Research On High-Strength Gel Plugging Agent

Slugs for sealing after water plugging or rubber plugs for plugging wellbore require high strength of gel.High-dosage polymer can produce high-strength gel.When the amount of ordinary polyacrylamide is high,the viscosity of the gellant will be large,and it will be difficult to pump.The use of low-molecular-weight polymers to prepare high-strength gel can simultaneously meet the requirements of low viscosity of the gellant and high strength after cross-linking.In this paper,low-molecular acrylamide/tert-butyl acrylate copolymer and low-molecular polyacrylamide are used to prepare high-strength gel.In this paper,the gel forming time,gel strength and long-term stability of the gellant are used as evaluation indicators.Through single-factor experiments,the two types of polymers are cross-linked with polyethyleneimine and phenolic systems,and the two types of gel forming laws are determined.The adaptability of the two types of gel is determined.The results of the study show that the gelation performance of the gellant formulated with acrylamide/tert-butyl acrylate copolymer and polyethyleneimine is not only affected by internal factors such as the dosage of polymer,the dosage of crosslinking agent,and the relative molecular weight of the crosslinking agent.It is also related to external factors such as temperature,salt water salinity,and p H value of gellant.Polyethyleneimine gel has good injection performance and plugging performance.It is suitable for the formation environment where the temperature is 100℃-130℃,the p H value is 8-9,and the salinity is lower than 43530mg·L^-1.The gelation performance of the gellant formed by the low-molecular polyacrylamide and phenolic system is not only related to the dosage of polymer and crosslinking agent,but also related to the addition of catalyst acetic acid and nano-micron particles.Phenolic gel is suitable for the wellbore environment where the temperature is lower than 150℃and the salinity is 10174 mg·L^-1.Comparing the two types of gel,it is found that the injection performance of polyethyleneimine gel is better than that of phenolic gel,but the viscoelasticity of phenolic gel is better than that of polyethyleneimine gel.Both perform well in terms of plugging performance,with a breakthrough pressure gradient of up to 19.85 MPa·m^-1.