NEW HYDRAULIC FRACTURING FLUID WITH MICROENCAPSULATED HEAT-GENERATING SYSTEM

During fracturing of low-temperature, shallow oil and gas reservoirs, it is difficult to break viscosity because of low activity of convention viscosity breaker at low temperature. To avoid those problems, a new microencapsulated heat-generating hydraulic fracturing fluid system was proposed. Studied the select for chemical heating system, prepare and evaluate oxalate capsule, heat generate of micro-capsule packing chemical and compatibility of conventional water base fracturing fluid. From experiment, NH4Cl-NaNO2 system was selected as chemical heat-generating system. According to reaction characteristics of this system, oxalic acid is chosen as catalyst of reaction and encapsulated using ethyl cellulose and paraffin as coating materials by phase separation method. Compounding with oxalic acid microcapsule, gel-breaker and 2.0 mol/L heat-generating agents, its final viscosity keeps to about 300 mPa·s when it is sheared at the rate of 170 s-1 in 2 hours,and after 4 hours, the viscosity of breaker is 12 mPa·s. And corresponding fracturing technology also is discussed here.