Underground Sources Of Drinking Water Research Articles

Nitrate source analysis of underground drinking water sources in Zhangjiakou main urban area and its health risk assessment

<p style="line-height:200%;text-align:justify;text-justify:inter-ideograph;"><span lang="EN-US">In order to investigate the main pollution factors of underground drinking water sources in semi-arid agricultural areas in China, and to reveal the threatening influence of pollutants on the normal water security of local society. Single-factor evaluation index, principal component analysis, basic data statistics are used to clarify the main pollution indicators of underground drinking water sources in Zhangjiakou main city and discuss the main influencing factors of the change of their pollution concentration, and evaluate the degree of health threat of its pollution to the drinking water of local residents. The results show that: the water sources of Taobeiying and Gushi are deeply affected by human activities, and nitrate, as the only exceeding substance under drinking water standards, is the most important indicator of groundwater pollution; and the nitrate con-centration of groundwater is higher in the pasture and nearby agricultural activities; nitrate contamination levels in groundwater are within the health acceptability range for the vast majority of the population, with only newborns in the Taobeiying drinking water source being exposed to a non-carcinogenic risk of nitrate. The results of the study will help to maintain a stable groundwater environment.</span></p>

Qualitative risk assessment of legacy wells based on publicly available data for class VI well permit applications—Illinois basin case study

Carbon Capture & Storage (CCS) refers to capturing the anthropogenic carbon dioxide (CO2) at a source followed by injecting and storing it safely in the subsurface. The success of the CCS projects therefore heavily relies on how efficiently the confining zones (containment seals) prevent migration of the CO2 to the surface and/or to the underground sources of drinking water (USDW) through leakage pathways. CCS projects requires drilling of Underground Injection Control (UIC) Class VI wells for permanent storage of CO2 in subsurface. Detailed information of all the wells within the Area of Review (AoR) is needed to develop the map and tabulation components of the Class VI well permit application. This paper discusses the generic process that can be used by permit applicants to develop the dataset necessary for preparing the map and tabulation components of the Class VI permit application and perform qualitative risk assessment of all the wells within the AoR. This methodology directs the corrective action plans as well as monitoring plans to some extent. Results of the application of the newly developed methodology for wells in Illinois basin is discussed in detail. This methodology can be applied to all wells including orphaned wells, abandoned wells, active oil and gas wells, stratigraphic wells, disposal wells, etc. This methodology generalized categorization of legacy wells that will help in easier comparison of different CCS projects across the globe. The qualitative risk assessment methodology discussed in this paper is a good starting point for developing crossflow modeling.

Immunological and genetic profile of the pediatric population in the nitrate geochemical province

BACKGROUND: Contamination of groundwater with nitrates may result in substantial adverse effects on the health of various population groups.
 AIM: To study the immune status and genetic profile of children residing in the nitrate geochemical province in the Perm Region.
 MATERIAL AND METHODS: We conducted a study on a total of 78 preschool children residing in areas with varying levels of nitrate in the underground drinking water sources. The children were divided into two groups for comparison purposes. The first group consisted of 43 children who consumed drinking water that met the acceptable standards for nitrate content. The second group comprised 35 children who consumed drinking water with elevated levels of nitrates. To assess the impact of nitrate content on the children’s health, several measurements were taken. Firstly, the level of nitrates in the household drinking water was analyzed. Additionally, the concentration of N-nitrosamines and nitrate ions in the children’s urine, was determined. To evaluate the immunoregulation parameters, the technology of flow cytometry and enzyme immunoassay were employed, along with PCR to examine genetic polymorphisms.
 RESULTS: A statistically significant difference (p 0.001) was observed in the nitrate content of drinking water between the observation area and the comparison area, with the former showing levels 2.8 times higher. Furthermore, children in the observation group exhibited a significant increase (p 0.05) of 2.3 times in N-nitrosodiethylamine content and 1.6 times in nitrate ion concentration in their urine compared to children in the comparison group. In addition, the observation group displayed a significant decrease (p 0.05) in the number of NKT cells and an increase in the levels of CD3+CD25+-, CD3+CD95+-cells, bax, IL-17, Annexin V-FITC+PI–-, and Annexin V-FITC+PI+-lymphocytes, when compared to the results obtained from the comparison group. Moreover, the presence of polymorphisms in candidate genes associated with tumor formation (CYP1A1 (rs1048943), MMP9 (rs17576), PPARD (rs2016520), BRCA1 G/A (rs3950989)) was also identified.
 CONCLUSION: Our results suggest that children who are exposed to chronic low-levels of nitrates (at a concentration of 1.2 MPC) through drinking water from underground sources exhibit an excessive presence of N-nitrosodiethylamine and nitrate ions in their urine. These findings, in conjunction with the genetic profile of genes responsible for tumor formation, influences the characteristics of the immune response.

