A. U. Utom, B. I. Odoh, D. Amogu, A. Ekwe, B. Egboka
Two azimuthal resistivity surveys were completed using the square array within the Mamu Formation, Enugu area, Nigeria, to characterize the orientation and porosity of fractures. The target consists of a shallow (30 m [98 ft]) fracture zone that corresponds to the average completion depth for the water supply wells in the study area. Fracture orientation, fracture porosity, and coefficient of anisotropy of the investigated media were determined from the azimuthal resistivity data. Results of the survey data indicate that the fractures trend generally in the northwest–southeast direction at depths of 7.1, 10.0, 20.0, and 28.3 m (23.3, 32.8, 65.6, and 92.8 ft). The fracture porosity ranged between 0.68% and 17%. The coefficient of anisotropy () ranges between 1.00 and 1.12. Fractures at localities with relatively high values of possess relatively high fracture porosity and relatively low specific surface area and thus are more likely to be permeable. These interpretations were in agreement with the information collected at bedrock outcrops during this and previous studies. It is therefore true that the data obtained from this study will enhance the understanding of the permeable zone, fluid migration pattern, and vulnerability of the groundwater to mine drainage problems in the Enugu area.
{"title":"Characterization of near-surface fractures for hydrogeological studies using azimuthal resistivity survey: A case history from the Mamu Formation, Enugu (Nigeria)","authors":"A. U. Utom, B. I. Odoh, D. Amogu, A. Ekwe, B. Egboka","doi":"10.1306/EG.11281212009","DOIUrl":"https://doi.org/10.1306/EG.11281212009","url":null,"abstract":"Two azimuthal resistivity surveys were completed using the square array within the Mamu Formation, Enugu area, Nigeria, to characterize the orientation and porosity of fractures. The target consists of a shallow (30 m [98 ft]) fracture zone that corresponds to the average completion depth for the water supply wells in the study area. Fracture orientation, fracture porosity, and coefficient of anisotropy of the investigated media were determined from the azimuthal resistivity data. Results of the survey data indicate that the fractures trend generally in the northwest–southeast direction at depths of 7.1, 10.0, 20.0, and 28.3 m (23.3, 32.8, 65.6, and 92.8 ft). The fracture porosity ranged between 0.68% and 17%. The coefficient of anisotropy () ranges between 1.00 and 1.12. Fractures at localities with relatively high values of possess relatively high fracture porosity and relatively low specific surface area and thus are more likely to be permeable. These interpretations were in agreement with the information collected at bedrock outcrops during this and previous studies. It is therefore true that the data obtained from this study will enhance the understanding of the permeable zone, fluid migration pattern, and vulnerability of the groundwater to mine drainage problems in the Enugu area.","PeriodicalId":11706,"journal":{"name":"Environmental Geosciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1306/EG.11281212009","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66168989","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Reprocessing of the SeisData6 coastal plain profile was motivated by the need to provide enhanced subsurface imaging critical to site characterization studies for CO2 storage within the South Georgia Rift (SGR) basin. The objectives were to identify and interpret subsurface reflectors for evidence of the buried Triassic basin and its underlying characteristics. Our new interpretation, supported by analysis of well data, has helped substantiate the presence of a Triassic basin beneath the coastal plain sediments in Southeast Georgia. This basin is approximately 2.2 km (1.7 mi) deep and 170 km (106 mi) wide and appears to coincide with the subsurface convergence of the southwest and northeast extensions of the Riddleville and Dunbarton basins that are subsidiaries of the main SGR. It is characterized by distinctively higher seismic velocities relative to the overlying coastal plain sediments and manifests a series of subhorizontal reflectors below the topmost reflector. We reinterpreted the topmost reflector to originate from a change in velocity and density between the Cretaceous coastal plain sediments and the underlying Triassic rocks. This does not always originate from the Pre-Cretaceous basalt contrary to previous interpretations. The interpreted absence of basalt from this study is consistent with Heffner et al. (2012) showing that basalt is not prevalent throughout the SGR basin. Seismic discontinuities in the southeast of the basin suggest Triassic normal faults. Our data show no clear evidence for the Augusta fault that was identified in other studies in the vicinity of the Piedmont–coastal plain boundary in Georgia and South Carolina.
