Properties of the MCB series Microcapsule Gel Breaker

In segmented fracturing of horizontal wells, gels of the fracturing fluids are often broken too early for the fluids to function properly. To solve this problem, two micro capsule gel breakers, MCB-1 and MCB-2, with different capsule cloths have been synthesized through emulsion polymerization, using ammonium persulfate as the core. The active contents, percent of encapsulation, rates of release and gel breaking retardation have been measured in laboratory experiments. The active contents of MCB-1 and MCB-2 are 38.56%and 39.69%, respectively, and the rates of encapsulation of MCB-1 and MCB-2 are 83.85%and 85.89%, respectively. Compared with the commercially available encapsulated gel breakers, MCB-1 and MCB-2 have comparatively slow release rates. The experiments also show that MCB-1 and MCB-2 gradually reduce the viscosity of the fracturing fluid in 4 hours, and the viscosity of the fracturing fluid after gel breaking is less than 10 mPa²s, indicating that the synthesized micro capsule gel breakers are effective in slowing down gel breaking, and the impairment of formation permeability caused by these gel breakers is less than 12%.