Flow Simulation and Experimental Validation of Crude Oil Hydrate Plugging in Pipelines using PIPESIM (Published)
This research attempts to improve upon the performance efficiency of crude oil pipelines in an oil field in south-south, Nigeria, comprising of flow lines 1, 2 and 3 of lengths (9874.6, 9265 and 12313) meters respectively. All with uniform ID of 0.254m, coated with 0.042m thick polyethylene. The well heads inlet pressures are (69.96, 72.18 and 76.85) bars. Flow Lines (FLs) have flow rates of (845.42, 650.0315 and 792.66) stb/d respectively. Pressure drop of (6.8 10.73 and 12.5) bar were recorded accordingly on these flow lines, with a cumulative output value of 2288.12 STB/d. PIPESIM software was utilized to model and simulate the following (0.2035m, 0.254, and 0.305m) IDs as sensitivity parameters for maximum (5000stb/d), normal (3000stb/d) and minimum (1000stb/d) flow rate cases. Out of which 0.2035m with 0.0635m insulation thickness was selected, for satisfying the optimal criteria, such as maximum flow rate of 5000 stb/d, and EVR max of 0.35 specified by API RP 14E. Hydrate formed at 16.51oC and 68.94 bar on Flow Lines. Performing sensitivity analysis on (FL) 1 enhanced pressure drop by 27.04% and flow rate improved by 70.9%. Pressure dropped by 29.17% with a flow rate improvement of 50.45% on (FL) 2, while on (FL) 3 it dropped by 19.92% and flowrate improved by 75.9%. The optimal operational temperature was 28.22oC. While, the Simulation validation with experimental results shows, that inlet pressure of 68.94785 bars, slowly dropped along the length of the pipeline to 64.62061 bars at 9875.52m; giving a difference of 4.32724 bar. Also, the experimental loop inlet pressure of 69.94785 bars gradually dropped to 65.91679 bars at 9875.52 m length, giving a pressure difference of 4.03106bar. The hydrate formation temperature in the loop was 17.4931 oC while that of simulation was 16.5112oC given 0.9819oC difference. The RMSE computed between the simulated and experimental pressures were 0.0523873, meaning 5.2% errors exist and that computed between the two predicted temperatures was 0.025995, accounting for 2.60% error. The R2 value for simulation and the experiment are 0.9995 and 0.9737, indicating a stronger correlation.
Keywords: Hydrate, PIPESIM, Simulation, crude oil, flow assurance. experimental validation, flow optimization