In order to investigate the properties of seawater mixing alkali-activated materials, the development law of hydration reaction, mechanics and corrosion resistance of seawater alkali-activated materials based on multi-component composite cementitious materials was studied. The results show that seawater mixing has a certain inhibitory effect on the hydration reaction of alkali-activated slag, and the compressive strength of SLCM at different ages also shows a decreasing trend to a certain extent, which is not conducive to the development of strength. Fly ash and silica fume can reduce the hydration reaction rate, early strength and toughness of the seawater alkali-activated materials, but their strength and toughness increase potential is significant in the later period, in which the strength and toughness growth rate of the silica-fly ash-slag terpolymer system from 7 days to 28 days reaches 50.9% and 86.7%, respectively. Compared with alkali-activated slag, adding fly ash and silica fume can improve the electric flux permeability and chloride ion mobility coefficient of alkali excited materials in seawater to a certain extent, which is consistent with their microstructure, but the three still belong to the same chloride ion permeability grade, i.e., medium permeability grade (electric flux method).

In order to study the prevention and control of power disaster induced by coal mining process, Brazilian splitting test of raw coal specimen was carried out to study the energy evolution law in the process of coal body tensile damage destruction, and the precursor information of coal body destabilization and destruction was identified. The results show that the coal body tensile damage process has significant nonlinear evolution characteristics, and it is possible to identify the critical point, destabilization point, and damage point of coal body damage. The energy evolution characteristics of coal body tensile damage in each stage are significantly different. In the elastic deformation stage, the input energy is mainly converted into elastic energy, and the dissipation energy remains stable, while in the destabilization stage, the dissipation-elasticity ratio shows a jumping growth. By calculating the energy release rate and energy dissipation rate, it is found that the index has abnormal response characteristics at the critical point, destabilization point and damage point of the coal body tensile process, and the appearance of the characteristic points all have significant precursor information. The nature of coal destabilization is the result of energy accumulation and dissipation, and the energy index of coal body can reveal the abnormal characteristics of energy evolution in the process of damage and destruction of the specimen, and identify the precursor information of coal body catastrophe, which is conducive to the over-warning, and escort for the safe mining of coal.

In order to accurately predict the water richness of the weathered bedrock aquifer, 28 groups of weathered bedrock pumping test borehole data in Zhangjimao minefield were used as training and verification samples, and the lithology combination index, weathering index, thickness, core recovery rate and burial depth of the weathered bedrock were selected as evaluation indexes. Based on whale optimization algorithm-support vector machines (WOA-SVM), a water-rich identification model for weathering bedrock aquifers was proposed. This model can predict the water-rich grade of the weathered bedrock in the area without pumping test data, and realize water-rich zoning of the weathered bedrock in the well field by comprehensive use of the geological information of 249 exploration boreholes. The study shows that the weathered bedrock of Zhangjiamao minefield is weakly water-rich as a whole, and its spatial distribution is uneven. There are strong water-rich areas in the central part of the field and the local area along Wulanbula Gully, but their distribution range is small, there are some moderately water-rich areas in the central-western and southeastern parts, and the northeastern and southwestern areas are weakly and very weakly water-rich almost all the time. The results predicted are more in line with the actual situation, and the research results can provide a reference for the safe production of the mine and a new way of thinking for the prediction of the water-richness of the weathered bedrock.

The pore structure of deep tight sandstone reservoir is complex and heterogeneous, and it is difficult to determine the influencing factors of pore microscopic parameters on the characteristics of gas-water phase permeability. Based on the fractal geometry theory, combined with the core mercury intrusion porosimetry (MIP) method, nuclear magnetic resonance (NMR) T₂ spectroscopy test and micron CT scanning results, the micro-pore throat parameters and various scale fractal dimensions of the reservoir were obtained. Through the mobile gas porosity and the maximum atmospheric phase relative permeability, the control mechanism of the fractal dimension and micro-pore throat structure parameters on the gas-water phase permeability characteristics was discussed. The results show that mercury injection and NMR fractal curves have obvious “three-stage” characteristics, and the total shape dimension of the reservoir describes the distribution of seepage and movable fluid more accurately when gas and water coexist. The maximum mercury saturation, average pore throat radius, total reservoir shape dimension and displacement pressure have significant effects on the mobile gas porosity during gas seepage. The average pore throat radius has a significant influence on the maximum effective gas phase relative permeability in gas seepage. The control mechanism of the micro-pore structure on the gas-water phase permeability can provide a powerful guide for the efficient development of water-producing gas reservoirs.

The effect of water flooding development in low permeability reservoir is generally poor, and CO₂ flooding can effectively improve the degree of crude oil recovery. In order to analyze various factors affecting the effect of CO₂-assisted gravity flooding, based on the research mechanism of gas-injection-assisted gravity flooding, a mechanism model of one injection and one production was established to analyze the influence law of geological factors and development factors, and the orthogonal experimental design method and Shapley value method were used for multi-factor analysis. The results show that the positive rhythm reservoir is more suitable for CO₂-assisted gravity flooding. Reservoir dip angle, average permeability and gas injection velocity are positively correlated with development effect. The ratio of vertical permeability to horizontal permeability and the difference of permeability stage were negatively correlated with the development effect. If the ratio of gas injection and dimensionless horizontal well section length is set to 0.8, the CO₂-assisted gravity flooding effect can be effectively improved. The ratio of vertical permeability to horizontal permeability has the highest influence on CO₂-assisted gravity flooding. The research results provide technical guidance and theoretical support for improving the development effect of CO₂-assisted gravity flooding in low permeability reservoirs.

