Continuous Gas Research Articles

Evaluation of an ionization chamber characteristics for 222Rn calibration.

The National Metrology Institute of Japan plan to use an inner-through-type ionization chamber (IC) as a working standard to calibrate radon monitors. Novel methods to calibrate the IC were described, and the calibration factor, CF [Bqm -3 A-1], of the IC with its expanded uncertainty (k=2) was evaluated to be (2.0±0.2)×1016Bqm-3 A-1 in the order of 10-13 A in the IC output current. In this study, the CFs, evaluated under sampling conditions between continuous gas flowing and stationary gas filled inside the IC, were in agreement within the uncertainty.

Distance-Based Fluorescent Immunosensor for Point-of-Care Test of Illegal Additives through the Gas-Producing Nanozyme.

The colorimetric point-of-care test (POCT) offers a rapid and efficient method for detecting specific targets in real samples. However, traditional colorimetric methods often rely on complex signal amplification techniques or electronic devices to enhance detection sensitivity, which can inadvertently increase both cost and time, thus contradicting the fundamental goals of visual detection methods. Here, we presented a distance-based fluorescent immunosensor that utilized a gas-producing nanozyme for continuous gas production reaction as a signal. Specifically, the SOM-ZIF-8@Pt nanozyme catalyzed the production of O2 from H2O2 to cause an obvious increase in the pressure within a sealed chamber, thus driving the production of H2S to quench the fluorescence of CsPbBr3 on the walls of the capillaries. Based on the competitive immunoassay, the fluorescence quenching lengths were relative with the concentration of aminopyrine in the range from 0.2 to 20 ng/L; thus, the fluorescent POCT-based homemade device was realized through the amplification of distance-based signals facilitated by the continuous gas production reaction. This strategy provides an effective way to realize POCT assays in resource-limited areas by transforming pressure variations into directly observable signals. Furthermore, distinguished by its high sensitivity, ease of operation, and portability, it also represents a significant advancement in biomedical diagnostics, particularly within home healthcare and clinical POCT.

Application End Evaluation of Electrostatic Precipitation for Control PM and NOx Emissions from Small-Scale Combustions

Electrostatic precipitators (ESPs) have shown promise in reducing particulate matter (PM) emissions, but their potential for simultaneous NOx reduction in small-scale combustion systems remains underexplored. This study focuses on using non-thermal plasma generated in a corona discharge to reduce PM and NOx emissions from small-scale combustion. ESP was specifically designed for a commercially available 15 kW boiler with wood pellet combustion and used with both positive and negative discharge polarity to control emissions without any chemical additives. ESP performance was evaluated across a range of specific input energies (SIE) in terms of particle mass and number concentrations and NOx concentrations obtained by continuous gas analysis. ESP ensured the reduction in PM concentrations from 48 mg/m3 to the magnitude of PM content in the ambient air. The highest precipitation efficiency was observed for particles in the 20–200 nm range. Concurrently, NOx emissions were reduced by up to 78%, from 178 mg/m3 to 39 mg/m3. These results were achieved at specific input energies of 36 for positive and 48 J/L for negative corona, which is significantly lower than those reported for many existing separate PM and NOx control systems. This study demonstrates the potential of ESPs as a compact, energy-efficient solution for simultaneous PM and NOx removal in small-scale combustion systems, offering promising implications for improving air pollution control technologies for small-scale combustion systems.

Deep deoxidation of water in a miniaturized annular rotating device: Experimental investigation and machine learning modeling

Conventional gas–liquid devices exhibit limitations, including inadequate dispersion efficiency and significant backmixing, leading to low conversion and large equipment volume. Thus, a miniaturized annular rotating device (m-ARD) was proposed based on microscale effects and rotating flow field to achieve efficient gas–liquid mass transfer and high conversion. Nitrogen-oxygenated water was selected as the experimental system to evaluate the performance of the m-ARD. The gas–liquid flow characteristics were investigated. The analysis focused on examining the impact of different factors on deoxygenation efficiency. The deoxygenation performance was optimized and compared with different devices. The study found that the m-ARD enables a continuous counter-current gas–liquid flow mode, with superior mixing performance and a narrow residence time distribution. The deoxygenated water with an oxygen concentration as low as 0.14 ppm can be produced, with a volumetric mass transfer coefficient (kLa) of 0.26 s−1, a theoretical stage value of 4.22, and a handling capacity of 30 mL/min under optimized experimental conditions. In addition, kLa was predicted using an artificial neural network model and showed good agreement with the simulated values. This work provides a promising reactor for chemical reactions that require high conversions.

