Study On Formation Water And Wellbore Corrosion And Scaling After CO₂ Flooding In Changqing

At present,CO₂ flooding technology has been widely used in major oilfields in the world as an important means to improve crude oil recovery.However,compared to overseas and domestic Jilin,Daqing and other oilfields,the CO₂ flooding pilot test carried out in Changqing Oilfield has high salinity of produced water(40 g/L?160g/L),high scale ion content,injected water and formation Water incompatibility.Previous studies have found that CO₂ flooding has serious problems of corrosion and scaling.Therefore,studying the corrosion and scaling rules of the wellbore after CO₂flooding can provide theoretical reference and technical support for future research on the anticorrosion measures of the CO₂ flooding injection production system,which is of great significance.In this paper,the effect of CO₂ on the static scaling of the reservoir was first studied,and the effects of temperature,pressure,and scale-forming ion concentration o n the scaling process of the reservoir were analyzed.The experimental results show:The injection of carbon dioxide will cause the rock to dissolve,and the scaling ions in the rock will be dissolved out.As the temperature and pressure decrease near the injection and production well,scaling problems will easily occur.The effects of temperature and flow rate on the scaling rate wer e analyzed by capillary method.The experimental results show:The faster the flow rate,the greater the degree of mixing of scale-forming ions in the solution,the faster the scaling rate;the higher the temperature,the less the CO₂ content in the solution,and the larger the p H value,resulting in faster scaling.In the study of CO₂ flooding on the wellbore corrosion law,the factors affecting the corrosion were analyzed using the hanging piece method and the weight loss method.The experimental results show:With the increase of the flow rate,the corrosion rate of the hanging piece accelerates;at 80?,the corrosion rate reaches a maximum;as the CO₂ partial pressure increases,the corrosion rate of the hanging piece accelerates.When the CO₂ partial pressure reaches a certain value,the corrosion product film on the surface of the hanging piece will reduce the corrosion rate;By comparing the corrosion under the scale with the blank corrosion,it is found that the scale film on the surface of the scale can inhibit the occurrence of corrosion to a certain extent,and plays a protective role.