scholarly journals Hydrological influences on long-term gas flow trends at locations in the Vogtland/NW Bohemian seismic region (German-Czech border)

2009 ◽  
Vol 50 (4) ◽  
Author(s):  
U. Koch ◽  
J. Heinicke
Keyword(s):  
Gas Flow ◽  
Seismic Region

scholarly journals Catalytic Micro Gas Sensor with Excellent Homogeneous Temperature Distribution and Low Power Consumption for Long-Term Stable Operation

Proceedings ◽  
2018 ◽  
Vol 2 (13) ◽  
pp. 927 ◽  
Author(s):  
Anmona Shabnam Pranti ◽  
Daniel Loof ◽  
Sebastian Kunz ◽  
Marcus Bäumer ◽  
Walter Lang
Keyword(s):  
Temperature Distribution ◽  
Low Power ◽  
Gas Sensor ◽  
Gas Flow ◽  
Pt Nanoparticles ◽  
Stable Operation ◽  
Catalytic Layer ◽  
Micro Gas Sensor ◽  
Homogeneous Temperature

This paper presents a long-term stable thermoelectric micro gas sensor with ligand linked Pt nanoparticles as catalyst. The sensor design gives an excellent homogeneous temperature distribution over the catalytic layer, an important factor for long-term stability. The sensor consumes very low power, 18 mW at 100 °C heater temperature. Another thermoresistive sensor is also fabricated with same material for comparative analysis. The thermoelectric sensor gives better temperature homogeneity and consumes 23% less power than thermoresistive sensor for same average temperature on the membrane. The sensor shows linear characteristics with temperature change and has significantly high Seebeck coefficient of 6.5 mV/K. The output of the sensor remains completely constant under 15,000 ppm continuous H2 gas flow for 24 h. No degradation of sensor signal for 24 h indicates no deactivation of catalytic layer over the time. The sensor is tested with 3 different amount of catalyst at 2 different operating temperatures under 6000 ppm and 15,000 ppm continuous H2 gas flow for 4 h. Sensor output is completely stable for 3 different amount of catalyst.

Cement Plug Sealing Studies of Silica Cement Systems

2019 ◽  
Author(s):  
Anisa Noor Corina ◽  
Nils van der Tuuk Opedal ◽  
Torbjørn Vrålstad ◽  
Sigbjørn Sangesland
Keyword(s):  
Gas Flow ◽  
Curing Temperature ◽  
Small Scale ◽  
The Past ◽  
Laboratory Setup ◽  
Gas Leak ◽  
Zonal Isolation ◽  
Cement Mixture ◽  
Cement Plug

Abstract A cement plug is widely applied for permanent abandonment phase to provide long-term zonal isolation against fluid flow. Maintaining cement plug integrity is a challenging task, and loss in cement sealing poses risks to the surrounding environment and surface safety. It is well-known that the cement performance is affected by cement material and downhole conditions. Nevertheless, investigations linking these influencing factors with the sealing of cement plugs are still limited, especially with the lack of proper equipment in the past. In the present work, a small-scale laboratory setup has been constructed to test the sealing ability of a cement plug. It has unique features that can simulate plugging operations at the downhole conditions and preserve the cement curing condition. By testing using this setup, it is possible to measure the minimum differential pressure required for gas to flow across the cement plug and the gas leak rate. The silica cement mixture was selected as the plug material, prepared using silica flour. Investigation of silica cement under the influence of expanding agent additive and various curing temperature was carried out. It was found that adding an expanding agent improved the sealing of cement plugs. Moreover, samples cured at a high temperature were less resistant to gas flow with the leak path observed at the cement/steel interface, indicating debonding.

scholarly journals The gas flow at mineral springs and mofettes in the Vogtland/NW Bohemia: an enduring long-term increase

Geofluids ◽  
2008 ◽  
Vol 8 (4) ◽  
pp. 274-285 ◽  
Author(s):  
U. KOCH ◽  
K. BRÄUER ◽  
J. HEINICKE ◽  
H. KÄMPF
Keyword(s):  
Gas Flow ◽  
Mineral Springs

scholarly journals Gas Network Development in Compact Bentonite: Key Controls on the Stability of Flow Pathways

