Study On The Synthesis And Properties Of Emulsifier In Oil-Based Drilling Fluid System

Compared with water-based drilling fluid,oil-based drilling fluid has a strong inhibition performance,which is conducive to wellbore stability,and also has temperature and salt resistance,good lubricity,high resistance reduction rate,and good reservoir protection.In oil-based drilling fluid system,emulsifier is the most important treatment agent,and its emulsification performance is an important index to measure the temperature resistance and emulsification stability of the system.According to the research status of emulsifier at home and abroad,this research designed the molecular structure which based on the mechanism of emulsifier,then strong hydrophilic group amide group is introduced,and the synthesis method,main reagents and reaction conditions are determined through investigation.The fatty acid of tall oil and organic amine are optimized to undergo incomplete amidation reaction at170?for 2h,so we get the intermediate product and with binary anhydrides are obtained at 250?.A kind of polyamide carboxylic acid emulsifier was synthesized by adding a certain amount of 5#white oil and stirring for 1h at 80?.The laboratory evaluation experiment shows that the emulsifier has high emulsification rate and fine emulsification stability under different oil-water ratio conditions;the temperature resistance is up to 200?,the concentration of anti CaCl₂ brine solution is up to 30%,and the interfacial tension is only 0.8mN/m,which is conducive to the stability of the emulsion;compared with other main emulsifiers,it has better emulsification performance at high temperature,and has better compatibility than the other oil-based drilling fluid treatment agents.With synthetic emulsifier as main emulsifier,auxiliary emulsifier,organic soil and filtrate reducer are selected,According to the orthogonal test method,the oil-based drilling fluid system with stable emulsification performance is selected,which is suitable for shale gas well development conditions:4%main emulsifier+2%auxiliary emulsifier+1.5%wetting agent+2.5%organic soil+5%filtrate reducer+2%CaO+barite.The system is better than others.It can resist high temperature to 200?;the system performance is stable under the density of 2.4g/cm³;it can resist the salt concentration of CaCl₂ to 40%,and according to the characteristics of salt invasion in actual production,the system performance is stable when NaCl solution is added to saturation into 25%CaCl₂ aqueous;when dilute water is added into the system to 14%,it is equivalent to changing the oil-water ratio to 70:30,and the performance is still within the normal range;when 8%shale cuttings of the Wei204H37-8 well is added into the system.The properties is still controllable.The rolling recovery rate of the system is 90.62%.The evaluation results show that the optimized oil-based drilling fluid system has good performance and can meet the requirements of drilling fluid with high temperature of 200?,density of 2.4g/cm³ and strong inhibition.