To compare and analyze the differences in pore structure characteristics of coal from Huainan and Huaibei, this study focuses on No. 13 coal from Liuzhuang Mine in Huainan mining area and No. 7 coal from Qidong Mine in Huaibei mining area. Using mercury intrusion porosimetry and low-temperature nitrogen adsorption methods, the pore structures were analyzed, and fractal theory was applied to study the fractal characteristics of the pore structures. The differences in pore structures between Huainan and Huaibei coals were compared and analyzed. The mercury intrusion results show that the total pore volume and specific surface area of No.13 coal from Liuzhuang are 3.488 mL/g and 0.02 m²/g, respectively, while those of No.7 coal from Qidong was 4.926 mL/g and 0.027 m²/g, respectively, with Qidong coal having a larger pore volume. Both coals show the largest pore volume in macropores and the smallest in mesopores. Low-temperature nitrogen adsorption results indicate that the specific surface area ratio of micropores in No.13 coal from Liuzhuang is 76.25%, showing the most developed micropores. The specific surface area ratio of small pores in No.7 coal from Qidong is 79.79%, showing the most developed small pores. Fractal analysis demonstrate that both coals exhibited fractal characteristics. From mercury intrusion data, the fractal dimensions of pores larger than 100 nm for No.13 coal from Liuzhuang and No.7 coal from Qidong are 2.805 6 and 2.756 7, respectively. From low-temperature nitrogen adsorption data, the fractal dimensions of pores smaller than 100 nm for No.13 coal from Liuzhuang and No.7 coal from Qidong are 2.727 5 and 2.037 2, respectively, all within the range of 2 to 3. This indicates that the pore structure of No.13 coal from Liuzhuang is more complex and heterogeneous, especially in the range of small pores and micropores, where the fractal dimension differences are more significant. This may be related to differences in maceral composition and mineral content, where vitrinite is the main component for pore development in coal and shows a positive correlation with pore fractal dimensions. Exinite and inertinite are not primary components for pore development and show a negative correlation with pore fractal dimensions. Uneven mineral distribution may increase the heterogeneity and complexity of the coal pore structure, thus showing a positive correlation between mineral content and fractal dimensions in the two types of Huainan and Huaibei coal samples.

The influence of hydrothermal fluids on fluid-rock interactions and hydrocarbon generation in basins is of great significance. The mineralogical and geochemical characteristics of hydrothermal activity in the black shale of the Wufeng Formation-Longmaxi Formation in southeastern Sichuan was investigated using advanced techniques such as large field splicing scanning electron microscopy, mineral quantitative analysis, X-ray diffraction, isotopes, and electron probes. The results show that non-metallic minerals such as barium ice feldspar, calcite, apatite, and barite, as well as metal minerals like sphalerite, pyrite, galena, and chalcopyrite, exhibit distinct characteristics of hydrothermal activity. The in-situ Sr isotope ratio of barite ranges from 0.719 76 to 0.723 94, with an average of 0.722 37. The carbonate mineral content is exceptionally high, up to 60%. Based on previous research, mineralogical and geochemical indicators for hydrothermal fluid activity in the Wufeng Formation-Longmaxi Formation of southeastern Sichuan were established, suggesting that hydrothermal fluids have detrimental effects on reservoir space.

Unconventional tight reservoirs are characterized by strong non-homogeneity, low resource abundance, low porosity and low permeability. Compared with onshore unconventional reservoirs, hydraulic fracturing of offshore tight gas reservoirs has greater safety risks greater and more operational difficulties, leading to greater difficulty in balanced reservoir modification. Therefore, deployment of horizontal wells for hydraulic fracturing development in offshore tight gas reservoirs requires precise evaluation of reservoir geomechanical characteristics, analysis of the fracturability of horizontal well sections, and fracturing of well sections with similar geomechanics, which can support precise, balanced and efficient development of offshore gas reservoirs. Taking a tight gas reservoir in offshore as the research object, in this study, an engineering fracturability analysis method based on brittleness and in-situ stress difference was proposed, and an engineering sweet spot prediction model was established by kernel density estimation method to estimate the probability density function and cumulative probability function of engineering fracturability. Based on the engineering sweet spot prediction, hydraulic fracturing segments were optimized to achieve a differentiated design of segment spacing. Based on the concept of integrated geological and engineering, hydraulic fracturing simulation and production prediction were carried out in this study. The simulation results verified the feasibility of hydraulic fracturing and the reliability of engineering sweet spot prediction in target reservoir, which provides a significant technical support for the optimization of horizontal well fracturing scheme and large-scale beneficial development of offshore tight gas reservoirs.

The injection head is the key equipment to drive the coiled tubing in the coiled tubing operation machine. A fault occurred during the operation of a LG450 injection head, and it was found that the chain drive system was seriously damaged after disassembly. The macro and micro morphology analysis of the chain drive system shows that there are arc-shaped scratches on the outer side of the gear teeth and inclined scratches on the tooth surface. The chemical composition test, hardness test and metallographic test were carried out on the sprocket teeth, and the results showed that the material met the process requirements. The finite element simulation of the meshing process of the sprocket and the chain is carried out. The results show that the contact pressure distribution is consistent with the friction marks on the tooth surface and side of the failed sprocket. It is revealed that the failure reason of the chain drive system of the injection head is the spatial intersection of the chain roller and the sprocket axis, and the abnormal meshing of the roller and the gear teeth. This study shows that the motion state of the sprocket chain will have an important impact on the safety of the injection head, which is of great significance to guide the design and processing of the injection head.