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-19 ◽  
Author(s):  
J. F. Harrington ◽  
C. C. Graham ◽  
R. J. Cuss ◽  
S. Norris
Keyword(s):  
Radioactive Waste ◽  
Gas Flow ◽  
Flow Network ◽  
Strongly Coupled ◽  
Gas Network ◽  
Compact Bentonite ◽  
Engineered Barrier ◽  
Flow Pathways ◽  
Stimulation Of

Compacted bentonite is proposed as an engineered barrier material within facilities for the geological disposal of radioactive waste. Barrier performance and its interaction with a free gas phase must be considered as part of sound repository design. This study involved the long-term experimental examination of gas flow in precompacted bentonite, with particular consideration of gas network stability. Results demonstrate that the stress field experienced by the clay is strongly coupled with gas flow. For the first time, three controls on this behaviour are considered: (i) injection flow rate, (ii) constant vs. variable gas pressure, and (iii) stimulation of the microfracture network. A detailed stress analysis is used to examine changes in the gas flow network. The results indicate a degree of metastability despite these changes, except in the case of stimulation of the microfracture network by removal of the primary drainage route. In this case, a rapid redevelopment of the gas flow network was observed. As such, availability of drainage pathways will represent a key control on the generation of peak gas pressures and distribution of gas within the engineered barrier. The cessation of gas flow is shown to result in crack closure and self-sealing. Observations from this study highlight that characterisation of the gas network distribution is of fundamental importance in predicting gas dissipation rates and understanding the long-term fate of gas in radioactive waste repositories.

The Evaluation of the PXQ for the Analysis of Cements and Related Materials

1958 ◽  
Vol 2 ◽  
pp. 215-227
Author(s):  
George Andermann ◽  
J. L. Jones ◽  
E. Davidson
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Applied Research ◽  
Production Control ◽  
Helium Flow ◽  
X Ray ◽  
Long Term Stability ◽  
Short And Long Term

AbstractThe analysis of cements and ores has been studied using the Applied Research Laboratories, Inc. Production Control X-ray Quantometer (PXQ), Elements included in the program were magnesium, aluminum, silicon, phosphorus, calcium and iron. The PXQ, utilizing the polychromator concept, allows the simultaneous determination of the listed elements.Focusing ADP, EDT, quartz and LiF crystals were used with flow Geigers or Multitrons. Helium paths were used as required. The choice of crystals, detectors, and slit widths was determined to give optimum results for each element.The effects of briquetting and ratioing to scattered background on accuracy were studied. Various instrumental factors such as helium flow rate, detector gas flow rate, short and long term stability were also investigated.

Degradation of Mechanical Properties for Polyethylene by Small-Deformation Damage

2014 ◽  
Author(s):  
P-Y Ben Jar
Keyword(s):  
Mechanical Properties ◽  
Stress Response ◽  
Yield Point ◽  
Gas Flow ◽  
Small Deformation ◽  
Strain Level ◽  
Tangent Modulus ◽  
Stress Whitening

Polyethylene (PE) has now been widely used to make plastic pipe for gas transportation. Because of its excellent ductility, processes for repair and maintenance of PE pipe allow squeeze-flattening the pipe to reduce the gas flow. Our previous study has shown that stretch of PE, even at a low strain level, can cause damage of the material, and significance of the damage depends on the strain rate. This paper presents results from a follow-up study, to investigate the possibility of quantifying the influence of damage on the mechanical properties. Coupon specimens used in this study have the same geometry as that used previously. Each specimen was tested twice. The 1st test was to introduce the damage, by stretching the specimen at a crosshead speed of 1 mm/min; the 2nd test to characterize the influence of the damage on the mechanical properties, by stretching the specimen at 1 μm/min. The two crosshead speeds were chosen because the former (1 mm/min) is known to introduce much more damage than the latter (1 μm/min) at a same strain level. Therefore, change in mechanical properties observed from the 2nd test should mainly come from the damage generated in the 1st test. To avoid influence of viscous recovery from the 1st test on the results from the 2nd test, the two tests were conducted more than one month apart. Test results show that even by stretching the specimen to a strain level below the yield point in the 1st test (i.e. with the strain less than 0.1), damage introduced to the specimen can cause a detectable decrease in the mechanical properties, such as the tangent modulus at the strain 0.01 and the stress response at the strain 0.1, from the 2nd test. The results also show that the rate of decrease of the above values with the increase of strain becomes significant when the strain level introduced in the 1st test is above the yield point. By stretching the specimen to a strain level about 0.5 in the 1st test, though yet to cause apparent necking or stress whitening, the tangent modulus and the stress response in the 2nd test are decreased by about one-third of the values for the virgin specimen. This amount of change is significant and should not be ignored for long-term applications such as for gas transportation.