Improved reactor design enables productivity of microbial electrosynthesis on par with classical biotechnology

Microbial electrosynthesis (MES) converts (renewable) electrical energy into CO2-derived chemicals including fuels. To achieve commercial viability of this process, improvements in production rate, energy efficiency, and product titer are imperative. Employing a compact plate reactor with zero gap anode configuration and NiMo-plated reticulated vitreous carbon cathodes substantially improved electrosynthesis rates of methane and acetic acid. Electromethanogenesis rates exceeded 10 L Lcatholyte–1 d–1 using an undefined mixed culture. Continuous thermophilic MES by Thermoanaerobacter kivui produced acetic acid at a rate of up to 3.5 g Lcatholyte−1 h−1 at a titer of 14 g/L, surpassing continuous gas fermentation without biomass retention and on par with glucose fermentation by T. kivui in chemostats. Coulombic efficiencies reached 80 %–90 % and energy efficiencies up to 30 % for acetate and methane production. The performance of this plate-reactor demonstrates that MES can deliver production rates that are competitive with those of established biotechnologies.

Volcanic tremor associated with successive gas emission activity at a boiling pool: Analyses of seismic array and visible image data recorded at Iwo-Yama in Kirishima Volcanic complex, Japan

Volcanic tremors are often observed during volcanic activity and volcanic eruptions, and their generation processes provide clues for understanding volcanic fluid activity underground and eruption dynamics. However, tremors are characterized by continuous oscillations that mask P- and S-waves; hence few studies have precisely located the source, which is the most fundamental information for understanding the generation mechanism. In this study, we focus on volcanic tremors excited by continuous gas emissions occurring at a vent called Y2a in Iwo-Yama, the Kirishima Volcanic Complex, Japan, to clarify the source process of the tremor as well as gas emission activity. We simultaneously observed the volcanic tremor by deploying a small aperture array consisting of six seismometers and the gas emission activity by using a newly developed visual IoT system that can be operated without commercial electricity. MUSIC analysis locates the tremor at depths ranging from the ground surface to approximately 200 m beneath the Y2a and Y2b vents, which are approximately 30 m apart, for approximately four months from November 2021 to February 2022. The source locations of the tremors in the 2 Hz (1.2–2.6 Hz), 4 Hz (3–4 Hz), and 5 Hz (4–5.5 Hz) ranges show some differences and changes with time. The source location tends to become deeper when the 2 Hz amplitude is large. The infrasound generated by gas emission activity is dominant in the tremor signals, which are recognized in the wave propagation velocity with an acoustic velocity of 330 m/s when the 2 Hz amplitude is small. The visual IoT system succeeded in detecting long-term changes in the gas emission activity, and we found that the 2 Hz amplitude of tremor was well correlated with the amount of hot water in the boiling pool of Y2a, which was controlled by precipitation and evaporation during non-rainy days. From these observations, we infer that the volcanic tremor is generated by resonance of volcanic gas and hot water in a crack-like structure beneath Y2a. The resonance was triggered by the counterforces of the gas emissions in the boiling pool, and the infrasound was dominant during periods of hot water depletion in the boiling pool. Temporal changes in the source depths may be caused by changes in the fluid properties, configuration of the resonator and/or the strengths of the underground sources and infrasound. Our simultaneous observations of seismic array and visual IoT system clarify that even the continuous gas emission activity that looks stable is controlled by external sources such as precipitation.

