Synthesis Of Phosphorus-Free Nanoscale Inhibitor Method And Its Transportability By Polymer Cross-Linking

In the process of oil and gas development,scale can deposit inside the formation and reduce the production and productivity of oil and gas wells.In the subsequent oil-water separation process,the scale particles will also affect the working efficiency of the oil-water separator,which may eventually lead to serious environmental pollution problems.In oilfield exploitation,the method of adding scale inhibitor is usually used to control scale.At present,organic phosphate scale inhibitors are still the most widely used scale inhibitors at home and abroad,but the discharge of phosphorus-containing substances will cause serious pollution to the water environment.In this study,a phosphorus-free nanoscale inhibitor was first synthesized by polymer cross-linking method using polyallylamine hydrochloride（PAH）,polystyrene sulfonic acid（PSS）and nano-silica as monomers.On the basis of studying the structure and scale inhibition performance of nanoscale inhibitor,its mobility and retention in formation were explored.The study results were as follows:（1）The effects of various factors in the cross-linking reaction on the stability of nanoscale inhibitors were studied by single factor and orthogonal experiments.The results showed that the mass ratio of monomers was PAH:PSS:SiO₂=1:4.8:20,the synthesis temperature was 4℃,the initial pH of PSS was 3,and the ultrasonic time was 5 min.The characterization results showed that the synthesized nanoscale antiscalants were nano-sized spherical particles with a spherical particle size of about 210 nm.（2）The relationship between the scale inhibition effect of nanoscale inhibitor and the amount of scale inhibitor,hardness,temperature and heating time were investigated by static scale inhibition experiment.The results show that the nanoscale inhibitor had good scale inhibition effect on barium sulfate,calcium carbonate and calcium phosphate;the study also showed that the nanoscale inhibitor had a threshold effect,and the scale inhibition efficiency of calcium phosphate and calcium carbonate increases with the increase of Ca²⁺concentration,the heating temperature increases and the heating time decreases.（3）The migration performance of nanoscale inhibitor was studied by migration experiment,and the relationship between the migration effect of nanoscale inhibitor and the pre-flushing solution,flow rate,temperature and particle size of formation medium（calcite）in the column experiment was investigated.The results show that the migration efficiency of nanoscale antiscalants is significantly improved than that of PSS.The pre-rinsing solution was a mixed solution of 0.2 wt%surfactant（AEC-9Na）and 0.2 wt%potassium chloride（KCl）solution.When the temperature is 20℃,the flow rate is 5.3 m/d,and the calcite particle size was 100-150μm,the migration efficiency of the scale inhibitor was 95%.The retention of nanoscale antiscalants was also investigated by simulating oil production backflow experiments.The results show that the service life of the nanoscale inhibitor had been greatly improved compared with that of PSS,and it can play a longer role in the produced water.To sum up,the nanoscale inhibitor has good scale inhibition performance,and has better migration and retention than PSS,and has great potential in the oilfield industry.