Improved Mechanisms of Asphaltene Deposition, Precipitation and Fouling.

Asphaltenes are compounds present in petroleum crude oil. They are called the "cholesterol of petroleum" because they can precipitate and form deposits that detrimentally affect the crude oil production by precipitating in reservoirs or during transport, and by fouling process equipment. It is important to determine the exact mechanism of precipitation and deposition of asphaltenes to adopt the best strategy to mitigate asphaltene deposition. Several models of asphaltene precipitation and deposition have been proposed over the years. However, they do not take into account the fact the asphaltenes are "polydisperse", i.e. they contain many different molecules which vary in mass and chemical functionality. This program aims to correct this simplification to obtain a more realistic mechanism of asphaltene precipitation and deposition and identify the sub-fraction of asphaltenes responsible (the "bad guys"). This goal is completed by research activities on how the asphaltene self-associate and interact with chemical inhibitors, injected during production to inhibit asphaltene precipitation, deposition, and fouling. The project requires a manifold of advanced instruments to characterize asphaltenes and determine their properties. Therefore, an international consortium of different research groups was established: -Ugelstad Laboratory at NTNU/Norway -University of Pau/France -University of Alberta/Canada -University of Parana/Brazil Each group is specialized in a specific domain and their competences and knowledge are complimentary to each other. The program is funded by the Norwegian Research Council and the following industrial sponsors: AkzoNobel, BP, Canada Natural Resources, Nalco Champion, Petro-bras, Statoil and Total. The sponsors bring their expertise and provide crude oils and chemical inhibitors to be studied. The results obtained in the project will allow us to better assess if asphaltenes can precipitate, form deposits and foul production facilities during crude oil production and transport: -A new fractionation method has been developed to separate asphaltenes into different fractions differing in their chemical properties. Measurements show that only one of these fractions is a likely candidate for the precipitation/deposition/fouling risks associated to asphaltenes. -A new apparatus, called Quartz Crystal Resonator has been built that allow to determine at which pressures and temperatures, asphaltenes precipitate. Consequently, it will be possible, by characterizing a crude oil sample with this apparatus, to determine if asphaltene will precipitate and, therefore, could give problems, during production. The program has also allowed to improve our knowledge on different aspects of asphaltene properties: -The mechanism by which asphaltene molecules interact with each other and form objects of different size (from the nanometer to the micrometer size) is now better known. This new knowledge will allow to develop better models to help predicting asphaltene precipitation/deposition/fouling risks. -The interactions between asphaltenes and chemical inhibitors has been studied as well as how the inhibitor prevents the adsorption or deposition of asphaltenes on stainless steel (mimicking pipeline surface). -The experimental work performed in the program was complemented by modelling activities to strengthen the conclusions obtained. The modelling technique is called Dissipative Particle Dynamics. This technique represents groups of atoms as particles interacting with each other. As a whole, we anticipate that the new competences and methods developed in this program will allow us to better predict asphaltene precipitation, deposition, and fouling and develop new and improved chemical inhibitors. One of the sponsors of the program has stated that the program has given them new insight into asphaltene phenomena. The data generated in the program will be used as input in the design of new improved inhibitors, in discussions with their customers and for marketing purposes. Different strategies were carried out to disseminate the results: -Since the start-up of the program, research partners have reported the results to the sponsors to bi-annual meeting hosted by one of the partners or sponsors. -All the results were published in renowned international scientific peer-reviewed journals (28 articles published). -The results were presented in national and international conferences as keynote lectures, oral, and poster presentations (total: 12). The program will be continued by better quantifying the interactions between asphaltenes and chemical inhibitors and the correlating the solubility of asphaltenes at ambient and high-pressure conditions to reduce the cost of asphaltene precipitation/deposition/fouling testing.

Asphaltenes represent heavy polar colloidal fraction in crude oils. Due to pressure variation, processing and production conditions of different crude oils, asphaltenes can precipitate and form organic deposits in oil reservoirs, in wells and on equipment s and pipe walls and induce fouling in general. These deposits can cause serious and costly irregularities in production and transport of oil. Several models have been proposed to explain these irregularities but they all suffer from inacurrate asphaltene chemistry. It is by now evident that in order to fully understand and account for the above-mentioned phenomena, the effect of the polydisperse functionality of the asphaltenes must be understood. In order to follow up the primary objective, the project will combine small scale tests both at atmospheric and elevated pressures, modelling and capillary loop tests. Finally based on the accumulated knowledge, chemical modifications together with inhibitors will be developed in order to minimize the molecular affinity to pipe surfaces and their interactions in solution. The project will be executedby four academic research groups with a strong industrial support. Each group is specialized in a specific domain and their competences are complimentary. They are : -The Ugelstad Laboratory/NTNU, Norway -The Department of Chemical Engineering/University of Alberta, Canada -The Laboratory of Complex Fluids and their Reservoirs/University of Pau,France -The Laboratory of Emulsions/Federal University of Paraná, Brazil Ugelstad Laboratory, the University of Alberta and the Federal University of Paraná have complementary competences in colloidal fluids at atmospheric pressure and University of Pau in high pressure and temperature characterization.