Overview and Challenges of Oilfield Fracturing Flowback Fluid and Its Treatment
1. Source of Oilfield Fracturing Flowback Fluids
Fracturing flowback fluid is the complex wastewater that returns to the surface after hydraulic fracturing (fracking) operations, a mix of the original fracking fluid chemicals, formation water from the rock, and reservoir byproducts, characterized by high salinity, TDS, COD, and suspended solids, posing significant environmental challenges for treatment and disposal. This fluid, returning from 10-20% of injected water, contains oil/gas, bacteria, and dissolved minerals, requiring specialized technologies for safe management, reuse (e.g., for other drilling), or disposal, with treatment methods constantly evolving.
2. Characteristics of Oilfield Fracturing Flowback Fluids
The fracturing flowback fluid has following characteristics:
a. Complex Mixture: Contains injected water, friction reducers, biocides, corrosion inhibitors, shale minerals, hydrocarbons, and radioactive isotopes.
b. High Salinity: Rich in chlorides, sodium, calcium, barium, and strontium.
c. High Contaminants: Elevated Chemical Oxygen Demand (COD), Total Suspended Solids (TSS), and bacterial content.
d. Variable: Composition changes with location, rock type, and treatment duration.
3. Conventional Treatment Processes for Oilfield Fracturing Flowback Fluids
4. Limitations of Conventional Treatment Processes
a. Poor Treatment Effectiveness:
Fracturing flowback fluid contains a wide variety and high concentration of organic substances, including high concentrations of guar gum and high molecular polymers, which are difficult to effectively remove with traditional methods. This is especially true for high-viscosity and severely emulsified flowback fluids, where traditional methods often fail to achieve ideal oil-water separation.
b. High Treatment Costs:
A large amount of chemicals, such as flocculants and oxidants, are required during the treatment of fracturing flowback fluid, and these chemicals are expensive. Additionally, the process consumes substantial energy, such as electricity and steam, further increasing treatment costs.
c. Large Land Area Requirements:
Traditional treatment processes typically require the construction of large-scale facilities like sedimentation tanks and filtration pools, which occupy a considerable amount of land. In areas with limited land resources, this can be a significant constraint to their application.
d. Low Automation Level:
Most traditional treatment processes rely on manual operation, resulting in low levels of automation. This not only increases operational difficulty and labor costs but may also lead to unstable treatment outcomes.
e. Significant Environmental Impact:
Traditional treatment processes may generate large amounts of wastewater and sludge. If not handled properly, this could lead to environmental pollution. Especially for flowback fluids containing harmful substances, traditional methods may not fully remove these contaminants, posing a potential risk to the environment.
f. Poor Technical Adaptability:
The water quality and volume of fracturing flowback fluid can fluctuate significantly, and traditional treatment processes may not be adaptable to such changes. When water quality or volume changes, it may be necessary to adjust the treatment process or add more equipment, increasing both the difficulty and cost of treatment.
