Study On Preparation And Performance Of Micro-nano Fracturing Fluid Microcapsule Breaker

The delayed fracturing of the fracturing fluid is of great significance to the fracturing process.Whether the fracturing technology is effective depends largely on whether the fracturing fluid can break the glue in a precise time.The commonly used fracturing fluid breakers have problems that the breaking time is difficult to control and the breaking is not thorough.Microcapsule technology is introduced into the field of fracturing technology.The microcapsule breaker has the function of delayed release.Aiming at the problem that the average diameter of pore throats in unconventional oil and gas fields is too small,and the particle size of microcapsules prepared by conventional methods such as physical and physical chemistry is too large,it is proposed to prepare nano-scale self-breaking microspheres,core-shell microspheres and microcapsules.This article uses three methods to achieve the delayed fracturing fluid fracturing function.The specific research content and main research work are as follows:(1)An anionic polypropylene Amide microspheres P(AM-AMPS)with selfdestructive fracturing fluid thickener was prepared by emulsion polymerization.The particle size of the microspheres was around 70 nm.The microsphere self-degradation process was analyzed.And through the degree of cross-linking or the concentration of peroxide initiator to achieve slow release of breaker.The microspheres with a concentration of crosslinking agent between 0.05% and 2% and a concentration of ammonium persulfate between 5% and 8% can delay gel breaking for more than 1 hour.(2)The poly(styrene-acrylamide)P(St-AM)core-shell microsphere and poly(vinyl acetate-acrylamide)P(Vac-AM)core-shell microsphere core coated with breakers were prepared by reverse phase microemulsion polymerization,the microsphere diameter is 50~100nm.Viscosity analysis and pH analysis show that P(St-AM)and P(Vac-AM)coated core-shell type microspheres inhibit the free radical degradation and oxidative degradation of polyacrylamide,and can achieve the effect of delayed fracturing fluid breaking for more than 1h.(3)Microcapsules with ammonium persulfate as the core material and polypyrrole as the shell material were successfully prepared by in-situ polymerization,and the particle size distribution was 100~300 nm.The change process of the conductivity of microcapsules in water indicates that the release process of microcapsules is osmotic release.By adjusting the amount of glycerin to change the release rate of ammonium persulfate.It was found that the microcapsules can delay gel breaking for more than 4h through a control degradation experiment with equal quality ammonium persulfate.