Treatment process of oil-containing sewage in low-permeability oil field

Abstract

The invention discloses a treatment process of oil-containing sewage in a low-permeability oil field in the technical field of petroleum exploitation. The process comprises the following steps: firstly, carrying out aeration pretreatment to remove sulfide in the oil-containing sewage; then, entering a biological contact oxidation system to degrade crude oil in the oil-containing sewage, wherein the biological contact oxidation system comprises at least two stages of biochemical pools which are connected in series, the biochemical pool is provided with a hydrophilic combined filling material, and the pool bottom of the biochemical pool is provided with an air aeration device; putting an oil-removing microorganism agent in an initial stage of starting in the biochemical pool, and then carrying out efficient aeration sedimentation treatment on extracellular polymers and other biochemically degradable organic substances; and finally, treating by an ultrafiltration membrane filtration system and then injecting into a water tank. The process has the characteristics of small system sludge amount, less oil content in sewage at the membrane inlet, little ultrafiltration membrane pollution,stable membrane flux and long chemical cleaning period of ultrafiltration membrane, and the quality of water at the water outlet of the system reaches the grade A water quality standard of the low-permeability oil field.

Description

technical field [0001] The invention relates to a sewage treatment method, in particular to a treatment method for oily sewage in an oil field. Background technique [0002] Low-permeability oilfields have the characteristics of small reservoir pores, thin throats, high seepage resistance, and poor conductivity, so they have higher requirements for injected water. The Petroleum and Natural Gas Industry Standard SY / T 5329-94 of the People's Republic of China "Recommended Indicators and Analysis Methods for Injection Water Quality in Clastic Reservoirs" stipulates that the suspended solids content in injection water for low-permeability oilfields should be less than 3mg / l, and the median particle size of suspended solids should be less than 3×10 ～3 mm, oil content <8mg / l. [0003] At present, the oil field mainly adopts gravity deoiling + coagulation + coarse filtration + fine filtration process, pressure deoiling (swirl flow, coarse granulation) + coagulation + coarse fi...

AI Technical Summary

Problems solved by technology

[0005] First, ordinary physical and chemical processes cannot effectively remove emulsified oil and organic matter. After fiber balls and fiber bundles are polluted by oil and organic matter, regeneration is difficult and the service life is short

[0006] Second, in the biological method + ultrafiltration membrane process, although the free oil, emulsified oil and other organic matter in the oily sewage are effectively removed by microorganisms, which reduces the pollution of the oil to the ultrafiltration membrane, the microorganisms produce a large amount of extracellular Polymers can seriously foul UF membranes

This method has the following disadvantages: ①Use a large amount of coagulant or coagulant, which increases the amount of oily sludge; ②Although microorganisms can effectively degrade crude oil, the extracellular polymer produced by microorganisms has not been effectively removed, which will cause Ultrafiltration membranes cause serious fouling, making membrane regeneration difficult

This method has the following disadvantages: ①The treatment process is too long, and the one-time investment in water treatment is high; ②The coalescence degreasing method can only remove part of the emulsified oil; Membrane causes severe fouling, making membrane regeneration difficult

This method has the following deficiencies: ①The treatment time of oily sewage by the biological pool is too short (3.5h), the oil content in the sewage cannot be effectively removed, which will cause blockage of the filter material of the biofilter; ②Extracellular polymers produced by microorganisms are not obtained Effective removal will also cause pollution and blockage to the filter material of the biofilter and the hollow fiber ultrafiltration membrane at the back end; ③The filter material of the biofilter needs to be backwashed frequently, the workload of flushing and maintenance is heavy, and it is difficult to replace and manage the filter material; ④The patent does not explain the cleaning cycle of the filter material of the biofilter and the pollution of the filter material; ⑤The above methods have no industrial application reports in the field of oilfield sewage treatment

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