Effect of Brine on Asphaltene Precipitation at High Pressures in Oil Reservoirs

Abstract

In this study, the effect of NaCl, KCl, CaCl₂, MgCl₂, MgSO₄, and CaCl₂ salts in brine in the range of low (1000−5000 ppm) and intermediate (5000−40 000 ppm) salinity water on the amount and offset pressure of asphaltene precipitation was investigated. The measurements were performed at reservoir temperature (350.15 K) and high pressures (0−100 bar). The IFT (Interfacial Tension) values increased with pressure and a sudden increase was observed at a specific pressure namely, an offset pressure of asphaltene precipitation in APE (Asphaltene Precipitation Envelope). For all brines, the amount of IFT with increasing concentration was in descending order and after a minimum value it changed to uptrend. Likewise, similar results were obtained for the precipitated asphaltene amount. All the brines intensified the asphaltene precipitation. Monovalent cations like Na⁺ and K⁺ showed higher values of IFT and hence more asphaltene precipitation, however, MgCl₂ showed the least IFT, offset pressure and the amount of asphaltene precipitation.