| Oil-based drilling fluid is a kind of working fluid commonly used in shale gas drilling.In recent years,it has been gradually applied in shale gas drilling site.Emulsifiers play an important role in the formulation of oil-based drilling fluids.At present,there are many researches on the optimization and compounding of existing emulsifiers such as soap salts of carboxylic acids,soap salts of sulfonic acids,organic acid esters and amines.And research on molecular structure design of emulsifiers is increasing.In this paper,the relationship between the structure and properties of the core treatment agent emulsifier in oil-based drilling fluid is studied in detail.The type and molecular structure of hydrophilic group,hydrophobic group and coupling group of emulsifier are designed to synthesize emulsifier NGE-1.Infrared analysis and mass spectrometry results show that the emulsifier NGE-1 is successfully synthesized,and the product structure is consistent with the design.Emulsifier NGE-1 has strong ability to reduce the interfacial tension between oil and water.The heat dampening voltage is 571 V at 200°C.It has strong resistance to high temperature and good emulsion stability.After the emulsion is aged at 200°C,the emulsion rate can still reach 96% after standing for 24 hours.On this basis,through the optimization of other core treatment agents in the oil-based drilling fluid system,the appropriate water phase activity and oil-water ratio are adjusted,and finally a set of oil-base drilling fluid system is formed.Its upper limit of density is up to 2.4g/cm3,and the temperature resistance up to 200 °C.The system can maintain stable performance for a long time under the condition of high temperature,and the longest aging time can reach 72 h.The system has good emulsion stability and resistance to high temperature.The system also has excellent performance against 15% water pollution and 15% salt contamination. |
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