Studies On Properties And Application Of Biological Enzymes Using In Oil Production

Fracturing fluid was an important part of oil production.Guar gum,as a thickener,has been widely used in gas-water-based fracturing fluid.The major points of oil production were based on fracturing fluid broken successfully and flowing back completely.Currently,the drawback of widely used chemical breaker like persulfate,was that it couldn't break gel completely and thus pollute the environment.Searching for a biological enzyme breaker was an urgent need.This paper aimed at researching the properties,application and the optimal culture condition of the ?-mannanase.The main conclusions were as follows:1.Studies showed that,the optimum temperature for enzyme reaction was 55?.The thermal stability range of the enzyme was 22?-60?.The enzyme exhibited maximum activity at pH8,and was stable at pH6-10.The effect of metal ion on the enzyme activity was studied.The enzyme activity was inhibited by Cr3+ at high concentration,Fe3+ and Cu2+ could significantly inhibit the enzyme activity;but Fe2+ could activate the enzyme activity.2.The results showed that the fracturing fluid additives had little influence on the enzyme activity,and that meant the enzyme had good compatibility with the fracturing fluid additives.The breaking gel condition had been studied too.At the conditions of 50?,the volume ratio between enzyme and fracturing was 1:19,gel broken for 1h,the viscosity of the fracturing fluid breaking agent was below 10 s at pH8,9,and 10;and the residue content was 140 mg/L,205 mg/L and 275 mg/L respectively.3.The optimal enzyme production conditions for strain:with guar gum as the only carbon sources,concentration for 10 g/L;peptone as a source of nitrogen,concentration for 4 g/L;fermentation temperature for 37?;medium initial pH8.By shaking culture,liquid volume for 50 mL/250 mL,fermentation time for 18 h;by fermentation tank culture,the dissolved oxygen in the medium should not less than 70%,and the fermentation time for 10.5 h.