Biotesting for the objectivization of the hygienic evaluation of the surface and underground drinking water sources

Introduction. An algorithm for evaluating the hygienic safety of drinking water sources based on biotesting and studying sanitary and chemical indicators has been developed and tested. Materials and methods. The research methods included sanitary and chemical analysis of water samples, as well as biotesting methods using single-celled green alga Chlorella vulgaris Beijer and bull spermatozoa. Results. For experimental approbation of the developed algorithm for determining the hygienic safety of water based on a two-component system of express biotesting and measurement of sanitary and chemical indicators, 6 underground and 5 surface water sources were evaluated. The response of test objects indicating the presence of acute toxicity in water samples taken from surface and underground in many cases correlates with the excess of MPC for individual indicators identified by sanitary and chemical analysis. For two water samples, differences were found between the results of biotesting and sanitary-chemical analysis, and therefore it is necessary to conduct an extended toxicological and chemical assessment to identify the source of toxic effects. Limitations. The two-component test system cannot be used separately without sanitary and chemical analysis of water media. Conclusion. Biotesting can be an addition to sanitary and chemical analyses, showing the presence of toxic substances that are not in the list of mandatory indicators to be determined (according to MR 2.1.4.0176-20 (in Russian)).

Risk matrix for legacy wells within the Area of Review (AoR) of Carbon Capture & Storage (CCS) projects

The success of CCS depends on the capacity, injectivity, and confinement by the storage medium. Thousands of wells drilled over the past century with the intention to find the trapped oil and gas may penetrate the containment seals. These wells may provide leakage pathways for the CO2 to escape and contaminate the underground sources of drinking water (USDW) or reach the surface in the worst-case scenario. Identifying the risky wells penetrating the containment seals and predicting their current as well as future well integrity is the most challenging task when limited data is available. This paper proposes a unique methodology for risk assessment of the wells penetrating the containment seals based on the proximity of these wells from the proposed injection location, mechanical integrity, and accessibility of these wells over the lifecycle of the CCS project. This helps in identifying the wells which need immediate attention from the wells that need little to no attention. It also highlights the corrective actions necessary for the success of the CCS project as well as help estimate the approximate cost required to perform the corrective actions. This methodology focuses on all wells (producers, injectors, orphan, abandoned, water, stratigraphic, etc) while the majority of the studies found in literature focused on wells with sustained casing pressure (SCP) reports and cement bond logs (CBL). The proposed risk matrix, if applied to future CCS projects across the globe, will uniformly categorize the wells within the Area of Review (AoR).

Underground sources of drinking water chemistry changes in response to potential CO2 leakage

The purpose of this study was to quantify changes to underground sources of drinking water (USDW) quality in response to potential CO2 leakage from geologic CO2 sequestration (GCS) reservoirs. We developed a framework of combined laboratory experiments and reactive transport simulations and used this framework to evaluate the Ogallala aquifer overlying the Farnsworth Unit (FWU), an active GCS site, as a case study. Using chemical reaction parameters obtained from laboratory experiments and numerical simulations, site-specific mechanisms of CO2-water-sediment interactions at the USDW aquifer were interpreted. Long-term risks of potential CO2 leakage were then evaluated with field-scale numerical models using the regional hydrogeological characteristics and reaction parameters obtained from our experiments and simulations. Results suggest that carbonate mineral impurity and cation exchange are key mechanisms for interactions between CO2 and the aquifer sediment. Additionally, for a large leakage rate of 0.1 % injection from one leaky well, the leakage plume might impact an area of 300 m in diameter and significantly affect the local water quality by changing pH and cation concentrations (e.g., Zn, Ba and Sr). After leakage ceases, the zone of impacted fluids would not migrate significantly in subsequent decades due to a low regional groundwater flowrate (for this case study). The relatively small area of impact might not be detected in a monitoring well given the broader spacing in a typical field scenario. Effective early leakage detection may require additional tools, e.g., borehole CO2 movement, four-dimensional seismicity, CO2 soil flux, samples from deeper aquifers, etc., to ensure effective leakage detection and long-term safety of GCS projects.