Long-term Corrosion of Zircaloy-4 and Zircaloy-2 by Continuous Hydrogen Measurement under Repository Condition

2013 ◽  
Vol 1518 ◽  
pp. 173-178 ◽  
Author(s):  
Tomofumi Sakuragi ◽  
Hideaki Miyakawa ◽  
Tsutomu Nishimura ◽  
Tsuyoshi Tateishi
Keyword(s):  
Corrosion Behavior ◽  
Gas Flow ◽  
Hydrogen Generation ◽  
Tetragonal Zirconia ◽  
Solution Ph ◽  
Naoh Solution ◽  
The Difference ◽  
Process Controls ◽  
Kinetics Of

ABSTRACTCorrosion behavior is a key issue for the waste disposal of irradiated metals, such as hulls and endpieces, and is considered to be a leaching source of radionuclides including C-14. However, little information about Zircaloy corrosion in anticorrosive conditions has been provided.In the present study, long-term corrosion tests of Zircaloy-4 and Zircaloy-2 were performed in assumed disposal conditions (dilute NaOH solution, pH 12.5, 303 K) by using the gas flow system for 1500 days. The corrosion rate, which was determined by measuring gaseous hydrogen and the hydrogen absorbed in Zircaloy, decreased with immersion time and was lower than the value of 2×10−2 μm/y used in performance assessment (1500-day values: 5.84×10−3 and 5.66×10−3 μm/y for Zircaloy-4, 1000-day values: 8.81×10−3 μm/y for Zircaloy-2). The difference in corrosion behavior between Zircaloy 4 and Zircaloy-2 was negligible. The average values of the hydrogen absorption ratios for Zircaloy-4 and Zircaloy-2 during corrosion were 91% and 94%, respectively.The hydrogen generation kinetics of both gas evolution and absorption into metal can be shown by a parabolic curve. This result indicates that the diffusion process controls the Zircaloy corrosion in the early corrosion stage of the present study, and that the thickness of the oxide film in this stage is limited to approximately 25 nm and may therefore be in the form of dense tetragonal zirconia.

Successful Barrier Enhancement Application of Epoxy Based Resin for Multiple Casing to Casing Annuli Having Tight Injectivity - Case Study from Saudi Arabian Peninsula

2021 ◽  
Author(s):  
Abdulmalek Shamsan ◽  
Alejandro De la Cruz ◽  
Walmy Jimenez
Keyword(s):  
Epoxy Resin ◽  
Gas Flow ◽  
Resin System ◽  
Gas Leakage ◽  
Well Integrity ◽  
Epoxy Resin System ◽  
Modified Surface ◽  
Flow Through ◽  
Tailored Design

Abstract This study describes the approach used for enhancing the well integrity that was compromised with gas flow through a casing-casing annulus (CCA). Extremely tight injectivity at a CCA demands a solid free solution which not only can be injected but also resist high differential pressures to provide a long-term barrier in CCA. In this paper a successful leak remediation using an epoxy resin system helped the operator save a well and restart its production. Several pressure tests were conducted for identifying an extremely tight casing leak which was causing formation gas travelling to surface through the annulus. This issue required the customer to look for an efficient remedial solution to seal off the gas leakage and regain productivity. Due to the extremely low injectivity, a conventional cement squeeze or any solid laden particle-based squeeze approach was prone to fail. Alternatively, a tailored solid free epoxy resin system was placed in the annulus using an unconventional placement technique resulted in barrier enhancement and helped the operator place the well back into production. For a mature well flowing through 7 × 9 5/8‑in. and 9 5/8 × 13 3/8‑in., a tailored epoxy-based resin system formulation was placed in the well bore with modified surface operations procedures which helped in eliminating current annular pressure to regain well integrity and production. Remedial operations were performed from the surface by squeezing to seal off the gas coming from the annulus. A Tailored design derived from rigorous lab testing and perfect field execution resulted in CCA pressure remediation in a single attempt of the treatment injection, proving that the concept of using a solids-free resin to enhance existing deteriorated barriers is a reliable method. This epoxy resin system helped the operator to regain the well integrity and production in the shortest time without expensive well intervention operations. Epoxy resin based systems have been identified as a novel solution to remediate barrier integrity for well construction and workover operations, hence such case histories with enhanced operations procedures are helpful in increasing awareness of the benefits that can be attained in challenging high-pressure, low-injectivity environments, and can improve well economics.

