Effect Of Star-type AM-AMPS Copolymer On Rheological Properties And Filtration Loss Of Water-based Drilling Fluids

Water-based drilling fluid in high temperature will turn rheological instability and the amount of filtration will also greatly increase.At present,the traditional methods at home and abroad usually use linear water-soluble modified natural polymer or synthetic polymer to control the rheology and filtration loss of water-based drilling fluid in the high temperature.These linear polymer treatment agents either undergo thermal degradation or own the ability to control the loss of drilling fluid,but will lead to a large drilling fluid system viscosity at high temperatures.The stability of rheology and the control of the loss of flux under high temperature are the technical problems that have not yet been solved.A plurality of star-shaped polymer is a linear branched rely chemically coupled to the same pivot center or branched polymer formed on the core.Compared to the linear polymers of the same molecular weight,star-shaped polymers have lower bulk and solution viscosities while star-shaped polymers have better thermal stability and solubility.The effects of star-shaped acrylamide and 2-acrylamido-2-methylpropanesulfonic acid copolymer on the rheological properties and filtration loss of water-based drilling fluids were studied in this paper.The main research contents are as follows:(1)Three kinds of star-shaped copolymers with different molecular weights were synthesized and characterized.Poly(St-alt-MAH),an alternating copolymer of styrene(St)and maleic anhydride(MAH),was prepared as a pendant group,and a water-soluble polyfunctional macromolecule initiator.Then,the multifunctional macromolecule initiator was used to copolymerize the aqueous solution of acrylamide(AM)and functional monomer 2-acrylamido-2-methylpropanesulfonic acid(AMPS)to prepare three different molecular weight centers for Poly(St-alt-MAH),a star-shaped copolymer having a branched chain of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid copolymer Poly(AM-co-AMPS),S-Poly(AM-co-AMPS).By characterizing,it was found that the thermal stability of S-Poly(AM-co-AMPS)was enhanced with the increase of molecular weight.(2)Exploring the effects of polymers with different molecular weights and different structures on the rheological properties of water-based drilling fluids.By using Bingham model and power law model,the effects of different molecular weight S-Poly(AM-co-AMPS)on the rheological properties of water-based drilling fluids before and after aging are investigated.L-Poly(AM-co-AMPS)and S-Poly(AM-co-AMPS)with the same molecular weight were synthesized and compared.The effects of polymers with different structures on the rheological properties of water-based drilling fluids were studied by ZNN-D6 six-speed rotational viscometer and Fann 50 SL high temperature and high pressure rheometer.It was found that S-Poly(AM-co-AMPS)with a concentration of 0.3% and a molecular weight of 20 million has stronger ability to stabilize the drilling fluid under high temperature conditions.(3)Investigating the effects of different molecular weights and polymers with different structures on the filtration loss of water-based drilling fluids.The effect of S-Poly(AM-co-AMPS)on the filtration loss and HTHP filtration before and after aging of water-based drilling fluids under different concentrations of L-Poly(AM-co-AMPS)with the same molecular weight were studied.It was found that S-Poly(AM-co-AMPS)with a molecular weight of 20 million and a concentration of 0.3% had a significant effect on the filtration loss of drilling fluid.