Fracturing flow-back fluid resourceful treatment method and system

Abstract

The invention discloses a fracturing flow-back fluid resourceful treatment method and system. The system comprises an adjusting tank, a pretreatment device, a reverse osmosis device, a DTRO disc tube type reverse osmosis device, a first nanofiltration device, a second nanofiltration device, an evaporative crystallization device and a carnallite treatment device. The method comprises the following steps of (1) homogenizing and averaging the fracturing flow-back fluid, (2) pretreatment, (3) enabling pre-treated produced water to enter a reverse osmosis device for primary concentration, (4) enabling reverse osmosis membrane concentrated water to enter a DTRO disc tube type reverse osmosis device for further concentration, (5) enabling the DTRO concentrated water to enter a first nanofiltration device for concentration and salt separation, and (6) further concentrating and separating salt by using a second nanofiltration device. The method is short in treatment flow, low in investment, good in economical efficiency and stable in operation; the water resource recovery rate exceeds 95%; meanwhile, the quality of the obtained sodium chloride crystal salt is superior to the secondary standard of industrial sodium chloride dry salt, the sodium chloride crystal salt can be directly used as a downstream raw material, the economic value is high, and the recycling rate of the crystal salt exceeds 85%.

Description

Technical field: [0001] The invention belongs to the technical field of fracturing flowback fluid treatment, and in particular relates to a method and system for recycling fracturing flowback fluid. Background technique: [0002] Hydraulic fracturing is a widely used oil and gas well stimulation measure. Hydraulic fracturing is currently the main form of natural gas extraction. It requires a large amount of water (ie, fracturing fluid) mixed with chemicals to be poured into shale formations for hydraulic fracturing. to release natural gas. Fracturing flowback fluid mainly refers to the residual fracturing fluid discharged from oil and gas wells after fracturing construction. Various additives, if the fracturing fluid returned to the ground is discharged without treatment, it will pollute the surrounding environment, especially crops and surface water systems. The main components of fracturing flowback fluid are as follows: [0003] [0004] The traditional treatment pr...

AI Technical Summary

Problems solved by technology

However, due to the complex composition of fracturing flowback fluid, which contains a variety of organic substances and inorganic salt ions, plus the produced oil, sand, salt and other components, it is extremely difficult to treat and discharge to meet the discharge standards

Although there are a lot of researches on the standard discharge, there are still many problems, and it is impossible to realize the engineering application

[0007] For example, patent CN201910711767.8 discloses a treatment method and system device for shale gas fracturing flowback fluid, which adopts "electrodialysis concentrated water enters reverse osmosis membrane device I for concentration and reduction treatment, and electrodialysis fresh water enters reverse osmosis membrane device Ⅱ carries out deep purification treatment; the fresh water produced by reverse osmosis membrane device Ⅰ and electrodialysis fresh water enter into reverse osmosis membrane device Ⅱ for advanced purification treatment, and the concentrated water produced by reverse osmosis membrane device Ⅰ enters the evaporation concentrator; The concentrated water and electrodialysis concentrated water enter the reverse osmosis membrane unit I for concentration and reduction treatment, and the fresh water produced in the reverse osmosis membrane unit II is the final effluent of the treatment process; the concentrated water entering the evaporative concentrator is evaporated and concentrated to produce crystalline salt and Condensate”, this treatment method has the following problems: According to the principle of electrodialysis, the main pollutants in electrodialysis enter the fresh water. The pollutants brought by the fresh water will all be trapped in the concentrated water of the reverse osmosis membrane device II, and further enter the reverse osmosis membrane device I. This operation will cause the pollutants to remain in the system; Pollutants will be mainly trapped in concentrated water and enter the evaporation system, eventually resulting in excessive crystalline salt pollutant content, which cannot be recycled and can only be treated as solid waste or even hazardous waste.

[0008] Patent CN201710019575.1 discloses a shale gas fracturing flowback fluid treatment system, which has the following two problems: 1. The nanofiltration product water has been concentrated by reverse osmosis many times before it enters the evaporation crystallization. The concentrating effect of this kind of reverse osmosis membrane is limited, can only adopt a variety of reverse osmosis membranes to concentrate step by step in series, resulting in a long system flow; 2. The nanofiltration concentrated water is returned to the No. 1 reaction tank, although the removal of pollutants in the system is guaranteed, but The backflow causes a large system load, that is, a lot of extra water needs to be treated

There are many problems in this process: 1. The amount of water after pretreatment is very large, and it directly enters the evaporation crystallizer, resulting in a large-scale crystallizer. At the same time, the price of the crystallizer itself is very expensive, resulting in very high overall equipment costs and poor economic efficiency; 2. Almost It is impossible for all pretreatments to completely remove pollutants, resulting in the low purity of crystalline salt produced by evaporation and crystallization, which cannot be used as a resource, or is still a waste; 3. The water quality of the effluent after biochemical treatment is relatively poor, containing a lot of salt , can only be discharged as surface water, a waste of water and easy to cause saline-alkali land

[0010] Deep well injection technology has a large number of applications mainly in the United States, but there is no case of large-scale application in my country, and it is still in the stage of research and exploration

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