Influencing Factors Of Pressure Fluctuation Flooding In Tight Reservoirs

Aiming at the problem that crude oil in tight reservoir is difficult to be driven,the method of using pressure fluctuation to displace crude oil in tight matrix is studied.Using natural cores and artificial cores,the law of pressure conduction of water in compact matrix and high permeability region is studied.It is found that the law of pressure conduction of water in the two areas is quite different.The experimental results show that the lower the permeability,the longer the time required for pressure balance at both ends of core,and the lower the velocity of pressure conduction.The influence of pressure fluctuation on water flow in heterogeneous reservoirs is experimentally studied by using parallel cores and combined injection and separate production cores.The experimental results show that,for single-phase fluids,pressure fluctuation inhibits the non-uniformity of liquid flow in reservoirs with barriers,and in reservoirs without barriers,pressure fluctuation enhances the non-uniformity of liquid flow.Using self-made 30 cm long homogeneous and heterogeneous cores,experiments of stable water injection,unstable water injection,stable gas injection and unstable gas injection for oil displacement were carried out respectively.The experimental results show that in homogeneous cores,the displacement efficiency of stable injection and unstable injection is basically the same,and the displacement efficiency of unstable gas injection is higher than that of stable gas injection.In heterogeneous cores,whether water or gas flooding,pressure fluctuation is conducive to enhancing oil recovery;unstable water flooding starts early,and oil recovery increases greatly;in the case of the same permeability gradient,gas flooding pressure fluctuation enhances oil recovery more greatly,which shows that unstable gas injection is an effective means of tight reservoir development.