CELL DEATH UNDER CONDITIONS OF HAPTIC CONTAMINATION OF BIOLOGICAL MEDIA BY STABLE STRONTIUM

Introduction: The conditions of haptic contamination with stable strontium disrupt the implementation of programmed cell death, forming early health disorders of the child population. Aim: to study the indicators, characterizing cell death, in children with excess haptic contamination of biological media with natural stable strontium. Methods: Research group: children consuming drinking water from underground drinking water sources with excess content of natural stable strontium, comparison group: children consuming drinking water of satisfactory quality in terms of strontium content.The study of indicators characterizing cell death was carried out by flow cytometry; polymorphism of candidate genes by real-time PCR. Results: It was found that in children exposed to strontium, the content of protein-oncosuppressor p53, proapoptotic reception of CD95+- lymphocytes, Annexin V-FITC+PI--lymphocytes with a simultaneous increase in an average of 1.7 times lymphocytic phenotypes of CD95+- lymphocytes and associated with necrotic death of Annexin V-FITC+PI+-lymphocytes are statistically significant (p < 0.001) decreased by an average of 2.5 times. An increased frequency of the heterozygous genotype of the matrix metalloproteinase gene MMP9 Gln279Arg is 2.5 times higher than the results obtained in unexposed children. Conclusion: The results of the studies allowed us to establish that strontium concentrations in the blood in the range from 0.040 to 0.091 mg/dm3 are associated with inhibition of apoptosis and switching to an alternative pathway of cell death-necrosis, which, against the background of polymorphism of candidate genes, creates a risk of autoimmune pathology.

A simulation study of carbon storage with active reservoir management

AbstractAs part of the Integrated Midcontinent Stacked Carbon Storage Hub (IMSCS‐Hub) project led by Battelle Memorial Institute, a study was conducted to determine the feasibility of storing carbon dioxide (CO2) in the stacked saline rock formations of the Sleepy Hollow Field (SHF), located in Red Willow County, southern Nebraska.A series of CO2 injection simulation scenarios, with and without active reservoir management (ARM; brine extraction), were evaluated to investigate the feasibility of storing 50+ million tonnes (Mt) of CO2. The results indicated CO2 injection combined with ARM may enable permanent storage of 50+ Mt of CO2.The area of review (AOR), the area in which underground sources of drinking water (USDWs) might be endangered during CO2 injection, was assessed for the simulation scenarios. In comparison to a case without ARM, brine extraction resulted in a much smaller AOR, covering an area of 42 square miles (108.8 km2), roughly one‐fourth the size of an AOR resulting from CO2 injection without ARM.The findings presented in this paper indicate that CO2 injection with ARM can improve the CO2 storage capacity of a geologic storage complex up to 100% while also reduce the rate of pressure buildup in the subsurface, resulting in a 75% reduction in AOR. This may help in lowering carbon capture and storage project costs, risks, and effort needed to meet monitoring requirements for a storage project. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd.

Risk‐based area of review estimation in overpressured reservoirs to support injection well storage facility permit requirements for CO2storage projects

AbstractThis paper presents a workflow for delineating a risk‐based area of review (AOR) to support a US Environmental Protection Agency (EPA) Class VI permit for a carbon dioxide (CO2) storage project. The approach combines semianalytical solutions for estimating formation fluid leakage through a hypothetical leaky wellbore with the results of physics‐based numerical reservoir simulations. The workflow is demonstrated using a case study for a hypothetical 180,000‐metric‐ton‐per‐year storage project located in the Plains CO2Reduction (PCOR) Partnership region, which includes all or part of 10 states in the United States and four Canadian provinces. Under the scenario where the leaky wellbore is open to a saline aquifer (thief zone) between the overlying seal (cap rock) and the underground sources of drinking water (USDW), the risk‐based AOR is no larger than the areal extent of the CO2plume in the storage reservoir because the pressure buildup in the storage reservoir beyond the CO2plume is insufficient to drive formation fluids up a hypothetical leaky wellbore into the USDW. However, even under the conservative assumption that the leaky wellbore is not open to a thief zone, the incremental leakage beyond the areal extent of the CO2plume is less than 400 m3over 20 years. The approach outlined in this paper is designed to be protective of USDWs and comply with the Safe Drinking Water Act requirements and provisions for the EPA Class VI Underground Injection Control (UIC) Program (Class VI Rule) and North Dakota Administrative Code Chapter 43‐05‐01. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd.

