This research aimed to investigate the spatial distribution of arsenic concentrations in shallow and deep groundwaters which were used as sources for drinking and domestic and agricultural uses. A ...geochemical modeling software PHREEQC was used to simulate equilibrium geochemical reactions of complex water–rock interactions to identify arsenic speciation and mineral saturation indices based on groundwater quality and hydrogeochemical conditions. In addition, the potential health risk from arsenic-contaminated groundwater consumption was assessed based on the method developed by the U.S. Environmental Protection Agency. The study area is located at the western part of the Lampang Basin, an intermontane aquifer, Northern Thailand. The area is flat and situated in a floodplain in the Cenozoic basin. Most shallow groundwater (≤10 m depth) samples from dug wells were of Ca-Na-HCO3 and Ca-HCO3 types, whereas deep groundwater from Quaternary terrace deposits (30–150 m depth) samples were of Na-HCO3 and Ca-Na-HCO3 types. High arsenic concentrations were found in the central part of the study area (Shallow groundwater: <2.8–35 mg/L with a mean of 10.7 mg/L; Deep groundwater: <2.8–480 mg/L with a mean of 51.0 mg/L). According to geochemical modeling study, deep groundwater contained toxic As(III), as the dominant species more than shallow groundwater. Arsenic in groundwater of the Lampang Basin may have been derived from leaching of rocks and could have been the primary source of the subsurface arsenic in the study area. Secondary source of arsenic, which is more significant, could be derived from the leaching of sorbed arsenic in aquifer from co-precipitated Fe-oxyhydroxides in sediments. Quantitative risk assessment showed that the average carcinogenic risk values were as high as 2.78 × 10−3 and 7.65 × 10−3 for adult and child, respectively, which were higher than the acceptable level (1 × 10−4). The adverse health impact should be notified or warned with the use of this arsenic-contaminated groundwater without pre-treatment.
Clay–oil interactions play a critical role in determining the wettability of sandstone oil reservoirs, which, in turn, governs the effectiveness of enhanced oil recovery methods. In this study, we ...have measured the adhesion between –COOH functional groups and the siloxane and aluminol faces of kaolinite clay minerals by means of chemical force microscopy as a function of pH, salinity (from 0.001 M to 1 M) and cation identity (Na+ vs. Ca2+). Results from measurements on the siloxane face show that Ca2+ displays a reverse low-salinity effect (adhesion decreasing at higher concentrations) at pH 5.5, and a low salinity effect at pH 8. At a constant Ca2+ concentration of 0.001 M, however, an increase in pH leads to larger adhesion. In contrast, a variation in the Na+ concentration showed less effect in varying the adhesion of –COOH groups to the siloxane face. Measurements on the aluminol face showed a reverse low-salinity effect at pH 5.5 in the presence of Ca2+, whereas an increase in pH with constant ion concentration resulted in a decrease in adhesion for both Ca2+ and Na+. Results are explained by looking at the kaolinite’s surface complexation and the protonation state of the functional group, and highlight a more important role of the multicomponent ion exchange mechanism in controlling adhesion than the double layer expansion mechanism.
As one of the solutions to tackle climate change caused by excess carbon dioxide (CO2) emission, CO2 geological storage has been increasingly implemented globally to store CO2 securely and ...permanently in the subsurface. In the current study, structural trapping, which shows the potential of initial CO2 containment and integrity of the subsurface structure, is experimentally investigated with CO2 leakage assessed. CO2 containment is quantified by CO2 column height, which describes the amount of CO2 accumulated in the formation underneath seal rock and is controlled by a balance between capillary and gravitational forces acting on formation brine and invading CO2. While previous studies considered only contributions from seal rock (i.e., “nonrelative”), the current study examines a concurrent contribution from reservoir rock as a seal–reservoir “relative” column height since CO2 storage as an analogy to petroleum reservoir is a structural trap consisting of the reservoir and impermeable seal covered. A distinctive discrepancy was found between the resultant relative and nonrelative column heights. The nonrelative column heights were positive (∼3000 m), implying a high potential for CO2 storage. On the contrary, with reservoir rock contribution considered, the relative column heights were negative (∼−1800 m), suggesting CO2 leakage through the structural trap. This was attributed to a relatively larger reservoir pore size (5.72 nm) than that of seal rock (4.04 nm). Hence, the contribution from reservoir rock characteristics is non-negligible when analyzing CO2 storage potential. Owing to CO2 dissolution in formation brine, CO2-induced effects including a geochemical reaction between acidic carbonated brine and rocks were also investigated. Rock dissolutions in both seal (claystone) and reservoir (limestone) rocks were observed with changes in the pore size, leading to lower storage potential. Further attempts to improve the column height were made by hydrophobizing seal rock via surfactant adsorption, although the changes were slight and could only facilitate a possible leakage (less negative height column).
