| 1. |
- Yang, Zhibing, et al.
(författare)
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Modeling of far-field pressure plumes and brine migration for CO2 geological storage
- 2013
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Ingår i: Geophysical Research Abstracts, Vol. 15.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Carbon sequestration in deep saline aquifers involves injection of large volumes of CO2 which causes pressureincrease in the reservoir formations. Recent work shows that the region of pressure increase can reach distancesfrom the injection well that are far beyond the CO2 plume itself. The adverse far-field impacts (e.g., for nearsurfacefresh-water aquifers) of the pressure build-up and brine migration can become a limiting factor for CO2storage capacity. It is therefore needed to carefully examine the evolution and impact of the pressure plume andfar-field brine migration caused by commercial scale CO2 injection under different conditions. Given the largesize of the domains of interest, this poses a challenging modeling and parameter estimation problem, includingissues of parameter upscaling. This study investigates the effect of several factors on the size of the propagatingpressure plume and the magnitude of the pressure build-up. These factors include: (i) formation geometry andboundary conditions; (ii) depth-dependent formation material properties; and (iii) brine leakage through fractureszones and/or faults in the overlying units. For the reservoir formation we consider both generic and site-specificlarge-scale models, the latter based on data from formations in the Baltic Sea region. Numerical simulations forthese large-scale models are conducted using both the full multiphase flow modeling approach and more simplifiedsingle-phase approaches. The simulation results are also discussed in terms of comparison to simple analytical andsemi-analytical solutions.
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| 2. |
- Moghadasi, Ramin, et al.
(författare)
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Role of critical gas saturation in the interpretation of a field scale CO2 injection experiment
- 2022
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier. - 1750-5836 .- 1878-0148. ; 115
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Tidskriftsartikel (refereegranskat)abstract
- Residual trapping of CO2, typically quantified by residual gas saturation (Sgr), is one of the main trapping mechanisms in geological CO2 storage (GCS). An important additional characteristic parameter is critical gas saturation (Sgc). Sgc determines at what saturation the trapped gas remobilizes again if gas saturation increases due to exsolution from the aqueous phase, rather than from further gas injection. In the present study, a pilot-scale CO2 injection experiment carried out at Heletz, Israel, in 2017, is interpreted by taking critical saturation into account. With regards to this experiment, the delayed second arrival peak of the partitioning tracer could not be captured by means of physical models. In this work, the hysteretic relative permeability functions were modified to account for Sgc. The results showed that accounting for the effect of Sgc during the secondary drainage indeed captured the observed delayed peak. The difference between the values of Sgr and Sgc, influenced both the time and peak height of the tracer arrival. To our knowledge this is first time that critical gas saturation has been considered in field scale analyses related to GCS. Accounting for Sgc is relevant where gas saturation during secondary drainage increases due to gas phase expansion or exsolution from the aqueous phase. This will happen in situations where pressure depletion occurs, e.g. due to gas leakage from fracture zones or wells or possibly because of pressure management activities. The findings also have implications for other applications such as underground gas storage as well as for geothermal reservoir management.
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| 3. |
- Moghadasi, Ramin, et al.
(författare)
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Pore-scale characterization of residual phase remobilization in geological CO2 storage using X-ray microtomography and pore-network modelling
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In this study, the pore-scale characteristics of trapped CO2 remobilization under pressure depletion conditions were studied with the use of 3D X-ray microtomography and pore-network modelling. Three-dimensional X-ray microtomographic images of a sandstone sample with a voxel size of 3.83 mm were acquired from which a pore network was extracted. Experimental results show that trapped CO2 remobilization during pressure depletion is an intermittent process in nature, due to which the CO2 relative permeability is significantly reduced. This serves as a safety enhancing feature as it delays CO2 remobilization and migration. Ostwald ripening plays a significant role in the CO2 phase redistribution, which could potentially lead to remobilization even in the absence of pressure depletion. According to the pore network simulation results, weakly wetting conditions enhances the reconnection of the trapped CO2 ganglia, which in turn promotes the remobilization of the trapped phase. The simulation and experimental results agree in terms of the saturation increment needed to remobilize the CO2 – approximately 0.06 – and the pressure at which the CO2 connects – around 7 MPa. The findings of the current study provide valuable insights into the pore-scale aspects of trapped phase remobilization, a phenomenon that affects the fate of CO2 residual trapping in both the short and long term.
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| 4. |
- Yang, Zhibing, et al.
