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Koohi A.D.,Tarbiat Modares University | Moghaddam A.Z.,Tarbiat Modares University | Sefti M.V.,Tarbiat Modares University | Moghadam A.M.,Gas and Thermodynamic TMU Research Group
Journal of Macromolecular Science, Part B: Physics | Year: 2011

A hydrogel was prepared by crosslinking of aqueous solutions of sulfonated polyacrylamide/chromium triacetate for use in water shut-off operations in oil reservoirs. The effects of pH, salinity, retarder and temperature, as well as co-polymer and crosslinker concentration, on the gelation time were investigated. The results indicated that as temperature increased, gelation occurred more rapidly. The activation energy was measured as about 86 kJ/mol. The effects of initial pH and retarder on the gelation time were also examined. The results showed that addition of retarder and increasing of pH increased and decreased the gelation time, respectively. The increase of co-polymer concentration in solution increased the gel swelling. However, the increase of crosslinker concentration decreased the gel swelling. In the presence of electrolytes, the gel swelling decreased by about 80%. Finally, some usable practical recommendations are offered for the gelling systems in reservoirs. © 2011 Copyright Taylor and Francis Group, LLC.


Moghadam A.M.,Gas and Thermodynamic TMU Research Group | Sefti M.V.,Gas and Thermodynamic TMU Research Group | Salehi M.B.,Gas and Thermodynamic TMU Research Group | Koohi A.D.,Guilan University | Sheykhan M.,Tarbiat Modares University
Journal of Macromolecular Science, Part B: Physics | Year: 2012

In this work, a hydrogel was prepared by crosslinking of aqueous solutions of sulfonated polyacrylamide/chromium triacetate for the purpose of water shut-off treatment in oil fields. In order to screen the factors that affect the gelation time and investigate their interactions, a 32 run fractional factorial design was used in experimentation with eight factors (pH, CaCl 2 concentration, crosslinker/copolymer ratio, NaCl concentration, copolymer concentration and presence or absence of sodium lactate, nanoclay, and thiouria) and one response (gelation time). Furthermore, the analysis of variance (ANOVA) was implemented as a significant tool to evaluate the quality of the quadratic model. The ANOVA results of the developed model showed it was significant with a 99% confidence limit. Among the eight factors, presence of sodium lactate, copolymer concentration, presence of nanoclay, presence of thiouria, and crosslinker/copolymer ratio had, in order, the main effects, and the interactions between sodium lactate and crosslinker/copolymer ratio and between pH and crosslinker/copolymer ratio were highly significant. © 2012 Copyright Taylor and Francis Group, LLC.


Salehi M.B.,Tarbiat Modares University | Sefti M.V.,Tarbiat Modares University | Moghadam A.M.,Gas and Thermodynamic TMU Research Group | Koohi A.D.,Tarbiat Modares University
Journal of Macromolecular Science, Part B: Physics | Year: 2012

Experiments were conducted to investigate the main effects of salinity (NaCl) concentrations and pH factors and their interactions on the gelation time response of a polymer gel used in a water shutoff system in oil field reservoirs. Central composite design (CCD) was used to design experiments and a mathematical model building. The main advantage of CCD was to generate the quadratic mathematical model for the gelation time as functions of salinity and pH factors. Tests were limited and optimized by CCD points including low star (axial), low factorial, central, high factorial, and high star points. The evaluation of the data and the developed model were performed through the examination of graphical trend of residuals and a numerical approach. Analysis of variance (ANOVA) was used to estimate the amount of data variations from the model predictions. It was found that the model was significant at the 99% confidence against test data. The results showed that the gelation time was dependent more on pH than salinity. For low pH, the gelation time increased with increasing of the salinity, while for a high pH (>4) the relationship was inversed. The research shows that CCD can effectively be applied for the modeling of gelation time and finding an optimum condition to achieve maximum or minimum gelation time for different salinity and pH factors. Copyright © Taylor & Francis Group, LLC.

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