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Microscopic Investigation of the Effect of Low Salinity Waterflooding on Asphaltene Precipitation and Deposition Using Microfluidic Method

Salari, Amir Hossein | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56079 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Ayatollahi, Shahabodin; Mahani, Hassan
  7. Abstract:
  8. Water injection, as one of the conventional methods to increase the oil recovery factor has always been at the center of research works for Enhanced Oil Recovery (EOR). The conducted studies show that by controlling the amount and type of ions in the injected water, the recovery efficiency can be improved. In the meantime, most of the investigations are focused on the interaction between water/rock/oil to trace the wettability alteration. However, these interactions especially between the injected water and the oil phase, would lead to change of surface charge distribution of the reservoir rock. Besides, this effect can change some of the characteristics of the fluid phases, especially in the interfaces of oil and water. It has been shown that these changes can lead to organic and inorganic deposits in the reservoir rock. Therefore, it is very necessary to carefully investigate the mutual effects of water/rock/oil in order to prevent damage to the formation caused by the organic components especially the formation of emulsion and asphaltene precipitation. In this research, the effect of rock presence and the interaction between water/rock/fluid were investigated through both static and dynamic tests. In the static tests, a new experimental protocol was developed wherein water/oil and sandstone grains are mixed and after equilibration and centrifugation the amount of UV absorption of bulk oil is measured. Besides, the interfacial tension (IFT), pH, the amount of asphaltene deposition were measured through the static teses. The results showed that the amount of asphaltene deposition follows a non-monotonic (an increasing/decreasing) trend with salinity. In other words, at the low salinity conditions, the amount of asphaltene deposition increases, while at high salinities, this amount decreases. Also, in the dynamics part, by creating an oil/water flow in a Hele-Shaw cell and then injecting normal pentane to promote the asphaltene rich areas to precipitate, the emulsions and the amount of asphaltene precipitation for each of the salinities were visually quantified. Other parameters including contact time, volume percentage of water in the emulsion, the amount of sandstone grains in the mixture were also examined in this research work. The results of the IFT, UV absorption, emulsion stability (based on droplet images), zeta-potential and FTIR tests indicate the instability in the emulsion under the conditions of adding sandstone grains to the system, as well as an increase in the amount of asphaltene deposition due to the creation of additional physical surfaces in the emulsion for asphaltene adsoption and deposition. In these experiments, it was determined with the help of FTIR that in all conditions, the functional groups separated from the bulk oil are the same, and the emulsion created with twice diluted sea water in all the situations of making the emulsion causes the most asphaltene precipitation and the most stable state is the emulsion, which the IFT results are also indicative of this importance, and by examining the sandstones separated from the emulsion, it can be seen that by the increase in salinity, the amount of asphaltene deposition on the grains increases, and formation water causes the highest amount of adsorption on sandstone grains (1.437 micrograms). Also, it is shown in the dynamic studies that the amount of asphaltene deposition in these conditions is in full agreement with the dynamic conditions and the twice diluted sea water is a low salt water with the highest amount of asphaltene deposition compared to the total volume of the Hele-Shaw cell. The creation of a more stable emulsion compared to other emulsions in these tests, the amount of this asphaltene deposition determined to be 7.25% of the total hele-shaw cell volume. According to the results of partial factorial design of experiments and analysis of variance, the greatest effect in the part related to absorption experiments is related to the effect of water type, amount of water, amount of rock, time, simultaneous effect of time and amount of rock, simultaneous effect of type of water and amount of rock, effect the simultaneous effect of water and the amount of water is the simultaneous effect of time and the amount of water, the simultaneous effect of the amount of water and rock, the simultaneous effect of time and the type of water. Also, in the section related to interfacial tension, the greatest effect is related to the effect of water type, amount of water, amount of rock, time, simultaneous effect of time and amount of rock, simultaneous effect of time and type of water, simultaneous effect of type and amount of water, simultaneous effect of type of water and amount rock is the simultaneous effect of water amount and rock is the simultaneous effect of time and water amount
  9. Keywords:
  10. Water-in-oil Emulsion ; Micromodel ; Asphaltene Precipitation ; Enhanced Oil Recovery ; Stone Presence Effect on Emulsion Instability ; Low Salt Water Injection ; Water Injection ; Low Salinity Water Flooding

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