Study On Chitosan Crosslinked Modified Acrylamide Plugging Agent

As the reduction of rich of no.1 oil reservoir,and the reservoir buried depth of about2000m,formation water salinity of 10000¹5000 mg/L,formation temperature is less than85?no.2 reservoir,no.3 of high temperature and high salt reservoir will be the basis of production of the important resources in the future.Acrylamide polymer gel is widely used as commonly used in polymer gel profile control water plugging,but it is prone to metal degradation,thermal degradation and breaking phenomenon under the condition of high temperature and high salt,then lost the meaning of the profile control water plugging.Crosslinking reaction can improve the performance of polyacrylamide gel,such as phenolic or organic metal crosslinking modification,but it is easily affected by the shearing action,then cause pollution to the environment in the process of using.In view of the oil field geological characteristics:such as high temperature and salt,polymer gel is easily affected by shearing action,poor heat resistance and poor salt resistance,that could cause pollution to the environment in the process of using.Biological macromolecule chitosan?CS?has the characteristics of nontoxic and rich natural resources,and the molecule contains a large number of hydroxyl,amino and hydroxyl methyl,then participate in a variety of reactions.This topic proposed CS as crosslinking agent,acrylamide?AM?and 2-acrylamide-2-methyl propane sulfonic acid?AMPS?as the main agent,potassium persulfate?K₂S₂O₈?as initiator,through free radical reaction grafting product,nucleophilic reaction of two-step to synthetic AM/CS polymer gel and AM/AMPS/CS polymer gel.The results:?1?Through the single variable method to select the best formula and experimental conditions:the best formula and experimental conditions of AM/CS system:AM concentration of 80g/L,CS concentration is 0.8g/L,K₂S₂O₈ concentration is 1.5g/L,Free radical grafting reaction temperature T₁ is 60?,reaction time t₁ is 2h,crosslinking reaction temperature T₂ is 100?,reaction time t₂ is 3h;the best formula and experimental conditions of AM/AMPS/CS system:AM concentration is 66.7g/L,AMPS concentration is6.67g/L,CS concentration is 0.67g/L,K₂S₂O₈ concentration is 1.33g/L,free radical reaction temperatureT₁ is 60?,reaction time t₁ is 2h,crosslinking reaction temperatureT₂is 110?,reaction time t₂ is 3h.?2?The polymer gel structure was certified by infrared spectrum analysis?FTIR?,thermo-gravimetric analysis?TG?and differential thermal analysis?DTA?,scanning electron microscopy?SEM?:comparative analysis infrared spectra of the CS and AM/CS system polymer gel,CS and AM/AMPS/CS system polymer gel,the first step and the second step of thermo-gravimetric endothermic and the location and size of a product and step and the second step of scanning electron microscopy,proved that the second product is a product on the basis of the crosslinking reaction in the first conducted,eventually synthesis of AM/CS polymer gel,and AM/AMPS/CS polymer gel.?3?Shear resistance,temperature tolerance,salt resistance,the breakthrough pressure,breakthrough pressure gradient and plugging rate performance was tested through indoor simulation experiment:the AM/CS system has good resistance to shear,suitable environmental temperature of 100¹20?,suitable salinity 0¹5×10⁴mg/L,the first step product breakthrough pressure is 0.0067 MPa,the second step product is 0.038 MPa,the biggest of the breakthrough pressure gradient can reach 0.820MPa·m^-1,plugging rate is92.67%;AM/AMPS/CS system has good resistance to shear,suitable environmental temperature of 110¹50?,suitable salinity 0²5×10⁴mg/L,the first product breakthrough pressure of 0.015 MPa,the second step product is 0.06 MPa,the biggest of the breakthrough pressure gradient can reach 1.250MPa·m^-1,plugging rate can reach 86%.?4?Compared to AM/CS system and AM/AMPS/CS system:both systems have good resistance to shear;By introducing a functional monomer AMPS,AM/AMPS/CS system has better heat resistance and salt resistance;AM/AMPS/CS system breakthrough pressure and breakthrough pressure gradient were greater than AM/CS system,relatively speaking,at the same case,the AM/CS system suitable for sealing small aperture,low permeability formation;AM/AMPS/CS system suitable for plugging large pore diameter and high permeability formation;Both system satisfies the requirement of oil well plugging,and can be used for oilfield water shutoff profile control agent.