Influence Factors of Supercritical CO2 Fracturing Fluid on Suspended Sand Performance of Shale Reservoirs
The extremely low apparent viscosity of supercritical CO2 fracturing fluid is associated with such defects as low sand carrying capacity and suspended sand,severe leakage,and weak fracturing effects.The paper designs and synthesizes a thickener significantly enhancing the viscosity of CO2 fracturing fluid,analyzes the effects of different geological conditions and chemical agents on the suspended sand performance of CO2 fracturing fluid,and reveals reasons on the sand suspension of supercritical CO2 fracturing fluid.The results indicated that an increased concentration of CO2 thickener not only could enhance the viscosity of the fracturing fluid but also enables the CO2 fracturing fluid to suspend sand particles.The viscosity of the CO2 fracturing fluid can increase to 3.2 mPa·s with the a 0.5%thickener and the gravel settlement would be 0.5 g with a gravel settlement time of 20 s,lower than the 1.2 g observed in pure CO2 fracturing fluid(0.04 mPa·s).Furthermore,an increase in reservoir pressure would help enhance sand suspension performance of supercritical CO2 on particles,whereas elevated reservoir temperature would impair supercritical CO2 fracturing fluid and sand suspension capabilities,which is predominantly attributed to the changes in microgrid density in supercritical CO2 fracturing system.The study would provide practical and effective approaches and projects for the high effective development of shale reservoirs and applications of supercritical CO2.
Oil and gas extractionEnhance oil and gas recoveryShale reservoir stimulationSupercritical CO2 fracturingSand carrying and suspended sand
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