Damage to insulation layer of buried oil pipelines will significantly change the distribution of the soil temperature field around the pipeline, thereby affecting the thermal performance and operational safety of the pipeline. Based on the theory of multi?physics field coupling, this study establishes a three?dimensional steady?state heat transfer model to quantitatively analyze the temperature drop characteristics of the pipeline and the evolution law of the soil temperature field under different soil types (clay, loam, sand). The model was solved using ANSYS Fluent 2022, with the effect of moisture intrusion considered. The numerical simulation results show that in sand soil, the critical number of segments with complete insulation damage is 15 segments (each 100 meters), corresponding to a critical damage distance of 1.5 kilometers. According to this critical distance, initial monitoring points are set, and a total of 56 monitoring points are required for an 80?kilometer pipeline. The temperature at each monitoring point shows a non?linear decreasing trend along the pipeline. The outlet temperature at the 28th monitoring point (42 kilometers away) drops to the wax precipitation point of 45 ℃ for the first time. The "critical distance segmented monitoring method" proposed in this study can achieve accurate monitoring of the pipeline damage status in the sand soil section, providing technical support for the safe operation of the pipeline.

Chemical wax inhibitors are widely used in the field of waxy crude oil extraction and transportation, providing an important guarantee for the safe and efficient operation of the waxy crude oil extraction and transportation process. At present, many basic experimental studies and numerical simulation studies on chemical wax removal have been carried out to explore the types, mechanism of action and application scope of chemical wax inhibitors. Common chemical wax inhibitors mainly include fused?ring aromatic hydrocarbon type wax inhibitors, surfactant type wax inhibitors, high molecular polymer pour point depressant type wax inhibitors and new nano?particle wax inhibitors. They usually prevent the association and deposition of wax crystals by water film theory or wax crystal modification theory. Among them, fused?ring aromatic hydrocarbon wax inhibitors, surfactant wax inhibitors, and polymer pour point depressant wax inhibitors have disadvantages such as poor environmental friendliness, poor environmental adaptability or poor economy. The focus of future research should be to explore green, efficient and general?purpose chemical paraffin inhibitors, use nanoparticles to improve the performance of paraffin inhibitors, and continue to explore more environmentally friendly chemical paraffin inhibitors.

When crude oil is extracted from oil wells, associated gas will be generated, and natural gas hydrates will be generated in high pressure and low temperature environments, which will block the transportation pipeline. Therefore, it is of great significance to study the hydrate formation in oil sand system (that is, the crude oil?containing system) and the pure quartz sand system (not including crude oil). The formation of methane hydrate and the final gas consumption in the oil sand system) and the pure quartz sand system were studied under the conditions of initial pressure of 4.00, 6.00, 8.00 MPa, quartz sand particle size of 20, 30, 60, 80 mesh, and constant temperature.The results show that in the oil sand system and under the same initial pressure conditions, the smaller the particle size of quartz sand, the shorter the induction period for hydrate formation, and the greater the rate of hydrate formation; the effect of particle size on the final gas consumption for hydrate formation It is found that as the particle size of the quartz sand decreases, the gas consumption first increases and then decreases. When the particle size of the quartz sand is 60 mesh, the gas consumption reaches the maximum, and its value is 0.19 mol. At the same time, the hydrate formation in the oil sand system and the pure quartz sand system was compared. The results show that, due to the presence of SDS (sodium dodecyl sulfate) solutions in the two systems, there is little difference in the formation rate of hydrates; the final gas consumption in the oil sand system is less than that in the quartz sand system under the same quartz sand particle size. This indicates that crude oil has an inhibitory effect on the formation of hydrates. In the oil sand system, it is found that the higher the pressure, the more favorable the formation of hydrates.