对SeisData6沿海平原剖面进行再处理的动机是需要提供增强的地下成像，这对南乔治亚裂谷(SGR)盆地内二氧化碳储存的现场表征研究至关重要。目的是识别和解释地下反射物，以寻找埋藏三叠纪盆地及其潜在特征的证据。我们的新解释得到了油井数据分析的支持，帮助证实了乔治亚州东南部沿海平原沉积物下存在三叠纪盆地。该盆地深约2.2公里(1.7英里)，宽约170公里(106英里)，似乎与主要SGR分支Riddleville和Dunbarton盆地西南和东北延伸的地下汇聚相吻合。它的特点是相对于上覆的海岸平原沉积物而言，地震速度明显更高，并且在最上面的反射体之下表现出一系列的次水平反射体。我们重新解释了最上面的反射物是由白垩纪海岸平原沉积物和其下的三叠纪岩石之间的速度和密度变化引起的。与以前的解释相反，这并不总是源于前白垩纪玄武岩。本研究中玄武岩的缺失与Heffner et al.(2012)一致，表明玄武岩在整个SGR盆地中并不普遍。盆地东南部地震不连续为三叠纪正断层。我们的数据显示，在乔治亚州和南卡罗来纳州皮埃蒙特海岸平原边界附近的其他研究中，没有发现奥古斯塔断层存在的明确证据。
{"title":"New constraints on buried Triassic basins and regional implications for subsurface CO2 storage from the SeisData6 seismic profile across the Southeast Georgia coastal plain","authors":"O. M. Akintunde, C. Knapp, J. Knapp, D. Heffner","doi":"10.1306/EG.10231212008","DOIUrl":"https://doi.org/10.1306/EG.10231212008","url":null,"abstract":"Reprocessing of the SeisData6 coastal plain profile was motivated by the need to provide enhanced subsurface imaging critical to site characterization studies for CO2 storage within the South Georgia Rift (SGR) basin. The objectives were to identify and interpret subsurface reflectors for evidence of the buried Triassic basin and its underlying characteristics. Our new interpretation, supported by analysis of well data, has helped substantiate the presence of a Triassic basin beneath the coastal plain sediments in Southeast Georgia. This basin is approximately 2.2 km (1.7 mi) deep and 170 km (106 mi) wide and appears to coincide with the subsurface convergence of the southwest and northeast extensions of the Riddleville and Dunbarton basins that are subsidiaries of the main SGR. It is characterized by distinctively higher seismic velocities relative to the overlying coastal plain sediments and manifests a series of subhorizontal reflectors below the topmost reflector. We reinterpreted the topmost reflector to originate from a change in velocity and density between the Cretaceous coastal plain sediments and the underlying Triassic rocks. This does not always originate from the Pre-Cretaceous basalt contrary to previous interpretations. The interpreted absence of basalt from this study is consistent with Heffner et al. (2012) showing that basalt is not prevalent throughout the SGR basin. Seismic discontinuities in the southeast of the basin suggest Triassic normal faults. Our data show no clear evidence for the Augusta fault that was identified in other studies in the vicinity of the Piedmont–coastal plain boundary in Georgia and South Carolina.","PeriodicalId":11706,"journal":{"name":"Environmental Geosciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1306/EG.10231212008","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66168039","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Timothy J. Considine, R. Watson, Nicholas B. Considine, J. P. Martin
Quantifying the success or failure of states in effectively and safely managing natural gas development is important for regulators, elected officials, and citizens to engage in productive dialog around natural gas development and the process of hydraulic fracturing. Accordingly, this study provides a detailed analysis of notices of violations from the Pennsylvania Department of Environmental Protection from January 2008 to August 2011, categorizing each violation for 3533 wells drilled. Of the 2988 violations, 1844, or 62%, were for administrative or preventative reasons. The remaining 38%, or 1144 notices of violations, were for environmental violations, which were associated with 845 unique environmental events. These events were classified into major and nonmajor categories based on the level and severity of the pollution. Blowouts, uncontrolled venting, and gas migration are considered as severe and, hence, are classified as major. The top quartile of water contamination and land spills is 400 gal and provides the threshold in this study for major events in these two categories. Of these major events, less than 1% or 25 involved these major impacts. In all but six of these cases, the resulting environmental impacts have been completely mitigated. The 820 nonmajor environmental events concern site restoration, water contamination, land spills, and cement and casing events, which do not involve what is classified as having major environmental impact. The number of polluting environmental events per well drilled declined by 60% between 2008 and August 2011, from 52.9% of all wells drilled in 2008 to 20.8% to August 2011. The regulatory data evaluated in this study may serve as an appropriate litmus test for neighboring states as they move forward with regulating shale energy development. In particular, we find that each of the underlying causes associated with these specific events could have been either entirely avoided or mitigated under the proposed regulatory framework of the New York State.
