BREAK Enzyme Breaking Technology Research And Application

The fracturing is an important step of the EOR in the low or ultra-low permeability reservoir. Fracturing fluid gel breaking is not timely, thorough and even the formation of cracks in the cake, reducing the diversion capacity of the reservoir. The effect of the fracturing fluids gel breaking directly influences the fracturing fluid flowback and the production. As traditional oxidation breaker will bring serious environmental and geological pollution, biological enzyme provides a safe and effective gel breaking means. Through evaluating a series of experiments of the BREAK enzyme breaker, this article studied the mechanism and performance characteristics of the breaker, and obtained the following main conclusions and cognition:As comparing with the APS, the surface tension of the gel breaking liquid after breaking by the BREAK enzymes is lower, and the filtration coefficient is smaller. Using the BREAK enzyme breaker is more conducive to reduce viscous resistance and macromolecular material blocking the reservoir, can increase the connectivity of the fracture and the wellbore and reservoir, and is easier for the gel breaking liquid backflow. The BREAK enzyme breaker can delay the effect of gel breaking, with good performance of fluid loss, minimize the fracturing fluid damage on the purpose layer, and achieve the purpose of improving reservoir flow conductivity. The compatibility of the BREAK enzyme breaker and fracturing fluid additive is good. There is no compatibility taboo between the ammonium persulfate (APS) and the BREAK enzyme breaker. Using the BREAK enzyme breaker and the ammonium persulfate together is better than using them alone, with less residue content, and the harm to the fracture diverting capacity also is minimal. With site construction test of30layer (24well) in Longdong area, fracturing operation is smoothly, and pressure is stable. The viscosity of flowback fluid is under5mPa·s, gel breaking effect is good, and the average recovery rate is79.59%.On the whole, that has obtained the good effect.