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 Bôas
Fávero 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
°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.
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