1,837 research outputs found
Thermal effects on geologic carbon storage
The final publication is available at Springer via http://dx.doi.org/10.1016/j.earscirev.2016.12.011One of the most promising ways to significantly reduce greenhouse gases emissions, while carbon-free energy sources are developed, is Carbon Capture and Storage (CCS). Non-isothermal effects play a major role in all stages of CCS. In this paper, we review the literature on thermal effects related to CCS, which is receiving an increasing interest as a result of the awareness that the comprehension of non-isothermal processes is crucial for a successful deployment of CCS projects. We start by reviewing CO2 transport, which connects the regions where CO2 is captured with suitable geostorage sites. The optimal conditions for CO2 transport, both onshore (through pipelines) and offshore (through pipelines or ships), are such that CO2 stays in liquid state. To minimize costs, CO2 should ideally be injected at the wellhead in similar pressure and temperature conditions as it is delivered by transport. To optimize the injection conditions, coupled wellbore and reservoir simulators that solve the strongly non-linear problem of CO2 pressure, temperature and density within the wellbore and non-isothermal two-phase flow within the storage formation have been developed. CO2 in its way down the injection well heats up due to compression and friction at a lower rate than the geothermal gradient, and thus, reaches the storage formation at a lower temperature than that of the rock. Inside the storage formation, CO2 injection induces temperature changes due to the advection of the cool injected CO2, the Joule-Thomson cooling effect, endothermic water vaporization and exothermic CO2 dissolution. These thermal effects lead to thermo-hydro-mechanical-chemical coupled processes with non-trivial interpretations. These coupled processes also play a relevant role in “Utilization” options that may provide an added value to the injected CO2, such as Enhanced Oil Recovery (EOR), Enhanced Coal Bed Methane (ECBM) and geothermal energy extraction combined with CO2 storage. If the injected CO2 leaks through faults, the caprock or wellbores, strong cooling will occur due to the expansion of CO2 as pressure decreases with depth. Finally, we conclude by identifying research gaps and challenges of thermal effects related to CCS.Peer ReviewedPostprint (author's final draft
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Lattice modeling of excavation damage in argillaceous clay formations: Influence of deformation and strength anisotropy
This paper presents modeling of mechanical anisotropy in argillaceous rocks using an irregular lattice modeling approach, namely the rigid-body-spring network. To represent the mechanical anisotropy, new schemes are implemented in the modeling framework. The directionality of elastic deformation is resolved by modifying the element formulation with anisotropic elastic properties. The anisotropy of strength and failure characteristics is facilitated by adopting orientation-dependent failure criteria into the failure model. The verification of the improved modeling procedures is performed against theoretical model predictions for unconfined compression tests with various bedding orientations. Furthermore, excavation damage and fracturing processes in rock formations are simulated for different geomechanical configurations, such as rock anisotropy and tectonic heterogeneity. The simulated excavation damage characteristics are realistic and comparable with the actual field observation at a tunnel located in an argillaceous clay formation. The simulation results provide insights into the excavation damage zone phenomena with an explicit representation of fracturing processes
Regional Flow Simulation in Fractured Aquifers Using Stress-Dependent Parameters
A model function relating effective stress to fracture permeability is
developed from Hooke's law, implemented in the tensorial form of Darcy's law,
and used to evaluate discharge rates and pressure distributions at regional
scales. The model takes into account elastic and statistical fracture
parameters, and is able to simulate real stress-dependent permeabilities from
laboratory to field studies. This modeling approach gains in phenomenology in
comparison to the classical ones because the permeability tensors may vary in
both strength and principal directions according to effective stresses.
Moreover this method allows evaluation of the fracture porosity changes, which
are then translated into consolidation of the medium.Comment: 10 pages, 7 figures, submitted to Ground Water 201
Coupled Dynamic Flow and Geomechanical Simulations for an Integrated Assessment of CO2 Storage Impacts in a Saline Aquifer
Pore pressure variation resulting from geological CO2 storage may compromise
reservoir, caprock and fault integrity. Therefore, we investigate the
mechanical impact of industrial-scale CO2 storage at a prospective Danish site
by coupled 3D hydro-mechanical simulations carried out by two independent
modelling groups. Even though the two chosen modelling strategies are not
identical, simulation results demonstrate that storage integrity is maintained
at any time. Vertical displacements are mainly determined by hydraulic fault
conductivity influencing spatial pore pressure elevation. The introduced fault
zone implementation in the hydro- mechanical model allows for localization of
potential leakage pathways for formation fluids along the fault plane
Implementation of the Barcelona Basic Model into TOUGH–FLAC for simulations of the geomechanical behavior of unsaturated soils
This paper presents the implementation of the Barcelona Basic Model (BBM) into the TOUGH-FLAC simulator analyzing the geomechanical behavior of unsaturated soils. We implemented the BBM into TOUGH-FLAC by (1) extending an existing FLAC{sup 3D} module for the Modified Cam-Clay (MCC) model in FLAC{sup 3D} and (2) adding computational routines for suction-dependent strain and net stress (i.e., total stress minus gas pressure) for unsaturated soils. We implemented a thermo-elasto-plastic version of the BBM, wherein the soil strength depends on both suction and temperature. The implementation of the BBM into TOUGH-FLAC was verified and tested against several published numerical model simulations and laboratory experiments involving the coupled thermal-hydrological-mechanical (THM) behavior of unsaturated soils. The simulation tests included modeling the mechanical behavior of bentonite-sand mixtures, which are being considered as back-fill and buffer materials for geological disposal of spent nuclear fuel. We also tested and demonstrated the use of the BBM and TOUGH-FLAC for a problem involving the coupled THM processes within a bentonite-backfilled nuclear waste emplacement tunnel. The simulation results indicated complex geomechanical behavior of the bentonite backfill, including a nonuniform distribution of buffer porosity and density that could not be captured in an alternative, simplified, linear-elastic swelling model. As a result of the work presented in this paper, TOUGH-FLAC with BBM is now fully operational and ready to be applied to problems associated with nuclear waste disposal in bentonite-backfilled tunnels, as well as other scientific and engineering problems related to the mechanical behavior of unsaturated soils
Modeling of coupled deformation and permeability evolution during fault reactivation induced by deep underground injection of CO2
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Development of a Numerical Simulator for Analyzing the Geomechanical Performance of Hydrate-Bearing Sediments
In this paper, we describe the development and application of a numerical simulator that analyzes the geomechanical performance of hydrate-bearing sediments, which may become an important future energy supply. The simulator is developed by coupling a robust numerical simulator of coupled fluid flow, hydrate thermodynamics, and phase behavior in geologic media (TOUGH+HYDRATE) with an established geomechanical code (FLAC3D). We demonstrate the current simulator capabilities and applicability for two examples of geomechanical responses of hydrate bearing sediments during production-induced hydrate dissociation. In these applications, the coupled geomechanical behavior within hydrate-bearing seducements are considered through a Mohr-Coulomb constitutive model, corrected for changes in pore-filling hydrate and ice content, based on laboratory data. The results demonstrate how depressurization-based gas production from oceanic hydrate deposits may lead to severe geomechanical problems unless care is taken in designing the production scheme. We conclude that the coupled simulator can be used to design production strategies for optimizing production, while avoiding damaging geomechanical problems
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