D*L), permeated with CO 2 saturated brine solution under confining pressure 24 Mpa at 100 o C.  The permeation velocity was maintained at 2.5 mL/min and was sustained for 130 hours.  Chemical species in the leachate and mineral compositions in porous media were analyzed.  It is noted that ion exchange is a significant mechanism (and cannot overlooked) governing the CO 2 -rock- saline interaction under field conditions with high pore pressure, stress and elevated temperature. Field simulation results a) Gas saturation distribution c) pH distribution b) Total dissolved solid (TDS) distribution d) Salinity distribution Conclusions  A THMC coupled model and simulator were developed in this study.  The model and programs were successively verified by laboratory scale cell test results.  The model resembles the inflation of pore space resulted from CO 2 injection relevant overpressure causing mechanical damage, i.e. “fracking” of repository rocks, and its subsequent closing of cracks after hydraulic re-equilibration.  Reactive solute transport in porous media under THMC coupled conditions was modeled with reasonable degree of correlation.  Ion exchange reaction occurs as the dominant mechanism for CO 2 -rock interaction.  Large scale simulation of CO 2 injection in field cases captures the time-dependent changes of major parameters, e.g. gas saturation, total dissolved solid, pH and salinity etc. Prospects  It is expected to extend the current modeling tool into risk analysis or environmental assessment for shallow aquifers in the context of deep geological repository for CO 2. Figure 6. Time-dependent variation of chemicals in leachate Figure 5. a) Diagram of testing conditions; b) Triaxial shear test results and prediction; c) Testdata on accumulated gas pressure at outlet and permeability comparative to prediction Figure 1. CCS schematic diagram Figure 2. Typical pore structure for sandstone Figure 4. Coupling algorithm, simulator components and variable updating Figure 3. Coupling mechanism of THMC factors and relevant programs accounting for coupled computations Figure 7. Spatial distribution of crucial parameters (up: t=10 yr; mid: t=50 yr; bot: t=100 yr)