Research On Reinjection Capacity And Plug Removing Measures Of Produced Water In Salt-resistant Polymer Flooding

In the process of oilfield development,with the industrialization of salt-resistant polymer flooding,the production of produced water by salt-resistant polymer flooding increases year by year and is applied in injection,while suspended matter,suspended oil droplets and residual polymer in injection water are the main factors causing reservoir blockage.It is of great significance to study the quality characteristics of produced water in salt-resistant polymer flooding and the influence law of reinjection on permeability of different oil layers for treating water quality index of reinjection and improving the development effect of oilfield water injection.In this paper,quality characteristics of salt-resistant polymer flooding produced water and the matching relationship between suspended particle size and core with different permeability were studied firstly.The core flow experiment was designed to obtain the influence of water injection with different water quality on oil layer and its blocking mechanism,so as to determine the injection boundary of oil layer with different permeability.The effects of different methods on the plugging of produced water in salt-resistant polymer flooding were compared through the plugging experiment.Core flow experiments show that: the concentration of suspended matter,oil content and residual salt-resistant polymer in produced water of salt-resistant polymer flooding will affect the injection and cause plugging.In order to ensure that the injection of produced water of salt-resistant polymer flooding causes low damage to oil layer,the concentration of suspended matter in the injection water of 100 m D core should not be higher than 10mg/L and the oil content should not be higher than 10mg/L.The concentration of residual salt-resistant polymer shall not be higher than 150mg/L;For 200 m D cores,the concentration of suspended solids in the reinjection water should not be higher than 15mg/L,the oil content should not be higher than 20mg/L,and the concentration of residual salt-resistant polymer should not be higher than 150mg/L.For400 m D cores,the concentration of suspended solids in the reinjection water should not be higher than 30mg/L,the oil content should not be higher than 20mg/L,and the residual salt resistant polymer concentration should not be higher than 150mg/L.The experiment of plug removal shows that the permeability recovery rate of each core is more than 60% and the plug removal rate is more than 40% after plug removal by chlorine dioxide solution.Chlorine dioxide can be applied to all kinds of reservoirs,and the best effect is achieved for reservoirs with high permeability and high plugging degree.Surfactants have a better plug removal effect on low permeability core than high permeability core,and are more suitable for oil reservoirs with low permeability and high residual oil saturation.Surfactants can mainly remove the adsorption of salt resistant polymers and reduce oil-water tension.The results of this study have a positive effect on water quality treatment index and reservoir protection of produced water reinjected by salt polymer flooding.