As a major risk source, slope in open-pit coal mine is one of the main challenges faced by mine safety production. Taking Wanyuan open-pit coal mine in Wuhai City, Inner Mongolia Autonomous Region as an example, based on detailed investigation of slope development characteristics, deformation and failure modes were analyzed, slope radar deformation monitoring was carried out, and early warning models were established, a monitoring and early warning platform was built to achieve risk control. The results show that the slope of Wanyuan open-pit coal mine involves reverse, cross and consequent rock slope and soil slope of dump, and its deformation and failure modes are respectively tensile fracturing, wedge failure, slip-bending and creep (-tensile cracking). There is a possibility of instability under the influence of mining, blasting, rainfall or unreasonable stacking. On this basis, in order to realize the monitoring of slope without blind area, two sets of slope radar were respectively installed at the stable bedrock on the northeast and southwest sides of the mine, and the slope safety grade was divided into four grades: blue (<3 mm/h), yellow (3~8 mm/h), orange (8~15 mm/h) and red (>15 mm/h). Combined with the organizational structure of mining enterprises, the slope safety management system from slope radar deformation monitoring data-early warning model-early warning platform-risk management and control are constructed, which can provide technical reference for the construction of regional coal mine safety production capacity.

CO₂ flooding is an important part of the CO₂ geological utilization process in CCUS(carbon capture, utilization and storage). The CO₂ flooding and storage project carried out in the Yanchang Oilfield has achieved good results in increasing production and storing CO₂. But the reasons of pipe string corrosion failure are still unclear during CO₂ injection. SEM(scanning electron microscopy), 3D confocal microscopy, EDS(energy dispersive spectrometer) and XRD(X-ray diffraction spectroscopy) were used to characterize the corrosion morphology of the gas injection pipe string in the CO₂ flooding and storage demonstration area of Wuqi Oilfield. The pipe string corrosion products are analyzed to clarify the reasons for pipe string failure caused by CO₂ corrosion. The results show that local corrosion dominated by CO₂ corrosion causes corrosion failure of the pipe string. Corrosion products include FeCO₃, high-priced oxides of Fe and a small amount of FeS. Continuous injection of low-temperature CO₂ cannot cause corrosion. However, the increase in wellbore temperature and the return of formation water caused by stopping CO₂ injection can create conditions for CO₂/H₂S corrosion in the pipe string. In addition, pipe string corrosion is accelerated when gas injection wells are converted into water injection wells. It is recommended to strengthen the sterilization and anti-corrosion measures for the pipe string during the period of stopping CO₂ injection and switching to water injection.

For the research on the characteristics and main controlling factors of volcanic rock reservoirs, core observation, casting thin section identification, physical property testing and logging data analysis were utilized to conduct the study on the characteristics, distribution and main controlling factors of the Carboniferous volcanic rock reservoirs in the Junggar Basin. The results show that in the Chepaizi uplift, the Carboniferous volcanic rock reservoirs mainly developed volcanic effusion facies, explosive facies, tuffaceous facies and volcanic sedimentary facies, and the lithologies are mainly andesite, basalt, volcanic breccia, tuff and tuffaceous sandstone. The reservoir spaces are classified into connected pore type, fracture type, fracture-pore type and pore-cavity-fracture type according to the configuration relationship between pores and fractures. Affected by lithology and lithofacies, weathering and leaching effects and tectonic actions, the reservoir properties have strong heterogeneity. The dominant reservoir lithologies are andesite, volcanic breccia and tuff. A three-layer weathering crust structure composed of clay layer, hydrolysis layer and weathering and leaching layer is developed at the top of the Carboniferous, which significantly improved the reservoir physical properties. Fractures are an effective supplementary factor for reservoir development. Different from the previous studies that mainly focused on characterizing the characteristics of the dominant volcanic rock reservoirs, based on the coupled controlling effects of lithology and lithofacies, weathering and leaching, and strike-slip faults on the reservoirs, it is innovatively recognized that two dominant volcanic rock reservoir development models, namely fault-block body and fault-fracture body, are mainly developed in the study area. The research results have certain guiding significance for the exploitation of the Carboniferous oil and gas resources from east to west in the Chepaizi uplift.

The sedimentary process and evolutionary model of crevasse fans are of great significance for predicting fluvial reservoirs and remaining oil potential. Taking the Dongyingzi fan in Liangcheng County as an example, based on satellite imaging and field geology, sedimentary features of Dongyingzi fan was analyzed. Using the SFM, the simulation gridding system, simulation parameters, and boundary conditions were designed to establish a numerical model of the crevasse fan. The plane distribution of sedimentary thickness, flow velocity and sand content at different numerical simulation stages were analyzed, as well as vertical sedimentary structure of the crevasse fan. The sedimentary model of crevasse fans was summarized to discuss its significance for Reservoir architecture. Research suggests that the crevasse fans consists of crevasse channels, composite proximal fans, and an distal fans. From a humid to an arid climate, the formation process of crevasse fans can be divided into four stages, which are river crevasse stage, proximal-fan forming stage, proximal-fan flourishing stage and diatal fan forming stage. As the flooding hydrodynamics decreases, crevasse channels, composite proximal fans and diatal fans are formed in sequence. The composite proximal and distal fans are sand-rich area, which are favorable types of sand bodies during the exploration. Crevasse channels are mud-rich area as the main type of interlayer. Composite proximal fans around the crevasse channels is the main site for residual oil enrichment in the later stage of hydrocarbon development.