•Effects of brine valency and concentration on crude oil displacement by spontaneous imbibition were examined.•Differences in brine composition and salinity induced variations on resulted wettability ...alteration and reduction in the interfacial tension.•Low-salinity brine mechanisms at micro-scale were emphasized on low-salinity brine recovery observed at core-scale.•Capillary force dominated imbibition process with an interplay between wettability alteration and reduction in the interfacial tension.
Brine fluids have recently been of high interest to enhanced oil recovery process in both academia and industry. Both diluted formation brines and specifically formulated brines were reported to improve crude oil displacement in porous rock, owing to either their bulk salinity or brine-type. Mechanisms for such an improvement were widely proposed, including microscopic interfacial phenomena: wettability alteration and reduction in the oil-brine interfacial tension (σ), although their synergistic or interlinked contributions were vaguely clarified. To elucidate insights into this “low-salinity” enhanced oil recovery, crude oil displacement by spontaneous imbibition was conducted in the current research with focus on the effects of brine valency and concentration. Monovalent (NaCl) and divalent (CaCl2) brines at elevated concentrations (10, 100, and 1000 mM) were examined as imbibing fluids. Changes in the three-phase contact angle and the crude oil-brine interfacial tension were also investigated. Imbibition results showed that NaCl brine at ‘suitable’ concentration (100 mM) displaced greater oil (95.8 %) than too-low (10 mM) or too-high (1000 mM) concentrations, and these monovalent brines displaced more effective than those of divalent CaCl2 due to an oil-wetting as a result of divalent ion bridging phenomenon. This echoes crucial influences of both brine valency and concentration. Since no direct individual contribution from either the contact angle or σ on the oil displacement was obtained, an interplay between these two parameters were thought to control. The imbibition results were a capillary-dominated process (capillary number < 2.1 × 10−6), re-confirmed by their correlations with the calculated capillary pressures and inverse Bond numbers. The findings revealed that in a given imbibition system a required σ is a wettability-dependent: water-wet system needs high σ to enhance a driving capillarity while oil-wet system prefers lower σ to weaken a resisting capillary force. Brine formula directly attributed to wettability and σ: NaCl brines secure water-wetting with high σ while CaCl2 brines reduced σ more effectively with an assured oil-wetting. Low-salinity enhanced oil recovery mechanism was thus found to be contributed from capillary effect, which was an interplay between the interfacial tension and wettability. Paring these two parameters by formulating imbibing brine to anticipate high oil recovery is crucial and of challenge.
Laplae, Mueang Uttaradit, and Tha Pla district, Uttaradit province, Thailand are considered as high potential landslide areas. Still, this disaster is difficult to address because of complex factors ...controlling its occurrence. Therefore, the prediction of the potential landslide area using a landslide susceptibility map has been able to accomplish as a great strategy for the disaster. A landslide susceptibility map was produced by the geographic information system (GIS) data. The methods were initially conducted by the selection of potential factors related to landslides, which were lithology, slope, aspect, plan curvature, profile curvature, distance to stream, land use, and rainfall. All factors were assigned coefficients weight, and analyses frequency ratio (FR). Then, the weighted variables have been combined and ranked into five different susceptibility levels, which were very low, low, medium, high, and very high. Finally, the produced landslide susceptibility map has been validated by the success rate and prediction rate. After the analysis, the high and the very high landslide susceptibility area were dominantly covered in the northern and northwest parts of the study area; and the factor of slope, land use, and lithology potentially caused the landslide risk indicated by high frequency ratio values. In addition, the produced landslide susceptibility map had high accuracy, about 90% of success rate and prediction rate, calculated from the area under the curve (AUC), this map would be beneficial for geological hazard management and land use planning. The landslide susceptibility map and the GIS-based methods can be applied to the regional area with additional benefits to well-being, society, and the environment.