In order to clarify the reservoir applicability of different acid systems, understand the influence of reservoir acid rock etching morphology on fracture conductivity, and give the optimal slug combination method for different horizons, acid erosion fracture conductivity experiments were carried out in the carbonate reservoirs of Sichuan and Chongqing, the results show that the conductivity of slug combinations between different acid systems to the dolomite of the Maokou Formation after acid etching is higher than that of the limestone. The morphology of acid-etched fractures after acid-etching is different between different single-acid systems, in which steering acid has extremely deep grooves after etching, and the grooves of authigenic acid are the shallowest. For Maokou Formation, when the alternation between gelling acid and fracturing fluid and the alternation between gelling acid and authigenic acid is tertiary, the conductivity is the highest, and the conductivity reaches 4.53 μm²·cm at 60 MPa after tertiary alternation between gelling acid and authigenic acid. The conductivity of Qixia Formation and Dengying Formation is the highest when secondary alternation of fracturing fluid and gelling acid was selected, and the conductivity of Qixia Formation and Dengying formation are 6.72 μm²·cm and 7.47 μm²·cm at 60 MPa, respectively. In the Sichuan Chongqing exploration area, on-site application and in-depth investigation were conducted to verify the acid corrosion fracture conductivity of the acid solution. The results show that the acid corrosion effect is good after the acid solution entered the well, and the gas testing effect after the transformation is 208×10⁴ m³/d, achieving the expected increase in production. It provides theoretical and experimental guidance for acid fracturing technology of carbonate reservoirs in Sichuan and Chongqing.

In order to study the solution properties of polyacrylamide at high temperatures at the molecular-atomic scale, the molecular models of partially hydrolyzed polyacrylamide(HPAM) and AM/AANa/AMPSNa copolymer [P(AM/AANa/AMPSNa)] have been established through a combination of experimental methods and molecular dynamics simulations. The solution properties of the two polymers at elevated temperatures were systematically investigated in terms of polymer chain rigidity and flexibility, hydrogen bonding, hydration layer, interaction energy and the effect of salt cation, and the micro-mechanism of temperature resistance of P(AM/AANa/AMPSNa) was explained. The results show that the introduction of side chains containing methyl and sulfonated groups into the molecular chain of P(AM/AANa/AMPSNa) could increase the rigidity of the molecular chain, more hydrogen bonds are formed between sulfonated groups and water and has longer lifetime. At the same time, the strong polar sulfonic acid group makes the hydration layer denser, which results in the weaker static shielding effect of the cations on the P(AM/AANa/AMPSNa). Under different temperature conditions, P(AM/AANa/AMPSNa) has stronger intermolecular non-bonding interactions, stronger water retention effect of the molecular chain at the microscopic level, and higher viscosity at the macroscopic level.

As China’s mountainous regions host more and more gas pipelines, incidents involving natural gas leaks that cause harm to the environment or injure people are growing increasingly common. To investigate the diffusion behavior and vertical hazard distance of leakage gas in mountainous regions, a three-dimensional model of pipeline-soil-air was created with CFD software. The impacts of various obstructions, soil types, burial depths, leak hole shapes, and leak directions on the propagation of natural gas pipeline leaks and hazard distances were studied separately. The results show that in proportion to the direction angle between the buoyant force and the leakage hole, the vertical hazard distance and the rate of gas diffusion to the ground decrease. Diffusion rates and hazard ranges are larger for square and triangle leaking holes compared to circular ones. As soil porosity and granularity increase, the rate at which escaping gases diffuse into the soil increases steadily. The time it takes for the gas leak to release will vary depending on the burial depth, and as soil burial depth increases, so will the vertical hazard distance. Obstructions will alter the diffusion path of the leaking gas and accelerate the vertical hazard distance. Culverts will allow the gas to accumulate in the ditch to form an area of high concentration.

Aiming at the problem of effective extraction and identification of rolling bearing fault information in complex environments, a fault diagnosis method for rolling bearings based on feature mode decomposition (FMD) combined with multiscale fuzzy dispersion entropy (MFDE) and zebra optimization algorithm (ZOA) optimization support vector machine was proposed. In order to solve the problem that the key parameters in FMD are not adaptive, the minimum envelope entropy was used as the objective function, and the beluga whale optimization (BWO) was used to optimize FMD to find the optimal parameter combination to achieve the optimal decomposition of fault signals. Multiscale fuzzy dispersion entropy was introduced to construct the eigenvectors under different modes after decomposition. Finally, the feature vectors were input into the support vector machine for training and recognition. The effectiveness of the proposed method was verified by the public dataset and the self-made experimental platform dataset.

The drilling process requires real-time measurement of drill string vibration, which is crucial for drilling and downhole safety. However, the traditional power supply mode used for downhole vibration sensors has been found to increase drilling costs and reduce drilling efficiency. Therefore, sensors with self-powered capabilities are considered more suitable for practical conditions. A downhole arrayed self-powered deformable vibration sensor was proposed based on the principle of triboelectric nanogenerators. Experimental results demonstrate that the sensor synchronized measurements of amplitude and frequency. The vibration frequency is measured within a range of 0 Hz to 11 Hz, with a measurement error of less than ±4%. Additionally, the sensor is able to measure three discrete amplitude values (10, 25, 40 mm) with a measurement error of ±3 mm. The sensor can working normally within a temperature range of 0 ℃ to 85 ℃. Furthermore, the sensor has power generation capabilities, with experiments revealing a maximum output power of 8.3×10^-7 W. Notably, when multiple sensors are used in parallel, the power generation capacity is significantly enhanced. These research findings provide new insights for the development of downhole sensors and downhole generators.