Study On Sewage Reinjection Technology In Youfangzhuang Oilfield

The youfangzhuang oil area of Dingbian oil production plant in Yanchang oilfield is located in the northwest of Shaanxi,covering Shaanxi and Gansu provinces.There is a serious water shortage in the region,and the wastewater reinjection and development not only solves the water shortage situation of oil fields,but also saves water resources.The developed area has the characteristics of low pressure and low permeability,and the waterflooding development efficiency is low.The sewage in oil region has the characteristics of high content of sulfide,bacteria and scale-forming ions,and it has stronger corrosion and scaling property.Sewage injection leads to serious formation scaling and pipeline equipment corrosion scaling.At present,pipeline anti-scaling technology can’t meet the development requirements.improper sewage treatment leads to underground water source pollution and damages the ecological system.In this paper,the composition of sewage in youfangzhuang oil region is determined by chemical analysis,and it is known that the bacteria content,dissolved oxygen content,iron content,sulfide content,aggressive CO₂,scale-forming ions and average corrosion rate in water are not up to standard.The physical property analysis and potential sensitivity evaluation experiments of the reservoir are carried out,and it is known that the formation has medium speed sensitivity and water sensitivity,the bound water content of the reservoir is too high,and the residual oil saturation after water flooding is too large.Using Oddo-Tomsom saturation index method,the scaling situation of carbonate and sulfate in pipelines is predicted,and it is thought that the scaling situation of pipelines already exists at normal temperature and pressure.Aiming at the blockage of stratum by reinjection sewage in youfangzhuang oil region,CQ-2 acid scale remover was screened out by EDTA titration method as the stratum scale remover.in order to analyze the appropriate dosage of the scale remover,static scale removal experiments were carried out,and it was concluded that CQ-2 acid scale remover needed more than 10mg/L;Aiming at the situation of pipeline corrosion caused by reinjection sewage in youfangzhuang oil region,the composition of corrosion products was analyzed by using indoor static corrosion coupon test,and KS-1 corrosion inhibitor was screened out as a corrosion inhibitor for pipelines.in order to analyze the appropriate amount of corrosion inhibitor,it was concluded that the investment of corrosion inhibitor KS-1 needed to be more than 30mg/L by using the test method of corrosion rate and corrosion inhibition rate in stable state under conventional pressure.Aiming at the situation that the scale inhibition rate of the traditional process can’t meet the industry standard,the application of strong magnetic anti-scaling technology in youfangzhuang oil region is put forward,and No.4 and No.5 strong magnetic anti-scaling instruments with 71%scale inhibition rate are screened out.