Brine fluids have recently been of high interest to enhanced oil recovery. Mechanisms for such improvement were widely proposed, including wettability alteration and reduction in the oil-brine ...interfacial tension (IFT), although their synergistic contributions were vaguely clarified. Crude oil displacement by spontaneous imbibition was conducted in the current research with focus on the effects of brine valency and concentration. Monovalent (NaCl) and divalent (CaCl2) brines at elevated concentrations were examined. Imbibition results showed that NaCl brine at suitable concentration (100 mM) displaced greater oil than too-low or too-high concentrations, and these monovalent brines displaced more effective than those of divalent CaCl2 due to an oil-wetting as a result of divalent ion bridging phenomenon. This echoes crucial influences of both brine valency and concentration. The findings revealed that in a given imbibition system a required IFT is a wettability-dependent, water-wet system needs high IFT to enhance a driving capillarity while oil-wet system prefers lower IFT to weaken a resisting capillary force. Brine formula directly attributed to wettability and IFT, NaCl brines secure water-wetting with high IFT while CaCl2 brines reduced IFT more effectively with an assured oil-wetting. Low-salinity enhanced oil recovery mechanism was thus found to be contributed from capillary effect, which was an interplay between the interfacial tension and wettability. Paring these two parameters by formulating imbibing brine to anticipate high oil recovery is crucial and of challenge.
The global crude oil consumption has sharply increased for half century; consequently, there has been a depletion of reserves and currently producing oil fields. Increasing the oil supply for the ...world markets can be achievable by either developing new oil reservoirs or by improving the recovery of current fields by means of enhanced oil recovery (EOR) technologies. The former choice requires new installations and infrastructure; resulting in high capital costs, environmental impact and the achievement of a productivity of only 30 to 50% of the original oil in place (OOIP). EOR techniques on the contrary do not require large capital costs and can greatly enhance the amount of recoverable oil, therefore extending the life of mature oil reservoirs. Low-salinity enhanced oil recovery (LSEOR) is one of the most interesting EOR methods because it is environmentally friendly, low cost, and has been proven to be able to achieve great effectiveness. It is a well-known fact that low salinity enhanced oil recovery (LSEOR) results from altering the wettability of the oil reservoir towards a more water-wet state. However, many theories exist regarding the determining fundamental mechanism controlling its effectiveness, with up to 17 having been invoked in the literature. Nevertheless, gaining this fundamental knowledge is crucial to increase the application of LSEOR in real-world conditions. In this work, we aim to understand how different chemical parameters (pH, concentration, cation type, ionic strength, Na+:Ca2+ ratio) of bine, clay, and model oil affect the wettability of kaolinite (and pyrophyllite) at the nano and microscopic scale. Kaolinite having been selected because of it is ubiquitous presence in the pore space within sandstones reservoirs, and because clay minerals have been singled out as crucial to LSEOR due to their well-known chemical reactivity. To this end, various techniques were utilized to study wettability and proxy of wettability of clay surfaces, including chemical force microscopy, thermogravimetric analysis and mass spectrometry, contact angle measurement, and, to a lesser extent, environmental scanning electron microscopy and Fourier-transform infrared spectrometry. The main parameters that influence wettability are: a) surface charge of kaolinite and pyrophyllite, b) cation type, significantly Ca2+ which plays a crucial role in increasing oil adhesion through cation bridging, rather than monovalent cation (Na+), c) concentration, increases of Ca2+ concentration directly relates to more oil adsorption, whereas changes of Na+ concentration presents only a small effect on the amount oil adsorption, d) pH which controls the protonation state of the polar molecules (decanoic acid) as well as the charge of clay surface and can lead to increases (or decreases) in the amount of oil sorbed, e) type of functional group in oil components. The main conclusion of the theses is that surface complexation and cation bridging are the most important mechanisms in controlling oil sorption (adhesion) but at some conditions the electrical double layer effect can also play a crucial role.
Laplae, Mueang Uttaradit, and Tha Pla district, Uttaradit province, Thailand are considered as high potential landslide areas. Still, this disaster is difficult to address because of complex factors ...controlling its occurrence. Therefore, the prediction of the potential landslide area using a landslide susceptibility map has been able to accomplish as a great strategy for the disaster. A landslide susceptibility map was produced by the geographic information system (GIS) data. The methods were initially conducted by the selection of potential factors related to landslides, which were lithology, slope, aspect, plan curvature, profile curvature, distance to stream, land use, and rainfall. All factors were assigned coefficients weight, and analyses frequency ratio (FR). Then, the weighted variables have been combined and ranked into five different susceptibility levels, which were very low, low, medium, high, and very high. Finally, the produced landslide susceptibility map has been validated by the success rate and prediction rate. After the analysis, the high and the very high landslide susceptibility area were dominantly covered in the northern and northwest parts of the study area; and the factor of slope, land use, and lithology potentially caused the landslide risk indicated by high frequency ratio values. In addition, the produced landslide susceptibility map had high accuracy, about 90% of success rate and prediction rate, calculated from the area under the curve (AUC), this map would be beneficial for geological hazard management and land use planning. The landslide susceptibility map and the GIS-based methods can be applied to the regional area with additional benefits to well-being, society, and the environment.
PDF
