An adsorptive retarder for acid job has been developed aimed at enhancing the stimulation effect of acid job.The retarder is synthesized using monomers such as monomeric sulfonate(MS),acrylamide(AM),allyl polyoxyethylene glycol(APEG-2400)and octadecyl dimethyl allyl ammonium chloride(DMAAC-18)in a concentration ratio of n(AM)∶n(MS)∶n(DMAAC-18)∶n(APEG-2400)=90∶5∶1∶4.The concentration of the monomers is 35%,the concentration of the initiator is 1.0%,the reaction temperature is 50℃and the reaction time is 5 h.These reaction conditions were determined through single-factor experiment.The characterization of the molecular structure of the retarder with FT-IR shows that the reaction product is what was expected.The retarding efficiency of the retarder at a concentration of 1.3%is 81.56%,and the system has its apparent viscosity stabilized at 3 mPa∙s,an excellent low viscosity property.At 110℃,the retarding efficiency of the retarder exceeds 83%,indicating that the retarder has good high temperature performance.This retarder has good compatibility with cleanup additives,iron ion stabilizers and corrosion inhibitors;no flocculation and precipitation exist when the retarder is used with other additives.This retarder is able to resist the contamination by 70,000 mg/L CaCl2.It also has good thermal stability;at 350℃,the rate of mass loss of the retarder is only 17.59%.Observation of the retarder under SEM shows that the retarder is adsorbed on the surfaces of the rocks and forms a dense layer of adsorption membrane.
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