Research

18 pages, 2800 KiB

Open AccessArticle

Lumped Approach for Reactive Transport of Organic Compound Mixtures through Simulated Aquifer Sands in Lab-Scale Column Tests

by Jin Chul Joo, Hee Sun Moon and Sun Woo Chang

Water 2020, 12(11), 3103; https://0-doi-org.brum.beds.ac.uk/10.3390/w12113103 - 04 Nov 2020

Viewed by 1617

Abstract

The feasibility of the lumped approach for reactive transport of 12 organic compounds in mixtures through simulated aquifer sands with different organic carbon content (f_oc) within soil columns was evaluated. From direct measurements of effluent samples and temporal and spatial [...] Read more.

The feasibility of the lumped approach for reactive transport of 12 organic compounds in mixtures through simulated aquifer sands with different organic carbon content (f_oc) within soil columns was evaluated. From direct measurements of effluent samples and temporal and spatial pore-water concentration profiles within soil columns, 12 organic compounds in mixtures were sorbed to different extents due to the different dependence of sorption on f_oc. Considering the tradeoff between accuracy and simplicity, four, five, and six pseudocompounds were determined for simulated aquifer sands with f_oc of 0.006%, 0.051%, and 0.221%, respectively, to approximate the reactive transport of 12 organic compounds in mixtures. Each pseudocompound presented obviously different reactive transport behavior in terms of both sorption capacity and nonlinearity, indicating that each pseudocompound contained components with relatively similar sorption capacities and nonlinearity. Similar to the results from batch equilibrium sorption tests, log K_oc can be used as the a priori grouping criterion, although the relative contributions of different forces to the overall sorption may differ for different composition of organic mixtures and f_oc values of aquifer sands. Finally, the assignment of the Freundlich sorption parameters of pseudocompounds using averages of Freundlich sorption parameters of their components led to reasonable prediction for reactive transport of organic compounds in mixtures through the soil columns. Further study is warranted to evaluate the effective coupling between lumped approach and reactive transport model using complex multicomponent mixtures within heterogeneous subsurface systems. Full article

(This article belongs to the Special Issue Injection-Induced Fluid Flows and Solute/Heat Transport Behavior in a Subsurface Environment)

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24 pages, 2865 KiB

Open AccessArticle

Barite Scale Formation and Injectivity Loss Models for Geothermal Systems

by Morgan Tranter, Marco De Lucia, Markus Wolfgramm and Michael Kühn

Water 2020, 12(11), 3078; https://0-doi-org.brum.beds.ac.uk/10.3390/w12113078 - 03 Nov 2020

Cited by 7 | Viewed by 2876

Abstract

Barite scales in geothermal installations are a highly unwanted effect of circulating deep saline fluids. They build up in the reservoir if supersaturated fluids are re-injected, leading to irreversible loss of injectivity. A model is presented for calculating the total expected barite precipitation. [...] Read more.

Barite scales in geothermal installations are a highly unwanted effect of circulating deep saline fluids. They build up in the reservoir if supersaturated fluids are re-injected, leading to irreversible loss of injectivity. A model is presented for calculating the total expected barite precipitation. To determine the related injectivity decline over time, the spatial precipitation distribution in the subsurface near the injection well is assessed by modelling barite growth kinetics in a radially diverging Darcy flow domain. Flow and reservoir properties as well as fluid chemistry are chosen to represent reservoirs subject to geothermal exploration located in the North German Basin (NGB) and the Upper Rhine Graben (URG) in Germany. Fluids encountered at similar depths are hotter in the URG, while they are more saline in the NGB. The associated scaling amount normalised to flow rate is similar for both regions. The predicted injectivity decline after 10 years, on the other hand, is far greater for the NGB (

64 %

) compared to the URG (

24 %

), due to the temperature- and salinity-dependent precipitation rate. The systems in the NGB are at higher risk. Finally, a lightweight score is developed for approximating the injectivity loss using the Damköhler number, flow rate and total barite scaling potential. This formula can be easily applied to geothermal installations without running complex reactive transport simulations. Full article

