Identification and Monitoring Technology of Leakage Risk in Ultra-High Pressure Water Injection Process

Ultra-high pressure water injection technology is mainly used in low permeability reservoirs. When the water injection pressure is generally higher than the fracture pressure of the formation, the formation around the water well will form micro-fractures, thus improving the oil recovery. In the process of high pressure water injection, there will inevitably be leakage, and oil leakage is an important problem affecting the urban ecological environment in oil region. Petroleum pollutants entering groundwater will seriously affect human health. Timely discovery and treatment is the key to protect the urban ecological environment in oil areas. Monitoring methods of petroleum pollutants in water include ultraviolet fluorescence method, infrared method and gravimetric method. Among many methods, ultraviolet fluorescence method is the national standard method for monitoring petroleum pollutants in water, and the monitoring accuracy can reach 10–10 g/mL, which requires a small sample size and is suitable for the analysis of trace pollutants. At present, the monitoring devices for oil pollutants in water based on Ultraviolet fluorescence method are mainly used for monitoring oil spills on sea surface. Imported monitoring devices are expensive and have poor versatility. Domestic equipment started late, and its core components mainly depend on imports, which is difficult to meet the monitoring of oil pollutants caused by ultra-high pressure water injection. Based on the ultraviolet fluorescence method, the fluorescence characteristics of crude oil in Shengli oil area were analyzed, and a monitoring device for petroleum pollutants was designed for ultra-high pressure water injection in Shengli oil area. The device has strong stability and high-test accuracy, and the relative standard deviation is less than 1% in the test of sample solution with concentration higher than 5 mg/L. The relative standard deviation of the sample solution at the concentration of 1–5 mg/L is about 5%. The relative standard deviation is about 6% when the concentration of sample solution is lower than 1 mg/L. It can effectively monitor the content of petroleum hydrocarbon pollutants in the groundwater of Shengli oil region and lay a solid foundation for groundwater environmental monitoring in Shengli oil region.