The flowback fluid during oil acidizing operation process would directly enter the gathering and transportation system,resulting in deterioration or invalidation of conventional treatment agents,such as demulsifiers.The flowback fluids from the Chengdao Oilfield were divided into two types ，one is high mass concentration,the other is low mass concentration.The high mass concentration flowback fluid is transported back by the operating ships to the shore for further treatment,and the low mass concentration flowback fluid is directly discharged into the gathering and transportation system under the ground.The flowback cycle is long and affected by sea conditions. In order to reasonably estimate the amount of high mass concentration flowback fluid produced by crude oil dehydration process,this paper analyzes the factors affecting the oil⁃water separation of acidified flowback fluid.The volume of flowback fluid and indicators of water in two acidified oil wells were monitored,and thermal deposition of mixed flowback fluid and crude oil were tested. According to the demulsification effect and the water content of crude oil form the joint station, the quantified critical control index are listed as: the pH value of the water from the acidified oil well is higher than 6, the iron ion concentration is lower than 250 mg/L；and the auxiliary control index: the amount of backflow reaches 6 times higher than that of the acid liquid. An inspection method is proposed for the on⁃site operation of the flowback fluid discharging into the gathering and transportation system, properly reducing the flowback time without adding a new processing flow, which is beneficial to increase the oil well production rate and improve economic efficiency.

The stability of emulsion of Shengli crude oil and variation of drop size were investigated using LUMisizer-LS610. At the same time, the influences of the emulsifier concentration，the wateroil ratio, temperature and electrolyte on the stability of emulsion and the drop size were also explored. The results show that the higher emulsifier concentration is, the smaller the drop size would be and the more stable crude oil emulsion is. The greater the proportion of oil phase in emulsion, the more stable the emulsion is. As the temperature increases, the good emulsified effect is obtained, however, the stability of the emulsion is reduced. The electrolyte can enhance the stability of the emulsion and reduce the drop size.