Water invasion performance of complex fracture-vuggy gas reservoirs based on classification modeling

   The complexity of the pore structure, spatial development, fractures, and pore distribution of fractured-vuggy carbonate reservoirs influences the water invasion dynamics of gas reservoirs, which is crucial in the dynamic research of strongly heterogeneous reservoirs. In this study, the collocation relationship of pore-vuggy fractures is described by the quantitative characterization of their attribute parameters. The discrete fracture network model is used to match and construct the fractures in different modes. The distribution classification method is used to model three-dimensional geological reservoirs in terms of their geometric and attribute characteristics. Bottom-water and edge-water gas reservoirs are constructed separately using numerical simulation, and the dynamic characteristics of water invasion are described. The results show that the proposed method is suitable for the geological modeling of fractured-vuggy gas reservoirs with strong heterogeneity and complexity. The modeling accuracy is improved because the gas reservoir heterogeneity and water invasion’s dynamic characteristics can be described accurately. Six stages of water invasion are identified from the numerical simulation of water invasion. This method provides theoretical guidance for the study of heterogeneous gas reservoirs with water.Cited as: Han, X., Tan, X., Li, X., Pang, Y., Zhang, L. Water invasion performance of complex fracture-vuggy gas reservoirs based on classification modeling. Advances in Geo-Energy Research, 2021, 5(2): 222-232, doi: 10.46690/ager.2021.02.1

Surface Coating of Cyclotetramethylenetetranitramine (HMX) Particles and Its Property Investigation

To improve the safety of cyclotetramethylenetetranitramine (HMX) particles, the polymer thermoplastic polyurethane elastomer (TPU) and nitrocellulose (NC) were introduced to coat HMX powder by water-solution suspension method and internal solution method, respectively. Scanning electron microscope (SEM) and X-ray photo-electron spectrometry (XPS) were employed to characterize the HMX samples and the role of NC and TPU in the coating processes were discussed. The impact sensitivity, friction sensitivity, and the thermal decomposition of coated HMX particles were investigated, and compared to the unprocessed ones. The results indicate that both TPU and NC can improve the wetting ability of the coating materials on HMX surface and reinforce the connection between HMX and the coating materials. The impact sensitivity and friction sensitivity of HMX samples decrease obviously after they have been surface coated; the drop height (H50) is increased from 35.24 cm to 50.08 cm, and the friction probability is reduced from 93.2 % to 58.3%. The activation energy (Ea) and the self-ignition temperature increase by 10.46 KJ·mol-1 and 1.8, respectively

The impacts of water vapour and co-pollutants on the performance of electrochemical gas sensors used for air quality monitoring

The analytical performance of low cost air pollution sensors under real-world conditions is a key factor that will influence their future uses and adoption. In this study five different electrochemical gas sensors (O3, SO2, CO, NO, NO2) are tested for their performance when challenged with cross interferences of water vapour and other gaseous co-pollutants. These experiments were conducted under both controlled laboratory conditions and during ambient air monitoring in urban background air at a site in York, UK. Signal outputs for O3, SO2 and CO showed a positive linear dependence on relative humidity (RH). The output for the NO sensor showed a negative correlation. The output for the NO2 sensor showed no trend with RH. Potential co-pollutants (O3, SO2, CO, NO2, NO and CO2) were introduced under controlled conditions using gas standards and delivered to each sensor in series along with variable RH. A matrix of cross-interference sensitivities were established which could be used to correct sensor signals. Interference-corrected sensor responses were compared against reference observations over an 18-day period. Once cross interferences had been removed the corrected 5 min averaging data for O3, CO, NO and NO2 sensors showed good agreement with the reference techniques with r2 values of 0.89, 0.76, 0.72, and 0.69, respectively. The SO2 sensor could not be evaluated in ambient air since ambient SO2 was below the sensor limit of detection

Direct observation of the formation and stabilization of metallic nanoparticles on carbon supports

Direct formation of ultra-small nanoparticles on carbon supports by rapid high temperature synthesis method offers new opportunities for scalable nanomanufacturing and the synthesis of stable multi-elemental nanoparticles. However, the underlying mechanisms affecting the dispersion and stability of nanoparticles on the supports during high temperature processing remain enigmatic. In this work, we report the observation of metallic nanoparticles formation and stabilization on carbon supports through in situ Joule heating method. We find that the formation of metallic nanoparticles is associated with the simultaneous phase transition of amorphous carbon to a highly defective turbostratic graphite (T-graphite). Molecular dynamic (MD) simulations suggest that the defective T-graphite provide numerous nucleation sites for the nanoparticles to form. Furthermore, the nanoparticles partially intercalate and take root on edge planes, leading to high binding energy on support. This interaction between nanoparticles and T-graphite substrate strengthens the anchoring and provides excellent thermal stability to the nanoparticles. These findings provide mechanistic understanding of rapid high temperature synthesis of metal nanoparticles on carbon supports and the origin of their stability

