Treatment of high viscosity fracturing flowback by electrolytic brine-catalyzed oxidation.

With the increasing application of hydraulic fracturing technology in exploration of tight oil and shale gas, the treatment of accompanying fracturing flowback fluids has become more urgent. Fe/Ni catalyst was successfully applied in the treatment of the flowback fluid for the first time in this paper. The effects of different oxidants and catalysts on the treatment of fracturing flowback were investigated. Electrolytic brine was an optimal oxidation gel breaker and molecular sieve loaded with Fe/Ni as catalyst for the treatment of fracturing flowback. Fe/Ni catalyst was characterized by SEM, EDS analysis, TEM and XRD, and the catalytic effect of the Fe/Ni proportion was explored. Fracturing flowback that dealt with catalytic oxidation was mixed with polyaluminum chloride (PAC) and polyacrylamide (PAM) for flocculation and sedimentation, through a filter, and was continuously treated for 20 days to simulate on-site operation. Finally, the suspended solids (SS) content of the fracturing flowback was steadily less than 15 mg/L, which meets the reinjection standard of fracturing flowback (SY/T 5329-2012 (China)). Hence, electrolytic brine-catalyzed oxidation treatment of high viscosity fracturing flowback possess broad application prospects.

Ultrasonic washing for oily sludge treatment in pilot scale.

Ultrasonic technology is a promising tool for washing oily sludge to remove oil, however, little information has been provided on the pilot scale application of ultrasonic washing. In this study, the ultrasonic conditions were optimized based on the pilot trial of the effects of ultrasonic properties on oil removal from oily sludge. An ultrasonic power of 0.24 w/cm2 was necessary to overcome the energy threshold for oil washing at the frequency of 25 kHz. The removal rate was changed from 46.0% to 60.7% with oily sludge content from 25.0% to 42.0%, respectively. The addition of surfactants could improve oil recovery, and the optimizing content for sodium petroleum sulfonate and Span 80 was 0.3% and 0.03%, respectively. A series of pilot scale test indicated that the oil removal rate could be 82-90% by ultrasound assistant with surfactants (Span 80). Thin-layer chromatographic flame ionization detection showed that the removal rate by ultrasonic wash was dropped with the increase of composition polarity. However, under the assistance of surfactants (Span 80), all compositions could be effectively removed. This pilot study will greatly improve the application of ultrasonic technology in oily sludge treatment.

Pilot study of oilfield wastewater treatment by micro-flocculation filtration process.

In order to meet the latest Environmental Protection Law of China on wastewater discharge standards, this paper studied a pilot-scale micro-flocculation filtration pretreatment process for the treatment of oilfield wastewater. The experiment showed that the removal rate of oil and suspended solids (SS) respectively increased from 91.52% to 95.38% and from 66.42% to 97.19%. After the treatment by the micro-flocculation filtration device, the relevant characteristics of the discharge wastewater satisfied the latest standards continuously. Moreover, the polyaluminum chloride (PAC) dosage was reduced from 200 mg/L to 100 mg/L (50 mg/L in micro-flocculation device and 50 mg/L in the cyclone reactor) at the same time. In order to decrease the degree of scaling in the filter, ceramsite was chosen as the filter material instead of quartz sand that is widely applied in the oilfields. The scaling experiment showed that the HCO3-, Ca2+ and Mg2+ contents in the extract from quartz sand after the scaling study were increased by 38.05, 35.91 and 0.28 mg/L, respectively. Meanwhile, the HCO3-, Ca2+ and Mg2+ contents in the extract from ceramsite were only increased by 13.14, 6.26 and 0.27 mg/L, respectively. Therefore, the ceramsite is not so prone to scaling as compared to quartz sand under identical test conditions, which avoided a hardened and impervious filter after operating for some time. These results suggest that the micro-flocculation filtration with the ceramsite as filter media is a suitable pretreatment process for the oilfield wastewater treatment.