Study On Synthesis And Application Of Oil-Soluble Copolymers

Drilling fluid is a commonly used working fluid in drilling operations.Oil-based drilling fluids are widely used in drilling engineering under extreme conditions such as deep wells and ultra-deep wells with high temperature and high pressure due to their excellent high temperature resistance and lubricity.The performance of drilling fluid is the key factor to determine the success or failure of drilling.However,there are many problems and shortcomings in key additives in domestic oil-based drilling fluids.For example,the amount of anti-high temperature emulsifier added is very large,it is easy to degrade at high temperature,and most of them rely on imports;there are few domestic research and reports on viscosity-increasing and cutting polymers,and there is a lack of practical products.These problems are restricting the development of oil-based drilling fluids.Therefore,we redesigned the molecular structure,different modifiers were selected to modify the polymaleic anhydride/linear α-olefin alternating copolymer.We prepared emulsifiers for oil-based drilling fluids,viscosity-increasing and shearing polymers for oil-based drilling fluids,and a class of betaine-type surfactants,and analyzed their structural characterization,performance evaluation,and functional applications.(1)The copolymer emulsifier with the structure of alternating tertiary amine moieties and alkyl groups was synthesized by the reaction of N,N-dimethylethylenediamine and the alternating copolymer of maleic anhydride with linear alpha-olefins.The structure,compositions and molecular weight of copolymer emulsifiers were characterized by FT-IR spectra,1H NMR spectra,elemental analyse and multi-angle laser light scattering.The thermal stability and interfacial activity of the copolymer were tested by thermogravimetric analysis and interfacial tensiometer.The emulsification properties of the copolymers were evaluated by static observation method,optical microscope and demulsification voltage,and the rheological properties of the copolymers in oil-based drilling fluids were also explored.The results show that the alternating molecular structure not only brings high interfacial activity and emulsifying performance,but also enhances the temperature and salt resistance due to the introduction of tertiary amine groups.Among them,the emulsion of GPM-16 maintains a stability rate of 98%at 232℃ for 16 h and standing for 6 h.The demulsification voltage exceeds 400 V,and it has stable rheology and stability in oil-based drilling fluids.(2)The above-obtained copolymer in which the alkyl chains and tertiary amine groups are alternately arranged is subjected to quaternization reaction with sodium chloroacetate to obtain a series of betaine-type macromolecular emulsifiers with different alkyl groups.Surface interfacial activity was tested by surface tensiometer and interfacial tensiometer.The solution properties of the copolymers were characterized by UV spectrophotometer,Zeta potential and viscometer;the emulsification properties were evaluated by static observation method and optical microscope.The results show that the emulsifier has high surface activity and good amphiphilicity,and the different alkyl chain lengths have obvious differences in solution properties and emulsification effects.Among them,the SPM-16 emulsion was hot rolled at 90 C for 16 h and kept at rest for 2 h,maintaining a stability rate of 95%,showing strong emulsifying performance.(3)The alternating copolymers of maleic anhydride and 1-tetradecene were modified with diethanolamine,ethanolamine and isopropanolamine,and three groups of viscosity-increasing and cutting polymers with different proportions of polar groups were obtained.The emulsion stability of polymer compound Span 80 was evaluated by demulsification voltage tester,static observation method and optical microscope;by testing the rheological properties of emulsion and weighted emulsion,the polymer in solid-free oil-based mud system viscous lifting and cutting performance.The results show that the introduction of an appropriate amount of polar groups can improve the stability of the emulsion and play a role in increasing the viscosity of the emulsion.Among them,when the modification ratio of polymer and diethanolamine is 1:1.5,it can play a strong role in increasing viscosity and cutting in emulsion and weighted emulsion.