Hydraulic fracturing is an effective measure to recover the permeabilityof reservoir and important to enhance oil and gas well production and water injection well. Fracturing fluid is the key factor in the fracture treatments. At present, water-based fracturing fluids are popular, because of low costs and steady performance, which has the largest applications. However, it performs badly in residue. The novel developed clearfrac fluid system named CF1 has lowresidue, cost affectivity, prior temperature resistance properties. Evaluation through a series of lab experiments, the experiments result show that the novel clearfrac fluid system can satisfy with the requirement of low damage and have favorable temperature resistance under 120 。C. The damage to the core matrix due to with the broken frac-fluid is low. Prior properties of the novel clear-fracturing fluid are suitable to high temperature and high pressure reservoirs. It is also a novel environmental friendly viscoelastic surfactant fracturing fluid. The development of the novel clear-fracturing fluid for hydraulic fracturing industry is significant.
Enrichment of aerobic denitrifier in activated sludge system was investigated, using intermittent aeration mode and nitrite as substrate in sequencing batch reactor (SBR). 70% of TN removal was observed when DO was 4-5mg/L, which indicated that aerobic denitrification occurred in activated sludge system. 30 strains were isolated from activated sludge, 10 strains of which had a high TN removal efficiency of more than 60%. Especially, 90.25% of TN removal was observed by strain Y23. The life cycle of Y23 was determined as 4 days and aerobic denitrification was mainly occurred at logarithmic phase (12-36h). After 4-day cultivation, TN removal efficiency and maximum removal rate was 90.25% and 3.47mg/ (L·h), respectively. In whole aerobic denitrification process, only 0.32mg/L NO3--N was accumulated. The characteristics of colony were circular, white and opaque, viscous and the cell of Y23 was rod, gram negative under microscope. Moreover, Y23 was identified as Acinetobacter sp. by 16S rDNA sequences analysis.
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