Fracturing flowback fluid refers to the liquid returned to the ground from the wellbore after hydraulic fracturing operations in oil and gas wells. Its generation is closely related to the core operation process of oil and gas exploitation, and it is an unavoidable industrial wastewater in the oilfield production process. Thoroughly clarifying its generation mechanism, composition and core characteristics is of great significance for optimizing treatment processes, reducing environmental protection burdens, and ensuring the normal production of oilfields.

The generation process of fracturing flowback fluid consists of two key stages. The first stage is the fracturing stage: during operation, fracturing fluid is injected into the formation through high-pressure equipment. The base components of this fracturing fluid include water, proppants and chemical additives. Under high pressure, fractures are formed in the formation to build channels for oil and gas exploitation. The second stage is the flowback stage: after the construction is completed, the formation pressure pushes the mixture of part of the fracturing fluid and formation fluids (including formation water, crude oil, natural gas, etc.) back to the ground, eventually forming fracturing flowback fluid. In terms of source composition, fracturing flowback fluid mainly includes four core components: first, the residual part of the injected fracturing fluid, accounting for about 20%-40%; second, formation water, which is characterized by high salinity and contains various metal ions such as calcium, magnesium and strontium; third, crude oil and dissolved gas; fourth, residual fracturing additives, such as friction reducers, bactericides, crosslinking agents and other functional chemical substances.

The complex sources determine the significant pollution characteristics of fracturing flowback fluid and greatly increase its treatment difficulty. Specifically, its core characteristics are reflected in three aspects: first, complex composition and enriched pollutants. In addition to the above-mentioned various basic components, it also contains many pollutants such as guar gum, formaldehyde, suspended solids and petroleum substances, with a wide variety and high content; second, special physical properties, featuring high viscosity, high suspended solid content and severe oil-containing emulsification, which further increases the difficulty of separation and treatment; third, strong fluctuation of pollutant components. Affected by operating conditions, formation differences and other factors, the types and contents of pollutants change greatly, leading to increased difficulty in matching treatment capacity and processes. These characteristics have gradually affected the normal production order of oilfields, significantly increased the environmental protection burden of oilfields, and become an urgent environmental problem to be solved in the process of oil and gas exploitation.

In the field of fracturing flowback fluid treatment, the traditional process is dominated by "ultrafiltration + reverse osmosis + MVR". In this process system, the membrane system undertakes the core tasks of deep pollutant removal and water quality optimization, and is a key link to ensure that the effluent water quality meets the standards. However, long-term practice has shown that the traditional process has many insurmountable drawbacks: first, high operating power consumption, which directly leads to high tonnage water operating costs; second, poor operating stability, the membrane module is prone to fouling, which in turn leads to reduced treatment flux and affects treatment efficiency; third, high maintenance costs, the membrane module requires frequent chemical cleaning, and daily maintenance work is cumbersome and frequent, further pushing up operating costs.

To solve the difficulties of the traditional process, Sinokle has developed a new type of treatment process, adopting the combined process of "single-stage CDFU (Cyclonic Dissolved Gas Flotation Unit) + sedimentation tank + single-stage CDOF (Cyclonic Dissolved Ozone Flotation) + KFM (Active Media Filter)". Through multi-stage synergy, efficient treatment of fracturing flowback fluid is achieved. The core functions of each link are as follows: CDFU can efficiently and quickly remove free oil, emulsified oil, suspended solids and other pollutants in wastewater by generating a large number of ultra-fine bubbles; the effluent from air flotation enters the coagulation sedimentation tank to further remove suspended solids and a small amount of colloids; CDOF integrates multiple technologies such as ozone multi-stage oxidation, cyclonic dissolved air flotation and coagulation, and can efficiently remove suspended solids, colloids and other pollutants in wastewater; the effluent from CDOF finally enters the KFM for deep oil and suspended solid removal to ensure that the effluent indicators meet the relevant standards.

Compared with the traditional process, the core advantage of Sinokle's new process lies in the construction of a full-process multi-stage synergistic treatment system of "air flotation → coagulation → advanced oxidation → filtration". This system can realize the comprehensive removal of oil, suspended solids, dissolved organic matter and other pollutants in fracturing flowback fluid. It not only improves treatment efficiency and effluent stability, but also effectively reduces operating power consumption and maintenance costs. It provides a new solution for the efficient and economical treatment of fracturing flowback fluid, and has important practical significance for promoting the upgrading of oilfield environmental protection governance and ensuring the green and sustainable development of the oil and gas exploitation industry.