Potential Chemical Impacts of Subsurface CO2: An Integrated Experimental and Numerical Assessment for a Case Study of the Ogallala Aquifer

AbstractLeakage from geologic CO2sequestration (GCS) reservoirs to overlying underground sources of drinking water (USDW) is a tangible risk. This study is an integrated assessment that combines column experiments and reactive transport simulations of sediments sampled from the Ogallala aquifer above an active commercial‐scale GCS site (the Farnsworth Unit in northern Texas). Experimental and simulation results suggest that carbonate mineral (calcite and dolomite) dissolution is the most significant reaction following CO2intrusion, and is also the dominant source of trace metal release. Cation exchange is another key mechanism controlling trace metal release by cation interference. Most of the trace metals, including Ba, Sr, As, Pb, and Zn, show a short‐term release and quickly drop to the baseline values, suggesting low risk to the overlying USDW quality. Other trace metals, such as Mn and U, exhibit a tangible increase of their concentrations in the beginning, and drop to a higher level compared to the baseline, which may become a potential concern of long‐term USDW quality change with CO2introduction. This study provides a comprehensive example of combining laboratory experiments and simulations for assessment of CO2‐sediment interactions with combined release mechanisms in shallow groundwater aquifers. Data presented here provides useful insights for quantitative risk assessment and effective public education regarding CO2geological sequestration, and trace metal reactive transport studies in shallow groundwater aquifers.

Fabrication of Manganese-Supported Activated Alumina Adsorbent for Defluoridation of Water: A Kinetics and Thermodynamics Study

Fluoride pollution frequently occurs in many underground drinking water sources due to discrepancies in the geological environment. To address this problem, a manganese-supported activated alumina (MnOOH-supported AA) adsorbent was proposed in the present study. The adsorbent was prepared with an impregnation method, then the morphology and microstructure were systematically characterized. Further, the adsorption kinetics and thermodynamics were systematically explored through static experiments to confirm the adsorption mechanism. The results showed that MnOOH was successfully loaded on the activated alumina (AA), and irregular and convex spinous structures were formed on the surface of particles. Compared with the AA, MnOOH-supported AA exhibited a significantly higher defluoridation rate, which has been doubled. The kinetic behavior of fluoride adsorption on MnOOH-supported AA was governed by the quasi-second-order kinetics model with regression coefficients of 0.9862, 0.9978 and 0.9956, respectively. The adsorption rate was mainly ascribed to the intra-particle diffusion. Additionally, the Freundlich isotherm equation fitted the adsorption thermodynamic process reasonably well compared with the Langmuir adsorption model. Specifically, the correlation coefficients were 0.9614, 0.9383 and 0.9852 at 25 °C, 35 °C and 45 °C, respectively. The adsorption–desorption isotherm plot was similar to the Type V isotherm. The whole fluoride adsorption was a spontaneous endothermic reaction, and controlled by chemical adsorption. These results demonstrated that MnOOH-supported AA as an alternative to the conventional AA showed promising potential for defluoridation in drinking water treatment.

Studying the kinetics mechanism of emulsified petroleum products recovery from waste waters in dynamic conditions

Petroleum products belong to the most common man-made pollutants of surface watercourses, and sometimes even underground drinking water sources. They get to the environment at the extraction and transportation of oil and oil products, as well as at industrial disasters. The oil-contaminated sewage waters produce the general-toxic, embryotoxic and carcinogenic effect, and weaken the immune system. To purify wastewaters from petroleum products the most efficient and environmentally friendly is the sorption method. This paper considers using a carbon-containing material, obtained by thermal modification at 450°C of waste kieselguhr sludge from vegetable oil extraction industry, as petroleum sorbent. The designed sorbent is characterized with mesoporous structure, high hydrophobic properties and the presence of oxygen-containing functional groups – carboxyl, hydroxyl and lactone – on the carbon layer surface. Research has been carried out in purification of test water media from emulsified petroleum products in dynamic conditions with the use of the designed sorbent. The number of passed sorption volumes to the «breakthrough» and the full saturation of the sorbent with oil products were determined. The calculated dynamic exchange capacity of the sorbent for petroleum products is 2.9 mg/g, the total exchange capacity – 8.4 mg/g. The limiting stage of petroleum products sorption process kinetics with the carbon-containing sorption material in the studied conditions is diffusion inside the sorbent grains.

