Research On The Biological Treatment Efficiency Of Oilfield Fracturing Flowback Based On The BESI Technology

With the continued exploitation of Daqing oilfield, low and ultra-low permeable oilfields become a new field of oil expl oration, and hydralic fracturing operations have become an important measure to increase production.However, fracturing flowback fluid which generated during fracturing operations, is difficult to treat,since it contains harmful and antibiodegradable substances.In order to protect the surrounding environment of oilfields, the fracturing flowback should be treated properly.During the actual production process, fracturing flowback treatment processes are complicated to operate, low treatment efficiency and high cost, research on high-performance low-cost treatment process has become an important issue of oilfields environment protection.In this paper, BESI(spherical filter) combined process and BESI(MBBR+microfiltration membrane) combined process treated the actual fracturing fluid for 60 days., continuously and respectively. The Operating conditions were as follows: HRT 72 h, DO 4~5mg/L, the reflux ratio 50%,and the temperature 35 ℃.By monitoring the water quality, the effluent oil content <20mg/L, SS<20mg/L in the stable operation period,which is superior to the oilfield wastewater reinjection standard. The effluent COD <100mg/L, ammonia nitrogen<1mg/L, meet Municipal Wastewater Treatment Plant Pollutant Emission Standards(GB18918-2002) second level and first level A, respectively.BESI(MBBR+microfiltration membrane) combined process has a shorter acclimatization period and lower effluent COD value and suspended solids value, compared with BESI(spherical filter) combined processs.Through the GC-MS analysis of water samples from the differient units of the two sets of biological combined process during the stable stage, it is bovious that anaerobic reactor can converte partially r efractory organics and improve the biodegradability of wastewater, and that effluent organic matters is indeed lower than the raw water in terms of the species and quantity. Through the high-throughput sequencing of the biological combined process samples a nd the analysis of biological diversity, difference and structure, the differient reactor units have rich biodiversity and a significant difference in species and quantiy.In this paper, static and dynamic ozone oxidation experimentes of fracturing flowback indicates that ozone oxidation method is not suitable for fracturing flowback treatment directly, but it can be used to strengthen the biological processes. Biological effluent is treated by ozone oxidation, the effluent COD <50mg/L, oil content below the detection limit, suspended solids content <5mg/ L. In this paper, the optimal process is as follows: BESI(MBBR+microfiltration membrane) as the main process, and ozone oxidation process as the advanced treatment process.