{"title":"Environmental regulation and compliance of Marcellus Shale gas drilling","authors":"Timothy J. Considine, R. Watson, Nicholas B. Considine, J. P. Martin","doi":"10.1306/EG.09131212006","DOIUrl":"https://doi.org/10.1306/EG.09131212006","url":null,"abstract":"Quantifying the success or failure of states in effectively and safely managing natural gas development is important for regulators, elected officials, and citizens to engage in productive dialog around natural gas development and the process of hydraulic fracturing. Accordingly, this study provides a detailed analysis of notices of violations from the Pennsylvania Department of Environmental Protection from January 2008 to August 2011, categorizing each violation for 3533 wells drilled. Of the 2988 violations, 1844, or 62%, were for administrative or preventative reasons. The remaining 38%, or 1144 notices of violations, were for environmental violations, which were associated with 845 unique environmental events. These events were classified into major and nonmajor categories based on the level and severity of the pollution. Blowouts, uncontrolled venting, and gas migration are considered as severe and, hence, are classified as major. The top quartile of water contamination and land spills is 400 gal and provides the threshold in this study for major events in these two categories. Of these major events, less than 1% or 25 involved these major impacts. In all but six of these cases, the resulting environmental impacts have been completely mitigated. The 820 nonmajor environmental events concern site restoration, water contamination, land spills, and cement and casing events, which do not involve what is classified as having major environmental impact. The number of polluting environmental events per well drilled declined by 60% between 2008 and August 2011, from 52.9% of all wells drilled in 2008 to 20.8% to August 2011. The regulatory data evaluated in this study may serve as an appropriate litmus test for neighboring states as they move forward with regulating shale energy development. In particular, we find that each of the underlying causes associated with these specific events could have been either entirely avoided or mitigated under the proposed regulatory framework of the New York State.","PeriodicalId":11706,"journal":{"name":"Environmental Geosciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1306/EG.09131212006","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66166948","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Open faults and fractures act as a major control of fluid flow in the subsurface, especially in fine-grained, low-permeability lithologies. These discontinuities commonly form a part of seal bypass systems, which can lead to the failure of hydrocarbon traps, CO2 geosequestration sites, and waste and injected fluid repositories. We evaluate mesoscale variability in fracture density, morphology and the variability in elastic moduli in the Jurassic Carmel Formation, a proposed seal to the underlying Navajo Sandstone for CO2 geosequestration. By combining mechanostratigraphic outcrop observations with elastic moduli derived from wireline-log data, we characterize the variability in fracture pattern and morphology with the observed variability in rock strength within this heterolithic top seal. Outcrop inventories of discontinuities show that fracture densities decrease as bed thickness increases and that fracture propagation morphology across lithologic interfaces vary with changing interface type. Dynamic elastic moduli, calculated from wireline-log data, show that Young's modulus ranges by as much as 40 GPa (5,801,510 psi) across depositional interfaces and by an average of 3 GPa (435,113 psi) across the reservoir-seal interface. We expect that the mesoscale changes in rock strength will affect the distributions of localized stress and thereby influence fracture propagation and fluid flow behavior within the seal. These data provide a means to closely tie outcrop observations to those derived from subsurface data and estimates of subsurface rock strength. The characterization of rock strength variability is especially important for modeling the response of caprocks to changing stress conditions associated with increased fluid pressures and will allow for better site screening and subsurface fluid management.
