scholarly journals How Insoluble Inclusions and Intersecting Layers Affect the Leaching Process within Potash Seams

2021 ◽  
Vol 11 (19) ◽  
pp. 9314
Author(s):  
Svenja Steding ◽  
Thomas Kempka ◽  
Michael Kühn
Keyword(s):  
Reactive Transport ◽  
Mechanical Stability ◽  
Transport Model ◽  
Heterogeneous Systems ◽  
Vertical Direction ◽  
Risk Assessments ◽  
Mining Operations ◽  
Reactive Transport Model ◽  
Zone Growth

Potash seams are a valuable resource containing several economically interesting, but also highly soluble minerals. In the presence of water, uncontrolled leaching can occur, endangering subsurface mining operations. In the present study, the influence of insoluble inclusions and intersecting layers on leaching zone evolution was examined by means of a reactive transport model. For that purpose, a scenario analysis was carried out, considering different rock distributions within a carnallite-bearing potash seam. The results show that reaction-dominated systems are not affected by heterogeneities at all, whereas transport-dominated systems exhibit a faster advance in homogeneous rock compositions. In return, the ratio of permeated rock in vertical direction is higher in heterogeneous systems. Literature data indicate that most natural potash systems are transport-dominated. Accordingly, insoluble inclusions and intersecting layers can usually be seen as beneficial with regard to reducing hazard potential as long as the mechanical stability of leaching zones is maintained. Thereby, the distribution of insoluble areas is of minor impact unless an inclined, intersecting layer occurs that accelerates leaching zone growth in one direction. Moreover, it is found that the saturation dependency of dissolution rates increases the growth rate in the long term, and therefore must be considered in risk assessments.

A Streamlined Workflow From Experimental Analyses to Dynamic Geochemical Modelling

2021 ◽  
Author(s):  
Ahmed M. S. Elgendy ◽  
Simone Ricci ◽  
Elena I. Cojocariu ◽  
Claudio Geloni
Keyword(s):  
Reactive Transport ◽  
Transport Model ◽  
Geochemical Modelling ◽  
Formation Water ◽  
Geochemical Model ◽  
Reactive Transport Model ◽  
Mineral Alteration ◽  
Experimental Analyses ◽  
Water Vaporization

Abstract Dynamic-geochemical model is a powerful instrument to evaluate the geochemical effects on CO2storage capacity, injectivity and long-term containment. The study objective is to apply an integrated multi-step workflow to a carbon capture and storage (CCS) candidate field (offshore), namely hereinafter H field. From experimental analyses, a comprehensive real data-tailored reactive transport model (RTM) has been built to capture the dynamics and the geochemical phenomena (e.g., water vaporization, CO2solubility, mineral alteration) occurring during and after the CO2injection in sedimentary formations. The proposed integrated workflow couples lab activities and numerical simulations and it is developed according to the following steps: Mineralogical-chemical characterization (XRD, XRF and SEM-EDX experimental techniques) of field core samples; Data elaboration and integration to define the conceptual geochemical model; Synthetic brine reconstruction by means of 0D geochemical models; Numerical geochemical modelling at different complexity levels. Field rocks chosen for CO2injection have been experimentally characterized, showing a high content of Fe in clayey, micaceous and carbonate mineralogical phases. New-defined, site-specific minerals have been characterized, starting from real XRD, XRF and SEM-EDX data and by calculation of their thermochemical parameters with a proprietary procedure. They are used to reconstruct synthetic formation water chemical composition (at equilibrium with both rock mineralogy and gas phase), subsequently used in RTM. CO2injection is simulated using 2D radial reactive transport model(s) built in a commercial compositional reservoir simulator. The simulations follow a step-increase in the complexity of the model by adding CO2solubility, water vaporization and geochemical reactions. Geochemical processes impact on CO2storage capacity and injectivity is quantitatively analyzed. The results show that neglecting the CO2solubility in formation water may underestimate the max CO2storage capacity in H field by around 1%, maintaining the same pressure build-up profile. Sensitivities on the impact of formation water salinity on the CO2solubility are presented. In a one thousand years’ time-scale, changes in reservoir porosity due to mineral alteration, triggered by CO2-brine-rock interactions, seem to be minimal in the near wellbore and far field. However, it has been seen that water vaporization with the associated halite precipitation inclusion in the simulation models is recommended, especially at high-level of formation brine salinity, for a reliable evaluation of CO2injectivity related risks. The proposed workflow provides a new perspective in geochemical application for CCS studies, which relies on novel labs techniques (analyses automation), data digitalization, unification and integration with a direct connection to the numerical models. The presented procedure can be followed to assess the geochemical short-and long-term risks in carbon storage projects.

