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.