{"title":"Predicting rock strength variability across stratigraphic interfaces in caprock lithologies at depth: Correlation between outcrop and subsurface","authors":"E. Petrie, T. Jeppson, James P. Evans","doi":"10.1306/EG.06011212001","DOIUrl":"https://doi.org/10.1306/EG.06011212001","url":null,"abstract":"Open faults and fractures act as a major control of fluid flow in the subsurface, especially in fine-grained, low-permeability lithologies. These discontinuities commonly form a part of seal bypass systems, which can lead to the failure of hydrocarbon traps, CO2 geosequestration sites, and waste and injected fluid repositories. We evaluate mesoscale variability in fracture density, morphology and the variability in elastic moduli in the Jurassic Carmel Formation, a proposed seal to the underlying Navajo Sandstone for CO2 geosequestration. By combining mechanostratigraphic outcrop observations with elastic moduli derived from wireline-log data, we characterize the variability in fracture pattern and morphology with the observed variability in rock strength within this heterolithic top seal. Outcrop inventories of discontinuities show that fracture densities decrease as bed thickness increases and that fracture propagation morphology across lithologic interfaces vary with changing interface type. Dynamic elastic moduli, calculated from wireline-log data, show that Young's modulus ranges by as much as 40 GPa (5,801,510 psi) across depositional interfaces and by an average of 3 GPa (435,113 psi) across the reservoir-seal interface. We expect that the mesoscale changes in rock strength will affect the distributions of localized stress and thereby influence fracture propagation and fluid flow behavior within the seal. These data provide a means to closely tie outcrop observations to those derived from subsurface data and estimates of subsurface rock strength. The characterization of rock strength variability is especially important for modeling the response of caprocks to changing stress conditions associated with increased fluid pressures and will allow for better site screening and subsurface fluid management.","PeriodicalId":11706,"journal":{"name":"Environmental Geosciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1306/EG.06011212001","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66165068","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The occurrence of several water crises in India over the years has resulted in the formulation of strategies that promote sustainable development of groundwater resources. For such planning efforts, the evaluation of groundwater recharge zones is a vital component of the water balance equation. Therefore, this study presents a systematic scientific analysis of various morphometric parameters relating to groundwater flow in hard rock terrain. The numerical classification scheme presented herein constitutes an integrated approach that shows how to leverage basic watershed information to evaluate prospective sites and measures at various scales for the purposes of water resources development and management. We have used our morphometric analysis of the Mamundiyar watershed of southern India to demonstrate the use of this classification scheme as a helpful tool in the watershed development planning process. The results of this relative ranking of Mamundiyar subbasins, using various parameters that are ultimately indicative of surficial rock permeability, show the usefulness of this classification scheme in identifying suitable rainfall infiltration sites. Together with an evaluation of the various hydrogeologic conditions in a given basin, this type of numerical classification scheme can be developed and applied to properly identify recharge sites in the planning stages of sustainable watershed development, as well as in already active watersheds, perhaps where extractive industries are working or certain land use practices exist, to evaluate potential relationships between hydrogeologic regimes and these anthropogenic activities.
