Tokyo Gas (Japan)

ABSTRACT This study presents a comprehensive characterization of the low‐efficiency reservoirs within the Chang 6 member of the Ordos Basin, elucidating their formation mechanisms and establishing quantitative identification standards. These reservoirs typically develop in low‐energy sedimentary microfacies, specifically the margins of underwater distributary channels and inter‐distributary bays. Petrological analysis reveals that the reservoirs consist of fine‐grained feldspar sandstones rich in plastic interstitial materials and carbonate cements (>5%), exhibiting ultralow physical properties (average porosity 7.12%, average permeability 0.27 mD) and a restricted pore structure (average displacement pressure 1.79 MPa, median throat radius 0.03 µm). The genesis of these low‐efficiency zones is governed by a sedimentary‐diagenetic coupling mechanism: Fine‐grained sedimentation facilitated intense mechanical compaction, whereas late‐stage carbonate cementation caused substantial porosity loss, solidifying the tight nature of the formation. Hydrocarbon accumulation follows a “densification before accumulation” model, driven by an overpressure difference of 6–7 MPa generated by the underlying Chang 7 source rocks, which facilitated migration through microfractures into the tight sand bodies. To address the challenge of identifying thin, low‐resistivity oil layers, Walsh inversion and resolution matching techniques were employed to enhance logging signal precision. On the basis of core‐log calibration, a quantitative identification standard was established, defining low‐efficiency oil layers by an acoustic transit time and deep resistivity . Despite their marginal petrophysical properties, the reservoirs exhibit a high brittleness index (>60%) and low horizontal stress difference, indicating that large‐scale volume fracturing is a viable strategy for commercial development.

Biogas upgrading and digester compactification are needed to expand the application scope of Anaerobic digestion (AD) technology. An anaerobic membrane bioreactor (AnMBR) is a promising reactor for in situ biogas upgrading and digester compactification. This study is the first report achieving in situ biogas upgrading by using a thermophilic AnMBR. Waste activated sludge and H2 were supplied to the AnMBR to increase the CH4 content in the biogas via biomethanation by hydrogenotrophic methanogens. The H2 addition at a 7.5:1 H2:CO2 ratio promoted biogas upgrading, increasing the CH4 content to 94%. With an organic loading rate of 0.78 g-VS/L/d, the CH4 production rate and CH4 yield reached 0.32 L/L/d and 0.38 L/g-VS, respectively. Methanothermobacter was the dominant group among methanogens. Notably, increasing the H2 partial pressure did not inhibit the AD process. In contrast to the AnMBR, a continuously stirred tank reactor did not achieve biogas upgrading, likely because of its lower biomass concentration and H2 conversion into acetic acid via homoacetogenesis. During 111 days of AnMBR operation, the transmembrane pressure remained below 20 kPa at a filtration flux of 4.6 LMH. Physical and chemical cleaning after the AnMBR operation restored 94% of the membrane’s water permeability.

Abstract This study investigated the strain-controlled low-cycle fatigue properties of X65 pipeline steel under cathodic hydrogen charging to assess the seismic resistance of hydrogen pipelines. In Japan, natural gas pipelines are designed to withstand a strain of 3% during earthquakes, a requirement based on the ASME fatigue design curve for steel and seismic wave velocity. To evaluate the seismic resistance of hydrogen pipelines according to these design criteria, low-cycle fatigue testing in a hydrogen environment is essential to determine whether the number of cycles to failure at a strain amplitude of 3% exceeds the design life based on the ASME fatigue design curve. However, the low-cycle fatigue properties of pipeline steels in hydrogen environments have not been fully elucidated. This study aimed to determine whether the allowable strain for natural gas pipelines under seismic conditions is also applicable to hydrogen pipelines. Pd-plated X65 pipeline steel specimens were exposed to hydrogen gas at a pressure of 7 MPa. Hydrogen content was measured using thermal desorption analysis. Cathodic hydrogen charging was performed under conditions where the hydrogen content was higher than that of the specimens exposed to hydrogen gas at a pressure of 7 MPa, and fatigue testing was conducted during ongoing charging. The results revealed that hydrogen adversely affects the low-cycle fatigue life of X65 steel. However, at a strain amplitude of 3% and a strain rate of 0.06 %·s−1 under cathodic hydrogen charging, the number of cycles to failure exceeded the design life based on the ASME fatigue design curve. Additionally, the influence of strain rate on fatigue life was examined, showing that the number of cycles to failure decreased as strain rate decreased, both in air and under cathodic hydrogen charging. This finding indicates that a strain rate of 0.06 %·s−1, which is lower than the strain rate expected during an earthquake, represents a conservative condition for low-cycle fatigue testing. From these results, the allowable strain (3%) for seismic resistance in natural gas pipelines, established using the ASME fatigue design curve and seismic waveforms, is also applicable to hydrogen pipelines made of X65 steel with an internal pressure of at least 7 MPa. This study contributes to the safety assessment of hydrogen pipelines subjected to seismic motion.