Caprock Safety Evaluation Method in CCUS Based on Latin Hypercube Sampling: A case study of a block reservoir

Abstract CO2 geological sequestration is one of the essential means to achieve carbon neutrality goals. However, substantial CO2 sequestration in formations can lead to leakage issues, primarily through the caprock, involving caprock rupture, leakage along caprock fractures/faults, and capillary leakage. Therefore, establishing a method to assess the safety of the caprock during CO2 storage processes is crucial. Firstly, a numerical simulation model is constructed based on parameters from the target block to study the influences of reservoir property, development parameters, and caprock parameters on CO2 flooding, gas injection, and CO2 storage. Latin hypercube sampling is employed for scheme design and subsequent result analysis, applying Spearman’s method to analyze the controlling factors in each CO2 storage. Secondly, using continuous gas flooding as an example, the migration pattern of CO2 in the formation is investigated, and the influence of the formation pressure distribution on caprock safety is analyzed. Finally, considering the comprehensive impact of different parameters on caprock safety, a fuzzy comprehensive evaluation of caprock safety in the target block is conducted. The study indicates that caprock permeability is the most critical factor affecting safety operation across all storage stages, with respective highest positive correlation coefficients of 0.413, 0.356, and 0.221 in different stages. The migration of CO2 in the formation is primarily influenced by the distribution of injection wells and gas migration channels. The established quantitative evaluation standard for caprock safety in the target block calculates a suitability degree of 3.43, suggesting a relatively secure caprock in the block suitable for achieving long-term stable CO2 storage. This research provides theoretical support for the safety analysis of caprock in different stages of CO2 flooding and storage, offering a scientific basis for the safety operation of CCUS schemes.

An implicit adaptive unified gas-kinetic scheme for steady-state solutions of nonequilibrium flows

In recent years, nonequilibrium flows have been frequently encountered in various aerospace engineering and micro-electro-mechanical systems applications. To understand nonequilibrium physics, multiscale effects, and the dynamics in these applications, a reliable multiscale scheme for all flow regimes is required. Following the direct modeling methodology, the adaptive unified gas-kinetic scheme employs discrete velocity space to accurately capture the nonequilibrium physics, recovering the original unified gas-kinetic scheme (UGKS). By adaptively employing continuous distribution functions based on the Chapman–Enskog expansion, it efficiently handles near-equilibrium flow regions. The two regions are dynamically coupled at the cell interface through the fluxes from the discrete and continuous gas distribution functions, thereby avoiding any buffer zone between them. In this study, an implicit adaptive unified gas-kinetic scheme (IAUGKS) is constructed to further enhance the efficiency of steady-state solutions. The current scheme employs implicit macroscopic governing equations and couples them with implicit microscopic governing equations within the nonequilibrium region, resulting in high convergence efficiency in all flow regimes. To validate the efficiency and robustness of the IAUGKS, a series of numerical tests were conducted for high Mach number flows around diverse geometries. The current scheme can capture the nonequilibrium physics and provide accurate predictions of surface quantities. In comparison with the original UGKS, the velocity space adaptation, unstructured discrete velocity space, and implicit iteration significantly improve the efficiency by one or two orders of magnitude. Given its exceptional efficiency and accuracy, the IAUGKS serves as an effective tool for nonequilibrium flow simulations.

An integrated dynamic modeling workflow for acid gas and CO2 geologic storage screening in saline aquifers with faults: A case study in Western Canada

This study investigates the feasibility of storing the acid gas produced from the oil and gas facilities in Southern Saskatchewan into the Basal Sand aquifer using a coupled wellbore-aquifer-compositional reservoir model. The simulations investigate the pressure change around the fault in proximity of the primary storage location incorporating the influence of reservoir permeability, fault transmissibility, and wellbore configuration, on the factors critical to safe and efficient storage, such as plume migration, pressure changes, and CO2 storage capacity. A compositional fluid model created using an equation of state was integrated into the reservoir model. Simultaneous incorporation of fault transmissibility, phase solubility, water salinity, temporal in-situ hysteresis and structural trapping, and in-situ compositional tracking of individual gas components is considered as the main novelty of this work. The main challenge of the study was the lack of available data to characterize the aquifer. To this end, a comprehensive workflow of reservoir studies and modeling was applied to reduce the uncertainties and evaluate the site selection. The Basal sand scoping models reveal that the aquifer is expected to handle the required disposal volume given its extent. The injected acid gas plume migrates laterally and preferentially towards the northwest, away from the fault, owing to the aquifer's geological structure. CO2 remains entirely in the supercritical state, offering storage advantages due to its lower volume. The reservoir permeability significantly impacts the pressure patterns with lower permeability formations triggering higher wellhead injection pressures. Substantial pressure increases around the sealing fault can be observed. Pressure changes of 110 kPa (16 psi) to over 400 kPa (58 psi) were observed at the fault segment after 20 years of continuous gas injection for the expected range of reservoir properties. Mitigation strategies to minimize the increase in fault pressure entail relocating the injection site away from the fault or utilizing a horizontal well trajectory and using an observation well near the fault for monitoring any pressure buildup and slippage.

