Simulations of asphaltene deposition in submarine pipelines by CFD

The transportation of heavy or waxy crude oils presents some special design problems, which must take into account the requirements for the control of asphaltene deposition on interior surfaces of the pipeline. With the asphaltene deposition of the crude oils, the effective cross-sectional area or flow passage of the pipeline will be shrunken continuously, which influences their flow properties and threatens their safe transportation. Therefore, the influence of asphaltene deposition on their flow properties should be known well to safely design and operate the pipeline. The focus in this paper is on the asphaltene deposition rate and the influence of the asphaltene deposition on flow properties. Simulations of heavy crude oil flow in different structural pipelines after various deposition patterns are presented using 3D CFD. The flow velocity of heavy crude oil increases with the reduction of the effective cross-sectional area of the pipe, which leads to its vibration and shorter service life. In the other hand, pressure and temperature in the shrunken effective cross-sectional area decrease with the increase of velocity, intensifying the asphaltene deposition and transportation difficulty. While flow properties vary depending on deposition patterns, flow rates and the pipe geometry. So the influence of asphaltene deposition on flow properties in different structural pipelines with various deposition patterns is diverse. The impact of deposition in bending and reducer pipelines is greater than that in straight ones. And the impact in serious deposition pipelines is greater than that in slight deposition ones. So flow properties change drastically in bending and reducer pipelines with serious asphaltene deposition, leading to rapid blockage of the pipelines. The results of this paper can provide a guide for safe design and transportation of heavy crude oil pipeline.