Study On AGE Block Quaternary Ammonium Salt Amphoteric Hydrophobic Association Polymer Oil Displacing Agent

Polymer flooding,as one of the crucial method for enhanced oil recovery(EOR),has been bringing with considerable and satisfactory financial benefits in the reservoirs behaving relatively heterogeneity,low temperature and low salinity.Nevertheless,with the enhancement of heterogeneity,high temperature and high salinity of the reservoirs,new problems that the dissolubility,temperature resistance and salt tolerance of EOR chemical can not meet the engineering requirements have restricted the extensive application.Therefore,the further study about the EOR chemical was important for the polymers used in high-temperature,high-salinity and heterogeneous reservoirs.In this paper,a sulfonate monomer 3-(allyloxy)-2-hydroxypropane-l-sulfonate(AHPS)and a quaternary ammonium salt hydrophobic monomer 2-(allyloxy)-N-(2-(2,4-dichlorophenoxy)ethyl)-N,N-diethyl-1-hydroxy ethanaminium bromide(ACDH)was designed and synthesized by using 2-((allyloxy)methyl)oxirane(AGE)as the original reactant.A ternary copolymer and a tetra copolymer containing AGE blocks,denoted as AM/AA/AHPS and AM/AA/AHPS/ACDH,were synthesized via copolymerization of acrylmide(AM),acrylic acid(AA)and the functionalized monomers AHPS and ACDH,respectively.Subsequently,the two copolymers were characterized by IR,NMR in order to confirm that the structure of the synthetic copolymers was consistent with that of the designed copolymers.The morphology of the aggregate of two copolymers was investigated by SEM.And the thermal stability of AM/AA/AHPS and AM/AA/AHPS/ACDH was investigated via TG-DTG techniques.The obtained optimum conditions of AM/AA/AHPS were as the follows,m(AM):m(AA):m(AHPS)= 8.0:1.5:0.5,the loading of initiator was 0.2 wt%,the temperature was 50 °C,the total monomer concentration was 20 wt%and pH was 7.And the viscosity-average molecular weight of the obtained AM/AA/AHPS could reach 6.5×106.The optimum conditions of AM/AA/AHPS/ACDH were as the follows,m(AM):m(AA):m(AHPS):m(ACDH)= 7.9:1.5:0.5:0.1,the initiator dosage was 0.2 wt%,the temperature was 50 °C,the total monomer concentration was 20 wt%and pH was 7.The the viscosity-average molecular weight of the obtained AM/AA/AHPS/ACDH was up to 6.3 ×106.The overall performance,including thickening ability,temperature resistance,salt tolerance and shear resistance,of AM/AA/AHPS/ACDH was superior to AM/AA/AHPS and HP AM.The results showed that the apparent viscosity of AM/AA/AHPS/ACDH solution could reach 410.5 mPa·s under the concentration of 2000 mg/L.The viscosity retention rate of 2000 mg/L AM/AA/AHPS/ACDH solution were 63.1%at 95 ℃ and 9.9%at the shear rate of 1000 s-1.After 11000 rpm of 20 s,the viscosity retention rate of AM/AA/AHPS/ACDH was 75.3%.In addition,elastic modulus of AM/AA/AHPS/ACDH was obviously larger than viscous modulus in the range of 0.01～10 Hz,which showed that AM/AA/AHPS/ACDH had excellent elasticity.The viscosity retention rate of 2000 mg/L AM/AA/AHPS/ACDH solution were 19.0%,17.8%and 15.2%under the concentration of 20000mg/L NaCl,2000 mg/L MgCl2 and 2000 mg/L CaCl2,respectively.The curves of the isothermal adsorption of AM/AA/AHPS and AM/AA/AHPS/ACDH containing AGE blocks on the surface of the quartz sand exhibited a state of L,which fitted well with the Langmuir adsorption model.Because of the introduction of the quaternary ammonium salt,the adsorption capacity of 1000 mg/L AM/AA/AHPS/ACDH solution(0.333mg/g)was higher than AM/AA/AHPS and HP AM solution,which was favorable to mobility control.Under the condition of good iniectivity,the remarkable resistance factor of 22.1 and residual resistance factor of 3.3 could effectively control the mobility ratio,which improved the sweep efficiency of the displacing fluid.The copolymer AM/AA/AHPS/ACDH may cooperate well with surfactant sodium dodecyl benzene sulfonate(SDBS),the obtained result wer similar with that the hydrophobically associating polymers cooperate with surfactant.The relationship between apparent viscosity of compounded system and SDBS dosage showed four stages.The apparent viscosity of the compounded system AM/AA/AHPS/ACDH-SDBS(2000 mg/L-2000 mg/L)can be up to 75.3 mPa s,and additional EOR of 4.65%could be obtained in comparision with AM/AA/AHPS/ACDH possessing EOR of 12.97%.