The flooding cap is the key equipment for the pre-commissioning of subsea pipeline. Its deep sea installation operation has high risks and strict requirements, which puts forward higher requirements for the safety performance of structural strength. In addition to bearing loads during installation, the flooding cap also needs to block huge internal pressure in the pipeline during pressure test. Its structural strength and bearing capacity directly affect the safety and reliability of the whole subsea production system pre-commissioning. The flooding cap used in a 1 500 m deep gas field in the South China Sea Lingshui area was taken as the research object. Based on the relevant standards of DNV and NORSOK, elastoplastic finite element modeling of the flooding cap and key pressure components was carried out to analyze the safety strength requirements under different working conditions. The results show that the maximum Von Mises stress of each component of the flooding cap is less than the allowable stress under lifting conditions, and the high stress is mainly concentrated at the bolt connection. Under the impact condition, the flooding cap simulation can meet the installation speed requirement of 0.5 m/s, and the overall structural strength can meet the relevant standards. Under pressure testing conditions, the pressure capacity of the flooding cap is calculated to be 823 bar, and the measured pressure during the pre-commissioning operation of the Linsgshui gas field in the South China Sea is 268 bar, which is far less than its pressure capacity, satisfying the finite element calculation results. The relevant research results can provide theoretical basis and technical reference for the design and field application of flooding cap.

The key factor to control the shape of salt cavern cavity is to control the depth of the interface between solvent and brine, and the accurate monitoring of the interface is the prerequisite for its control. The current two-phase media interface monitoring technology has the disadvantages of poor real-time performance and low precision. A special algorithm for two-phase media monitoring in cavity well was proposed. Distributed optical fiber was used to collect the temperature data in the vertical direction of the cavity, and the original temperature curves were respectively processed by local weighted regression analysis and Kalman filtering. Through the difference calculation of the treated curve, the region with the most obvious temperature difference was identified, and the interface position of the two-phase medium was preliminatively determined. Then, the temperature curve in the initial location area was processed by convolutional smoothing filtering, the weighted rate of change of the convolutional smoothing filter curve was calculated, the maximum value of the temperature change rate was found, and the specific location of the interface of the two-phase medium was finally determined. The algorithm was used to monitor the interface of two phase media under actual conditions. The experimental results show that the error of the measured data obtained by this system is controlled within 0.3 m compared with that obtained by neutron logging method. Compared with the traditional optical fiber monitoring technology, the proposed algorithm has the advantages of simple operation, high measurement accuracy and high reliability.

Aiming at the problem of determining the effective design range of parameters during the optimization design of planetary gear transmission system, the dynamic sensitivity of two-stage planetary gear transmission system parameters was studied. Taking the two-stage planetary gear transmission system of vehicle as the research object, the natural vibration model of the system was established by Lagrange, the vibration modal characteristics of the two-stage planetary system were summarized, the expression of the vibration energy of the planetary system was deduced, the distribution state and the law of the vibration energy transfer in the same order were studied, and the mode change mechanism of the natural frequency of the system was further explored. The vibration energy transfer essential of the system natural frequency mode transition triggered by parameter change was analyzed. The parameter sensitivity equation of the natural frequency of the system is derived, the influence law of the modal transition phenomenon on the parameter sensitivity was studied, and the dynamic change law of the natural frequency sensitivity with the change of the parameter value was revealed. The method of dividing the parameter sensitivity interval based on the modal transition phenomenon was proposed, which realizes the effective guidance for the selection of the variable value range in the optimization design stage.

To solve the problem of bearing fault and complex sound field environment, taking H7009C full ceramic angular contact ball bearing as the research object, the dynamic analysis model of full ceramic angular contact ball bearing was established, and the error of theoretical calculation and simulation of rolling body was compared to verify the validity of the model. Based on the transient dynamic analysis of the influence of inner ring fault on the bearing dynamic characteristics, the surface SPL (sound pressure level) of bearings caused by different faults was calculated, and the SPL characteristics of high-speed bearings were compared under the action of variable speed and variable load. The results show that the sound pressure level of the faulty inner ring bearing increases with the increase of speed, and increases first and then decreases with the increase of load. When the ratio of the lowest sound pressure level frequency to the vibration frequency is close to 0.75 or the ratio of the highest sound pressure level frequency to the vibration frequency is close to 4, it can be identified as an inner ring fault.

In the manufacturing process of wind turbine blades, gluing is an important part of ensuring the structural strength and tightness of the blades. In view of the low efficiency, uneven gluing, low quality of glue line and glue overflow on the surface of parts caused by the manual sealing and gluing operations commonly used in the gluing process of wind turbine blades, a kind of intelligent rubber shoe for wind turbine blade gluing with servo motor and reducer as driving components was developed, and the gluing process was introduced in detail. ANSYS analysis was carried out on the key components, and after simulation analysis, it was found that the structure of the intelligent rubber shoe could meet expectations. After experiments, it is verified that the shape of the rubber road is full, the two sides are smooth and flat, and the width and thickness of the rubber road meet expectations. The use of rubber shoes can not only reduce the work intensity of workers, but also reduce the use of 10% of the glue amount when gluing, and improve the efficiency and quality of gluing.

Due to the special double salient pole structure of switched reluctance motor, there will be large Torque ripple during operation. In order to reduce the peak current and torque ripple during phase commutation, a novel TSF (torque sharing function) control method is proposed. Firstly, considering the relation between torque and inductance, the exchange was divided into two subintervals by inductance boundary points, and different TSF curves were designed in different intervals. Secondly, with the increase of motor speed and load, the fixed overlap Angle will reduce the efficiency of the motor, and an online overlap Angle optimization control strategy was proposed. Finally, the simulation and experimental results show that compared with the traditional cubic torque distribution function, the torque ripple and current peak value of the proposed method are reduced by 3.6%, 12%, and 1.1 A, 3.2 A respectively at a load of 5 N·m and a speed of 500 r/min and 1 000 r/min respectively. The proposed method can effectively reduce torque ripple and current peak value.