Development of a new chemical solvent package for increasing the asphaltene removal performance under static and dynamic conditions

Abstract

In this work, a new solvent package (named TPMDS) for asphaltene removal under static and dynamic conditions was developed through a set of experiments. TPMDS consists of toluene, pyridine, methanol, surfactant dodecylbenzenesulfonic and sodium hydroxide. The optimum concentrations of TPMDS components were determined based on the efficiency evaluation of the chemical reagents to eliminate the asphaltene precipitation under static conditions. The highest effectiveness of the developed solvent package under static conditions was found to be 98%, which was observed at a soaking time of 6 h and a mass concentration of 1%. TPMDS had high performance (more than 97.5%) for asphaltene removal in four different oil samples containing various asphaltene concentrations. The results of the turbidity and dissolution rate experiments of asphaltene in the presence of TPMDS and toluene showed that the performance of TPMDS for asphaltene removal is significantly better than toluene. In addition, core flood tests were carried out with the use of TPMDS and toluene. Pressure drop due to asphaltene precipitation in the carbonate core samples was reduced eight times using the developed solvent package. The damaged permeability due to asphaltene deposition was 51% of the initial rock permeability before injection of any solvent. The results of core flood tests showed that the rock permeability has reached about 94% and 71% of the initial permeability after injection of TPMDS and toluene, respectively. Despite the increase in the amount of asphaltene precipitation in the core samples by increasing injection rate, the efficiency of the developed solvent was not decreased by changing the injection rate since the performance of the TPMDS was improved by the appearance of a synergistic effect for asphaltene dissolution. Furthermore, oil viscosity reduction with the use of TPMDS was more significant than with the use of toluene. The corrosion rate of the metal samples in the presence of the developed solvent package solution was less than 0.08 mm/year in a temperature range from 25 °C to 100 °C, which is less than an acceptable threshold corrosion rate of 0.1 mm/year. Moreover, the results of field analysis showed that the oil production rate could be enhanced by 3.3 times after treatment by TPMDS. Asphaltene removal effectiveness in the production wells using the industrial reagent and TPMDS has reached 84 and 96%, respectively. The rock permeability after treatment by TPMDS was increased by about 290%. TPMDS can be used for asphaltene removal in the near-wellbore region, production equipment, and tubing.