If the sludge discharged from oilfield sludge treatment is discharged directly without treatment, it not only occupies a large amount of land, but also contains a large number of heavy metals and bacteria, which will produce odor and cause serious pollution of water, soil and atmosphere. At present, there are many treatment technologies for oily sludge. According to the requirements of reduction, harmfulness, recycling and comprehensive utilization, the relevant treatment methods can be summarized as follows: solvent extraction technology, chemical hot wash treatment technology, chemical hot wash treatment technology, pyrolysis treatment technology, etc.

1. Solvent extraction technology for oil sludge treatment
Solvent extraction technology refers to adding extraction solvent to oil-bearing sludge, making extraction reaction between solvent and oil in sludge through sufficient mixing and stirring, so as to achieve the purpose of separating oil from sludge. Moreover, oil extraction agent can be separated and recycled through steam house, and recycled oil can be recycled. Most of the traditional extraction agents are organic solvents. Zhang Xiuxia et al., Che Chengdan et al., respectively, selected trichloro-methyl burning and petroleum ether as extraction agents to treat oily sludge, and the oil removal rate of sludge reached more than 90%. The recovery rate of oil from extraction alone is not very high, but can be improved to some extent if combined with other technologies. Practice shows that the sludge oil separation effect is usually ideal only after multiple extraction processes, and in the process of multiple cycle extraction, the extraction solvent can not guarantee 100% recovery, which increases the cost. Therefore, the key to the development of this technology is to find a cost-effective extraction solvent.

2. Chemical hot washing technology for oil sludge treatment
The oily sludge was diluted with water and then heated. At the same time, a certain amount of chemical reagent was added to wash the paint repeatedly to make the oil desorbed or aggregated from the solid surface. Chemical hot wash treatment system includes sludge pretreatment, mixing, migration, dosing, primary cleaning, secondary cleaning, separation and water treatment, etc. The screening and use of chemical reagents is the key of chemical hot wash process. At present, chemical hot washing technology is widely used in the United States, the United Kingdom, the Netherlands and Canada, such as thermal chemical cleaning technology, solvent - low frequency acoustic separation technology. In addition, combining this process with other technologies, such as "thermochemical washing + ultrasonic", "surface pretreatment + hot wash paint", "chemical hot wash + biological treatment", "hot wash - ultrasonic - swirling" separation process, can better realize the harmless treatment and resource utilization of oily sludge.

3. Chemical hot washing technology for oil sludge treatment
The contaminated soil is spread on the ground, through tillage ventilation or adding minerals, nutrients and water, etc., to enhance the activity of building microorganisms in the soil, and use microbial metabolism to degrade diameter substances in pollutants. The treatment effect is mainly affected by the rate and frequency of sludge application, the pH content, temperature, water capacity and nutrient balance of soil. The United States has used this technology to deal with the pollution of underground oil storage, and Saudi Arabia has also adopted this technology to deal with oily sludge under hot and dry conditions. However, improper site selection has caused the pollution of surrounding soil and groundwater.
Composting is a combination of traditional composting and biological treatment. Appropriate materials (such as strains, moisture, nutrients, fillers, etc.) are mixed with sludge and stacked. Natural microorganisms are used to promote biodegradable organic matter to humus in a controlled way. Composting of sludge can produce natural fertilizer, improve soil fertility and facilitate crop growth. In foreign countries, there have been successful cases of composting treatment, but in China, it is still in the laboratory research stage, and the engineering technology is not mature enough to meet the industrialization of promotion.
(2) Both bioreactor tillage and composting are open systems, which are largely affected by uncertain changes in air temperature and soil moisture, so their application time and area are limited to some extent. Bioreactor is a device system that uses enzymes or organisms to carry out biochemical reactions in vitro, which can realize artificial control of oxygen, temperature, nutrients and other operating conditions. The biodegradation rate of hydrocarbons is faster than that of other biological processes. The core mechanism is the biodegradation process of native or exogenous microorganisms. The bioreactor method is not only suitable for the treatment of oily sludge, oily soil and oily drilling cuttings, but also can be used for the pretreatment of petroleum industry wastes to reduce the amount of oil, and then for other treatment.

4. Pyrolysis technology for oil sludge treatment
Pyrolysis treatment technology refers to the decomposition of heavy oil in oily sludge into volatile hydrocarbon fuel, liquid fuel and solid carbon under the condition of heating. Pyrolysis reaction is related to heating speed, temperature, time and composition of raw materials. The gas recycled is mainly methane, carbon dioxide, gas, etc.; the liquid reeireulation is mainly diesel, which can be used directly as fuel; but the solid reeireulation is mainly used as building material. Therefore, this technology has good direct economic and social benefits, and is worth popularizing. At present, pyrolysis technology can be divided into low temperature steam chamber technology, high temperature pyrolysis technology and aerobic pyrolysis technology.