{"title":"Groundwater development in hardrock terrain using morphometric analysis","authors":"I. Dar, K. Sankar, Mithas Ahmad Dar","doi":"10.1306/EG.06011212003","DOIUrl":"https://doi.org/10.1306/EG.06011212003","url":null,"abstract":"The occurrence of several water crises in India over the years has resulted in the formulation of strategies that promote sustainable development of groundwater resources. For such planning efforts, the evaluation of groundwater recharge zones is a vital component of the water balance equation. Therefore, this study presents a systematic scientific analysis of various morphometric parameters relating to groundwater flow in hard rock terrain. The numerical classification scheme presented herein constitutes an integrated approach that shows how to leverage basic watershed information to evaluate prospective sites and measures at various scales for the purposes of water resources development and management. We have used our morphometric analysis of the Mamundiyar watershed of southern India to demonstrate the use of this classification scheme as a helpful tool in the watershed development planning process. The results of this relative ranking of Mamundiyar subbasins, using various parameters that are ultimately indicative of surficial rock permeability, show the usefulness of this classification scheme in identifying suitable rainfall infiltration sites. Together with an evaluation of the various hydrogeologic conditions in a given basin, this type of numerical classification scheme can be developed and applied to properly identify recharge sites in the planning stages of sustainable watershed development, as well as in already active watersheds, perhaps where extractive industries are working or certain land use practices exist, to evaluate potential relationships between hydrogeologic regimes and these anthropogenic activities.","PeriodicalId":11706,"journal":{"name":"Environmental Geosciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1306/EG.06011212003","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66165270","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Olga H. Popova, M. Small, S. McCoy, A. C. Thomas, B. Karimi, A. Goodman, Kristin M. Carter
Today, an increased emphasis on the distribution, potential volume, and cost to develop CO2 geologic sequestration resources exists. In the presence of climate change, the need to make accurate and clearly understandable assessments of carbon sequestration potential, which can be used by the government and industry to plan for technology deployment, has never been greater. We compare three CO2 storage assessment methodologies: the approach applied by the U.S. Department of Energy in its Carbon Atlas III, the modified U.S. Geological Survey methodology, and the CO2 Geological Storage Solutions methodology. All three methodologies address storage resources in porous geologic media in sedimentary basins, namely oil and gas reservoirs and saline formations. Based on our analyses, these methodologies are similar in terms of computational formulation. We find that each of the proposed methodologies is science and engineering based. As such, they are important in identifying the geographical distribution of CO2 storage resource and regional carbon sequestration potential at the national and basin-scale levels for use in energy-related government policy and business decisions. Policy makers need these high-level estimates to evaluate the prospective function that carbon capture and sequestration technologies can play in reducing CO2 emissions over the long term. The value of these high-level assessments of CO2 storage resource is to help inform decision makers in governments and industry as to whether carbon capture and sequestration is a climate mitigation option worth pursuing in particular regions.
{"title":"Comparative analysis of carbon dioxide storage resource assessment methodologies","authors":"Olga H. Popova, M. Small, S. McCoy, A. C. Thomas, B. Karimi, A. Goodman, Kristin M. Carter","doi":"10.1306/EG.06011212002","DOIUrl":"https://doi.org/10.1306/EG.06011212002","url":null,"abstract":"Today, an increased emphasis on the distribution, potential volume, and cost to develop CO2 geologic sequestration resources exists. In the presence of climate change, the need to make accurate and clearly understandable assessments of carbon sequestration potential, which can be used by the government and industry to plan for technology deployment, has never been greater. We compare three CO2 storage assessment methodologies: the approach applied by the U.S. Department of Energy in its Carbon Atlas III, the modified U.S. Geological Survey methodology, and the CO2 Geological Storage Solutions methodology. All three methodologies address storage resources in porous geologic media in sedimentary basins, namely oil and gas reservoirs and saline formations. Based on our analyses, these methodologies are similar in terms of computational formulation. We find that each of the proposed methodologies is science and engineering based. As such, they are important in identifying the geographical distribution of CO2 storage resource and regional carbon sequestration potential at the national and basin-scale levels for use in energy-related government policy and business decisions. Policy makers need these high-level estimates to evaluate the prospective function that carbon capture and sequestration technologies can play in reducing CO2 emissions over the long term. The value of these high-level assessments of CO2 storage resource is to help inform decision makers in governments and industry as to whether carbon capture and sequestration is a climate mitigation option worth pursuing in particular regions.","PeriodicalId":11706,"journal":{"name":"Environmental Geosciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1306/EG.06011212002","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66165222","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Concerns about potential climate change related to greenhouse gas emissions have spurred researchers across the world to assess the viability of geologic storage of CO2. In the Illinois Basin in the United States, the Cambrian Mount Simon Sandstone has been targeted as a reservoir for carbon capture and storage (CCS). In this CCS system, the Eau Claire Formation is expected to serve as the primary seal to prevent upward migration of the CO2 plume; however, little work has been done to specifically determine how well it will function as a seal. Although the lateral extent and thickness of the Eau Claire Formation, along with its generally low permeability, certainly make it a prime candidate to serve in this capacity, the primary depositional fabric and mineralogy, which are the fundamental controls on the petrophysical charter of this unit, remain poorly constrained. Therefore, the purpose of this study is to investigate the lithologic, mineralogical, and petrophysical properties of the Eau Claire Formation in an effort to characterize its potential as a functional seal in a CCS system. Sixty-six core-derived Eau Claire Formation samples from seven wells within the Illinois Basin are described using a combination of petrography, reflectance spectroscopy, x-ray diffraction, geochemical, and petrophysical analyses. These analyses show that the Eau Claire Formation contains five different lithofacies (sandstone, clean siltstone, muddy siltstone, silty mudstone, and shale) with fine-scale heterogeneities in fabric and mineralogy that greatly influence the petrophysical properties. Porosity, permeability, and entry-pressure data suggest that some, but not all, lithofacies within the Eau Claire Formation have the capability to serve as a suitable CCS seal. Abundant authigenic minerals and dissolution textures indicate that multiple generations of past fluid-rock interactions have occurred within the Eau Claire Formation, demonstrating that much of the formation has behaved as a fluid conduit instead of as a seal. Minerals that would be potentially reactive in a CCS system (including carbonate, glauconite, and chlorite) are common in the Eau Claire Formation. Dissolution of these and other phases in the presence of carbonic acid could potentially jeopardize the sealing integrity of the unit. Although complexities in the sealing properties exist, the dynamics of the CCS system and the potential for precipitation of new minerals should allow the Eau Claire Formation to serve as an adequate seal.
