Investigation of Asphaltene Deposition at High Temperature and under Dynamic Conditions

Asphaltene deposition is one of the major flow assurance problems that can potentially deteriorate due to the current tendencies to produce from the deep-water environment or as a result of enhanced oil recovery operations based on miscible gas injection. The deposited asphaltenes in the wellbores and on the surface of the oilfield pipelines can impede the productivity of the wells significantly. The comprehensive understanding of the mechanisms and the techniques to control asphaltene deposition at high temperature and under dynamic conditions can help resolve this critical issue. Thus, it is imperative to develop reliable, straightforward, and inexpensive tools to investigate the asphaltene deposition tendency and the performance of asphaltene inhibitors in the laboratory. In this work, a new stainless steel packed bed column deposition system that was inspired by the work of Vilas Boas Favero et al. was successfully developed. The packed bed design allows the feasibility of investigating a variety of factors affecting the deposition process under a wide range of temperature (20-300 degrees C) and gauge pressure (0-3000 psi). The impacts of operating temperature, type of precipitant, degree of asphaltene stability, and chemical additives on the deposition tendency of asphaltenes were investigated. It was found that the solubility of asphaltenes, the diffusion of precipitated asphaltenes, and the formation of aged asphaltene aggregates were competing factors controlling the deposition of asphaltenes under different operating temperatures. Additionally, asphaltenes precipitated by n-pentane induced more deposition than those destabilized by n-heptane. The liquid-like deposits collected from the experiment with n-butanol provided evidence that stronger ability to retain the softness reduced their tendency to build up aged asphaltene deposition on the metallic surface. Variation of the precipitant-to-oil ratio showed that the rate of asphaltene deposition increased linearly with the driving force toward asphaltene precipitation. Furthermore, a comparison between the capillary flow loop and the packed bed column on the assessment of asphaltene inhibitors was conducted. It was found that higher dosage of the asphaltene inhibitor seemed to delay the onset of deposition but did not further reduce the amount of deposition. With this packed bed column operating at high-pressure and high-temperature conditions, advanced simulation tools to predict asphaltene deposition under more realistic production conditions can be developed. Also, it can be used to assess asphaltene deposition inhibitors and solvents to prevent and remediate the asphaltene deposition problems.