Oil leakage caused by failure accident of submarine pipeline can harm marine environment and affect oil transportation. For different water flow velocities and leakage directions in the case of halfburial pipe, a 2D leakage under water model was calculated by flow filed analysis software FLUENT. The simulation results show that water velocities and leakage angles would effect oil diffusion underwater directly|greater diffusion would occur when oil leakage go against stream with 45°|with larger water flow velocity, more time would be spent for oil floating upon seaair surface, and larger effects on oil diffusion caused by leakage direction would be enhanced. The conclusions of the present work could provide reasonable basis to oil leakage emergency underwater .

When buried pipeline was running, there were many factors could cause shutdown phenomenon. This could cause serious economic losses. Oil temperature and soil temperature were the important parameters for pipeline shutdown security. So it was significant to study oil temperature field and soil temperature field for the safe operation of buried pipeline. It was simulated that the excavation area temperature during the shutdown of the pipeline. And the simulation was threedimensional. Calculation areas contained three parts: soil area, pipeline internal area and the excavation area. These temperature fields were changed after excavation. And the changes of these three areas were simulated. The safety shutdown time was obtained by pipeline internal oil temperature changes. The oil temperature was declined after excavation. The influence of excavation area was obtained by observing the oil temperature. The temperature decline reflected the influence range. The results provided a reference for the safety production.

The three dimensional model of the pipe leakage in the open ground was established and the grid refinement was made to aim at the highspeed leak areas. Using CFD commercial software FLUENT 6.3 for gas pipeline leakage process was simulated. The different wind speed, the influence of the initial velocity and leak mouth shapes (round and diamond) under the condition of leak were examined. The numerical simulation results showed that the wind speed had a great influence on jet angle on gas leak. The diffusion range increased with the diffusion height. The initial velocity had a great influence on jet height. The diffusion height increased with the initial velocity increasing. The wider range of hydrogen sulfide leak was circle leak mouth. The simulation results had certain significance for long distance natural gas pipeline leakage diffusion laws awareness and accident prevention.

Buried depth of pipeline has important effects on the temperature field and thermal characteristics of soil around the pipe. Corresponding to different buried depth, the temperature field of soil around pipeline was also different. With different buried depth of pipeline, the temperature field of soil around the pipeline was simulated and calculated by using water thermal coupling model and heat transfer model. The analysis of the calculation results of two models showed that the embedded depth had certain influence on the temperature field of soil around the buried pipeline, and so do moisture migration and the water phase transition. Comparing with the temperature difference obtained by the two kinds of models in the same temperature, the results show that with different buried depth, the influence of moisture migration and the water phase change also had different influence on the soil temperature. The shallower the buried depth of pipeline was, the bigger the difference of temperature of the two models in the same place was. In order to get actual calculation results, the moisture migration and the water phase as well as water heat coupling problems in calculating should be considered.

The heavy oil electric heat pipe tracing twodimensional unsteady model was established to analyze the influence and the laws of heavy oil pipeline safety shutdown time under the thickness of pipe insulation, the number of heating pipes and location parameters. The results show that in the case of a single tube with heat, when the pipe thickness was respectively 60, 70 mm, and 80 mm, corresponding security shutdown time was about 26, 30 h, and 34 h| in the case of double pipes heating, the change of the angle between the two tubes had the smaller impact on the safety shutdown time, and the safety shutdown time was about 36 h.