Study On The Effect Of Reinjection Of Produced Water On Reservoir Damage

With the continuous reduction of water resources in the world,the phenomenon that produced water is injected into the reservoir more and more frequently.The produced water is a mixture of complex components.It usually contains suspended oil droplets,solid matter,microorganism,chemical addition agent and other substances.If they are injected into the formation with produced water,which will cause a certain degree of damage to the formation and affect the performance of water injection development.Therefore,it is of great value to analyze the mechanism of particle retention and plugging in porous media,the combined influence mechanism of oil-water mobility and solid particles,the kinetics model of scaling of barium sulfate,and the chemical balance mechanism of scaling.This paper mainly studies from the following aspects:Firstly,on the basis of reservoir damage evaluation model,the mechanism of particle blockage is analyzed,and the deep bed filter model is studied to fit the impedance of the formation stage of the internal filter cake.According to the deep bed filter model,the core impedance curve of the inner filter cake is fitted,when the injection water specification is in the A-level standard of SY/T5329-94,and artificial core conditions of length 5cm,porosity 10%,gas permeability 1×10-3μm2.The coefficient of filtration and the damage coefficient of reservoir are obtained by the simultaneous impedance slope equation,and the relationship between the two and the reservoir damage is analyzed.Secondly,the impedance curves of internal filter cake and outer filter cake were separately fitted,and the conversion time was determined by using impedance model including the ratio of water-oil mobility.When injection water of solid particle concentration 30mg/L,diameter 1.5μm and 2μm,and artificial core conditions of length 5cm,porosity 10%,gas permeability 1 × 10-3μm2,the quadratic function is used to fit the core impedance of the internal filter cake in the impedance model containing the water-oil mobility ratio.After the production of the outer filter cake,the transformation time,reservoir damage coefficient and filter coefficient are determined by fitting the impedance curve with a piecewise function,and the variation of parameters is analyzed with the impedance model.Then,according to the barium sulfate scaling model,the concentration distribution equation of barium ion and sulfate ion was obtained,and the change trend of scaling ions in core was simulated when The ion concentration ratio is within the range of 0.1381 to 2,2096 and artificial core conditions of length 5cm,porosity 10%,gas permeability 1×10-3μm2.Combined with the chemical equilibrium constant,the mass balance equation in barium sulfate scaling model is improved,and the impedance slope equation for producing barium sulfate scale and calcium sulfate scale in reservoir is derived.The dynamic response coefficient and reservoir damage coefficient are calculated by image method,and the distribution of scaling anions cations in core is simulated.