Chemical Impacts of Potential CO2 and Brine Leakage on Groundwater Quality with Quantitative Risk Assessment: A Case Study of the Farnsworth Unit

Potential leakage of reservoir fluids is considered a key risk factor for geologic CO2 sequestration (GCS), with concerns of their chemical impacts on the quality of overlying underground sources of drinking water (USDWs). Effective risk assessment provides useful information to guide GCS activities for protecting USDWs. In this study, we present a quantified risk assessment case study of an active commercial-scale CO2-enhanced oil recovery (CO2-EOR) and sequestration field, the Farnsworth Unit (FWU). Specific objectives of this study include: (1) to quantify potential risks of CO2 and brine leakage to the overlying USDW quality with response surface methodology (RSM); and (2) to identify water chemistry indicators for early detection criteria. Results suggest that trace metals (e.g., arsenic and selenium) are less likely to become a risk due to their adsorption onto clay minerals; no-impact thresholds based on site monitoring data could be a preferable reference for early groundwater quality evaluation; and pH is suggested as an indicator for early detection of a leakage. This study may provide quantitative insight for monitoring strategies on GCS sites to enhance the safety of long-term CO2 sequestration.

Optimization of defluorination and iron reduction effect of manganese-loaded activated alumina by Response Surface Methodologyology

Influenced by geological environment, both fluoride ion and iron ion exceed the standard in underground drinking water sources in some areas. Aiming at this problem, the experiment was designed by Response Surface Methodologyology(RSM). With the goal that fluoride ion in the effluent meets the Standards for Drinking Water quality (GB 5749-2006) and the concentration of iron ion in the effluent drops significantly, the adsorption time, pH value and temperature were taken as independent variables, and the primary and secondary relationship of influencing factors on fluoride and iron reduction of manganese-loaded activated alumina was explored, then the process parameters were optimized. The remarkable relationships are AF(adsorption time)>BF(pH value)>CF(temperature), BFe(pH value) > CFe(temperature)>AFe(adsorption time).Under the conditions of adsorption time 8h, pH value 4 and temperature 25°C, when the mass concentrations of iron and fluorine in raw water are 2mg/L, the removal rates of fluoride and iron can reach 68% and 59.5%, and the mass concentrations of effluent are 0.61mg/L and 0.81mg/L, respectively.

Evaluation of Annulus Pressure Buildup During Injection Operations

Abstract More than 300 million barrels of saltwater is produced everyday from oil and gas production wells. Most of this volume is injected through either saltwater disposal wells or used for water flooding and enhanced recovery purposes. Usually, the regulations require the injection to be conducted through the injector well tubing that is isolated from the well annulus to protect the underground source of drinking water (USDW) by preventing any possible leak through the well casing. Monitoring of the annulus pressure during injection ensures the well integrity. The annulus pressure changes can occur by one of the following mechanisms: thermal expansion of the annulus fluid; ballooning of the injection tubing; communication between the tubing and the annulus; or fluid migration behind the casing. Determining the communication mechanism can be a complex process and a need may arise to run several testing procedures and inspect all the wellbore components. Successful evaluation of the annulus pressure values and trends can directly identify the root cause of the annulus pressure buildup and simultaneously save time and reduce the cost associated with the workover operations. The seven case studies presented in this paper focus on the details pertaining to the annulus pressure buildup under different well conditions and purposes the interpretation technique for each case.

