Preparation And Performance Study Of Solid Scale Inhibitor For Oil Field

Most land oilfields in China have entered the middle and later stage of mining.With content of water in oil fields increasing continuously,the scale phenomenon in oil fields affected seriously the normal production of water flooding,which of inhibition has become the focus of current researchIn this paper,both MA/SSA/VAc and MA/AMPS/HPA terpolymers were named MSV and MAH,respectively,which were synthesized by the method of aqueous radical polymerization,with 2-acrylamido-2-methylpropanesulfonic acid(AMPS),ethenyl ethanoate(VAc),Sodium p-styrenesulfonate(SSA)and maleic anhydride(MA),hydroxypropyl acrylate(HPA)as raw materials,ammonium persulfate as initiator.The structure of the products was characterized by infrared spectrum analysis.The preparation conditions of two kinds of terpolymer were optimized by a single factor method,and the relationship between molecular weight and scale inhibition was discussed.As a result,the optimum preparation conditions of copolymer MSV were obtained as follows:n(MA):n(SSA):n(VAc)= 4:2:1,the ratio of initiator to total mass of the monomers was 10 wt%,the amount of molecular weight regulator isopropanol was 20 wt%of the mass of the monomer,the reaction time was 4 hours and the reaction temperature was 80?.Under these condition,the solid content was 22 wt%,the yield was 91%,the intrinsic viscosity of was 9.4 mL/g and the relative molecular weight was 7208.Then the optimum reaction condition of terpolymer MAH were as follows:n(MA):n(AMPS):n(HPA)= 5:3:1,and the ratio of initiator to total mass of the monomers was 8 wt%,the amount of molecular weight regulator isopropanol was 15 wt%of the mass of the monomer,the reaction time was 3 hours and the reaction temperature was 85 ?.Under these condition,the solid content was 33 wt%,the yield was 96%,the intrinsic viscosity was 8.1 mL/g and the relative molecular weight was 5643.The thermal stability of the two terpolymers was analyzed by the thermogravimetry.The scale inhibition performance of the two kinds of terpolymers was evaluated from the concentration of the terpolymers in aqueous solution,test temperature and pH of the solution.The results showed that the scale inhibition rate for calcium carbonate scale reached 100%,and that for calcium sulfate scale reached over 97%.MSV and MAH were compounded with ethylenediamine tetramethyl phosphonic acid sodium(EDTMPS)organic phosphine scale inhibitor and epoxy sodium succinate(PESA)friendly environmentally scale inhibitor to improve the scale inhibition performance.The results showed that the scale inhibition performance of the complex system against barium sulfate increased from 72.3%of the original single agent to 92.6%,and scale inhibition performance of strontium sulfate increased from 75.2%of the original single agent to 94.8%.The scale inhibition mechanism for calcium carbonate and barium sulfate scale samples was preliminarny studied by SEM,EDS and XRD analysis.Scale inhibitors clange the apparent morphology of scale-fonmng crystallites by lattice distortion and dispersion,but the type of crystal inside the scale was not changed.A slbwly released solid scale inhibitor was prepared with polyvinyl alcohol as the carrier material,which needed 85 days to dissolve completely and the released rate of which was 2.70 mg/h at room temperature.The controled-release performance of solid scale inhibitor was test under different temperatxre.The results showed it was dissolved completely in formation water over 48 days when the environment temperature of 60 ? and scale inhibitor rate for simulated formation water reached 96%of 64 hours from introducing solid scale inhibitor.When the temperature of the environment is tower 80 ? scale inhibitor rate of solid scale inhibitor for simulated formation water reached over 90%and it was dissolved completely in formation water over 20 days,which reached the intended target.