1、 Technical Introduction
Surfactants mainly emulsify crude oil by reducing the interfacial tension between oil and water, changing the wettability of oleophilic rock surfaces, and reducing viscosity fingering phenomena to improve oil displacement efficiency.
On the basis of nitrogen huff and puff technology, surfactants for oil displacement are added. Under the high pressure of the gas, the agents enter deeper well zones, quickly stripping off more crude oil from the pores, forming a water in oil emulsion with lower viscosity, and improving oil washing efficiency.
The composite throughput method has a wide range of applicability and there are no strict conditional limitations. It can be used for heavy oil or thin oil; It can be used for both high permeability reservoirs and low-permeability reservoirs. For small fault blocks and complex lithology reservoirs with poor inter well circulation and ineffective other recovery methods, it has more advantages.
2、 Oil increase mechanism
This technology mainly involves the synergistic injection of surfactants into the formation and nitrogen gas. Due to the fact that chemical agents are mainly composite surfactants with good temperature resistance, salt resistance, emulsification and other properties, they have the following mechanisms of action to improve the oil well throughput effect and extend the production cycle.
（1） Under the high pressure of gas, the agent can enter deeper well zones, quickly stripping away more crude oil from the pores and improving oil washing efficiency;
（2） Under the synergistic effect of gas and surfactant amphiphilic molecules, the interfacial tension between oil and water is greatly reduced, facilitating the formation of water in oil emulsions with lower viscosity and reducing the flow resistance of crude oil during the permeation process.
（3） After surface active agents are adsorbed on the surface of rocks, they change the wetting properties of reservoir rocks, making it easier for crude oil to flow out.
（4） The inorganic components in surfactants can have a certain shrinkage effect on rock binders, increase the permeability pores of reservoir rocks, reduce permeability resistance, thereby extending the production cycle of oil wells and improving their liquid production capacity.
（5） Composite throughput combines the advantages of steam injection throughput and surfactant solution injection throughput, and through synergistic effects, the oil increase effect is more significant.
3、 Adapt to well conditions
4、 Technical application cases
The pilot test of nitrogen foam flooding in five well groups, such as L80-60 of C6 block in XX Oilfield, has achieved good results, with cumulative oil increase of 80000 tons and enhanced oil recovery of 6%.
