Study On Preparation And Performance Of Sustained-Release Hyperbranched Polymer Scale Inhibitor

With the development of low permeability oil fields in China,fracturing technology is more and more widely used.In the production process after fracturing,with the outflow of high salinity formation water,a large area of formation water scales,which affects the production of oil wells after fracturing.In view of the difficulty of using conventional scale inhibitors in complex formation environment,two series and eight types of new hyperbranched polymer scale inhibitors were synthesized by Michael addition and amidation reaction.Through the scale inhibition performance test,a scale inhibitor with high temperature resistance,wide p H application range and excellent scale inhibition performance was optimized,and the scale inhibitor was filled into porous ceramsite to prepare a sustained-release hyperbranched polymer scale inhibitor which can be used for scaling formation water.In this paper,three types of hyperbranched polyamide-amines were synthesized from ethylenediamine（EDA）,diethylenetriamine（DETA）and triethylenetetramine（TETA）,methanol as solvent and methyl acrylate（MA）as raw materials.Then it was modified with hydroxyethylidene diphosphonic acid（HEDP）and maleic anhydride（MAH）as capping agents.The prepared 1.0-generation phosphonic acid-terminated hyperbranched polyamide-amine is named PEP-1,PDP-1 and PTP-1.The 1.0 generation carboxyl-terminated hyperbranched polyamide-amine was named PEC-1,PDC-1 and PTC-1.The 2.0-generation phosphonate-terminated/carboxyl-terminated hyperbranched polyamide-amine was named PEP-2 and PEC-2 respectively.By FT-IR,elemental analysis and thermogravimetric analysis,it is found that the prepared hyperbranched polymer scale inhibitors are all target products and have good heat resistance.According to the scale inhibition performance test,when the concentration is 500mg/L,the scale inhibition rates of PEP-1,PDP-1,and PTP-1 for CaSO₄ scale are 98.5%,95.4%and 94.2%respectively,and for CaCO₃ scale are 90.1%,88.3%and 86.4%respectively.When the concentration is 400mg/L,the scale inhibition rates of PEC-1,PDC-1,and PTC-1 for CaSO₄ scale are 96.4%,95.1%and 94.9%respectively,and for CaCO₃ scale are 90.2%,89.9%and 88.9%respectively.When the concentration is 300mg/L,the scale inhibition rates of PEP-2 and PEC-2 for CaSO₄ scale are 100%,and for CaCO₃ scale are 98.1%and 88.7%respectively.And the scale inhibitors has stable scale inhibition performance,and can be put into use in high salinity,high temperature,strong acid and strong alkali environments.Through the study of dispersion performance,it was found that the prepared scale inhibitor had excellent dispersion performance,which was higher than that of commercially available hydroxyethylidene diphosphonic acid and maleic anhydride.Through SEM analysis,it was found that the crystal structures of CaSO₄ and CaCO₃ were seriously damaged,the mechanical properties were reduced,the crystal forms were transformed and the crystal lattice was distorted under the action of scale inhibitors.It is speculated that the scale inhibition mechanism is mainly related to the three-dimensional structure of hyperbranched polymer,high dispersibility of polymer and introduced functional groups.With PEP-2 as scale inhibitor,porous ceramsite as carrier and aluminum dihydrogen tripolyphosphate（ATP）as coating,sustained-release hyperbranched polymer scale inhibitor was prepared by negative pressure filling,solution impregnation and spray coating.Through the analysis of physical and chemical properties,the particle size of scale inhibitor is 20-40 meshes,the scale inhibitor loading is 48-50g/100g（porous ceramsite）,and the scale inhibitor has high temperature resistance of 300℃and good crushing resistance.Through slow-release performance testing,it was found that at 60 days under static and dynamic conditions,the scale inhibition rates of the scale inhibitor on CaSO₄ scale are 95.6%and 92.1%,respectively,and the scale inhibition rates on CaCO₃ scale are 93.2%and 89.8%,respectively.At 26 days in the simulated state,the scale inhibition rates of the scale inhibitor on CaSO₄ and CaCO₃ scales are 84.6%and 82.9%,respectively.It is known that the prepared sustained-release hyperbranched polymer scale inhibitor has a long-term sustained-release scale inhibition cycle,which provides important reference value in scaling of formation water after fracturing.