Probabilistic risk-based Area of Review (AoR) determination for a deep-saline carbon storage site

Regulatory oversight of a geologic carbon sequestration (GCS) project relies on iterative estimations, throughout the project lifetime, of the area where increased risks to underground sources of drinking water (USDWs) may occur due to injection of CO2. This area, referred to as Area of Review (AoR), is typically delineated by predicting the migration of fluid between the reservoir and the lowermost USDW via an open wellbore using predictions from physics-based reservoir simulators. The inherent uncertainty in input parameters used in reservoir modeling therefore affects the accuracy of determining the AoR for a project. Furthermore, the standard analytical approaches for calculating a critical pressure to delineate the risk area yield an infinite AoR for cases where the injection reservoir is overpressured relative to the USDW. A methodology is presented here to better characterize the risk to USDWs while accounting for the uncertainty in reservoir modeling, with an application to a permitted GCS project with an overpressured injection formation, FutureGen 2.0. The methodology is demonstrated using the National Risk Assessment Partnership’s open-source integrated assessment model (NRAP-Open-IAM) to develop a probabilistic estimate of impact risk to USDW quality. CO2 and pressure predictions from the reservoir modeling conducted using the STOMP-CO2 simulator for the FutureGen 2.0 site are used in a NRAP-Open-IAM model with reservoir, wellbore, and aquifer components to: (1) assess the extent of potential leakage into the USDW for the predicted reservoir pressure conditions; (2) evaluate the extent of potential impact using “no-net-degradation” thresholds; and (3) account for uncertainty in reservoir permeabilities.

Empirical Evidence Demonstrating Injection Containment and Absence of Injection-Induced Fracturing, Wilmington Oil Field Case Study

Summary Waterfloods in California operate under the US Environmental Protection Agency's Class II underground injection control regulations, which are tasked with the protection of underground sources of drinking water (USDW) within the state. A key aspect of this regulatory framework is the operation of water injection wells under a maximum allowable surface pressure (MASP) to ensure that injected water does not induce and/or extend formation fractures that could create a potential conduit connecting the hydrocarbon zone with identified USDWs. Determination of the MASP for individual injection wells has typically been calculated using a step rate test (SRT), but this method has been shown to be inappropriate for multilayered, unconsolidated sandstone reservoirs (Ershaghi and Ershaghi 2018), which are prevalent in Wilmington Field. To avoid the potential for misinterpretation of SRTs to imply fracturing in this context, in this paper we summarize the evidence demonstrating both the effective geologic containment of injected fluid in the hydrocarbon-bearing zones and the absence of injection-induced fracturing. In addition, a series of field tests were conducted to assess the stress sensitivity of the Wilmington reservoirs and investigate in-situ changes in the reservoir at higher injection pressures by combining multirate injection tests with injection profile surveys. These results provide data supporting the noted challenges associated with MASP determination for multilayered, unconsolidated reservoirs. In this paper, we give operators and regulators working in these types of fields a framework for assessing both injection containment and injection-induced fracturing that account for the unique properties of these formations.

Reactive transport modeling of produced water disposal into dolomite saline aquifers: Controls of barium transport

Experimental results on barium transport in dolomite are used to formulate, calibrate, and validate a reactive transport model of produced water disposal into dolomite saline aquifers. The model accounts for sorption, dissolution/precipitation reactions of minerals (dolomite, calcite, barite, gypsum, and witherite) and complexation and acid-base reactions of most abundant ionic species (H+, HCO3−, SO42−, Ca2+, Mg2+, and Cl−) in produced waters including Ba2+ which is the most common and abundant heavy metal present in produced water from oil and gas reservoirs. The model is applied to determine the chemical controls of barium transport in Arbuckle dolomite aquifers. The simulated scenario corresponds to produced water disposal through a Class II injection well located near an abandoned well that can facilitate the transport of barium to underground sources of drinking water (USDW). Simulation results reveal that most suitable dolomite aquifers to prevent the contamination of USDW by barium are dolomite aquifers of high SO42− content (>1000 mg/L). The mobility of barium which is promoted by the formation of Ba(Cl)+ and competition of cations (Ca2+ and Mg2+) for hydration sites of dolomite can be suppressed by the precipitation of barium as barite in dolomite saline aquifers of high SO42− content. A sensitivity analysis conducted using a two-level factorial design of experiments indicates that barium transport can be controlled by the initial concentration of a single ionic specie (mostly SO42−) or the concentration of various ionic species (e.g., SO42−, Cl−, and Mg2+). This depends on the chemical composition of both the dolomite saline aquifer and injection produced water. This work highlights the potentiality of a reactive transport simulation approach to conduct compatibility analysis of dolomite saline aquifers and produced waters to select dolomite aquifers and/or decide on treatment methods to prevent the contamination of USDW by barium.