The impacts of water vapour and co-pollutants on the performance of electrochemical gas sensors used for air quality monitoring

The analytical performance of low cost air pollution sensors under real-world conditions is a key factor that will influence their future uses and adoption. In this study five different electrochemical gas sensors (O3, SO2, CO, NO, NO2) are tested for their performance when challenged with cross interferences of water vapour and other gaseous co-pollutants. These experiments were conducted under both controlled laboratory conditions and during ambient air monitoring in urban background air at a site in York, UK. Signal outputs for O3, SO2 and CO showed a positive linear dependence on relative humidity (RH). The output for the NO sensor showed a negative correlation. The output for the NO2 sensor showed no trend with RH. Potential co-pollutants (O3, SO2, CO, NO2, NO and CO2) were introduced under controlled conditions using gas standards and delivered to each sensor in series along with variable RH. A matrix of cross-interference sensitivities were established which could be used to correct sensor signals. Interference-corrected sensor responses were compared against reference observations over an 18-day period. Once cross interferences had been removed the corrected 5 min averaging data for O3, CO, NO and NO2 sensors showed good agreement with the reference techniques with r2 values of 0.89, 0.76, 0.72, and 0.69, respectively. The SO2 sensor could not be evaluated in ambient air since ambient SO2 was below the sensor limit of detection

Risk factors for hypoxaemia following hip fracture surgery in elderly patients who recovered from COVID-19: a multicentre retrospective study

ObjectivesTo explore the risk factors associated with postoperative hypoxaemia in elderly patients who have recovered from coronavirus disease (COVID-19) and underwent hip fracture surgery in the short term.DesignMulticentre retrospective study.SettingThe study was performed in three first 3A-grade hospitals in China.ParticipantsA sequential sampling method was applied to select study participants. Medical records of 392 patients aged ≥65 years who had recovered from COVID-19 and underwent hip fracture surgery at three hospitals in China between 1 November, 2022, and 15 February, 2023, were reviewed.InterventionsPatients were assigned to hypoxaemia or non-hypoxaemia groups, according to whether hypoxaemia occurred after surgery. Univariate and multivariate logistic regression analyses were used to identify independent risk factors for postoperative hypoxaemia.ResultsThe incidence of postoperative hypoxaemia was 38.01%. Statistically significant differences were found between the two groups in terms of age, body mass index (BMI), American Society of Anesthesiologists (ASA) classification, presence of expectoration symptoms, preoperative hypoxaemia, chronic obstructive pulmonary disease, pulmonary inflammation, time between recovery from COVID-19 and surgery, anaesthetic mode, surgical procedure, intraoperative blood loss, intraoperative infusion, duration of surgery, and length of hospital stay (p < 0.05). Furthermore, patients with BMI ≥28.0 kg/m2, expectoration symptoms, presence of preoperative hypoxaemia, ASA classification III, time between recovery from COVID-19 and surgery ≤2 weeks, and general anaesthesia were potential risk factors for postoperative hypoxaemia.ConclusionObesity, expectoration symptoms, preoperative hypoxaemia, ASA classification III, time between recovery from COVID-19 and surgery ≤2 weeks, and general anaesthesia were potential risk factors for postoperative hypoxaemia in elderly patients who recovered from COVID-19 and underwent hip fracture surgery in the short term

Crowdsourcing hypothesis tests: Making transparent how design choices shape research results

To what extent are research results influenced by subjective decisions that scientists make as they design studies? Fifteen research teams independently designed studies to answer fiveoriginal research questions related to moral judgments, negotiations, and implicit cognition. Participants from two separate large samples (total N > 15,000) were then randomly assigned to complete one version of each study. Effect sizes varied dramatically across different sets of materials designed to test the same hypothesis: materials from different teams renderedstatistically significant effects in opposite directions for four out of five hypotheses, with the narrowest range in estimates being d = -0.37 to +0.26. Meta-analysis and a Bayesian perspective on the results revealed overall support for two hypotheses, and a lack of support for three hypotheses. Overall, practically none of the variability in effect sizes was attributable to the skill of the research team in designing materials, while considerable variability was attributable to the hypothesis being tested. In a forecasting survey, predictions of other scientists were significantly correlated with study results, both across and within hypotheses. Crowdsourced testing of research hypotheses helps reveal the true consistency of empirical support for a scientific claim.</div