In the pipeline system for liquid carrying particle, local erosion wear broken has become the main damage mechanism of pipe in the fracturing operations of oil-gas engineering as a large number of particles continually impact on the inner surface of pipes. Computational Fluid Dynamics simulation was performed to determine the evolutionary process of erosion wear in tubing connector, which was the weakness of pipeline system, and a new way to predict the pipeline safety was provided. Based on the Euler method, the volume fraction of the particulate phase and interphase momentum exchange were included in the liquid flow equations due to the influence of dense particle on fluid flow, and the particle trajectory were calculated in the Lagrange frame by analyzing the forces from the interaction of liquid and particle and particles collision. With the erosion damage model, the erosion rate/depth in the connector was calculated to reconstruct the mesh model of shoulder with 5 tori. Torus 1 is closest to axis while torus 5 is on the outmost wall of the connector. During the erosion event, greatest erosion and hence surface deformation occurs on tori 1 and 2, and this affects the surrounding flow and particle movement. After 10 h, there was a dramatic drop in the maximum erosion rate, which illustrated a conservative prediction for pipeline service life if the initial erosion rate was used. A physical erosion experiment was also performed to identify the weight loss and erosion characteristic of the inner surface with erosion time of 55 h. It was observed that the erosion simulations provided relative errors within 18% for erosion length and weight loss compared to the experimental values and a valid simulation method for the erosion evolution was proposed to predict the erosion life of tubing connector.

To study the movement law of a plunger air lift and liquid discharge efficiency, this paper observes the plunger movement and leakage through indoor experiments, based on which the CFD method is applied to establish a numerical model with the same experimental conditions, and compares the simulation results with the experiments, verifies the feasibility of the CFD simulation, and optimizes the structure of the plunger, and researches the change rule of the bottom-hole pressure and the wellhead pressure in a 200 m long wellbore. The results show that the error between CFD simulation and experimental data is 12.5%. When the depth of the plunger groove is 10 mm, the width of each groove is 10 mm, and the number of grooves is 12, the leakage is minimal; in addition, to ensure the smooth lifting of the plunger, it is necessary to control the wellhead pressure and keep the pressure difference with the bottom of the well. When the wellbore pressure is 10 MPa, the wellhead pressure should be no more than 7 MPa, and when the wellbore–wellhead pressure difference is kept at a certain level (7 MP), the plunger cannot continue to move up when the wellhead pressure is more than 18 MP, so it is necessary to control the wellbore pressure as it cannot be too big and increase the wellbore–wellhead pressure difference as much as possible. The above study of the plunger lifting law provides a reference basis for the determination of the above research plunger process parameters.

As a vital unconventional oil and gas resource, the efficient exploitation of oil shale relies on breakthroughs in pyrolysis conversion technologies. Based on thermogravimetric analysis and related thermal analysis studies, this paper systematically reviews the technologies, kinetics and influencing factors of oil shale pyrolysis, following the framework of “rock properties—pyrolysis technologies and conditions—kinetic characterization—reaction and product formation—engineering factors and responses.” First, typical oil shale deposits, including the Green River (USA), Fushun and Maoming (China), Estonian Kukersite and Brazilian Irati, are compared in terms of kerogen type, mineral composition, oil yield and pyrolysis kinetic parameters. Rock properties are shown to be the fundamental determinant of pyrolysis behaviour. Second, the characteristics of surface retorting (gaseous/solid heat carriers) and in situ pyrolysis (conduction, convection, radiation and reaction-heat heating) are summarized, emphasizing that experimental observations from surface retorting cannot be directly extrapolated to the in situ scale. Third, the applicable conditions and limitations of the Arrhenius, Coats–Redfern, Friedman, FWO and KAS methods are systematically compared. Isoconversional methods (Friedman, FWO and KAS) are shown to effectively capture the dynamic evolution of activation energy with conversion degree, making them more suitable for characterizing the multi-stage and heterogeneous nature of oil shale pyrolysis. Furthermore, hydrocarbon generation pathways and product distribution patterns are analyzed from the perspectives of pyrolysis staging, primary kerogen conversion and secondary cracking. Secondary cracking is identified as the critical process governing oil composition under high-temperature conditions. Finally, the effects of particle size, heating rate, pyrolysis temperature and pressure on product yield and composition are discussed. Future research should advance from “kinetic parameter calculation” toward “product yield prediction,” providing theoretical references for multi-field coupling simulation and engineering-parameter optimization of in situ oil shale pyrolysis.

Aiming at the problem that casing deformation can easily occur in tight oil horizontal well fracturing, based on the rock mechanics experiments and probability statistics, the distribution characteristics and law of the near-wellbore stress field of the reservoir in STH M56 were solved and analyzed by using the finite element modeling numerical method. The research shows that (1) the max/min horizontal stress ratio of the M56 tight oil reservoir is 1.2, the difference is less than 8 MPa, and this characteristic condition is more conducive to the formation of complex fracturing network in the reservoir during fracturing. (2) In M56, the Mises stress isoline near the borehole is symmetrically distributed. Stress concentration has four dangerous points (30°, 150°, 210° and 330°); a sector-shaped high dangerous stress zone is formed along the four dangerous points. As the pumping pressure increases, the vertical Mises stress first increases and then decreases, while the horizontal Mises stress first decreases and then increases. The max-Mises stress at the casing wall is linearly and positively correlated with the stress uniformity coefficient. When the pumping pressure is 80 MPa, the Mises stress exceeds the safe pressure limit of the casing. A pumping pressure of 70 MPa fracturing is the safe pumping pressure for the reservoir casing. (3) It is found that the 90° and 270° horizontal fixed plane perforations can avoid the dangerous stress zone, increasing and decreasing the injection flow rate of the fracturing pump step by step ( ) at the start and stop stages of fracturing; the control of the pump pressure during the whole process of fracturing is within 70 MPa, which can prevent the casing deformation.

Erosion damage in bend is severe due to solid particle repeated impact on the inner wall. A method of liquid-solid coupling simulation for predicting erosion in bend is investigated. Previously, on the assumption that wall thickness of model is unchanged during erosion, erosion rate, erosion site in bend was simulated based on Euler-Lagrange approach and available erosion prediction model. By solving the Euler model for fluid flow and Lagrange model for particle subsequently, move trajectory, impact force, impact angle were calculated for each particle. However, the simulation did not include the influence of reduced wall thickness on the flow field when the erosion is severe, which would affect the movement of particles entrained in the fluid in succession. As a result, dynamic meshes are used in simulation to update the computed model transiently according to the erosion deformation, which includes the interaction of structure and fluid. Compared with previous simulation, fluid-solid coupling simulation is feasible to improve the erosion prediction.