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Experimental Investigation of Asphaltene Precipitation and Deposition in Enhanced Oil Recovery by Low Salinity Waterflooding

Hosseini, Ali | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51823 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Ayatollahi, Shahabadin; Fatemi, Mobin
  7. Abstract:
  8. Asphaltenes are a polydisperse mixture of the heaviest and most polarizable fractions of the crude oil. They are defined according to their solubility properties as being soluble in aromatic solvents but insoluble in light paraffin solvents. Asphaltenes are usually responsible for many problems like wettability changes of the reservoir rock, pore clogging in the reservoir porous matrix and fouling in wellbore tubing and production surface facilities. Most of the studies in the literature, addressing the asphaltene precipitation and deposition (APD), are investigating natural depletion or gas injection process such as CO2 flooding. These studies show that asphaltene deposition and precipitation depend on many parameters such as rate of depressurization, asphaltene type, temperature, presence/absence of resins and etc. In mature oil reservoirs (with active aquifer or under waterflooding) water coproduces with the oil. At such condition production of water-in-oil emulsions is most likely unavoidable. As a result, most of the papers regarding APD problems which are assessing the presence of water are dealing with water-oil emulsions. The main result is that asphaltene stabilizes these emulsions. Few studies investigated the APD that might happen in the porous media during waterflooding. This is especially true for carbonate rocks, which is the objective of the present study.As a result, the aim of this research is to qualify and quantify the APD during waterflooding. fluid/fluid interactions will be scrutinized. The effect of some pertinent parameters such as brine salinity, brine composition, asphaltene type, presence/absence of naphtenic acids was investigated.In this study, the effect of MgCl2, CaCl2, Na2SO4 salts in brine in the range of low(1000-5000 ppm) and intermediate(5000-45000 ppm) salinity water on the amount of asphaltene precipitation was investigated. For all brine the amount of IFT with increasing concentration was in descending order and after a minimum value it changed to uptrend. Likewise, similar results were obtained for the precipitated asphaltene amount.Measuring asphaltene precipitation for a period of 2, 10, 20 and 40 days, illustrates the strong effect of the contact time and brine salinity on the dissociation of polar components and physical properties of the crude oil and brine. By increasing the ionic strength of the brine, the solubility of Naphthenic Acids in the aqueous solution increases, hence, the asphaltene precipitation decreases
  9. Keywords:
  10. Asphaltene ; Enhanced Oil Recovery ; Low Salinity Water Flooding ; Smart Water ; Deposition

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