pH- and temperature-dual responsive polymer emulsion for rapid release of drag reducer
Slick water fracturing fluid is widely used in major oil fields due to its low cost and high drag reduction. Polyacrylamide emulsions drag reducers play a decisive role in slick water fracturing. The dissolution rate of polymer emulsions drag reducers was increased by adding hydrophilic surfactants, but the stability of the emulsions is poor, which limits its wide application. In order to solve the contradiction between the stability of polymer emulsion and rapid release of drag reducer. Here, a P(AA-AM-AMPS) polymer emulsion drag reducer with dual stimulation response of pH and temperature was designed. Surfactant (D400/OA) with dual responses to pH and temperature is synthesized by using oleic acid (HOA) and polyether amine 400 (D400). D400/OA shows a remarkable pH- and temperature-responsive behavior due to the pH- and temperature-induced structural transformation of D400/OA. Interestingly, D400/OA-stabilized monomer emulsion exhibits an obvious pH- and temperature-induced structural transformation. Meanwhile, The D400/OA-stabilized monomer emulsion has remarkable stability, which benefits the inverse emulsion polymerization of P(AM-AA-AMPS) polymer. The obtained P(AM-AA-AMPS) polymer emulsion maintain stability whose particle size nearly unchanged by storing for 15 days. Interestingly, P(AM-AA-AMPS) polymer emulsion can be released completely by changing the pH or temperature of the aqueous solution. The apparent viscosity of P(AM-AA-AMPS) polymer, in either the alkaline (pH=10.31) solution of 25±2 °C or neutral (pH=7) solution of 70±2 °C, respectively required 40 s and 8 min to reached a maximum value of 96 mPa·s. The release rate of P(AM-AA-AMPS) polymer emulsion is further enhanced under the dual responsive of temperature (70±2 ℃) and pH (10.31) and it takes only 20 s, In addition, the drag reduction rate of P(AM-AA-AMPS) polymer emulsion is 72 % when completely released under the dual responsive of temperature and pH, showing a remarkable drag reduction property. The D400/OA-stabilized P(AM-AA-AMPS) polymer emulsion are expected to meet the demand for the production enhancement of the oil and gas reservoirs.
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