{"title":"Lithologic, mineralogical, and petrophysical characteristics of the Eau Claire Formation: Complexities of a carbon storage system seal","authors":"Ryan J. Neufelder, B. Bowen, R. Lahann, J. Rupp","doi":"10.1306/EG.02081211014","DOIUrl":"https://doi.org/10.1306/EG.02081211014","url":null,"abstract":"Concerns about potential climate change related to greenhouse gas emissions have spurred researchers across the world to assess the viability of geologic storage of CO2. In the Illinois Basin in the United States, the Cambrian Mount Simon Sandstone has been targeted as a reservoir for carbon capture and storage (CCS). In this CCS system, the Eau Claire Formation is expected to serve as the primary seal to prevent upward migration of the CO2 plume; however, little work has been done to specifically determine how well it will function as a seal. Although the lateral extent and thickness of the Eau Claire Formation, along with its generally low permeability, certainly make it a prime candidate to serve in this capacity, the primary depositional fabric and mineralogy, which are the fundamental controls on the petrophysical charter of this unit, remain poorly constrained. Therefore, the purpose of this study is to investigate the lithologic, mineralogical, and petrophysical properties of the Eau Claire Formation in an effort to characterize its potential as a functional seal in a CCS system. Sixty-six core-derived Eau Claire Formation samples from seven wells within the Illinois Basin are described using a combination of petrography, reflectance spectroscopy, x-ray diffraction, geochemical, and petrophysical analyses. These analyses show that the Eau Claire Formation contains five different lithofacies (sandstone, clean siltstone, muddy siltstone, silty mudstone, and shale) with fine-scale heterogeneities in fabric and mineralogy that greatly influence the petrophysical properties. Porosity, permeability, and entry-pressure data suggest that some, but not all, lithofacies within the Eau Claire Formation have the capability to serve as a suitable CCS seal. Abundant authigenic minerals and dissolution textures indicate that multiple generations of past fluid-rock interactions have occurred within the Eau Claire Formation, demonstrating that much of the formation has behaved as a fluid conduit instead of as a seal. Minerals that would be potentially reactive in a CCS system (including carbonate, glauconite, and chlorite) are common in the Eau Claire Formation. Dissolution of these and other phases in the presence of carbonic acid could potentially jeopardize the sealing integrity of the unit. Although complexities in the sealing properties exist, the dynamics of the CCS system and the potential for precipitation of new minerals should allow the Eau Claire Formation to serve as an adequate seal.","PeriodicalId":11706,"journal":{"name":"Environmental Geosciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1306/EG.02081211014","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66163528","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study has evaluated the hydrogeochemistry of some parts of the aquifer underlying and near Abakaliki City, Nigeria, to better understand the local groundwater quality conditions. Twelve representative groundwater samples from water boreholes (wells) in the study area were analyzed for their hydrogeochemical properties: pH, electrical conductivity (EC), turbidity, total dissolved solids (TDS), total hardness, chemical oxygen demand, Ca2+, Mg2+, Na+, K+, , , Cl, , and . The aquifer is situated in the fractured shales of Abakaliki Formation. The dominant ions in most samples are Ca2+, Mg2+, , and Cl. Furthermore, strong positive correlations exist between EC-TDS, Na+-TDS, , and . Piper trilinear diagrams were used to classify the hydrogeochemical facies, which included Ca-Mg-Cl and Ca-Mg-Na-Cl-SO4 water types. Ratios of Na-Cl ranged from 0.12 to 0.73, with a mean of 0.55, which is consistent with those of fresh water. The results of this study indicate that the groundwater local to the Abakaliki City poses no threat to human consumption, health, or the environment because the concentrations of physicochemical parameters that can be used to evaluate drinking water quality are within the World Health Organization standard specification.
