technical field

The invention relates to a treatment method for oilfield oil production sewage, in particular to a micro-nano bubble treatment method for oilfield oil production sewage, belonging to the technical field of sewage treatment and oilfield development.

background art

A large amount of sewage is generated during the exploitation process of oil fields, and direct discharge can easily cause serious environmental pollution. Therefore, the harmless treatment or resource utilization of oil fields sewage has become an urgent problem to be solved. On the other hand, in the middle and late stages of oilfield development, polymer (partially hydrolyzed polyacrylamide, PHPA) enhanced flooding technology is widely used to enhance oil recovery. At present, clear water is mainly used to prepare polymer flooding systems (referred to as compounding polymers), which consumes a large amount of fresh water resources. Oilfield produced sewage has the characteristics of high salinity, high oil content and high suspended matter content. It has poor oil displacement effect due to its low viscosity when directly used to formulate polymer flooding systems.

Micro-nano bubbles refer to bubbles with a diameter of less than 50μm. Compared with ordinary bubbles, micro-nano bubbles rise slowly in water and exist for a long time, and collisions and ruptures between bubbles mostly occur below the water surface. When micro-nano bubbles rupture,·OH free radicals are generated, which are conducive to the degradation of organic matter in sewage, so they have been used in the treatment of organic matter sewage. Ions, suspended matter and oil existing in the emulsified state in oilfield sewage affect the compounding effect. Micro-nano bubbles are used to treat oilfield sewage. Their role is different from that of organic sewage. It mainly plays a role in demulsification, aggregation and promotion. The reaction between ions, which in turn plays a role in reducing the oil content, suspended matter content and salinity. After searching, there are no reports on the micro-nano bubble treatment method for oilfield oil production wastewater.

summary

Aiming at the problems that the current polymer flooding system is mainly prepared with clean water, which consumes a large amount of fresh water resources, and at the same time, a large amount of sewage is generated during the oil production process, which is directly discharged and causes serious environmental pollution, the invention provides a micro-nano bubble treatment method for oil production sewage in an oil field.

The micro-nano bubble treatment method for oilfield oil production sewage disclosed by the invention is characterized by: Introduce the micro-nano bubbles generated by the micro-nano bubble generator into a position 2-60cm below the liquid level of the oilfield oil production sewage from the bottom of the container or the bottom of the pool. Based on the salinity of the oilfield oil production sewage ranging from 5000 to 60,000 mg·L-1, the oil content ranging from 10 to 200mg·L-1, and the suspended matter content ranging from 1 to 100mg·L-1, the treatment is carried out at a ventilation rate of 0.5 to 4 liters of air/(water·hour) for 0.5 to 10 hours.

In the above-mentioned micro-nano bubble treatment method for oilfield oil production sewage, a preferred embodiment is to introduce the micro-nano bubbles generated by the micro-nano bubble generator into a position 8-20cm away from the bottom of the container or the bottom of the pool below the liquid level of the oilfield oil production sewage, and treat it at a ventilation rate of 1 - 2 liters of air/(water·hour) for 2 - 6 hours.

The mineralization, oil content and suspended matter content of the oilfield sewage treated by the micro-nano bubble treatment method of the invention are significantly reduced, and the viscosity of the prepared polymer oil displacement system is significantly improved compared with that before treatment, so it can be used instead of clean water to prepare the polymer oil displacement system, which not only solves the environmental pollution problem of sewage, but also saves fresh water resources.

The above-mentioned polymer flooding system is a partially hydrolyzed polyacrylamide solution commonly used in oil fields.

Advantages:

1. Micro-nano bubble method for treating oilfield sewage has simple process and low cost;

2. The micro-nano bubble method treats oilfield sewage without adding other chemicals to avoid secondary pollution;

3. When the polymer flooding system is prepared with oilfield sewage treated by the micro-nano bubble method, its viscosity is significantly increased compared with that before treatment. It can be used instead of clear water to prepare the polymer flooding system on the oilfield site. While eliminating environmental pollution from oilfield sewage, it saves fresh water resources.

detailed description

The polymer solution described below was a partially hydrolyzed polyacrylamide (PHPA) solution at a concentration of 2000mg L-1. Viscosity was measured using an NDJ-1E viscometer at room temperature (25℃) and a rotating speed of 60rpm. The micro-nano bubble generator is produced by Shanghai Zhongchen Digital Technology Equipment Co., Ltd., with an average bubble diameter of 537nm and a gas production of 6 - 12 liters/hour. The quality of sewage is analyzed and determined in accordance with the oil and gas industry standards of the People's Republic of China "Oil and Gas Field Water Analysis Method"(SY/T5523-2000),"Method for Determination of Oil Content in Oilfield Sewage Spectrophotometry"(SY/T0530-93) and the national standard of the People's Republic of China "Determination of Suspended Matter in Water Quality and Gravity Method"(GB11901 -89).

Example 1

Sewage from the 9-1 polymer distribution station of Gudong Oil Production Plant in Shengli Oilfield was collected. See Table 1 for water quality analysis results.

Take 6L? 9-1 Add sewage from the polymerization station to the water tank, turn on the micro-nano bubble generator, and introduce the micro-nano bubbles into a place 12cm below the level of the sewage and the bottom of the container. Start counting when the bubbles fill the water tank. The ventilation volume is 6 liters/hour.

The ion content, oil content and viscosity of the prepared polymer solution for different treatment times are shown in Figures 1, 2 and 3 respectively. It can be seen that with the extension of treatment time, the ion content and oil content decrease, and the viscosity of the prepared polymer solution increases.

The salinity, oil content, pH and suspended matter content of the sewage after 180 minutes of treatment are shown in Table 1. The degree of mineralization dropped from 11402mg·L-1 to 10833mg·L-1; the oil content dropped from 21.1 mg·L-1 to 10.2 mg·L-1; the suspended matter content dropped from 12mg·L-1 to 6mg·L-1; the pH value increased slightly. The viscosity of the polymer solution prepared from sewage before treatment was 8.1mPa.s. After 180 minutes of micro-nano bubble treatment, the viscosity of the polymer solution prepared from sewage was 13.7mPa.s, and the viscosity increasing rate was 69%.

Example 2

Sewage from the entrance of No. 2 Unit of Gudong Oil Production Plant in Shengli Oilfield was collected. See Table 1 for water quality analysis results.

Take 12L? Add the sewage at the inlet of Couple No. 2 into the water tank, turn on the micro-nano bubble generator, and introduce the micro-nano bubbles into the sewage level 20cm away from the bottom of the container. Start counting when the bubbles fill the water tank. The ventilation volume is 6 liters/hour.

The ion content, oil content and viscosity of the prepared polymer solution for different treatment times are shown in Figures 1, 2 and 3 respectively. It can be seen that with the extension of treatment time, the ion content and oil content decrease, and the viscosity of the prepared polymer solution increases.

The salinity, oil content, pH and suspended matter content of the sewage after 180 minutes of treatment are shown in Table 1. The degree of mineralization dropped from 15254mg·L-1 to 14619mg·L-1; the oil content dropped from 18.8 mg·L-1 to 7.7 mg·L-1; the suspended matter content dropped from 22mg·L-1 to 15mg·L-1; the pH value increased slightly. The viscosity of the polymer solution prepared from sewage before treatment was 10.4 mPa. s. After 180 minutes of micro-nano bubble treatment, the viscosity of the polymer solution prepared from sewage was 15.7 mPa. s, and the viscosity increasing rate was 51%.