Gas extraction generation of gas mixtures of polar organic compounds at trace concentration levels

The patterns of generating gas mixtures of polar organic compounds at the level of their MAC (several µg/m³) were studied using the method of continuous gas extraction from aqueous solutions with a known concentration in combination with dilution by a stream of diluent gas. The necessary distribution coefficients of phenol, isomeric cresols, nitrobenzene, and alkanols С4–С6 between the aqueous and gas phases (nitrogen) were determined. A two-stage generation scheme is proposed, based on saturating the sorbent (activated carbon) with a flow of extraction gas containing the target components at a specified concentration, followed by desorption by a flow of pure extraction gas.

Detrended fluctuation analysis to determine physiologic thresholds, investigation and evidence from incremental cycling test.

Training zones are generally assessed by gas-exchange thresholds (GET). Several mathematical analyses of heart rate variability (HRV) are proposed for indirect GET determination. Our study aimed to investigate the accordance of the detrend fluctuation analysis (DFA α1) for determining GET with first (VT1) and second ventilatory (VT2) thresholds in well-trained subjects. Eighteen female and 38 male sub-elite cyclists performed a maximal incremental cycling test of 2-min stage duration with continuous gas exchange and HR measurements. Power output (PO), Oxygen uptake ( O2) and HR at VT1 and VT2 were compared with DFA α1 0.75 (HRVT1) and 0.50 (HRVT2). Agreements between PO, O2 and HR values were analyzed using Bland-Altman analysis. Large limits of agreement between VT1 and HRVT1 were observed for measures of O2 expressed in mL.min-1.kg-1 [-21.3; + 14.1], HR [39.2; + 26.9] bpm and PO [-118; + 83] watts. Indeed, agreements were also low between VT2 and HRVT2 for measures of O2 [-26.7; + 4.3] mL.min-1.kg-1, HR [-45.5; + 10.6] bpm and PO [-157; + 35] watts. Our results also showed a sex effect: women obtained worst predictions based on DFA α1 than men for HR (p = 0.014), PO (p = 0.044) at VT1 and (p = 0.045), HR (p = 0.003) and PO (p = 0.004) at VT2. There was unsatisfactory agreement between the GET and DFA α1 methods for VT1 and VT2 determination in both sex well-trained cyclists. Trial registrationnumber 2233534 on 2024/03/05 retrospectively registered.

Effects of inhibitors and slit incorporation on NH3 and N2O emission processes after urea application

