A novel salt-responsive zwitterion polymer tackifying-fluid loss additive
As deep,ultra-deep and unconventional oil and gas production advances continuously,salt contamination in the process of well drilling has brought a serious challenge to water-based drilling fluids under the conditions of extreme salinity and high temperature,and it can deteriorate the rheology and filtration performance of drilling fluid rapidly.In this paper,a novel zwitterion polymer tackifying-fluid loss additive(PAMN)with"salt-responsive"characteristics is synthesized through free radical polymerization reaction.In addition,its molecular structure,thermal stability and viscosity increasing and filtration reducing performance are characterized by infrared spectroscopy(FT-IR),nuclear magnetic resonance hydrogen spectroscopy analysis(1H-NMR),thermogravimetric analysis(TGA),molecular simulation technology(MS),scanning electron microscopy(SEM),and drilling fluid rheological and filtration analysis,and its"salt-responsive"mechanism is revealed.And the following research results are obtained.First,the PAMN synthesized in this paper has a thermal degradation temperature of 285℃,and its molecular chains have much larger mean square displacement,diffusion coefficient and gyration radius in saturated saline than in pure water.The gyration radius in saturated saline and pure water are 12.5 Å and 3.8 Å,respectively.Second,when the sodium chloride content is 0,the positive and negative ion groups within or between PAMN molecular chains form a spatial network shape through electrostatic attraction and curl into the spherical structure.As the sodium chloride content increases,the molecular chains gradually transform into more soluble flexible chain structures,exhibiting positive responsiveness to sodium chloride.Third,PAMN can increase the apparent viscosity of saturated-saline drilling fluid by 542.9%,and reduce the fluid loss from 194 mL to 4.8 mL,which indicates its good performance in tackifying and fluid-loss reducing.In conclusion,the successful development of PAMN has fundamentally transformed the traditional drilling fluid treatment agent from"salt-resistant"to"salt-responsive",and this product has promising application prospects in the oil and gas developmentof salt-gypsum-bearing deep and ultra-deep strata.
Deep and ultra-deep strataSalt-gypsum bedWater-based drilling fluidSalt responsiveTackifyingFluid-loss reductionZwitterion polymer
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