Effective Removal of Asphaltene Deposition in Metal-Capillary Tubes

Abstract

Summary We describe asphaltene deposition and removal processes in metal capillaries. We induce asphaltene precipitation by adding an asphaltene precipitant, heptane, to a petroleum fluid. The mixture is then injected through a laboratory-scale capillary and allowed to deposit. We assess the reversal of the deposition by means of the use of two separate chemical treatments: (1) a strong organic acid surfactant and (2) an aromatic solvent. The strong organic acid surfactant, dodecyl benzene sulfonic acid (DBSA), was shown to completely dissolve asphaltenes by means of acid-base chemistry reactions at heteroatomic sites on the asphaltene molecules. We investigate the use of DBSA as an efficient removal agent, injecting it in a mixture of petroleum fluid after the deposit was already formed. An aromatic solvent, toluene, is also investigated in such a fashion to assess its ability in removing deposited asphaltenes. We find that DBSA can effectively remove asphaltene deposits within one pore-volume (PV) of injection and at concentrations roughly ten times less than that required by an aromatic solvent such as toluene. To the best of our knowledge, our current study is the first laboratory-scale investigation with surfactant chemicals to reverse asphaltene deposition in capillaries.