{"title":"Hydrogeochemical properties of groundwater in parts of Abakaliki City, southeastern Nigeria","authors":"B. Odoh, A. U. Utom, H. Ezeh, B. Egboka","doi":"10.1306/EG.10051111006","DOIUrl":"https://doi.org/10.1306/EG.10051111006","url":null,"abstract":"This study has evaluated the hydrogeochemistry of some parts of the aquifer underlying and near Abakaliki City, Nigeria, to better understand the local groundwater quality conditions. Twelve representative groundwater samples from water boreholes (wells) in the study area were analyzed for their hydrogeochemical properties: pH, electrical conductivity (EC), turbidity, total dissolved solids (TDS), total hardness, chemical oxygen demand, Ca2+, Mg2+, Na+, K+, , , Cl, , and . The aquifer is situated in the fractured shales of Abakaliki Formation. The dominant ions in most samples are Ca2+, Mg2+, , and Cl. Furthermore, strong positive correlations exist between EC-TDS, Na+-TDS, , and . Piper trilinear diagrams were used to classify the hydrogeochemical facies, which included Ca-Mg-Cl and Ca-Mg-Na-Cl-SO4 water types. Ratios of Na-Cl ranged from 0.12 to 0.73, with a mean of 0.55, which is consistent with those of fresh water. The results of this study indicate that the groundwater local to the Abakaliki City poses no threat to human consumption, health, or the environment because the concentrations of physicochemical parameters that can be used to evaluate drinking water quality are within the World Health Organization standard specification.","PeriodicalId":11706,"journal":{"name":"Environmental Geosciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86970392","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Producers adjacent to a natural-gas storage field claimed that the natural gas they were producing was native gas from the area and not storage gas being pulled from the nearby gas storage field. The objective of this work is to apply a combination of area-specific and generic geochemical fingerprinting techniques to determine the source(s) of the natural gas being produced by third-party producers outside the gas storage field and to determine the extent of storage gas migration beyond geologic faults that lie between the production area and the gas storage field. An extensive set of natural-gas samples from the storage field, observation wells around the field, and third-party wells was analyzed for gas hydrocarbon and nonhydrocarbon compositions, as well as stable carbon isotopic compositions of methane and ethane. Gas chemical compositional data, including concentrations of the natural native gas tracer, helium, and ethane carbon isotope, were used to establish the unique fingerprints of native gas and storage gases (end-member sources) and to compare those end-member-source fingerprints to those of natural gas in the third-party wells. The analysis determined that gas in both the observation wells and third-party wells was, in fact, storage gas.
