(74e) Understanding the Effect of Inhibitors on Controlling Asphaltene Precipitation and Aggregation Phenomena

Understanding
the Effect of Inhibitors on Controlling Asphaltene
Precipitation and Aggregation Phenomena

Mohammad Tavakkoli^{1, 2}, Miguel
Garcia-Bermudes¹, Ariana Melendez¹, Caitlin Garcia¹,
Sarah Correa¹, Quinton Cox¹ and Francisco Vargas^1, *

1. Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas, USA.

2. Department of Chemical and Petroleum
Engineering, Sharif University of Technology, Tehran, Iran.

* fvargas@rice.edu

Asphaltenes tend to precipitate and deposit during oil production and clog the
wellbore and production facilities. This can cause an excessive downtime and
high cleaning costs running into several millions of dollars. Therefore, a
mitigation technique such as using asphaltene
inhibitors is necessary. To improve the efficiency of the current inhibitors or
develop a new generation of asphaltene inhibitors, it
is necessary to study the effect of inhibitors on controlling asphaltene precipitation, aggregation and deposition
processes.

In this study, we have investigated the effect of different
commercial inhibitors on asphaltene precipitation and
aggregation processes. It needs to be clear whether the inhibitors make changes
on the asphaltene precipitation such as changes on
the onset and the amount of precipitation or they only affect the asphaltene aggregation process by dispersing asphaltene aggregates and changing the particle size
distribution. To do so, three commercial inhibitors were used and asphaltene precipitation and aggregation phenomena were
studied using two different techniques: ?Direct spectroscopy? and ?indirect
method?. The experiments were conducted at ambient conditions and asphaltenes were precipitated using light normal alkanes
such as n-pentane and n-heptane. Using direct spectroscopy technique, we found
that asphaltene particle size distribution changes by
adding the inhibitors to the crude oil especially at high amount of the added
precipitant. The inhibitors break the asphaltene
agglomerates and form smaller size aggregates. Indirect method, which is a
combination of gravimetric and spectroscopy methods and is a novel technique
for studying asphaltene precipitation, showed that
there are no changes on the onset and the amount of asphaltene
precipitation when the inhibitor is added to the crude oil prior to adding the
precipitant. Therefore, one can conclude that the commercial inhibitors can
disperse the already precipitated and aggregated asphaltenes
and form smaller particles, but it is still under investigation whether this
working mechanism of inhibitors always prevents asphaltene
deposition in the wellbore or may worsen the problem in some cases.

Keywords: Asphaltene Precipitation, Asphaltene Aggregation, Commercial Inhibitors, Indirect
Method.