Study On The Synthesis And Performance Of Anti-high Temperature Oil Well Cement Fluid Loss Agent

During the cementing operation,the purpose of fluid loss additives is to prevent the excessive loss of water from the cement slurry and cause the failure of the cementing.At present,with the exploitation of oil and gas resources from conventional oil and gas reservoirs to low-permeability and unconventional elongation,from land to sea,and from shallow to deeper levels,the existing fluid loss additives can no longer meet the requirements of high temperature and high salinity environment of cementing operation.In this paper,based on the hydration mechanism of cement and the action mechanism of fluid loss additives,the fluid loss additives of oil well cement suitable for deep wells and ultra-deep wells is designed and synthesized,and then the structure is characterized and its performance is evaluated.Finally,a preliminary study on the working mechanism of fluid loss additives was conducted.In this paper,the monomer used to synthesize to the fluid loss additives for oil well cement contains Sodium styrene sulfonate(SSS),a vinyl monomers containing amide group(XS-1)and itaconic acid(IA)and potassium persulfate(K2S2O8)as initiator.A terpolymer as fluid loss additives for oil well cement is synthesized by free radical copolymerization.The fluid loss was used as evaluation standard,the optimum synthesis conditions were obtained by orthogonal experiments.The monomer ratio(molar ratio)SSS:XS-1:IA was 4:5:2,the reaction temperature was 65?,and the initiator dosage was 0.8%,the pH was 10,and the reaction time was 5h.The elements,molecular structure,heat resistance and molecular mass of the copolymer were tested.Elemental analysis,infrared spectroscopy(FTIR),1H-NMR and X-ray photoelectron spectroscopy(XPS)results showed that all monomers participated in the copolymerization reaction.The elements in the copolymer were derived from the monomers reacted and the copolymer did not contain unsaturated carbon-carbon double bonds.The results demostrated that the synthesis product was the target product.TG test results indicated that the polymer has excellent heat resistance and the highest heat resistance temperature can reach 401'C.The GPC test results showed that the Mn of the copolymer was 16.90 x 104 g/mol and the DPI was 1.622.ESEM test showed that the microcosmic morphology of the copolymer is a film-like structure containing pores,which is conducive to the adsorption of cement particles.The performance of the copolymer was evaluated.The results indicated that the copolymer had excellent temperature resistance and salt tolerance.In fresh water cement slurry,the lowest fluid loss can be controlled within 20mL.Furthermore,the fluid loss in three kinds of cement slurry system,freshwater slurry,semi-saturated brine slurry,saturated brine slurry,can be controlled within 100mL.On the other hand,the addition of the fluid loss additives has little effect on the rheological properties of the cement slurry and the compressive strength of the cement stone,and it is beneficial to improve the sedimentation stability of the cement slurry.To reveal the adsorption amount of copolymer in the cement particles,TOC,Zeta potential and ESEM of cement slurry is analyzed.Micromorphology and hydration product composition of the cement stone were tested by SEM-EDS,XRD and TG-DTG.The results indicated that fluid loss additives adsorbs on the surface of cement particles which results in compactness in the cement filter cake increased and reduce fluid loss from cement slurry.