Preparation And Properties Of The Nano-composite Hydrogels And Hydrophobic Association Hydrogels For Well-killing Application

Gel has advantages of low cost and high operability when it is used as killing fluids during underbalanced drilling.The strength of the traditional gel is weak and its sealing performance becomes poor after it is penetrated by sieve tube.According to the disadvantages of the traditional gel,monodisperse nano-silica composite hydrogel with high strength,hydrophobic association hydrogels and starch composite hydrophobic association hydrogels with self-healing characteristic were preparaed here.Static strength,pressure resistance properties,rheological properties and thermostability were studied by visual code method,pressure-resistance device,HAAKE RS600 rheometer and TGA/DSC STA,respectively.The microstructure and reinforced mechanism of the composite hydrogels were studied by SEM and FT-IR measurements.The results showed that,with the increase of the content of nano-silica,the static strength,breakthrough pressure,viscoelastic moduli and thermostability of the nano-silica dispersion/polymer composite gel were increased.The SEM images and FT-IR data indicated that the nano-silica particles were adsorped on the polymer chains by physical adsorption which made the gel pores smaller and the polymer chains thicker,therefore,the gel properties were improved.For HA-gels synthesized by AM and different hydrophobic monomers(LJ-02?LJ-05?LJ-06?LJ-07),NaCl had no obvious effect on gel gelling and healing,and the self-healing ability became better under 50?.Especially,the viscoelastic moduli after self-healing of association hydrogel sprepared by hydrophobic monomer LJ-06 reached 100% of the initial moduli.The association hydrogel synthesized by 2% hydrophobic monomer LJ-06 AM and starch had good self-healing capability.After self-healing,its viscous modulus reached 400% of the initial modulus and elastic modulus reached 380% of the initial modulus.And the breakthrough pressures before and after self-healing were 100kPa·m-1 and 60 kPa·m-1 respectively,which could meet the requirement of gel strength needed in well killing application.