Perpustakaan Digital ITB

Tubing pickling is a well operation aimed at removing scale deposits from the inner surface of production tubing to restore flow efficiency and prevent operational damage prior to acidizing operation. In this study, a predictive model was applied to simulate acid consumption and magnetite (Fe?O?) scale removal during the tubing pickling process, focusing on determining the optimum pumping rate under various acid concentrations. The study examined six scenarios, combining three acid concentrations (15, 7.5, and 3 wt% HCl) with two magnetite scale thicknesses (0.01 and 0.001-inch), representing a range of possible wellbore conditions. Acid volume requirements were calculated based on the assumed scale thickness parameter, with magnetite evenly distributed along the tubing. For lower acid concentrations, additional volumes were determined through sensitivity analysis to ensure complete magnetite scale dissolution at a minimum operational pumping rate of 1 bbl/min. Results demonstrated that for 0.01-inch magnetite thickness, the optimum tubing pickling design was achieved using 15 wt% HCl at 3 bbl/min with a volume of 1052 gallons, while for 0.001-inch magnetite thickness, the optimum design used 7.5 wt% HCl at 1.8 bbl/min with 218 gallons. All optimum designs achieved more than 95% magnetite scale removal. Lower acid concentrations required significantly larger volumes to meet the same dissolution target, with 3 wt% HCl at 0.01-inch magnetite thickness requiring six times the acid volume of the base case (15 wt%). The analysis also revealed operational phenomena, such as the unexpected higher peak HCl concentration at 1 bbl/min in one of the cases, explained by early reaction saturation in the tubing. Such insights emphasize the importance of matching acid volume and pumping rate to the scale thickness and acid specification, preventing prolonged acid–metal contact that could damage the tubing’s base metal.