Application of natural fatty acids as asphaltenes solvents with inhibition and dispersion effects: A mechanistic study

Asphaltenes precipitation, flocculation, and deposition may cause severe damages to reservoirs, wells, and production facilities. Asphaltenes precipitation may occur during all production stages, e.g., primary depletion, acidizing jobs, and the injection of rich gas or carbon dioxide. The organic deposition removal is considered a costly workover job with the current oil prices. The solvents that are usually used are toluene and xylene, which are considered carcinogenic and toxic chemicals. Also, the use of a dispersant to inhibit the organic deposition can be expensive, as it is required for the life of the well. The objective of the present study is to propose new types of chemicals that can be primarily used as asphaltenes solvents while they can exhibit asphaltenes inhibition and dispersion effects as well. The efficiencies of these natural fatty acids were compared with the effectiveness of the combination of nonylphenol formaldehyde resin as a synthetic dispersant and toluene, in terms of the inhibition of asphaltenes precipitation as well as dissolving and dispersion of deposited asphaltenes. A Kuwaiti crude oil sample was used in this study with an API of approximately 38 degrees and asphaltenes content of 2 wt%, yet showing severe asphaltenes precipitation problem during production stage. The effects of the tested chemicals on the behavior of crude oil and its asphaltenes content were evaluated using infra-red spectroscopy, UV-vis spectroscopy, and dynamic light scattering. The results of this study show that the natural fatty acids can inhibit asphaltenes precipitation and disperse aggregates of asphaltenes. Asphaltenes size distribution was decreased from 10 mu m in the neat sample to 1-2 mu m in the treated solutions. Moreover, the asphaltenes precipitation onset point was delayed after the model oil was treated with these fatty acids. The primary advantages of these fatty acids when used as solvents are their high flash points, green nature, and abilities to inhibit asphaltenes precipitation and disperse asphaltenes aggregates. The main working mechanisms for these chemicals were determined to be acid-base reactions and steric hindrance through aliphatic side chains. Despite of their lower efficiencies compared to nonylphenol formaldehyde resin when used solely in the treatment, since these chemicals are naturally occurred, environmentally friendly, and cost effective, they would be proper substitutions for the commercial dispersants.