In order to research of submarine pipeline operation in the process of fluid flow area and transportation capacity variation. To Bohai x oils likely lost sea pipe as an example, through the deposition properties of sand (mud) simulation experiment and critical deposition velocity theory calculation, and according to the actual temperature drop, IR drop analysis, confirmed the possibility of reduced diameter tube sand deposition and the pipeline. Research shows that: the seabed oil and gas pipeline in the long run, sediment deposition in the pipeline caused reduced diameter pipeline, crude oil flow area is reduced, increase the pressure drop, oil capacity of declining.S#$NLKeywords：submarine；long distance oil pipeline；shrinkage；Simulation experiment； calculation analysis； BohaiS