Impact of Water Cut on Asphaltene Deposition Tendency

Abstract

A systematic lab study was conducted to investigate the impact of water on asphaltene deposition tendency, with emphasis on percent water cut and ion composition. Two crude oils from Gulf of Mexico with different properties were applied as probe oils to study asphaltene deposition using a capillary deposition flowloop. Distilled (DI) water and a synthetic brine with 6.5% NaCl salinity were used to create water-in-oil emulsions to study the impact of water on asphaltene deposition. For one oil sample, it was observed that adding as few as 2 vol% DI water to the oil/n-heptane mixture could cause as much as 56% reduction on deposition rate. When DI water was replaced by the synthetic brine, the reduction in deposition rate decreased. However, when the synthetic brine also contained ferric ion (Fe 3ϩ ) or aluminium ion (Al 3ϩ ), the deposition rate was restored back to the same or an even higher level as the base case without water. ICP analysis revealed that deposits collected from tests with ferric ion or aluminium ion also contains significant amount of those two ions, plus remarkable increases on other divalent ions including Ni and V. In the second oil, adding 10 -20% synthetic brine also reduced deposition rate 10 -25%. With only 10 ppm ferric ion in the brine, the deposition rate for the second oil was largely restored back to the original level without water.

Investigating the Effect of Salinity on the Behavior of Asphaltene Precipitation in the Presence of Emulsified Water

“…Wang et al in 2014 referred to the chelating effect in their investigation and declared that the presence of cations in the system promotes asphaltenes agglomeration by ions-bridging or chelate formation and accelerates asphaltenes deposition in a flow loop. 15 Demir et al in 2015 expressed the similar conclusion and said that in the presence of Ca 2+ and Na + , the agglomeration tendency of asphaltenes is increased. They attributed this phenomenon to the ion-bridging feature and declared that in the presence of cations with the higher charge, this tendency increases.…”

“…The same result was attained in other studies. Wang et al in 2014 referred to the chelating effect in their investigation and declared that the presence of cations in the system promotes asphaltenes agglomeration by ions-bridging or chelate formation and accelerates asphaltenes deposition in a flow loop . Demir et al in 2015 expressed the similar conclusion and said that in the presence of Ca 2+ and Na + , the agglomeration tendency of asphaltenes is increased.…”

“…The results showed that the deposition rate in the presence of Ferric ions and aluminum ions increased more than the case that there was no water in the system. 15 In 2016, Demir et al studied the stability of asphaltenes in the presence of CaCl 2 and NaCl 2 salts. Five different crude oils were probed with a microscopy method.…”

“…To explore the effect of cations with high charge, Ferric ions (Fe 3+ ) and aluminum ions (Al 3+ ) were added to the system. The results showed that the deposition rate in the presence of Ferric ions and aluminum ions increased more than the case that there was no water in the system . In 2016, Demir et al studied the stability of asphaltenes in the presence of CaCl 2 and NaCl 2 salts.…”

Critical Review of Underlying Mechanisms of Interactions of Asphaltenes with Oil and Aqueous Phases in the Presence of Ions

“…Wang et al stated that asphaltene onset did not significantly change in the live oil-containing water. Tharanivasan et al conducted a series of experiments to examine the change in the onset of asphaltenes in a system composed of water and diluted crude oil with heptane (Athabasca bitumen and Gulf of Mexico crude oil).…”