The rheological parameters of drilling fluid have an important impact on accurately predicting the hydraulic parameters of deepwater and ultra-deepwater drilling wells. The rheological experiments were carried out on commonly used HEM(high efficient mud) drilling fluids and synthetic-based drilling fluids in the deep waters of the South China Sea under conditions of 4 to 210 ℃ and 30 to 180 MPa. The variation laws of rheological parameters such as apparent viscosity, plastic viscosity, and dynamic shear stress with temperature and pressure were revealed in a wide range of temperature and pressure. Based on the experimental data, nine existing rheological models were compared and evaluated. It was found that the Ross model is suitable for synthetic-based drilling fluid, and the Herschel-Bulkley model is suitable for HEM drilling fluid. On this basis, a general predictive model for rheological parameters of HEM and synthetic-based drilling fluids was created, which is applicable to alternating high and low temperatures, high and low pressures. The maximum error of this model is 11.95%, with an average error of 0.62%, which is better than existing models.The bottom hole pressure error is 0.28% when using HEM drilling fluid and 0.181% when using synthetic drilling fluid, which can meet the requirement of deep water drilling in the South China Sea.

In order to enhance the output performance of axial flow helical turbine drilling tools, it is crucial to conduct research on the structure and hydraulic performance of the turbine. Firstly, an analytical computational model for the hydraulic characteristics of two types of helical turbines, namely constant thickness blade and variable thickness blade, was established using calculus principles. Secondly, the blade profile equation was constructed to analyze the influence of helix angle on the hydraulic performance of the turbine. Finally, based on the design example of an underground helical turbine generator, the output performance parameters of the two types of helical turbines and the impact of helix angle were analyzed. Furthermore, a mud pulse generator was manufactured based on the optimized analysis results of the helical turbine, and indoor experiments were conducted to study the impact of different displacements on the power generation performance. The research findings show as follows. Under given conditions, the variable thickness helical turbine exhibits significantly higher hydraulic performance compared to the helical turbine with constant blade thickness. The turbine output characteristics curve sharply decreases as the helix angle of the blade increases. However, the decrease in turbine output characteristics becomes insignificant when the helix angle exceeds a certain value (approximately 30°). With 7 blade counts and a helix angle of 38°, the underground turbine generator reaches a maximum power of 300 W with a load of 8 Ω. Through indoor testing, the power of the generator meets the requirements of underground tools. This research provides a reliable power source for underground intelligent drilling equipment.

In order to study the erosion behaviour of the gooseneck pipe in the drilling fluid environment and the evaluation of the surface strengthening effect, the influence of the drilling fluid density on the erosion behaviour of the gooseneck pipe and the evaluation method of the surface strengthening of the inner lumen were investigated by the finite element simulation and analysis method. The results show that: the erosion rate of gooseneck pipe is the largest in the inner diameter of the bend, and the maximum erosion rate becomes larger with the density of drilling fluid becoming higher, but the maximum erosion rate still occurs in the inner diameter of the bend. The maximum deformation displacement can be effectively reduced by 34.23% after surface strengthening of the inner lumen of the gooseneck pipe. It can be seen that the effect of drilling fluid density on the erosion behaviour of the gooseneck pipe cannot be ignored, and surface strengthening can effectively reduce the maximum deformation displacement.

In order to solve the problem of difficulty in determining the optimal measurement points for bearing signal acquisition. Taking the NU306 bearing-housing system as the research object, the bearing housing to carry out multi-measurement points vibration test experiment. The local linear embedding algorithm was used to linearly reduce the multi-dimensional space data of the bearings to obtain the sensitivity matrix of the measurement point. The optimal position of the measuring point under varying load and rotation speed was studied when the inner or outer ring are defective. The results show that for bearings with outer ring failures, the optimal measurement point is the one closest to the location of the failure when the load or rotational speed increases. For bearings with inner ring failures, the optimal measurement point is the one at lower loads far from the center of the housing when the load or rotational speed increases. The results can provide an effective reference for the selection of measurement points under different operating conditions.

To further meet the plasma heating requirements of EAST (experimental advanced superconducting tokamak) device, NBI (neutral beam injection) system requires higher beam power. Accordingly, the EAST NBI laboratory has developed a 120 keV accelerator for this purpose. The analysis of the whole accelerator needs to be carried out from various perspectives such as beam optics, insulation support, active cooling and materials. Taking into account factors such as plasma parameters, electrostatic lens, voltage resistance between grids, and assembly errors, the numerical simulation program was utilized to beam optics analysis for the slit tetrode ion source accelerator. Beam trajectory, electric field strength distribution, and beam divergence angle were investigated and optimized to preliminarily determine the grid parameters of the new multi-slit accelerator. The accelerator obtains the beam with the minimum divergence angle of 0.6° in the vertical direction with perveance of 1.52 μp, meeting the design criteria for beam current intensity of 60 A and divergence angle below 1° of the ion source.

The switching of power devices in servo drive can lead to bus voltage ripple, which may result in performance degradation, electromagnetic interference, and harmonic issues in permanent magnet synchronous motor AC servo systems. To address these issues, the influence of the switching process of power device on the voltage ripple of bus was analyzed and studied for the DC power supply servo drive system. Firstly, based on the working principle of PMSM (permanent magnet synchronous motor)and SVPWM (space vector pulse width modulation) algorithm, the ripple current of the busbar capacitor was analyzed. Then, according to the law of charge conservation, the relationship between the busbar capacitance, busbar voltage and current amplitude under the seven-stage and five-stage SVPWM modulation was analyzed theoretically, and its simplified expression was given. Finally, the theoretical results were verified by simulation experiments.