A risk-based approach to evaluating the Area of Review and leakage risks at CO2 storage sites

The U.S. Environmental Protection Agency’s Class VI regulations for underground carbon dioxide (CO2) injection require owners and operators of storage projects to identify (1) an Area of Review (AoR) that represents the region that may be affected by the injection of CO2, and (2) leakage risks that might impact the quality of underground sources of drinking water (USDWs). This article describes how such risks can be determined by accounting for the physical and chemical properties of all components of a CO2 storage site using elements of the National Risk Assessment Partnership Integrated Assessment Model for Carbon Storage (NRAP-IAM-CS). We used practical data from three sites that are part of two CarbonSAFE (Carbon Storage Assurance Facility Enterprise) projects to demonstrate application of the NRAP-IAM-CS toolset to determine project risk areas.NRAP-IAM-CS was used to estimate the project risk area that could represent the AoR and the impact of leakage through legacy wells to overlying drinking waters at these candidate CO2 storage sites. Our study shows that risk to USDWs is minimal despite (1) the presence of multiple legacy wells at these sites where the AoR approximates the maximum extent of injected CO2 or (2) the presence of a much larger AoR approximating the pressure front caused by the injection of CO2.

Downhole pressure and chemical monitoring for CO2 and brine leak detection in aquifers above a CO2 storage reservoir

We assess the effectiveness of downhole monitoring of pressure and chemistry for detecting CO2 and brine leakage into underground sources of drinking water (USDW) overlying a geologic CO2 storage (GCS) reservoir. This assessment uses synthetic data sets generated in an uncertainty quantification (UQ) model framework. This framework combines the results of three model types: (1) a model of a hypothetical, 50-yr, 5-MT/yr GCS operation in the Vedder Fm. at the Kimberlina site in the southern San Joaquin Basin in California, USA, (2) models of CO2/brine leakage in legacy wells into overlying aquifers, and (3) models of CO2/brine plume migration in those aquifers. Leakage into overlying aquifers causes changes in pressure, CO2 saturation, and total dissolved solids (TDS), the latter being related to the solubility and speciation of CO2. This study captures the influence of leakage depth along the legacy well, regional groundwater flow, and aquifer heterogeneity on leak detection using downhole pressure and TDS monitoring.We consider CO2/brine leakage for legacy wells located at various distances from the CO2 injector at the Kimberlina site. Because gaseous CO2 is much less dense than supercritical CO2, the depth where leakage occurs along the wellbore is a key factor affecting the CO2, TDS, and pressure plumes. Supercritical CO2 that migrates upwards to depths less than 800 m undergoes a phase change to gaseous CO2, with the large volumetric expansion causing a large rise in pressure and a large spread in the TDS and pressure plumes. Because the pressure and TDS plumes migrate with the CO2 plume, they are strongly affected by regional groundwater flow and aquifer heterogeneity.We evaluated the likelihood of leak detection over a wide range of CO2/brine leakage-mass magnitude for downhole monitoring at various sensor depths, as well as for locations upgradient, downgradient, and laterally from the leaking well. Leak-detection effectiveness of downhole monitoring improves as the volumes of the CO2 and TDS plumes increase with cumulative CO2/brine leakage mass, groundwater gradient, and aquifer permeability. The effectiveness of pressure monitoring also increases strongly with CO2 leakage rate and can be useful for early detection of large leaks. Because TDS and pressure plumes migrate with the regional groundwater flow, downgradient monitoring wells are more effective than lateral or upgradient wells. Pressure monitoring is found to be more effective than TDS monitoring for shallow depths, while TDS monitoring is more effective at depths greater than about 600 m for this site. The addition of two monitoring depths to a single-depth monitoring well greatly improves leak detection. Monitoring three (shallow, medium, and deep) depths in the same well is found to be equally effective for pressure and TDS for the Kimberlina site. However, these comparisons are affected by the choice of detectable TDS and pressure thresholds, which depend on the level of unfilterable background noise for a specific site. For GCS sites like the Kimberlina site, with a thick sequence of overlying aquifers, unbroken by confining, low-permeability aquitard layers, an effective use of an individual monitoring well would be to monitor pressure at a shallow (<600 m) depth and to monitor TDS at a medium-depth (600−900 m) interval and for at least one deep (>900 m) interval. Because pressure and TDS changes evolve so gradually, continuous monitoring is not necessary.