Microwave-assisted rock breaking is widely used in the field of rock engineering. In order to explore the fracture characteristic of different types of rocks under microwave irradiation, the semi-circular bending (SCB) test of sandstone and granite after microwave irradiation were carried out. The crack development, fracture energy and micro-morphology of specimens under microwave irradiation were analysed. The results show that the surface colour of the two kinds of rock specimens changes after microwave irradiation, and cracks appear on the surface of the some sandstone specimens under high power irradiation for a long time. The surface temperature of the two rock increases with the increase of irradiation time. Under the given power, the fracture toughness and fracture energy show the same change trend, that is, with the increase of irradiation time, the fracture toughness and fracture energy increase first and then decrease; the fractal dimension of the two rocks shows an upward trend. The mechanism of the influence of microwave irradiation on rock is explained from two aspects: Microwave irradiation generates thermal stress within rocks, leading to microcrack propagation, whereas elevated temperatures induce both mineralogical alterations and mass loss processes in rock components.

Abstract In this study, we investigated a method of utilizing the drone itself as a wind speed sensor without mounting a special observation device on the drone. As a result, we constructed a calibration formula to convert the flight record data to an arbitrary wind speed. Next, we applied this method to the airflow measurement in the wake region for the utility-scale wind turbine and succeeded in reproducing the airflow characteristics caused by the wind turbine wake phenomenon.

BackgroundThe gut bacteriome influences host metabolic and physiological functions. However, its relationship with reproductive performance remains unclear. In this study, we evaluated the relationship between the gut bacteriome and reproductive performance in beef cattle, such as Japanese black heifers. Artificial insemination (AI) was performed after 300 days of age, and the number of AI required for pregnancy (AI number) was evaluated. The relationship of the fecal bacteriome at 150 and 300 days of age and reproductive performance was visualized using statistical structural equation modelling between traits based on four types of machine-learning algorithms (linear discriminant analysis, association analysis, random forest, and XGBoost).ResultsThe heifers were classified into superior (1.04 ± 0.04 cycles, n = 26) and inferior groups (3.87 ± 0.27 cycles, n = 23) according to the median frequency of AI. The fecal bacteria of the two groups were examined and compared using differential analysis, which demonstrated that the genera Rikenellaceae RC9 gut group and Christensenellaceae R-7 group were increased in the superior group. Subsequently, correlation analysis evaluated the interrelationships between bacteriomes, which demonstrated that the patterns exhibited distinct characteristics. Therefore, four machine-learning algorithms were employed to identify the distinctive factors between the two groups. The directed acyclic graphs carried out by DirectLiNGAM based on these extracted factors inferred that the family Erysipelotrichaceae and the genera Clostridium sensu stricto 1 and Family XIII AD3011group at 150 days of age were strongly associated with an increase in AI number. Furthermore, a pathway involved in creatinine degradation (PWY-4722) at 150 days of age was related to an increase in AI number. However, bacteriomes and/or pathways at 300 days of age were not necessarily related to AI number.ConclusionsIn this study, a causal inference methodology was applied to investigate AI-dependent gut bacterial communities in pregnant cattle. These findings suggest that AI numbers, which are crucial for beef cattle production management, could be inferred from the fecal bacterial patterns nearly six months before the AI, rather than immediately before. This study provides a novel perspective of the gut environment and its role in reproductive performance.Graphical

Abstract Natural gas-fired internal combustion engines (ICEs), as an alternative to traditional fuel-fired ICEs, are a technological innovation to implement the “double reduction” policy by utilizing clean energy. The academic community is interested in the topic of controlling air pollutant emissions from natural gas internal combustion engines. In this paper, a three-dimensional model of internal combustion engine operation and a natural gas hydrodynamic model are constructed successively, and numerical simulation is carried out using fluent software. A non-dominated genetic algorithm is introduced to solve the air pollutant emission control problem of the internal combustion engine, and the Pareto optimal solution of pollutant emission is determined by the TOPSIS decision-making method. The error of the numerical simulation results in this paper is less than 5%, and the maximum transient temperature of the natural gas internal combustion engine is approximately 1940 K. The NOx generation has a double hump-like distribution. In the case of Pareto’s optimal solution, the system efficiency of the new scheme is 56.82%, the carbon dioxide emission rate is 353.31kg/(Mwah), and the total annual cost is 6.45×108¥, which is better than the original scheme, which verifies the effectiveness of the proposed method.

Abstract Next-generation sequencing (NGS) technology through barcoding of DNA in highly-digested diet samples has become a powerful tool for diet reconstruction in food webs. However, traditional single markers can only detect very few prey species, and the constructed food web cannot reflect all effective feeding information. Here, we used multi-locus NGS with COI-M, COI-m, 18S and 16S markers to analyze the feeding habits of carnivorous fishes in Bohai Bay, China. We compared the prey identification results of single markers and multiple markers on the gut content analysis, and integrated examined the feeding characteristics of carnivorous fishes to reconstruct the food web. Our findings revealed that a four-marker combination could detect up to 56 orders and 156 species of preys in the diets of these fishes, which are 1.5 − 6.2 and 1.7 − 9.2 times that of detected by single markers, respectively. Calanoida was detected as one of the primary food sources of carnivorous fishes expect for Gobiiformes and Decapoda at order level, contrasting with the previous researches. Network structure analyses showed significant modularity in the food web of carnivorous fishes and their preys. Species Scomberomorus niphonius, Odontamblyopus rubicundus, Chaeturichthys stigmatias, Platycephalus indicus and Cynoglossus joyneri were found to be divided into three different modules in the food web, indicating that specific and directional proliferation strategies should be advocated to be adopt for their population recoveries. This study reported a detailed trophic network of the carnivorous fishes, providing valuable insights for effective conservation and restoration strategies to enhance fisheries structure and stabilize the marine ecosystem.