(This article belongs to the Special Issue Injection-Induced Fluid Flows and Solute/Heat Transport Behavior in a Subsurface Environment)

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19 pages, 5384 KiB

Open AccessArticle

Numerical Simulation of Shallow Geothermal Field in Operating of a Ground Source Heat Pump System—A Case Study in Nan Cha Village, Ping Gu District, Beijing

by Yaobin Zhang, Jia Zheng, Aihua Liu, Qiulan Zhang, Jingli Shao and Yali Cui

Water 2020, 12(10), 2938; https://0-doi-org.brum.beds.ac.uk/10.3390/w12102938 - 21 Oct 2020

Cited by 3 | Viewed by 2667

Abstract

The inefficient use of single energy and cold accumulation in the shallow geothermal field seriously affect the efficient operation of the ground source heat pump system (GSHPS). The operation of solar-assisted GSHPS can effectively solve the above problems. In this paper, a shallow [...] Read more.

The inefficient use of single energy and cold accumulation in the shallow geothermal field seriously affect the efficient operation of the ground source heat pump system (GSHPS). The operation of solar-assisted GSHPS can effectively solve the above problems. In this paper, a shallow geothermal utilization project in Nan cha Village, Ping Gu District of Beijing, is chosen as the study area. A three-dimensional numerical model of groundwater flow and heat transfer considering ambient temperature and backfill materials is established, and the level of model integration and validation are novel features of this paper. The thermal response test data in summer and winter conditions are used to validate the model. The results show that increasing hydraulic gradient has a positive impact on the heat exchange. The mixture of sand and barite powder is recognized as a more efficient and economical backfill material. The changes of thermal influence radius, heat balance, and shallow geothermal field are simulated and analyzed by three schemes. It is demonstrated that the thermal influence radius is 5 m, 3.9 m and 3.9 m for Scheme 1, Scheme 2 and Scheme 3, respectively. The ground temperature is always lower than the initial formation temperature in Scheme 1 and Scheme 2; however, under Scheme 3 it is higher than the initial values. The closer the hole wall is, the larger the difference between the initial formation temperature and the ground temperature, and vice versa. The thermal equilibrium of Scheme 1, Scheme 2 and Scheme 3 is −728 × 106 KJ, −269 × 106 KJ and +514 × 106 KJ. Through comprehensive analysis of the above three factors, Scheme 3 is regarded as the most reasonable scheme for a solar system to assist GSHPS. Full article

(This article belongs to the Special Issue Injection-Induced Fluid Flows and Solute/Heat Transport Behavior in a Subsurface Environment)

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19 pages, 6957 KiB

Open AccessArticle

Evaluation of Ground Temperature Changes by the Operation of the Geothermal Heat Pump System and Climate Change in Korea

by Seong-Kyun Kim and Youngmin Lee

Water 2020, 12(10), 2931; https://0-doi-org.brum.beds.ac.uk/10.3390/w12102931 - 20 Oct 2020

Cited by 8 | Viewed by 3600

Abstract

To evaluate long-term temperature changes caused by the operation of a geothermal heat pump (GHP) system, temperatures near borehole heat exchangers (BHEs) of the GHP system in Korea were measured. The temperature measurements showed increasing rates of 0.135 °C/year at a depth of [...] Read more.

To evaluate long-term temperature changes caused by the operation of a geothermal heat pump (GHP) system, temperatures near borehole heat exchangers (BHEs) of the GHP system in Korea were measured. The temperature measurements showed increasing rates of 0.135 °C/year at a depth of 10 m and 0.118 °C/year at a depth of 50 m for approximately 10 years. Simulations for the analysis of climate change effects on measured temperature fluctuations showed that a rate of temperature increase was 0.010 °C/year at a depth of 50 m owing to changes in surface air temperatures (SATs). From two-dimensional heat transfer simulations, the discharged heat measuring 16.7 W/m in the cooling season and extracted heat measuring 12.4 W/m in the heating season could cause an annual mean temperature increase of 0.109 °C over approximately 10 years. Additionally, results of simulations for future prediction of ground temperatures assuming that the GHP system retains its level of operation showed that in 2050, temperature at a depth of 50 m will increase by approximately 3.00 °C from that in 2005. Thus, balancing the heat discharged into and extracted from the ground by considering climate change to minimize long-term changes in the ground temperature is necessary. Full article