The use of urea fertilizers in agriculture is associated with many negative environmental impacts and is a source of ammonia (NH3) and nitrous oxide (N2O) emissions. Such losses from urea fertilizer can be avoided by different mitigation techniques. Three different mitigation principles, urease inhibitor (N-(2-Nitrophenyl) phosphoric triamide, 2-NPT) (UI) alone and urease inhibitor in combination with nitrification inhibitors (N-[3(5)-methyl-1 H-pyrazol-1-yl) methyl] acetamide, MPA) (NI) and closed slit incorporation of urea fertilizer into the soil, were compared on a sandy loam soil at a soil water level of 70 % water-holding capacity. An in vitro microcosm approach with open dynamic incubation chambers was used to monitor NH3 emissions over two weeks with NH3 sampling by washing bottles. N2O emissions were studied over ten weeks in slow throughflow mesocosms with continuous gas chromatographic (GC) measurements. To get insights into N2O production and consumption processes, gas samples were taken after six weeks and N2O isotopocules were analyzed by isotope ratio mass spectrometry (IRMS). Slit injection showed the greatest effect on NH3 emission reduction by 79.6 % (40.6 % by UI, and 46.7 % by UINI) compared to surface applied urea. Minor pollution swapping to N2O was observed at the beginning of the trial due to incorporation but not in the cumulative emissions over the entire incubation time. The reduction effect of UINI on N2O emissions decreased over time with no cumulative emission reduction at the end of experimentation. N2O isotopocules confirmed the high contribution of nitrification to N2O production. In contrast and bacterial denitrification, nitrifier denitrification and fungal denitrification were involved on a much lower level and N2O reduction to N2 was not pronounced. All NH3 mitigation measurements where effective to decrease NH3 emissions while their effects on N2O emission varied over time. Factors as crop N uptake and rainfall would further modify the overall effect on N2O emissions and need to be considered for final pollution swapping assessment. Further research on the impact of NI on non-target microbial communities is warranted to elucidate potential environmental consequences and long-term efficacy of inhibitor compounds.

Investigations on the Heat Balance of the Melt Pool during PBF-LB/M under Various Process Gases

During the powder bed fusion of metals using a laser beam (PBF-LB/M), an inert atmosphere is maintained in the build chamber to avoid reactions of the liquid metal with ambient air leading to the creation of oxides or nitrides, which alter the mechanical properties of the processed part. A continuous gas flow is guided over the process zone to remove spatters and fumes. This flow induces a convective heat transfer from the molten metal to the gas, which, depending on the level of the heat flow, may alter the melt pool dimensions by influencing the cooling rate. The present work investigated these phenomena with single-line trials, both experimentally and numerically. For this reason, a smoothed-particle hydrodynamics model was utilized to investigate the temperatures of the melt pool, cooling rates, and the integral heat balance with various gas atmospheres. In parallel, an on-axis pyrometer was set up on an experimental PBF-LB/M machine to capture the surface emissions of the melt pool. The atmosphere in the simulations and experiments was varied between argon, helium, and two mixtures thereof. The results showed a slight increase in the cooling rates with an increasing fraction of helium in the process gas. Consistently, a slight decrease in the melt pool temperatures and dimensions was found.

Effect of insulator matrix on electrical transport properties of iron-insulator discontinuous multilayers

This work presents the results of the study of structural and electrical transport properties of the iron-insulator discontinuous multilayers (DMIMs). SiO2, HfO2, and MgO were chosen as the materials for the insulating layers. The discontinuous multilayers were prepared by the sequential magnetron sputtering on ceramic substrates. Obtained systems were annealed at different temperatures in an Ar + N2(2 %) environment using an annealing furnace with a continuous gas flow. Crystal structure analysis showed that the effect of annealing on the crystal structure of the samples varies and depends on the annealing temperature and the type of insulator. It has been demonstrated that the formation of iron oxide during annealing can be reduced by using HfO2 as the insulating layer material. The resistivity and temperature coefficient of resistance variation with temperature and the effective thicknesses of the ferromagnetic layers were analyzed.

Formic Acid Dehydration Using Mechanochemically Prepared TiO2‐Graphite Composites

AbstractCommercial high surface area graphite (HSAG300) and commercial TiO2 were used to produce composite materials through a simple mechanochemical method involving milling and ultrasonic treatments. The acid and basic sites exposed on the surfaces of these materials were characterized by temperature‐programmed desorption (TPD) of ammonia and carbon dioxide. The catalytic materials were tested in the dehydration reaction of formic acid to produce hydrogen‐free CO. While HSAG300 is practically inactive under reaction conditions (continuous gas flow at temperatures in the range of 100–250 °C), all samples containing TiO2 are active, exhibiting high selectivity to CO without significant deactivation at moderate reaction temperatures. It is demonstrated that the presence of graphite in the catalysts enhances the specific catalytic activity of TiO2. Assuming that the dehydration reaction is catalyzed by acid sites on the TiO2 surfaces, a comparative evaluation of the surface sites reveals that the graphite‐TiO2 interactions not only change the density of surface sites but also modify the strength of the acid centers of TiO2. In summary, the interaction of HSAG300 with TiO2 modulates the surface properties of the prepared composite catalysts, decreasing the total number of basic surface sites and increasing the strength of acidic sites compared to bare TiO2.

