Experimental Study On Nano-stabilized Nitrogen Foam Flooding Mechanism In Carbonate Reservoir

Because of complex reservoir structure and harsh formation conditions,it is difficult to develop the fracture-vuggy carbonate reservoir.In the process of water flooding,the water content increases quickly and recovery efficiency is very low.Due to cracks and karst caves gas flooding followed by water flooding causes gas channeling.And water flooding and gas flooding have limited degree of enhanced oil recovery,large amount of remaining oil is left.It is due to high viscosity,foam can control fluid flow velocity and increase fluid sweep volume to improve oil recovery.For severe conditions such as high temperature,high salt in fractured-vuggy carbonate reservoirs in Tahe Oilfield,the Waring Blender method was used to study nano-stabilized foam system for fractured-vuggy reservoirs.For complex fractured-vuggy reservoirs according to Tahe Oilfield,the 2D and 3D visual physical models are designed and made by using the similarity criterion,and then water flooding,gas flooding and nano-stabilized nitrogen foam flooding experiments were carried out to figure out the utilization and distribution of remaining oil at each stage.Research the oil displacement mechanism of nano-stabilized nitrogen foam system in fracture-vuggy carbonate reservoir.It provides theoretical guidance for the application of nano-stabilized nitrogen foam in fracture-vuggy carbonate reservoir.It is found that the nano-black sheets stabilized nitrogen foam system has good temperature resistance,salt resistance and oil resistance,this systerm can adapt to the harsh conditions of fractured-vuggy reservoir well.Follow-up oil displacement experiment prove that nano-stabilized nitrogen foam can control gas mobility restrain viscous fingering that improve recovery efficiency of fracture-vuggy carbonate reservoir after different development stages.The nano-stabilized nitrogen foam increases recovery in fracture-vuggy reservoirs by improving oil flow degree,diverting flow channel to multiple directions,discontinuous displacement,reducing interfacial tension,and cooperating with gas and water to expand the volume of the wave.Nano-stabilized nitrogen foam can effectively sweep three kinds of microscopic residual oil and five kinds of macroscopic residual oil in fracture-cavity reservoir,which has a good effect of enhancing oil recovery.