Chinese Journal of Applied Chemistry ›› 2023, Vol. 40 ›› Issue (1): 134-145.DOI: 10.19894/j.issn.1000-0518.220139

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Enzymatic Properties and Gel Breaking Performance of Low-temperature β-Mannanase

Yu-Hua XIONG, Lei ZHOU, Shi-Zhong YANG, Bo-Zhong MU()   

  1. East China University of Science and Technology Institute of Applied Chemistry,Biological Oil Recovery Engineering Research Center of the Ministry of Education,Shanghai 200237,China
  • Received:2022-04-17 Accepted:2022-10-08 Published:2023-01-01 Online:2023-01-28
  • Contact: Bo-Zhong MU
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The gel breaking of flowback fluid and low temperature oil fracturing fluid is a difficult problem currently faced in the development of shale and tight oil and gas reservoirs. Due to the high temperature required for the use of chemical gel breaker, it is difficult to meet the requirements of completely gel breaking under low temperature conditions. To this end, a high-throughput screening methodis used to screen out high-efficiency low-temperature β-mannanase-producing bacteriafrom the mixed samples of oilfield fracturing flowback fluid and konjac land. The enzymatic properties and gel-breaking performance of this low-temperature β-mannanase are studied. The results show that, among the 40 screened strains, strain O5 is identified as Pseudomonasstutzeri. The optimum temperature for β-mannanase ME-O5 (ME-O5) is 50 ℃, and its enzyme activity could still maintain more than 60% at 5~20 ℃. The low temperature activity is outstanding, and the thermal stability is good in the middle temperature region. The optimum pH for ME-O5 is 7.0, with a certain pH adaptability and a wide pH tolerance range. At both 5 and 20 ℃, ME-O5 reduces the viscosity of guar gum to less than 5 mPa·s, the viscosity reduction rate is more than 99%, and the effect of viscosity reduction is remarkable. At 10, 20 and 50 ℃, after the fracturing fluid is treated by gel breaking for 3 h with ME-O5, the apparent viscosity of the gel breaking fluid is less than 5 mPa·s, the surface tension is less than 28 mN/m, the interfacial tension is less than 2 mN/m, and the amount of residue is less than 600 mg/L. The results meet or exceed the requirements of Oil and Gas Industry Standard SY/T 6376-2008. It shows a good application prospect inlow temperature gel breaking of oil field fracturing.

Key words: β-Mannanase, Low temperature activity, Enzymatic properties, Gel breaking performance, Low-temperature enzyme gel breaker

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