scholarly journals A Mathematical Model of Gas and Water Flow in a Swelling Geomaterial—Part 1. Verification with Analytical Solution

Minerals ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 30 ◽  
Author(s):  
Elias Ernest Dagher ◽  
Julio Ángel Infante Sedano ◽  
Thanh Son Nguyen
Keyword(s):  
Mathematical Model ◽  
Numerical Model ◽  
Analytical Solution ◽  
Analytical Solutions ◽  
Gas Flow ◽  
Numerical Models ◽  
Model Verification ◽  
Model Complexity ◽  
Gas Migration

Gas generation and migration are important processes that must be considered in a safety case for a deep geological repository (DGR) for the long-term containment of radioactive waste. Expansive soils, such as bentonite-based materials, are widely considered as sealing materials. Understanding their long-term performance as barriers to mitigate gas migration is vital in the design and long-term safety assessment of a DGR. Development and the application of numerical models are key to understanding the processes involved in gas migration. This study builds upon the authors’ previous work for developing a hydro-mechanical mathematical model for migration of gas through a low-permeable geomaterial based on the theoretical framework of poromechanics through the contribution of model verification. The study first derives analytical solutions for a 1D steady-state gas flow and 1D transient gas flow problem. Using the finite element method, the model is used to simulate 1D flow through a confined cylindrical sample of near-saturated low-permeable soil under a constant volume boundary stress condition. Verification of the numerical model is performed by comparing the pore-gas pressure evolution and stress evolution to that of the results of the analytical solution. The results of the numerical model closely matched those of the analytical solutions. Future studies will attempt to improve upon the model complexity and investigate processes and material characteristics that can enhance gas migration in a nearly saturated swelling geomaterial.

scholarly journals Glasgow University Radiocarbon Measurements VIII

Radiocarbon ◽  
1976 ◽  
Vol 18 (2) ◽  
pp. 161-171 ◽  
Author(s):  
M J Stenhouse ◽  
M S Baxter
Keyword(s):  
Gas Flow ◽  
Liquid Scintillation ◽  
Operating Voltage ◽  
Term Study ◽  
Counting System ◽  
Background Count ◽  
Long Term Study ◽  
Adsorption Desorption ◽  
Nuclear Weapon Tests

The analytical facilities at Glasgow have been extended to include gas proportional (CO2 and CH4) and liquid scintillation (C6H6) counting laboratories. The results presented here were obtained during 1972-1974 using the CO2 gas counting system only. In brief, organic samples, after pretreatment as described in the text, are burned in a tube combustion unit and the evolved CO2 absorbed in KOH solution. BaCO3 is precipitated and acid-hydrolyzed in vacuo using H3PO4. Evolved CO2 is purified via adsorption/desorption on CaO and is stored prior to counting. The 2.6L proportional counter is surrounded by a gas-flow Geiger anticoincidence guard and 10cm thick Pb shielding to reduce background count rates to ca 4.9 cpm at 1 atm filling and barometric pressures. A barometric sensitivity in background of −0.01cpm/mbar is observed. Constant gas gain is ensured by monitoring the coincidence meson spectrum and normalizing the detector operating voltage. All sample activities are related to the NBS oxalic acid standard count rate which averages 14.71 cpm at 1 atm filling pressure and 15°C. Mass spectrometric assay of CO2 after counting is performed on a VG Micromass 602B instrument to a precision of 0.05% (±1σ). Since uncertainties quoted on all results represent 1σ counting errors alone, they are related to precision of measurement rather than accuracy. The bulk of data quoted here are connected with a long-term study of the medical aspects of artificial 14C from nuclear weapon tests. These results should therefore be assessed in conjunction with those pub previously (Harkness and Walton, 1972; Farmer et al, 1972).

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