scholarly journals Understanding of Long-Term CO2-Brine-Rock Geochemical Reactions Using Numerical Modeling and Natural Analogue Study

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-16
Author(s):  
Huixing Zhu ◽  
Tianfu Xu ◽  
Hailong Tian ◽  
Guanhong Feng ◽  
Zhijie Yang ◽  
...  
Keyword(s):  
Reactive Transport ◽  
Transport Model ◽  
Measured Data ◽  
Natural Analogue ◽  
Reactive Transport Model ◽  
Analogue Study ◽  
Geochemical Reactions ◽  
Acidic Conditions ◽  
Simulation Results

To further understand the interactions of CO2-brine-rock at geological time scales, in this study, a 1D reactive transport model of CO2 intrusion into sandstone of the Longtan Formation (P2l) in the Huangqiao area, China, was constructed based on site-specific data. The simulation time is consistent with the retention time of CO2 in the Longtan sandstone Formation and is set to 20 Ma. The reactive transport model is calibrated and revised using the measured data for sandstone samples from Well X3 (i.e., the natural analogue). By comparing the simulation results with measured data for the natural analogue, the long-term geochemical reactions are investigated. The simulation results indicate that the brine-rock interactions induced by CO2 can be roughly divided into two stages. First, susceptible minerals (e.g., chlorite, ankerite, calcite, and feldspar minerals) dissolve rapidly under acidic conditions formed by the dissolution of CO2. The precipitation of siderite is facilitated by the dissolution of ankerite and chlorite. Smectite-Ca and dawsonite precipitate due to the dissolution of anorthite and albite, respectively. Dawsonite begins to convert into smectite-Na when albite is completely dissolved. As the reactions continue, intermediate products (i.e., illite, smectite-Na, and smectite-Ca) generated in the first stage become the reactants and subsequently react with CO2 and brine. These three clay minerals are not stable under acidic conditions and transform into kaolinite and paragenetic quartz in the later stage of reaction. Comparing the simulation results of the Base Case with the measured data for the natural analogue and inspired by previous studies, the scour of kaolinite is supposed to have occurred in this region and is considered in the revised model by introducing a coefficient of the scour of kaolinite (i.e., Case 2). The simulation results of Case 2 fit well with the measured data on mineral assemblage, and the trend of the sandstone porosity growth caused by the CO2-brine-rock reaction is captured by our simulation results. The combination of numerical simulation and natural analogue study indicates that the joint effects of long-term CO2-brine-rock reactions and scour of kaolinite increase the pore space of the host rock and result in an increase in quartz content in the sandstone.

Development and verification of a reactive transport model for long-term alteration of bentonite–cement–seawater systems

2008 ◽  
Vol 33 ◽  
pp. S285-S294 ◽  
Author(s):  
T. Yamaguchi ◽  
F. Yamada ◽  
K. Negishi ◽  
S. Hoshino ◽  
M. Mukai ◽  
...  
Keyword(s):  
Reactive Transport ◽  
Transport Model ◽  
Reactive Transport Model

scholarly journals Spatial and Temporal Evolution of Leaching Zones within Potash Seams Reproduced by Reactive Transport Simulations

Water ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 168
Author(s):  
Svenja Steding ◽  
Thomas Kempka ◽  
Axel Zirkler ◽  
Michael Kühn
Keyword(s):  
Reactive Transport ◽  
Temporal Evolution ◽  
Transport Model ◽  
Significant Risk ◽  
Mining Operations ◽  
Reactive Transport Model ◽  
Potash Salt ◽  
Rock Interface ◽  
Temporal And Spatial ◽  
Hybrid Forms

Leaching zones within potash seams generally represent a significant risk to subsurface mining operations and the construction of technical caverns in salt rocks, but their temporal and spatial formation has been investigated only rudimentarily to date. To the knowledge of the authors, current reactive transport simulation implementations are not capable to address hydraulic-chemical interactions within potash salt. For this reason, a reactive transport model has been developed and complemented by an innovative approach to calculate the interchange of minerals and solution at the water-rock interface. Using this model, a scenario analysis was carried out based on a carnallite-bearing potash seam. The results show that the evolution of leaching zones depends on the mineral composition and dissolution rate of the original salt rock, and that the formation can be classified by the dimensionless parameters of Péclet (Pe) and Damköhler (Da). For Pe > 2 and Da > 1, a funnel-shaped leaching zone is formed, otherwise the dissolution front is planar. Additionally, Da > 1 results in the formation of a sylvinitic zone and a flow barrier. Most scenarios represent hybrid forms of these cases. The simulated shapes and mineralogies are confirmed by literature data and can be used to assess the hazard potential.

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