{"title":"Use of natural-gas compositional tracers to investigate gas migration from a gas storage field","authors":"T. Saba, P. Boehm","doi":"10.1306/EG.12291111011","DOIUrl":"https://doi.org/10.1306/EG.12291111011","url":null,"abstract":"Producers adjacent to a natural-gas storage field claimed that the natural gas they were producing was native gas from the area and not storage gas being pulled from the nearby gas storage field. The objective of this work is to apply a combination of area-specific and generic geochemical fingerprinting techniques to determine the source(s) of the natural gas being produced by third-party producers outside the gas storage field and to determine the extent of storage gas migration beyond geologic faults that lie between the production area and the gas storage field. An extensive set of natural-gas samples from the storage field, observation wells around the field, and third-party wells was analyzed for gas hydrocarbon and nonhydrocarbon compositions, as well as stable carbon isotopic compositions of methane and ethane. Gas chemical compositional data, including concentrations of the natural native gas tracer, helium, and ethane carbon isotope, were used to establish the unique fingerprints of native gas and storage gases (end-member sources) and to compare those end-member-source fingerprints to those of natural gas in the third-party wells. The analysis determined that gas in both the observation wells and third-party wells was, in fact, storage gas.","PeriodicalId":11706,"journal":{"name":"Environmental Geosciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1306/EG.12291111011","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66168886","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Most surface water and shallow groundwater occurring in northeastern Nebraska are of the calcium bicarbonate type, with minor concentrations (e.g., 10–200 mg/L) of sulfate (SO4). Examination of historical water quality data (major cations and anions) for Ponca Creek, a predominantly ephemeral stream in northeastern Nebraska, revealed that SO4 concentrations ranged from about 110 to almost 1000 mg/L and contribute to a calcium sulfate hydrochemical facies. Consequently, most SO4 concentrations were above the U.S. Environmental Protection Agency secondary maximum contaminant level in drinking water of 250 mg/L. Sulfate concentrations for the same period for a nearby stream, Verdigre Creek, range from about 20 to 120 mg/L. Research into probable sources of the elevated SO4 in Ponca Creek revealed that a Late Cretaceous shale, the Pierre Shale, occurs at or near the land surface throughout most of the creek's drainage area, whereas alluvium, other Quaternary deposits, or the Tertiary Ogallala Formation comprises the streambed in Verdigre Creek. The Pierre Shale, encompassing soils formed on this Cretaceous shale, is rich in sulfate-bearing minerals (e.g., gypsum, pyrite, jarosite) that comprise the principal source of the high sulfate in drainage basin soils, alluvium, creek discharge, and shallow groundwater of the Ponca Creek watershed. A public domain geochemical speciation software (Visual MINTEQ) was used to investigate aqueous SO4 geochemistry of Ponca Creek flow. Calculated saturation indices for Ponca Creek waters suggest that they are slightly undersaturated with respect to gypsum and anhydrite despite significant sulfate dissolution and are slightly supersaturated with respect to calcite in numerous samples.
{"title":"Geochemical evaluation of high sulfate levels in Ponca Creek, northeastern Nebraska","authors":"J. C. Atkinson","doi":"10.1306/EG.12141111012","DOIUrl":"https://doi.org/10.1306/EG.12141111012","url":null,"abstract":"Most surface water and shallow groundwater occurring in northeastern Nebraska are of the calcium bicarbonate type, with minor concentrations (e.g., 10–200 mg/L) of sulfate (SO4). Examination of historical water quality data (major cations and anions) for Ponca Creek, a predominantly ephemeral stream in northeastern Nebraska, revealed that SO4 concentrations ranged from about 110 to almost 1000 mg/L and contribute to a calcium sulfate hydrochemical facies. Consequently, most SO4 concentrations were above the U.S. Environmental Protection Agency secondary maximum contaminant level in drinking water of 250 mg/L. Sulfate concentrations for the same period for a nearby stream, Verdigre Creek, range from about 20 to 120 mg/L. Research into probable sources of the elevated SO4 in Ponca Creek revealed that a Late Cretaceous shale, the Pierre Shale, occurs at or near the land surface throughout most of the creek's drainage area, whereas alluvium, other Quaternary deposits, or the Tertiary Ogallala Formation comprises the streambed in Verdigre Creek. The Pierre Shale, encompassing soils formed on this Cretaceous shale, is rich in sulfate-bearing minerals (e.g., gypsum, pyrite, jarosite) that comprise the principal source of the high sulfate in drainage basin soils, alluvium, creek discharge, and shallow groundwater of the Ponca Creek watershed. A public domain geochemical speciation software (Visual MINTEQ) was used to investigate aqueous SO4 geochemistry of Ponca Creek flow. Calculated saturation indices for Ponca Creek waters suggest that they are slightly undersaturated with respect to gypsum and anhydrite despite significant sulfate dissolution and are slightly supersaturated with respect to calcite in numerous samples.","PeriodicalId":11706,"journal":{"name":"Environmental Geosciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1306/EG.12141111012","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66169320","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：