(författare)
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Macro-scale constitutive relationships for CO2 migration in heterogeneous geological formations
- 2012
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Numerical models have been developed and applied to migration of geological stored carbon dioxide for site performance and risk assessment studies at the reservoir scale. However, due to the restriction in computational time and resources, reservoir scale models have limitations in accounting for the multi-scale heterogeneities. In order to address the heterogeneity issues, appropriate upscaling methods are needed. In this study, we present macro-scale capillary pressure – relative permeability – saturation relationships for grid-block properties used in the full-scale modeling. We develop a macroscopic percolation model for the upscaling procedures. The macro-scale constitutive relationships are obtained through simulation procedures of CO2 displacing brine in a porous domain with spatially correlated random permeability fields. Sensitivity of the derived constitutive relationships to the statistical parameters representing the local heterogeneity is shown. Comparison of the percolation-based method to other approaches is demonstrated.
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| 5. |
- Larsson, Martin, 1980-, et al.
(författare)
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A new approach to account for fracture aperture variability when modeling solute transport in fracture networks
- 2013
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Ingår i: Water resources research. - : American Geophysical Union (AGU). - 0043-1397 .- 1944-7973. ; 49:4, s. 2241-2252
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Tidskriftsartikel (refereegranskat)abstract
- A simple yet effective method is presented to include the effects of fracture aperture variability into the modeling of solute transport in fracture networks with matrix diffusion and linear sorption. Variable apertures cause different degrees of flow channeling, which in turn influence the contact area available for these retarding processes. Our approach is based on the concept of specific flow-wetted surface (sFWS), which is the fraction of the contact area over the total fracture surface area. Larsson et al. [2012] studied the relationship between sFWS and the standard deviation σln K of the conductivity distribution over the fracture plane. Here an approach is presented to incorporate this into a fracture network model. With this model, solute transport through fracture networks is then analyzed. The cases of sFWS=0 and sFWS=1 correspond to those of no matrix diffusion and full matrix diffusion respectively. In between, a sFWS break point value can be defined, above which the median solute arrival time is proportional to the square of sFWS. For values below the critical sFWS (more channeled cases), the change is much slower, converging to that of no matrix diffusion. Results also indicate that details of assigning sFWS values for individual fractures in a network are not crucial; results of tracer transport are essentially identical to a case where all fractures have the mean σln K (or corresponding mean sFWS) value. This is obviously due to the averaging effect of the network.
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| 6. |
- Yang, Zhibing
(författare)
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Multiphase Contamination in Rock Fractures : Fluid Displacement and Interphase Mass Transfer
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Multiphase flow and transport in fractured rock is of importance to many practical and engineering applications. In the field of groundwater hydrology an issue of significant environmental concern is the release of dense non-aqueous phase liquids (DNAPLs) which can cause long-term groundwater contamination in fractured aquifers. This study deals with two fundamental processes – fluid displacement and interphase mass transfer – concerning the behavior of the multiphase contaminants in fractured media. The focus of this work has been placed on improving the current understanding of small-scale (single fracture) physics by a combined effort of numerical modeling analysis, laboratory experiments and model development. This thesis contributes to the improved understanding through several aspects. Firstly, the effect of aperture variability, as characterized by geostatistical parameters such as standard deviation and correlation length, on the DNAPL entrapment, dissolution and source-depletion behaviors in single fractures was revealed. Secondly, a novel, generalized approach (adaptive circle fitting approach) to account for the effect of in-plane curvature of fluid-fluid interfaces on immiscible fluid displacement was developed; the new approach has demonstrated good performance when applied to simulate previously published experimental data. Thirdly, the performance of a continuum-based two-phase flow model and an invasion percolation model was compared for modeling fluid displacement in a variable-aperture fracture and the dependence of fracture-scale capillary pressure – saturation relationships on aperture variability was studied. Lastly, through experimental studies and mechanistic numerical modeling of DNAPL dissolution, kinetic mass transfer characteristics of two different entrapment configurations (residual blobs and dead-end pools) were investigated. The obtained understanding from this thesis will be useful for predictive modeling of multiphase contaminant behavior at a larger (fracture network) scale.
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| 7. |
- Basirat, Farzad, et al.
