Study On Emulsification System For Cold Heavy Oil Production In Gudao Oilfiled

In view of the problems of low waterflooding recovery in Gudao ordinary heavy oil reservoirs and unsuitable for thermal recovery,emulsification and viscosity reduction flooding is one of the effective methods to improve the recovery of heavy oil cold recovery.Existing heavy oil emulsification flooding systems are usually formed under strong shear conditions,but it is difficult to achieve under actual reservoir driving conditions.Therefore,it is of great significance to construct a flooding system with good emulsification effect on heavy oil under low shear conditions for chemical cold recovery of heavy oil.Therefore,in this paper,the emulsifying ability,interfacial tension,and performance of forming emulsion of different types of surfactants were evaluated under micro-dynamic conditions by using micro-dynamic emulsifying experimental equipment,and the emulsifying displacement system with different performance was constructed.The microstability of emulsions formed by different emulsion displacement systems and Gudao heavy oil was analyzed by multiple heavy light scattering method.On this basis,the displacement performance of different emulsified systems was evaluated by the sand filling pipe displacement experiment,and the microscopic displacement mechanism was studied by using the glass etching model.Two kinds of emulsifying systems were constructed based on the microdynamic conditions.One was the strong emulsifying system with low interfacial tension:0.2%KPS and 0.3%DB/AC（1:1）,the interfacial tension reached 0.01 m N·m^-1 and the coefficient of emulsifying instability was 0.1.The other was the strong emulsifying system with ultra-low interfacial tension:0.2%SBT and 0.3%OB/AC（3:2）,the interfacial tension reaches 0.0004 m N·m^-1,and the emulsification instability coefficient was 0.The multiple light scattering stability analyzer was used to study the mechanism of emulsion aggregation and demulsification and stability formed by different emulsification systems.The results showed that the ultra-low interfacial tension and strong emulsification system OB/AC formed the emulsion with the smallest median particle size.The diameter distribution is concentrated near the median value,and the demulsification behavior of small oil droplets coalescing into large oil droplets is the least likely to occur.The stability parameter is the lowest,and the emulsion formed is the stablest.The results of sand-packing pipe flooding experiments show that the emulsification system OB/AC with strong emulsification,ultra-low interfacial tension and good micro-stability has the best effect in enhancing oil recovery,reaching 11.20%.The mechanism of oil displacement was proved by microscopic visualization experiments.The main mechanism of oil displacement was as follows:depending on its strong emulsifying ability,it can quickly emulsify dispersed oil blocks to form fine oil-in-water emulsions,which can then be carried by the displacement liquid to improve the oil washing efficiency;at the same time,relying on its ultra-low interfacial tension,it is easy to gradually pull the island oil into oil wire and break it into tiny oil droplets,which effectively starts the whole island residual oil;relying on its excellent peeling ability,the wetting competition of the remaining oil film on the glass surface can be gradually reduced until peeled off,thus reducing the residual oil saturation of the oil film and improving the recovery of heavy oil.