Experimental Study On Phase Permeability Characteristics Of Emulsion Flooding In Heavy Oil Reservoirs

The heavy oil chemical compound cold recovery technology is an important means to further improve the recovery of oil reservoirs.The use of chemical viscosity reduction instead of heating to reduce viscosity solves the problems of high emissions,high cost,and poor efficiency in thermal recovery of heavy oil.It is an effective replacement technology to increase the recovery rate after huffing and puffing,and has the advantages of low carbon and low cost.In the process of oil displacement with viscosity reducer in heavy oil reservoirs,the viscosity reducer and crude oil form an emulsion,which can adjust the plugging system,expand the scope of the viscosity reducer,and achieve the purpose of greatly improving the oil recovery.However,the current understanding of the mechanism of the effect of viscosity reducers with crude oil emulsification,percolation,and oil displacement is unclear,and there is an urgent need to carry out research on the chemical composite cold recovery and oil displacement mechanism.In view of the high viscosity of heavy oil,the dispersion effect of the emulsion prepared by the mechanical stirring method is poor,so the ultrasonic dispersion method was used to prepare the thick oil emulsion.The effects of different surfactant concentrations,oil-water ratios and kinetic conditions on the type,stability,microscopic characteristics,and rheological properties of the emulsion were studied,thereby revealing the properties and characteristics of the heavy oil emulsion,and based on this,the stability is preferred Good emulsion system.Carry out one-dimensional O/W emulsion flooding heavy oil seepage experiment,water flooding W/O emulsion seepage experiment,and combine with the microscopic experiment,clarify the effect of different oil-water ratio,surfactant concentration,heavy oil viscosity and other factors.The influence mechanism of the two-phase permeability curves of O/W emulsion and heavy oil,and W/O emulsion and water.The results show that the emulsion system prepared by the ultrasonic dispersion method has good stability,and the centrifugal dispersion does not stratify.When the concentration of the surfactant solution is higher than 0.1 wt% and the oil-water ratio is less than 1:3,an O/W type emulsion is formed,the particle size reaches the nanometer level,and it is a shear thickened swelling fluid.When the surfactant concentration is less than 0.1 wt% and the oil-water ratio is greater than 1,a W/O emulsion is formed,which is a shear-thinning pseudoplastic fluid.In the W/O emulsion-heavy oil two-phase percolation experiment,the higher the surfactant concentration and the greater the oil-water ratio,the higher the relative permeability of the emulsion under residual oil saturation,and the O/W emulsion The larger the two-phase flow span with the oil phase,the higher the recovery factor.In the W/O emulsion-water two-phase percolation experiment,the greater the oil-water ratio,the greater the surfactant concentration,and the higher the relative permeability of the emulsion under residual oil saturation,the water phase and the W/O emulsion.The larger the two-phase flow span of the two phases,the higher the waterflooding recovery factor.In the microscopic experiment,when the O/W emulsion drives the heavy oil,the sweeping effect of the emulsion itself produces higher displacement energy and drives out the residual oil.The surfactant solution in the system will emulsify the residual oil a second time,produce small emulsified oil droplets,block the channeling flow channel,expand the spread,and improve the oil recovery.The plugging ability of W/O emulsion is determined by its viscosity.The greater the oil-water ratio,the lower the viscosity of the W/O emulsion,the easier it is to form flow channels during water flooding,the larger the volume of the sweep,and the higher the recovery rate.