Optimizing gas lift for enhanced recovery in the Asmari formation: a case study of Abu Ghirab field in Southeastern Iraq

The gas lift technique applies gas bubble injection into the vertical wells to raise production. Gas and liquid rates, shifts in flow regimes, and system equilibrium influence this process. This study explores the efficient implementation of gas lift techniques to maximize production from the Asmari Formation in the Abu Ghirab Field, southeastern Iraq, using a continuous gas lift for maximum production rate by PIPESIM TM software. The results of the gas lift design for the four wells (AGCS-33, 26, 28, and 36) show that the Vogel method provided the best results for the gas lift design, and faults and facies distribution impact the gas lift injection and oil production rates. These will become evident with wells AGCS-33 and 36 as their proximity to faults will increase oil production rates with a gas injection rate limit of 7 MMSCF/d. Conversely, for wells 26 and 28, the limit will marginally rise, starting at 5 MMSCF/d. In addition, the effect of gas lift is clearly in the middle western of the crest, which shows an increasing percentage of oil production of 136.6% at minimum rate and 198.5% at maximum for the well AGCS-26, 89.7% and 105.7% for the well AGCS-36. Wellhead pressure has a significant impact on gas-lift performance, and improving gas-lift efficiency can be accomplished using an electric control valve. The feasibility of implementing gas lift in the Asmari Formation depends on the water cut, well location, and water saturation distribution within the Formation.

Removal of livestock odor gas ammonia, hydrogen sulfide, methanethiol by electron beam in a continuous flow system

Odor is becoming one of the serious environmental issues as the industry develops. Electron beam technology has recently attracted attention as an AOP (Advanced Oxidation Process) for air purification, water treatment, and soil remediation. This work studied the removal of major livestock odor such as ammonia (NH3), hydrogen sulfide (H2S), and methanethiol (CH3SH) using a continuous gas flow electron beam treatment process. The effects of initial odor gas concentration, type of background gas, absorbed dose of the electron beam, voltage of the electron accelerator, and odor gas flow rate on the removal of odor gas were all studied in this continuous gas flow treatment system. As the absorbed dose of electron beam was increased, the removal efficiencies of odor gases NH3, H2S, and CH3SH all increased gradually. As the initial concentration of odor gas was decreased and as the flow rate of odor gas was increased, the removal efficiencies also increased. Regarding background gas, the odor gas removal efficiency was found to be in descending order of O2 > air > N2. The lower the voltage (MeV) of the electron beam, the higher the odor gas removal efficiency. This was attributed to the fact that, to set the same absorbed dose (kGy), as the voltage decreases, the current value (mA) increases. For the byproducts, as the absorbed dose of electron beam was increased, the concentration of byproducts increased. Regarding the gas-phase continuous electron beam treatment reactions, the optimal operating conditions must be derived by considering various operational variables, including the initial concentration, electron beam dose, background gas type, gas flow rate, and electron beam voltage. The results of this study show that, among several possibly relevant variables in removing odor gases in the continuous flow electron beam irradiation process, the current value can be considered one of the most important variables, along with the initial concentration and background gas.