(This article belongs to the Special Issue Injection-Induced Fluid Flows and Solute/Heat Transport Behavior in a Subsurface Environment)

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10 pages, 1768 KiB

Open AccessArticle

Distortion of the Estimated Hydraulic Conductivity from a Hydraulic Test in Fractured Rock Due to Excessive Injection or Extraction

by Sung-Hoon Ji, Byeong-Hak Park and Kyung-Woo Park

Water 2020, 12(10), 2712; https://0-doi-org.brum.beds.ac.uk/10.3390/w12102712 - 28 Sep 2020

Cited by 3 | Viewed by 2028

Abstract

In this study, we discussed distortion of the estimated hydraulic conductivity from a hydraulic test due to excessive injection or extraction of groundwater by evaluating the influence of nonlinear flow. Pulse, slug, and constant head withdrawal tests with various head displacements were conducted [...] Read more.

In this study, we discussed distortion of the estimated hydraulic conductivity from a hydraulic test due to excessive injection or extraction of groundwater by evaluating the influence of nonlinear flow. Pulse, slug, and constant head withdrawal tests with various head displacements were conducted in fractured granite rock, and the changes of representative Reynolds numbers (Re) during the tests were calculated. The Forchheimer equation and cubic law were used to evaluate the influence of nonlinear flow on the hydraulic tests, and thus the possibility of distortion of the estimated hydraulic conductivity. Our results showed that there was little possibility that nonlinear flow occurred during the pulse tests in the test zones. In the slug tests at several test zones, however, the estimated hydraulic conductivities were likely to be distorted due to nonlinear flow. Except for the test zones with low permeability, the scale effects of the estimated hydraulic conductivities from different types of tests were observed. These results indicated that the scale effect and distortion of the hydraulic parameters can be evaluated by conducting various types of hydraulic tests. Full article

(This article belongs to the Special Issue Injection-Induced Fluid Flows and Solute/Heat Transport Behavior in a Subsurface Environment)

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27 pages, 11269 KiB

Open AccessArticle

Changes in Geochemical Composition of Groundwater Due to CO₂ Leakage in Various Geological Media

by Jisu Jeong, Sung-Wook Jeen, Hyoun-Tae Hwang and Kang-Kun Lee

Water 2020, 12(9), 2597; https://0-doi-org.brum.beds.ac.uk/10.3390/w12092597 - 17 Sep 2020

Cited by 10 | Viewed by 2544

Abstract

This study evaluated the effects of CO₂ leakage on the geochemical composition of groundwater in various geological media through long-term column experiments. Four columns were set up with soil representing a silicate aquifer; clean sand; a sand and limestone mixture; and alluvium [...] Read more.

This study evaluated the effects of CO₂ leakage on the geochemical composition of groundwater in various geological media through long-term column experiments. Four columns were set up with soil representing a silicate aquifer; clean sand; a sand and limestone mixture; and alluvium soil, respectively. The experiments were conducted under the same experimental conditions for approximately one year. As the CO₂-saturated synthetic groundwater was introduced into the columns, a decrease in pH and increases in electrical conductivity (EC), alkalinity, and concentrations of cations and trace elements were observed in all geological media. However, different patterns of changes were also observed depending on the mineralogical and physico-chemical characteristics of each material. As the column operation continued, while the pH decreased and low alkalinity values were more evident in the silicate soil and clean sand columns, the carbonate column continued to show high alkalinity and EC values in addition to high concentrations of most cations. The alluvium soil showed distinctive cation-exchange behaviors during the initial introduction of CO₂. The results indicate that changes in the geochemical composition of groundwater will depend on the characteristic of the geological medium such as pH buffering capacity and cation exchange capacity. This study can be useful for monitoring and managing the impacts of CO₂ leakage in various aquifer environments. Full article

