Experimental study of the effect of commercial dispersants on the precipitation, aggregation and deposition of asphaltenes
Melendez Alvarez, Ariana A
Vargas, Francisco M.
Master of Science
Asphaltene precipitation and subsequent deposition is a potential flow assurance problem for the oil industry nowadays. Moreover, because oil production is moving to more difficult production environments – e.g. deeper waters – or is focusing on extracting residual oil using enhanced oil recovery techniques, the significant changes of pressure, temperature and/or composition can aggravate asphaltene deposition problems. One of the most common strategies to prevent or at least reduce asphaltene deposition is the utilization of chemical additives. However, there are still several unresolved challenges associated with the utilization of these chemicals: First, the experimental conditions and results obtained in the lab are not always consistent with field observations. Also, in some cases these chemical additives seem to worsen the deposition problem in the field. Therefore, there is a clear need to revisit the commercial techniques used to test the performance of asphaltene inhibitors and to provide a better interpretation of the results obtained. In this work, a technique based on NIR spectroscopy is presented to evaluate the performance of three commercial asphaltene dispersants. The results are also validated using a digital optical microscope. This technique is faster and more reproducible compared to available methods such as Asphaltene Dispersion Test (ADT) and Solid Detection System (SDS). Also, unlike the ADT test, the proposed method can evaluate the performance of the dispersants in a wide range of temperatures and compositions. The chemical additive dosage, aging time and temperature effect on asphaltene aggregation process are also discussed in this manuscript. A new system to study asphaltene deposition on metal surfaces that offers advantages over capillary systems was developed. This new apparatus is based on a column packed with carbon steel spheres. The current version of this device operates at ambient pressure and has potential for the fabrication of a high-pressure system in the near future. The work presented in this dissertation will contribute to a better understanding of the variables that affect the performance of asphaltene dispersants, and the true effect these chemicals have on the complex multi-step mechanism of asphaltene precipitation, aggregation and deposition.