Application of Thermal Resistant Gemini Surfactants in Highly Thixotropic Water-in-oil Drilling Fluid System

摘要

Traditional water-in-oil drilling fluids are limited by their shear thinning behavior.In this article,we propose the synthesis of a thermal resistant quaternary ammonium salt gemini surfactant DQGE-I.This surfactant was synthesized using monomers such as N,N-dimethyl-1,3-propanediamine,organic acids and epichlorohydrin,as well as blocking groups such as N-vinylpyrrolidone(NVP).The prepared surfactant exhibited various advantages over traditional surfactants,including excellent thermal stability,good emulsifying and wetting capability.The use of these surfactants was shown to improve the compactness of emulsifier molecules at the oil/water interface,as well as the overall emulsificaiton effect.Laboratory studies revealed that water-in-oil emulsions prepared using DQGE-I showed high emulsion breaking voltage,low liquid precipitation and small and uniformly distributed emulsion drops.Highly thixotropic water-in-oil drilling fluids based on DQGE-I showed low viscosity,high shear rate and thermal tolerance up to 260°C.Additionally,the proposed fluid was applied in 16 wells(including WS1-H2,GS3 and XS1-H8) in the Daqing Oilfield.Testing showed that DQGE-1 exhibited excellent Theological behavior and wall-building capability.The emulsion breaking voltage exceeded 1500 V,and the yield point/plastic viscosity ratio exceeded 0.4.The use of this surfactant can help to solve problems such as high formation temperature and poor well wall stability.