CO2-foam flood with wettability alteration for oil-wet carbonate reservoirs

Carbon dioxide (CO2) flooding in carbonate reservoirs often suffers from poor sweep efficiency, attributed to unfavorable mobility ratio, gravity segregation, and reservoir heterogeneity. CO2-foam injection is a promising strategy to control CO2 mobility. The stability of CO2-foam is affected by reservoir wettability. This study aims to systematically investigate the effectiveness of CO2-foam flood coupled with wettability alteration in an initially oil-wet carbonate rock at a pressure below the minimum miscibility pressure. Three types of surfactants, including a nonionic surfactant Soloterra 843, a cationic surfactant CETAC-30, and a zwitterionic surfactant LMDO, were evaluated as potential foaming agents. Contact angle tests were conducted to assess the wettability alteration capability of these surfactants. Bulk foam stability tests and foam rheology tests were conducted under reservoir conditions. Finally, foam core flood experiments were performed using oil-wet carbonate core samples. Results from contact angle experiments indicated that only CETAC-30 was effective at altering rock wettability from oil-wet to water-wet by removing the negatively charged organic acid components from the rock surface. Foam stability and rheological tests revealed that LMDO exhibited highly stable CO2-foam in the absence of crude oil. However, the presence of crude oil adversely affected CO2-foam stability for all the surfactants. Core flooding experiments demonstrated that injecting wettability alteration surfactant, CETAC-30, in form of foam could not only alter the wettability of rocks, but also enhance the foam strength. Continuous gas injection (without foam) increased oil recovery by 14.4 % due to the near-miscibility of CO2 and oil. Both CETAC-30 and LMDO surfactants increased the oil recovery by about 35 % after waterflood, but the wettability altering surfactant showed the highest mobility reduction factor (MRF). These findings provide valuable insights into the complex interplay between near-miscibility, wettability alteration and foam strength in carbonate reservoirs, offering a basis for optimizing CO2-foam flooding strategies for enhanced oil recovery and carbon sequestration.

A multivariable submersible sensor for monitoring in real-time industrial flotation cells

This paper describes the development and validation of a submersible sensing technology for industrial flotation cells. The sensor provides simultaneous real-time measurements of gas and solid holdups, as well as the density and viscosity of the slurry in the pulp zone of flotation machines. The submersible device comprises a gas exclusion cell, which resembles an inverted truncated cone assembled to a single-straight tube Coriolis meter. When the sensor device is vertically immersed in the aerated slurry, a continuous bubble-free flow of slurry is induced through the device, which allows the Coriolis meter to provide measurements of the slurry flow, density, and viscosity. The magnitude of the induced flow is a primary function of the sensor’s geometry and gas holdup. Applying the Bernoulli equation reveals that gas holdup can be expressed as the square of the induced flow velocity. A discharge coefficient parameter is introduced to compensate for variations in the velocity profile and flow losses. This coefficient is a function of the fluid Reynolds number, calculated in real-time based on the Coriolis measurements. The sensing technology was assessed in a pilot column operated in a water–air system and industrial forced-air and self-aspirated large flotation cells. Results demonstrate the sensor’s capabilities to provide reliable, accurate, real-time, long-term continuous gas dispersion and solid suspension-related variables, which could be used for supervision, control, and optimization applications.

Estimating the Maximum Magnitude of Induced Earthquakes in the Groningen Gas Field, the Netherlands

ABSTRACT Gas production in the Groningen field in the northern Netherlands began in 1963. Since 1991, many production-induced earthquakes have occurred—the largest reaching magnitude M 3.5 in 2012. In October 2023, the Dutch government closed the field—a decision that was justified by the potential threat of larger earthquakes occurring with continued gas extraction. This outcome highlights how the estimation of maximum magnitude for induced earthquakes can have important implications for risk perception by regulators and the public. Thus, the estimation of maximum magnitude for induced earthquakes that are not physically realizable can lead to unwarranted conservatism. Over almost three decades, considerable effort has been invested by several researchers to estimate the maximum magnitude of induced earthquakes in Groningen. These efforts culminated in international workshops focusing exclusively on this question in 2016 and 2022. The purpose of these workshops was to inform the decision-making of an expert panel charged with formulating a logic tree for the maximum magnitude of Groningen earthquakes. We argue that the evaluation of the final distribution of maximum magnitudes is overly conservative in terms of the largest events induced in the reservoir and, most importantly, the likelihood of triggering even larger tectonic earthquakes outside the gas-producing reservoir. Given the serious and far-reaching consequences of maximum magnitude estimates, we reconsider the approach of these assessments to draw lessons that may be critical for future energy-related projects associated with induced seismicity.