Synthesis, aggregation behavior of alternating copolymer emulsifier in oil solution and its application in oil-based drilling fluids

In order to solve the emulsification problem of oil-based drilling fluids under high-temperature conditions, 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 1-octadene (PMAO). The structure compositions and molecular weight of copolymer emulsifiers were characterized by FT-IR spectra, H-1 NMR spectra, elemental analyse and multi-angle laser light scattering. The influence of tertiary amine moieties proportion in copolymer emulsifier on aggregation, interfacial activity, pH-response and emulsion stability were studied. The abundant presence of tertiary amine makes copolymer stabilize water-in-oil emulsion under neutral and weak alkaline conditions while destabilizing the emulsion under acidic conditions. Combining the above experimental data and the stability of water-in-oil emulsions prepared by the copolymer emulsifier, it was found that the emulsifier which has a high proportion of tertiary amine was indeed better at the performance of salt resistance under high temperature. When the copolymer emulsifier (D-100) was used in an oil-based drilling fluid system, the electricity stability is greater than 1000 V and the filtrate volume is only 0.6 mL after aging at 232 degrees C for 16 h. (C) 2021 Elsevier B.V. All rights reserved.