Synthesis Of A New Type Of PBTCA Modified Terpolymer Scale Inhibitor And Its Appliciation In Oil Field

With the rapid economic and social development,the domestic demand for oil in various industries is gradually increasing,and the oil industry has become an important industry related to the lifeline of the national economy.At present,scaling is one of the important reasons that affect oilfield production,because in the process of oilfield production,the content of calcium ion,carbonate and sulfate in water is very high,forming a large number of calcium carbonate and calcium sulfate scale.Therefore,it is necessary to find some new scale inhibitors with good effect,low phosphine and environmental protection,which are also suitable for high temperature and high hardness oilfield water.In this paper,terpolymer scale inhibitor（AA-APES-HPAY）was prepared by free radical polymerization of acrylic acid（AA）,hydroxypropyl acrylate（HPAY）and allyl polyethoxyammonium sulfonate（APES）modified by 2-phosphate butane-1,2,4-tricarboxylic acid（PBTCA）in aqueous solution,which has good scale inhibition performance.At the same time,FT-IR and ¹H-NMR was used to characterize the structure of copolymer,and then the thermal stability of AA-APES-HPAY was analyzed by thermogravimetric analysis.The results showed that the end group of hydroxypropyl acrylate was successfully modified by PBTCA,AA,HPAY and APES were successfully polymerized,and AA-APES-HPAY also had good thermal stability.The effects of different monomer ratio,reaction temperature,reaction time and the amount of initiator ammonium persulfate on the scale inhibition efficiency of the polymer were investigated.According to the static scale inhibition performance test method of oilfield,when the dosage of AA-APES-HPAY is 21 mg/L,the scale inhibition rate of Ca CO₃can reach 89.2%,when the dosage is 3 mg/L,the scale inhibition rate of Ca SO₄is 92.4%,and when the dosage is 6 mg/L,the scale inhibition rate of Ba SO₄ can reach 70.1%.AA-APES-HPAY was compared with the water treatment agent used in the market.According to the static scale inhibition performance test method of oilfield,when the dosage of AA-APES-HPAY is 21 mg/L,the scale inhibition rate of Ca CO₃ is 89.2%,and when the dosage is 3 mg/L,the scale inhibition rate of Ca SO₄ is 92.4%.AA-APES-HPAY was compared with the water treatment agent used in the market.It was found that AA-APES-HPAY had obvious advantages,and its performance was better than most of the commercial scale inhibitors.Scanning electron microscope（SEM）and X-ray diffraction（XRD）were used to analyse the surface morphology,crystal form and crystal size of calcium carbonate,calcium sulfate and barium sulfate scale were analyzed.The results show that the morphology and crystal form of calcium scale and barium scale change obviously after adding scale inhibitor.Therefore,we propose a scale inhibition mechanism:AA-APES-HPAY not only prevents polymers from forming calcium gels,adsorbing crystals,interfering with and slowing down the growth process of crystals,but also chelating the cations in water to prevent the growth of active centers.AA-APES-HPAY can achieve scale inhibition by chelating dispersion,adsorption and electrostatic repulsion.AA-APES-HPAY contains carboxyl group,sulfonic group,ether bond,phosphonyl group and other functional groups.Carboxyl group can chelate with iron ion,sulfonic group and ether bond can increase the water solubility of the chelate and play the role of dispersing iron oxide.