Evolution of Oilfield Fracturing Flowback Fluid Treatment Technology and Breakthroughs in New Processes

Fracturing oil recovery is an important measure for increasing oil and gas production: high pressure is used to create fractures in the formation, and an appropriate amount of proppant (such as sand particles with a certain viscosity) is injected to maintain fracture conductivity. The key to successful implementation lies in building a well-performing fracturing fluid system to ensure the proppant effectively enters the formation.

Since the technology was first applied in the 1950s, fracturing fluid systems have evolved significantly. Early systems were mainly oil-based, achieving fracturing by mixing viscous fluids into gasoline. However, such systems lose viscosity significantly under high-temperature well conditions, affecting operational efficiency, and pose safety hazards that limited their wide application. By the 1990s, water-based fracturing fluid systems using water as the solvent and biopolymer guar gum and its derivatives as thickeners gradually matured and achieved good engineering results.

Schematic of the fracturing process

      With China's environmental requirements becoming increasingly strict, the harmless disposal of fracturing flowback fluid has become an industry focus. Clean fracturing fluid systems that are easy to prepare, economical in dosage and low in formation damage have made significant progress. At present, most oilfields still use conventional water-based fracturing fluid systems, whose flowback fluid is complex in composition: besides oil, chemical additives and proppant, it also contains various infiltrated microbial communities. Overall, this type of flowback fluid has the following typical characteristics:

(1) The fracturing fluid system uses a wide variety of additives; after gel breaking, the flowback wastewater has high turbidity, chroma and COD. Uncontrolled discharge would cause considerable harm to the surrounding environment.

(2) Incomplete gel breaking results in high viscosity, high organic content, high suspended solids, high suspended oil and poor biodegradability. The flowback fluid is also complex in composition: high broken-polymer content, high viscosity, high levels of various organic and inorganic additives, plus SBR bacteria, sulfides and metals. Viscosity reaches 20 mPa·s, with high stability and severe emulsification that resists settling.

(3) Fracturing flowback fluid is discharged intermittently and in large volumes.

At present, the fracturing flowback fluid generated in China's oilfields is mainly handled in three ways:

First, treating it to a certain standard for use as reinjection water for waterflood production or for injection into waste formations;

Second, treating it for compliant discharge;

Third, recycling it as water for preparing fracturing fluid. Most oilfields use the oil separation - coarse granulation - coagulation - oxidation - filtration - sterilization method and then use the water for reinjection. This scheme is not only complex in flow and limited in treatment effect, but with the continuous growth of tertiary recovery wastewater, its treatment capacity can no longer meet actual demand.

Fracturing flowback fluid treatment process flow diagram

To address the technical bottlenecks in fracturing flowback fluid treatment, SINOKLE, drawing on its deep experience in oilfield water treatment, has innovatively developed the combined "ozone catalytic oxidation - cyclonic flotation (CDOF) + cyclonic dissolved-air flotation (CDFU )" process. Years of engineering practice show that this technology offers rapid gel breaking and viscosity reduction, fully automatic operation and other advantages; it can efficiently remove polymers, chemical additives, miscellaneous bacteria and calcium and magnesium ions from the flowback fluid and significantly reduce sludge production, successfully overcoming the technical difficulties of fracturing flowback fluid treatment, and it is suitable for onshore oilfields, offshore production platforms and other operating environments.

Fracturing flowback fluid treatment case