Preparation And Performance Study Of Polyacrylamide Weak Gel For Enhanced Oil Recovery

In the Enhanced Oil Recovery(EOR),partially hydrolyzed polyacrymide(HPAM) can improve its viscosity,expand the waterflood sweep efficiency,reduce water permeability, thus improve the oil displacement effect.Because of the poor heat resistance and the poor salt resistance of HPAM, losing its viscosity under the environment of high temperature and high salinity reservoir, it is hard to meet the conditions of enhanced oil recovery technology requirements. As a result, improving the heat resistance salt resistance of HPAM has a great practical significance.This article used Gabriel reaction to achieve the amino modification of block polyether F127(PEOioo-PPO65-PEOioo) and have got the product named as F127-NH2, we mixed F127-NH2 with HPAM.In the composite of HPAM/F127,there are intermolecular hydrophobic association between F127 and hydrogen bonding interation.In addition to the above two actions,the composite of HPAM/F127-NH2 has covalent bonding effect between F127-NH2 and HPAM,which can improve the viscosity-temperature characteristics of HPAM,enhance the heat resistance and salt resistance of HPAM.By studying the viscosity and the viscoelastic modulus of HPAM/F127-NH2 aqueous solution and mineralized water under different temperature,we study the crosslinking condition of HPAM/F127-NH2 as well as the interaction mechanism of HPAM/F127-NH2.The result show that,consider the temperature effect on apparent viscosity of the system only,the apparent viscosity of HPAM/F127-NH2 and HPAM/F127 are almost the same under the temperature of 20℃,350C,45℃,55℃.As the temperature raises,the viscosity of these two system reduce from 240 mPa · s to 220mPa · s while the viscosity of HPAM reduce from 200mPa · s to 140mPa·s. F127 and F127-NH2 can improve the appatent viscosity of HPAM.When the temperatue raises continually,the apparent viscosity of HPAM/F127-NH2 is higher than HPAM/F127,about 20-40mPa· s.There are not only hydrophobic association and hydrogen bonding interation,but also covalent bonding interation between HPAM and 127-NH2. F127-NH2 can enhance the visicosity of HPAM better than F127.We research the viscosity increasing effect of F127-NH2 to HPAM mineralized water under general formation temperature and salinity:under 55℃,the apparent viscosity of HPAM mineralized water is 120 mPa · s,the viscosity loses 37.5% after placed for 1 day;the HPAM mineralized water containing 0.12wt% F127-NH2has a viscosity of 450 mPa · s, the viscosity loses 11.1% after placed for 1 day. Under 65℃, the apparent viscosity of HPAM mineralized water is 110 mPa·s,the viscosity loses 36.4% after placed for 1 day;the HPAM mineralized water containing 0.12wt% F127-NH2has a viscosity of 430 mPa · s, the viscosity loses 7.5% after placed for 1 day.It can be found the in the conventional reservoir temperature and salinity conditions, F127-NH2 can effectively improve the apparent viscosity of HPAM mineralized water, reducing the viscosity loss.And rise of temperature is benefit to cross-linking of F127-NH2 and HPAM.The composite solution of HPAM and F127-NH2 has a favorable heat resistance and salt resistance,which is suitable for deep well operation.In addition,the apparent viscosity and viscoelastic modulus of HPAM/F127-NH2 mineralized water are influenced by the amount of F127-NH2.We can achieve the control of viscosity by changing the amount of F127-NH2.Under 65℃,when the amount of F127-NH2 rises from 0wt% to 0.12wt%, the viscosity of the solution rises from 100 mPa · s to 430 mPa ·s.At the viscoelastic modulus curves of HPAM/F127-NH2 mineralized water,the sample with 0.05wt%F127-NH2 has the first node which is corresponding to the minium critical angle frequency and maxium relaxation time,the HPAM/F127-NH2 system is mostly stable.As the amount of F127-NH2 grow,the interactions between HPAM and F127-NH2 are influenced,the heat resistance and the salt resistance reduce.By the viscoelastic modulus test,we can find the best amount of F127-NH2.According to the normal construction situation of oil field,the most appropriate ratio of HPAM/F127-NH2 at room temperature are:the amount of HPAM is 0.06-0.14wt%,the amount of F127-NH2is 0.02-0.1wt% and the total salinity is 0-1000mg/L.The apparent viscosity of the mineralized water is bwtween 20-100 mPa · s.According to the simulation study,the solution has a good heat resistance and salt resistance which can maintain a better apparent viscosity.