Synthesis And Evaluation Of Compound Temperature-tolerant And Salt-tolerant Fluid Loss Control Agent

With the development of exploration technology for high and deep wells and high salinity wells,as an important part of drilling fluid additive,drilling fluid filtrate reducer is faced with severe test of high temperature and high salinity intrusion.The development of high temperature and high salinity filtrate loss reducing agents has become a major issue in the world oil and gas exploration field.During this study,the surface of nano-SiO2 was modified by using silane coupling agent KH-570,and the conditions as follows,the concentration of KH-570 is 20.0 wt%,the pH value is 4.5,the reaction temperature and time is 65 ? and 2.0 h,respectively.Here,the reaction solvent is ethanol and water,and the volume ratio 3:1.The FT-IR analysis shows that the modified nano silica contains the absorption peak at the wavelength of 2942.97 cm-1,and the absorption peak is contained at the wavelength of 1626.90 cm-1,corresponding to the related absorption peak of KH-570,as a result,it was confirmed that the nano-SiO2 was successfully modified by KH-570.The filtrate reducer P(AASD)/nano-SiO2 was synthesized by using AM,SSS,DMDAAC,AA and modified nano-SiO2 through free radical aqueous solution polymerization.It is worth mentioning here that the initiator is APS.Moreover,the optimum reaction conditions were obtained by using the method of single factor analysis.As a result,it was confirmed that the content of nano-SiO2 is 1.0 wt%,monomer ratio n(SSS):n(AM):n(AA):n(DMDAAC)is 0.5:1:1:0.2,the reaction temperature is 65 ? the pH value is 7.0,single body concentration is 20 wt%and the initiator dosage is 0.6 wt%(APS).Besides,the results of infrared spectrum analysis(FT-IR)and nuclear magnetic resonance spectroscopy(1H-NMR)show that the molecular structure of P(AASD)/nano-SiO2 meets the designed.The average molecular weight(Mn)is 115172,weight average molecular weight(Mw)is 303323 and molecular weight distribution index of the product is 2.63.The application properties,such as filtration loss performance,temperature resistance,salt resistance and rheological properties,were evaluated systematically.As a result,when the filtrate loss agent P(AASD)/nano-SiO2 added in the fresh water slurry is 2.0%,the medium pressure filtration loss at normal temperature and 200 ? is 6.6 mL and 9.6 mL the plastic viscosity is 24.0 mPa ·s,12.0 mPa ·s,and the pressure loss of the brine base slurry and the saturated brine base slurry is 6.8 mL and 9.8 mL.Thus,it was confirmed that the P(AASD)/nano-SiO2 has excellent filtration,temperature resistance,and salt tolerance.For the fresh water based drilling fluids system with 2.0 wt%P(AASD)/nano-SiO2,the dynamic shear force is 24.0 mPa·s,the dynamic shear force is 2.0.The sedimentation stability showed that within a certain range with the increase of the addition of polymer drilling fluid,the upper liquid is less and less,more and more stable system.The filtration mechanism of the synthesized P(AASD)/nano-SiO2 was analyzed by different experimental means.The influences of P(AASD)/nano-SiO2 on the liquid morphology of aqueous solution and water based drilling fluids were studied by using SEM analysis,and the results show that a network structure was formed by the polymer.The results of SEM show that the P(AASD)/nano-SiO2 was absorbed on the surface of mud cake and formed a hydrated membrane.The results of laser particle size analyzer show that the clay particles were stabilized and dispersed by P(AASD)/nano-SiO2.The Zeta potential shows that the absolute value of Zeta potential increases with the increase of polymer dosage,and its adsorption capacity is strengthened.