(författare)
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Hydraulic Modeling of Induced and Propagated Fractures : Analysis of Flow and Pressure Data From Hydromechanical Experiments in the COSC-1 Deep Borehole in Crystalline Rock Near Åre, Sweden
- 2021
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Ingår i: Water resources research. - : American Geophysical Union (AGU). - 0043-1397 .- 1944-7973. ; 57:11
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Tidskriftsartikel (refereegranskat)abstract
- To characterize the coupled hydromechanical behavior of rock fractures, the step-rate injection method for fracture in-situ properties (SIMFIP) was conducted with a specialized downhole probe developed by Guglielmi et al. (2014, https://doi.org/10.1007/s00603-013-0517-1). In June 2019, a field campaign was carried out near Åre, Sweden, where the SIMFIP probe was applied in the Collisional Orogeny in the Scandinavian Caledonides-1 scientific borehole to understand the dynamics of injection-induced fracture initiation, fracture opening, and shearing due to water injection-withdrawal in a borehole interval isolated by two packers. Three intervals were investigated at ∼500 m depth: (a) an unfractured section (intact rock), (b) a section with non-conductive fractures, and (c) a section with hydraulically conductive fractures. Pressure, injection flow rate, and borehole wall displacement were simultaneously measured during the tests. In the present study, the geometry of the induced fracture and deformation of existing fractures at different time stages of the tests are determined based on a hydrologic model by using the measured pressure and flow data during each time stage of the experiment. A numerical model for the fluid flow within the fracture and the packed-off borehole interval is implemented within COMSOL Multiphysics. By matching model simulations with observed data for all three sections, estimates of the induced and propagated fractures' radius and aperture at successive time stages have been obtained in each case. We could also determine the non-linear relationship between fracture aperture and pressure for values above fracture opening pressures. The model results provide insights for the understanding of pressure-induced fracture initiation and propagation in crystalline rock.
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| 8. |
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| 9. |
- Yang, Zhibing, 1982-, et al.
(författare)
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Modeling of dense nonaqueous phase liquid entrapment and dissolution in variable aperture fractures
- 2009
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Ingår i: Proceedings of TOUGH2 Symposium 2009. - Lawrence Berkeley National Laboratory, Berkeley, California.
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Konferensbidrag (refereegranskat)abstract
- This study investigates dense non-aqueous phase liquid (DNAPL) entrapment and dissolution in single, variable-aperture fractures. Log-normally distributed aperture fields with local permeabilities following the cubic law are assumed. Special attention is given to the capillary pressure-liquid saturation function to account for the specific drainage and wetting characteristics of fractures. DNAPL migration and immobilization is modeled by using the iTOUGH2/T2VOC models, and dissolution is simulated using the TMVOC model. Multiple realizations with different sets of aperture statistics and fracture inclination angles are analyzed.The results suggest that the entrapment geometry of DNAPL in a heterogeneous fracture is highly sensitive to the aperture statistics. Larger correlation length or standard deviation produces a wider range of total entrapped DNAPL volume. Modeling of different fracture inclination angles reveals that gravity force plays an important role as well. Subsequent dissolution modeling shows that mass transfer will also be strongly influenced by the different DNAPL entrapment architectures corresponding to the different aperture correlation lengths and standard deviations.
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| 10. |
- Larsson, Martin, 1980-, et al.
(författare)
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Understanding the effect of single fracture heterogeneity from single well injection withdrawal (SWIW) tests
- 2013
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Ingår i: Hydrogeology Journal. - New York : Springer-Verlag New York. - 1431-2174 .- 1435-0157. ; 21:8, s. 1691-1700
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Tidskriftsartikel (refereegranskat)abstract
- The single well injection withdrawal (SWIW) tracer test on a fracture or fracture zone is a method used to estimate its tracer retardation properties. In this study, the effects of single fracture aperture heterogeneity on SWIW test tracer breakthrough curves are examined by numerical modelling. The effects of the matrix diffusion and sorption is accounted for by using a particle tracking method through the addition of a time delay added to the advective transport time. For a given diffusion and sorption property value (Pm) and for a heterogeneous fracture, the peak concentration is larger compared to a homogeneous fracture. The cumulative breakthrough curve for a heterogeneous fracture is similar to that for a homogeneous fracture and a less sorptive/diffusive tracer. It is demonstrated that the fracture area that meets the flowing water, the so-called specific flow-wetted surface (sFWS) of the fracture, can be determined by comparing the observed breakthrough curve for a heterogeneous fracture with that for a homogeneous fracture. SWIW tests are also simulated with a regional pressure gradient present. The results point to the possibility of distinguishing the effect of the regional pressure gradient from that of diffusion through the use of multiple tracers with different Pm-values.
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