Research On Acid Stimulation Diverting Agent For Carbonate Reservoir

For oil well of carbonate reservoir containing water,water cut often increases after acidizing during the improper fluid placement.Paper explores acid stimulation diverting technology of water-in-oil(W/O)emulsion and salt sensitivity sol.Firstly,the paper systematically and deeply studied emulsion.W/O type emulsion was prepared by diesel oil as raw material.Alkyl polyethylene polyamine NEWJ-18,a switchable surfactant,was selected as emulsifier,by which diesel and high salinity water can form stable W/O type emulsion with oil-water ratio ranging from 1:9 to 4:6.This emulsion can be destroyed easily when contacting with acid because of the alternation of surfactant hydrophilic-lipophilic balance by acid,thus no problem of emulsification weakening flowback of spent acid exists.Evaluation of rheological properties of emulsion indicates that the lower the oil water ratio is,the higher the viscosity is.So emulsion with oil-water ratio of 4:6,which don't exhibit high viscosity,is suggested to be a diversion agent.During injection,the emulsion continues to develop when contacts with formation water until the water layer was blocked.Moreover,single tube mode and dual tube mode were designed to evaluate the injectivity and selective plugging of emulsion.The results show that the resistance factors reach more than 14 in the cores with permeability of 0.084?m2,0.10?m2,0.27?m2 when emulsion was respectively injected.In experiments of parallel cores with permeability ratio of 3.7,7.6,30.2,42.1,the experiments showed that the block rate of high permeable core could reach over 92%,and the block rate of low permeable core was less 12%,which demonstrated that emulsion has excellent plugging ability.At last,two groups of parallel natural carbonate cores with permeability of 0.0157?m2-0.0034?m2,0.0146?m2-0.0054?m2 were injected emulsion before acid.The results indicate that low permeability cores can achieve effective acidizing.In addition,the paper also studied salt sensitivity sol,after which mixed with simulated formation water or hydrochloric acid it's concluded that precipitation or gel generated after mix.Thus,salt sensitivity sol can be used as plugging agent of high permeable layer before acidizing.For core permeability,high water cut Salt sensitivity sol has selective plugging effect.When the permeability distinction of high permeable core and low permeability core is not big,low permeable cores were injected a small amount of salt sensitivity sol,which reduces the permeability of low permeable cores.