Study On Synthesis And Oilfield Application Of Ternary Copolymer Tackifier

As the demand for crude oil continues to rise in the world,protecting oil wells and improving oil recovery have become a hot topic in the world.As a natural macromolecule,starch has many advantage,the price is cheap,resource is very plenty,non-poisonous and degradable.The modified starch have been used in petroleum and natural gas industry for a long time because of their special structure,and now has been extensively studied.Firstly,the foreign samples were analyzed and tested to determine the main components.Secondly,the graft copolymers were synthesized by aqueous solution polymerization using corn starch,acrylamide and sodium acrylate in the condition of ammonium persulfate and anhydrous sodium bisulfite as composite initiators,which can be used for petroleum exploration.Different starch raw materials were screened,and the synthesis conditions such as the amount of Na AA,reaction time,reaction temperature and the amount of initiator added on the polymerization were discussed.The effects of the synthesis conditions were investigated from the results of apparent viscosity,monomer conversion and grafting ratio of the copolymer.The optimal reaction conditions were as follows: 0.3mol/L of the amount of Na AA,reaction time 3 h,reaction temperature 50℃,initiator dosage 3% of the total monomer mass.At the same time,the mathematical model was established by using the Box-Behnken central combination.According to the prediction model,the order of influence of each factor on apparent viscosity is: reaction temperature > initiator dosage > reaction time.The structure of the grafted product was analyzed by using each instrument.FTIR spectra showed that the product had characteristic peaks of each monomer,which proved the success of the grafting reaction.It can be observed from the TG analysis curve that the product has a higher thermal decomposition temperature than the corn starch,which proves that the reaction enhances its thermal stability.XRD curves and SEM photographs show that the structure of the corn starch was destroyed during the reaction,and the crystal structure was disappeared.The apparent viscosities of ternary graft copolymers in aqueous solution were measured in the presence of different salt ions.It was found that the effects of salt ions on apparent viscosity were the same,and the degree of viscosity decrease was different.Among them,in the presence of high valence salt ions,the loss of water solution viscosity is more.At the same time,the apparent viscosity of the aqueous solution at high temperature was determined,and it was found that the aqueous solution still had a good viscosity at high temperature.The copolymer product was added to four different types of drilling muds,and the rheology and filtration properties of the muds were measured.Experiments show that the product has better salt tolerance in drilling fluids of various types,but the temperature resistance is poor.Therefore,the application performance of the copolymer in petroleum exploitation needs to be improved.