An Approach for Simulation of Paraffin Deposition in Pipelines as a Function of Flow Characteristics With a Reference to Teesside Oil Pipeline

Abstract

Abstract Paraffin deposition is experienced in pipelines during transportation of oil when the oil temperature is cooled below its paraffin deposition temperature. The formed paraffin crystals in the bulk flow is believed to be transported by molecular, Brownian diffusion and shear dispersion(1,2,3). Gravity settling mechanism in previous work in our laboratory has shown to contribute to the total paraffin deposition, however, to a lesser extent than the above mentioned mechanisms. The work done here demonstrates that the paraffin deposition by molecular diffusion mechanism is a dominant one. This is in agreement with other previous studies done on the paraffin deposition(4,5). In this study, however, experimental design was made to quantify this statement. The paraffin concentration gradient (dc/dr) is the driving force of the molecular diffusion mechanism (where r is the pipeline radius). In pipelines the cooling rate is one of many other factors that affect the paraffin deposition profile. Equipment was designed to simulate the flow characteristics at pipeline pressure. A three dimensional model was developed for paraffin deposition rates at various flow regimes. The developed experimental approach and the designed equipment for simulating the pipeline conditions are presented in this paper. Introduction The Main mechanisms by which the paraffin deposition occur are molecular diffusion, shear dispersion and Brownian diffusion(1,6). These mechanisms are the driving forces for the transportation of dissolved and/or precipitated paraffin to the pipeline wall. The gravity settling mechanism has also been identified(7). However, molecular diffusion is the predominant mechanism(1,7).