Study On Temperature And Salt Resistant Acrylamide Composite Water Blocking Agent

The polymer plugging agents with high blocking strength are widely used in production wells of oil and gas.However,the plugging agents are affected by metal ions under high temperature conditions,resulting in thermal degradation or dehydration.The inorganic plugging agents are with wide raw materials,great temperature resistance and other characteristics.To improve the temperature and salt resistance,it is of great significance to prepare the organic/inorganic compound plugging agents which have the advantages of both of plugging agents.The AM/AMPS/AA copolymer for oilfield was synthesized by the way of aqueous solution polymerization,which used AMPS,AM and AA as the main monomers.The influences of the synthesis temperature,synthesis time and initiator dosage on the apparent viscosity were investigated.The optimal conditions of the synthesis were determined through the orthogonal experiments.It showed that the mole ratio was 11:3:1 for AM,AMPS and A A,the hydrolysis time was 1.5h,the initiator dosage was 1.2wt%,the hydrolysis temperature was 45 ?.The apparent viscosity of 2wt%plomyers solution tended to be constant when the degree of mineralization was to reach 6000mg/L in solution.It was found by FT-IR spectral analysis that the molecular chain contained carboxyl,sulfonic acid and amide groups.The molecular weight?Mn?of the optimal copolymer was 2.32×105,the weight average molecular weight?Mw?was 4.59×105 by gel permeation chromatography?GPC?,which indicated that the molecular weight distribution was broad.The new compond plugging agent was prepared where the montmorillonite?MMT?was introduced into the polymers.The polymer/montmorillonite complexs contained Si-O-Si characteristic absorption peaks and characteristic absorption peaks of sulfonic acid and amide groups by the FT-IR spectrum.The montmorillonite particles were in the form of microns distributing in polymer by scanning electron microscopy?SEM?.And the thermal stability was better than that of ordinary polymers without montmorillonite.The effects of polymer dosage,gelation temperature and monomer ratio on the water absorbency were investigated.The optimal conditions of the synthesis were determined through the orthogonal experiments.It showed that the mole ratio of AM,AA and AMPS was 12:2:4,the ratio of cross-linking agent in polymer was 0.4wt%,the gelation temperature was 70 0C,the composite polymer ratio in system was 10wt%,the montmorillonite dosage was 12.4wt%.The comprehensive properties of the plugging agent such as the thermal stability,water absorbency,gelation time had been investigated experimentally.The results showed that in 105mg/L NaCl solution at 700C,the gel still had excellent hydrogel strength after 15 days.With the same degree of salinity,the order of their effects on gelatinization time was as follow:NaCl>MgCl2>CaCl2.The thermal stability of the composite gel was better than normal gel's?without MMT?.The water absorbency of the normal gel was better,but temperature resistance was weaker than the composite gel's.The water absorbency was the best at 90 0C,which could be 18.29 g/g in 4×104 mg/L simulated formation water for 12h.Besides,the plugging agent was with great plugging performance.The blocking rate of matrix core was more than 99%,and the breakthrough pressure gradient was 123.85 MPa·m-1.The nano-SiO₂ was modified by silane coupling agent KH-550,which was introduced into the polymer to prepare compound plugging agent.There was a methylene stretching vibration peak in FTIR spectra of the composite polymer.And the overall composition and the crystal structure of the material had no changed by X-Ray Diffraction analysis.Besides,the dispersion stability was better after the modification.The optimal conditions of the synthesis were determined through the orthogonal experiments.It showed that the monomer ratio of AM,AMPS and AA was 12:2:8,the cross-linking dosage was 0.1 g,the modified SiO₂ was 5wt%?50mL solution?.The study of its dehydration performance showed that under the condition of water,the effect of three cations on dehydration shrinkage had the following order:Al3+>Ca2+>Na+.The dehydration rates of gel in Al3+,Ca2+ and Na+ solutions were around 90%,50%and 20%,respectively.In kerosene,it was with good oil-water selectivity,and the speed of gel dehydration could be slowed down by the addition of SiO₂.Under the condition of air,the dehydration kinetic performance of the plugging agent was studied at 1000C.The dehydration reaction series of the gel without SiO₂ and the compound gel were 0.49 and 0.52,respectively,which indicated that the addition of SiO₂ could enhance the thermal stability of the gel.