# Numerical Simulation of Oil Pipeline Leakage Diffusion in Dashagou Yellow River Crossing Section
## 5 Conclusions  
Through numerical simulation of the river crossing pipeline in the Yellow River section of the Dashagou, the following conclusions were obtained from the analysis of resistance coefficient, apparent velocity, groundwater solute transport and surface water oil spill. The leakage flux is 0.05 kg/s, 0.13-0.15 kg/s and 0.6\(\sim\)0.62 kg/s when the radius of the leakage opening is 10 mm, 20 mm and 50 mm, indicating that the leakage flux is smaller and the leakage time is longer in the pulverized sandy soil/sandy pulverized soil, and the corresponding risk of leakage and the emergency response window time are relatively small. Under the same radius of the leakage opening, the overall effect of the location of the leakage opening on the leakage flux is not significant. Under the same leakage pressure condition, the size of the leakage port has a more significant effect on the leakage volume. Combined with the conclusions reached by [PERSON], [PERSON] and [PERSON] et al. [34], who used high-density resistivity imaging to investigate the light non-aqueous phase liquid transport patterns in low-permeability clays as a reference, the following conclusions are drawn: The effect of soil lithology properties on fluid distribution is crucial; usually the finer the particles, the greater the resistance, the stronger the oil leakage pressure energy attenuation and the smaller the diffusion distance and range. During the oil leakage in the crossing section of the Dashagou, when the oil equivalent of the leakage becomes extremely large, its flow trend may still be affected by gravity, and its final flow trend is still dominated by vertical downward movement. The difference in the soil lithology's blocking effect on the leakage flow is very significant. The simulation results for a 24 h period indicate that the maximum distance of vertical upward oil diffusion is approximately 8.14 m, while the range of lateral upward diffusion over the same period is approximately 22 m\({}^{2}\). These findings suggest that the range of lateral upward diffusion is not significant. Given that the distance of vertical diffusion is larger, it can be deduced that the main tendency of the oil leakage in the Dashagou region is vertical downward transport and diffusion. The apparent flow rate of oil leakage decreases gradually, the soil volume affected by the leakage is 22.19 m\({}^{3}\) in 24 h, the oil leakage is 5.67 tons, and the apparent flow rate of \(Z\)-axis is 0.34 m/h. Due to the resistance of the sandy chalk layer, the apparent flow rate is 1 cm/h after 14 h of leakage, and the flow rate is stable in a longer period of time. Regarding the process of diesel oil migration through the groundwater, the flow rate is the same slow decay due to the leakage port being extremely small. After a long time of leakage into the groundwater, it is still undetected, the leakage of oil has not gone through the effective leakage of pollutant removal measures, the groundwater solute-phase pollutants can enter the Yellow River after 730 days, and the Yellow River water quality can produce a more significant impact on the environment. The groundwater solute-phase pollutants of crude oil can enter into the Yellow River after 850 days of groundwater transport under the condition of a continuous source strength of 10 mg/L and can reach quasi-static equilibrium when migrating downward about 190 m. The pollutants do not enter into the Yellow River but form a stable equilibrium state in the Dasha Gully; due to the lower solubility of crude oil in water, compared with the groundwater migration of benzene, the migration capacity of crude oil solute-phase pollutants is significantly higher than that of benzene. Compared with the groundwater transport of benzene, the solute-phase pollutants of crude oil in the groundwater dynamics process have a significantly weaker migration ability. The oil spill occurred in the Yellow River crossing section during the dry water period from the beginning of the oil spill to 40 min later.