The Research On Scale Inhibitor Of Circular Injection Sewage In Oilfield

In oilfield, water-injection exploition is a kind of production way being common used, the water injection rate is more and more greater with the expolition degree gets deeper and deeper. Main of injection water is circular injection sewage, but there is a distinct specialty in oilfield sewage circular injection process, the sewage contains abundant Ca2+,Mg2+ and so on, these ions can form scale. When temperature or other conditions change, these ions are prone to separate out on pipeline wall and from scale then influence rutine production of oilfield. In this article, we synthesize,analyze and appraise scale-inhibitor aiming at the practicality of the fourth region in second oil-production plant based on thorough understanding of domestic and foeign scale-inhibitor history,actuality and developing current. Through expriments, we get that main of the scale is CaCO3 and circular injection water contains Ca²⁺28.45g/L,Mg²⁺2.94 g/L. By research, we find that polmers having sulfonic matrix possess predominant scale inhibiting and dispersing capability. But the price of common used monomer AMPS is very high.In order to reduce cost, we choose SAS as monomer, take MA,SAS,AM and AA as raw materials to synthesize MA-SAS,MA-SAS-AM and AA-SAS water solubility polymer scale inhibitors, find out the best technical conditions, and research the influences of different conditions on scale inhibiting capability. Through espriments, we find that the best technical condition to synthesize MA-SAS is: n(MA):n(SAS)=1:1, inititator takes 10～15% of monomor total quality, system pH=4.0～4.5, rection temperature 75～80℃, reaction time 4～5h. The best technical conditions to synthesize MA-SAS-AM is: system pH=4.0～5.0, monomor ration n(MA):n(SAS): n(AM)=1:1:0.5～0.6, inititator takes 9～12% of monomor total quality, rection temperature 75～85℃, molecular weight regulator takes 2.0～5.0% of monomor total quality, reaction time 5h. The best technical conditions to synthesize AA-SAS is: n(AA):n(SAS)=3:1～4:1, inititator takes 6～8% of monomor total quality, adding some molecular weight regulators in polymerization process can improve scale inhibiting capability of AA-SAS. On this base, we use on-spot circular injection sewage to estimate these three kinds of polymer scale inhibitors. Through static scale inhibiting test and dynamic simulating test, we find that the scale inhibiting capability of MA-SAS is better than MA-SAS-AM and AA-SAS, the best adding dosage is 16mg/L. Lower than the dosage, scale inhibiting rate is getting higher with adding dosage. Higher than the dosage, scale inhibiting rate is getting lower with adding dosage. The scale inhibiting capability is better than HEDP that is common used now , and MA-SAS has good compatibility with other treating agents common used in oilfield. Through scale inhibiting kinetics analysis, we get that the main process of MA-SAS scale inhibiting is adsorption, it's adsorption on CaCO3 and CaSO4 minicrystal accords with Langmuir singale temperature adsorption. The adsorption is single molecule adsorption, take distinct restrain effect on growth of crystal so get the purpose of scale inhibiting. Take on-spot tests, use MA-SAS in ten wells belong to the fourth region of second oil production plant, tha scale inhibiting ratio can get 90%, effect is distinct. So we can take MA-SAS as a kind of perfect water solubility scale inhibitor.