The Transient Characteristics And Safety Analysis Of Carbon Dioxide Gas Pipelines In Shengli Oil Field

With the rapid development of global CO₂ pipelines, more and more attentions are paid on CO₂ pipeline transportation characteristic and transportation safety. CO₂ gas pipeline is the main research object. As a basis,to study pipe conveying fluid physical propertiers of the fluid transported are calculated. The transient conditions of CO₂ gas pipeline are simulated to achieve the changing characteristics of flow parameters such as temperature and pressure, during the transient operating conditions. The study of CO₂ pipeline risk assessment is the key point. The diffusion ranges of CO₂ gas pipeline after a leak are calculated and the influences to the health of humans and the environment of the diffusion are analysed, in order to provide technical basis for guaranteeing the pipeline safe operation.The flow safety of CO₂ gas pipelines is mainly analyzed in this article in the fields of the influence of impurities, the change of flow parameters under the transient conditions and diffusion characteristics after pipeline leakage. The physical parameters of pure CO₂ and CO₂ with a impurity are calculated using PR EOS. The effects of different types and different contents of impurities on the physical properties and phase characteristics are compared. Through optimizing calculation formula of CO₂ fluid saturated water content, PRSV EOS is selected to determine the minimum water content. At the same time, the hydrate formation conditions of binary mixture are studied. Combining with the foreign experience of CO₂ pipeline, the recommendations of fluid quality are given. Using the simulation software, the transient characteristics of CO₂ gas pipeline are calculated during block valves closure, leak or pipeline shutdown and restart,in order to get the changing rules of the flow parameters and analyse the characteristics of fluids from different sources. The calculation results shows that there are dramatic changes of the flow parameters under the unsteady states, the different types of impurities in the CO₂ fluid have some impact on the flow parameters’ changes under transient conditions, especially the presence of H2, which will affect the safe operation of pipelines in the end. As to the CO₂ pipeline risk assessment technology, the key research is focused on Shengli oil field CO₂ gas pipeline diffusion characteristics. Combined with CO₂ explosure limit concentration, the inlet boundary conditions are imported to the calculation software, to calculate the diffusion area. The important parameters such as the wind speed, spray angle, leak types and leakage rate are selected. The main parameter sensitivity are analysed to get the influence of different parameters on the diffusion characteristics. The leakage conditions leading to the most serious consequences are determined and the flow safety of the CO₂ gas pipeline is analysed. The research shows that the leakage and diffusion characteristics of CO₂ gas pipeline are mainly affected by wind speed, leakage rate, jet angle and the leakage type, the horizontal jet leads to the biggest diffusion range and the consequence of instantaneous leakage is more severe than continuous leakage. The safety distance of CO₂ pipelines should be determined according to the downwind diffusion distance under the most severe conditions.