Preparation Of The Designed Multipolymer Antiscalant And Its Mechanism Research

In oilfield exploitation,as the moisture content of produced fluid increases,scaling phenomenon become more and more obvious.Especially with the application of asp flooding technology,the pH of injected water increases,making production system scaling more seriously and affecting the production work.So it is very urgent to develop efficient scale inhibitor.Copolymer scale inhibitor has become the emphasis of research,because it has advantages in controlling structure and molecular weight compared with other kinds of scale inhibitors.Based on the multivariate monomer copolymerization,two kinds of scale inhibitors have been prepared,and their antiscale efficiency has been studied.Then their compounded property with other kind of scale inhibitors has been explored.Finally,the mechanism of scale inhibitor is studied.An efficient technological solution is made to control the CaCO₃in the production system of oilfield.The specific experimental methods and results are as follows.A maleic anhydride-acrylic acid scale inhibitor is prepared with different dosing ratio of maleic anhydride?MA?and acrylic acid?AA?.Infrared spectrum?IR?and nuclear magnetic resonance?NMR?have been used to characterize the structure of the copolymer.Petrochina standard has been used to evaluate its scale inhibition rate.The relationship between the structure and performance of scale inhibitors has been discussed.Meanwhile,the Synergistic effect between MA-AA and oilfield commonly used scale inhibitor has been studied.The results show that the optimum reaction conditions is that the molar ratio of monomers is 1:1,the mass fraction of initiator is6%,the reaction temperature is 85?and reaction time is 4 h.Under this condition,the scale inhibition rate is 96.0%.The structure and the antiscale efficiency of the synthesized copolymer are in conformity with the design requirements.There are some important relationships between molecular weight and the scale inhibition rate.Scale inhibition rate of this copolymer is high when molecular weight is in2653²823.When this copolymer and?hydroxyethylidene?diphosphonic acid?HEDP?are mixed at a quality ratio of 1:0.4,the scale inhibition rate is 98.2%.MA-AA-AMPS ternary polymer is prepared with maleic anhydride,acrylic acid and 2-acrylamide-2-methyl propane sulfonic acid?AMPS?.Its structure and performance have been studied.It turns out that the optimum reaction conditions is that the molar ratio of monomers is 1:1:0.15,the mass fraction of initiator is 5%,the reaction temperature is 90?and reaction time is 4 h.Under this condition,the scale inhibition rate is 92.5%.The structure and the antiscale efficiency of this copolymer are in conformity with the design requirements.Factors such as dosage of initiator and reaction temperature have important effects on its molecular weight.Scale inhibition rate of this copolymer is greater than 90.0%when molecular weight is in3423³445.It is weaker than MA-AA in the property of alkali resistance.The best blend ratio for MA-AA-AMPS and HEDP is 1:0.2,and the scale inhibition rate is95.8%.Related tests have been studied in the condition of oilfield injection water.The best blend ratio for MA-AA and HEDP has been studied again,and its best dosage has been explored.Under the distilled water condition,methods and instruments such as dispersion ability of calcium carbonate,SEM and XRD have been used to explore the inhibiting mechanism of MA-AA.It turns out that the best blend ratio for MA-AA and HEDP is 1:0.2 in the oilfield injection water,and the best dosage is 55 mg/L.The inhibiting mechanisms of MA-AA copolymer contain chelate,dispersion and lattice distortion.