(This article belongs to the Special Issue Injection-Induced Fluid Flows and Solute/Heat Transport Behavior in a Subsurface Environment)

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15 pages, 4994 KiB

Open AccessArticle

Hausdorff Fractal Derivative Model to Characterize Transport of Inorganic Arsenic in Porous Media

by Xiaoxiao Hao, HongGuang Sun, Yong Zhang, Shiyin Li, Jia Song and Kate Salsky

Water 2020, 12(9), 2353; https://0-doi-org.brum.beds.ac.uk/10.3390/w12092353 - 21 Aug 2020

Cited by 3 | Viewed by 2127

Abstract

The increasing severity of arsenic pollution has progressively threatened human life and attracted much attention. One of the important topics in environmental sciences is to accurately describe the inorganic arsenic transport in heterogeneous porous media, occurring anomalous diffusion phenomenon, which ultimately benefits the [...] Read more.

The increasing severity of arsenic pollution has progressively threatened human life and attracted much attention. One of the important topics in environmental sciences is to accurately describe the inorganic arsenic transport in heterogeneous porous media, occurring anomalous diffusion phenomenon, which ultimately benefits the control of arsenic pollution. In this paper, we re-evaluate the dataset of the inorganic arsenic transport in porous media in previous work by using a time-Hausdorff fractal model (HADE). Transport experiments of arsenic-carrying (As(V)) ferric humate complex colloids through a quartz sand column were carried out under varying dissolved organic matter (humic acid) concentrations, pH values, ionic strengths, and ferric concentrations. The results show that under our experimental settings, arsenic migration is promoted with the increase of concentrations of HA, ferric ion and sodium ion, and pH to varying degrees. The intensity of arsenic sub-diffusion behavior is opposite to that of arsenic transport. The HADE model can describe the migration behavior of arsenic well, and the value of the time fractal derivative can reflect the diffusion intensity of arsenic migration to a certain extent. By comparing the HADE model, ADE model, and time-fractional model (fADE) to the experimental data, the HADE model can significantly improve all the simulation results of capturing As(V) breakthrough curves (BTCs). Full article

(This article belongs to the Special Issue Injection-Induced Fluid Flows and Solute/Heat Transport Behavior in a Subsurface Environment)

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20 pages, 2278 KiB

Open AccessArticle

Characterization of Aquifer Hydrochemistry from the Operation of a Shallow Geothermal System

by Hanna Choi, Jaeyeon Kim, Byoung Ohan Shim and Dong-hun Kim

Water 2020, 12(5), 1377; https://0-doi-org.brum.beds.ac.uk/10.3390/w12051377 - 13 May 2020

Cited by 9 | Viewed by 3150

Abstract

The use of shallow geothermal energy systems utilizing groundwater temperature for the air-conditioning of buildings is increasing worldwide. The impact of these systems on groundwater quality has become crucial for environmental regulations and system design. For the long-term operation of geothermal systems, it [...] Read more.

The use of shallow geothermal energy systems utilizing groundwater temperature for the air-conditioning of buildings is increasing worldwide. The impact of these systems on groundwater quality has become crucial for environmental regulations and system design. For the long-term operation of geothermal systems, it is important to evaluate their influence on the geochemical properties of groundwater, including precipitation and dissolution of secondary minerals. This research was conducted in a real-scale geothermal system, consisting of a groundwater heat pump (GWHP). Hydrochemical data were obtained from samples collected from an aquifer before heating, during heating, and before cooling operations of the GWHP. The Langelier Saturation Index and Ryznar Stability Index were calculated, and the saturation index was simulated with the PHREEQC program. Evidence from water table variation, temperature change, and

^{87}

Sr/

^{86}

Sr isotope distribution showed that groundwater flows from a well located on the northwest side of the geothermal well. The saturation index values showed that the pristine groundwater favors carbonate dissolution, however, manganese oxides are more sensitive to temperature than carbonate minerals. In addition, mineral precipitation and dissolution were found to vary with depth and temperature. Full article

(This article belongs to the Special Issue Injection-Induced Fluid Flows and Solute/Heat Transport Behavior in a Subsurface Environment)

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