Cause Analysis Of Under Injection In Xinzhan Oilfield And Research On Injection Increasing Measures

After the development of Daqing oil field,the production capacity of new water injection wells is not increased,and the injection rate of water injection wells in the periphery is seriously reduced.In order to clarify the cause of under injection of water injection wells in Xinzhan oilfield and increase the injection volume of injection wells,this paper carried out the reservoir sensitivity evaluation experiment of Xinzhan Oilfield by using the equipment of scanning electron microscope,X-ray diffraction and laser particle size analyzer,combined with the indoor core displacement experiment,and analyzed the influence of different production conditions and injected fluid on the fluid flow capacity of reservoir;Test and analyze the water quality of water injection wells to clarify the reasons for insufficient injection of water injection wells in Xinzhan oilfield;Finally,the optimization experiments of different plugging removal agents are carried out to determine the plugging removal and injection increase scheme of water injection wells.The results show that the reservoir of Xinzhan oilfield belongs to medium weak velocity sensitive,strong water sensitive and medium weak acid sensitive reservoir;Affected by the salinity,suspended solids,oil content and bacteria and microorganisms in the formation injection fluid,the causes of under injection are relatively complex,but the whole can be divided into organic blockage and inorganic blockage.Oil contamination was found in some of the injected water,with a total oil content of 23-61mg/L,indicating that the injection well will be affected by the oil content in the injected water.In addition,under the restriction of profile control technology,some polymer gel will block the formation of the water injection well after profile control,which will affect the water absorption capacity of the formation and cause the pollution of organic matter.In addition,the content range of suspended solids in the injected water is 10-154mg/L.The median particle size range of suspended solids is 4.623 ～15.67 μm.Iron oxide particles in the metabolites of sulfate reducing bacteria,iron bacteria,saprophytic bacteria and other bacterial microorganisms are also one of the reasons for blocking the formation.The salinity of injected water in block M is low,between575.0-635.0mg/l,which is easy to cause formation water sensitivity.B.The salinity of the injected water in Block D is relatively high,between 5136.4-5804.1mg/L,but the injected water contains bicarbonate ions,calcium ions and magnesium ions.At a certain temperature,bicarbonate ions combine with calcium ions and magnesium ions to form precipitation,resulting in underinjection of water injection wells.Through the screening and compounding of agents,the injection increase schemes for injection wells with different plugging removal causes are determined: inorganic plugging removal formula: 12.5% hydrochloric acid +1.875% HF + 1.0% HBF4 as the main plugging removal agent,1% oil-soluble demulsifier,HLX corrosion inhibitor with mass concentration of 2.4%,1.3% WDJ clay stabilizer,3.5%WF-100 iron ion stabilizer,3% citric acid secondary precipitation control agent 1% YCH-1thickener and 1.25% cationic polymer YLZ-a reservoir protector;The organic plugging removal formula is: 1% DH-II + 1% JFC.