Abstract

From the using history, we can see that conventional slickwater and guar fracturing fluid will be widely replaced by viscous slickwater in unconventional oil/gas fracturing. The viscous slickwater combines the advantages of slickwater and guar fracturing fluid but avoids the disadvantages of both, that includes drag reduction and good sand carrying capacity. This paper will analyze the viscous reducer’s molecular structure and viscoelasticity to find out the sand carrying mechanism. Using Haake RS6000 rheometer to test the elastic modulus and viscous modulus of conventional slickwater and viscous slickwater, reveal the sand-carrying performance from the perspective of viscoelasticity; using JEM 2100 LaB6 transmission electron microscope to test the molecular structure of two polymers, from the molecular space structure to analysis of its drag reduction performance. Finally, systematically evaluated the viscosity, drag reduction rate, sand-carrying, and gel-breaking properties of the viscous slickwater. The polymer enhances the viscous slickwater’s sand carrying performance by increasing the elastic modulus of fluid and reduces the drag in the flow through the intermolecular framework structure. The comprehensive performance evaluation results show that: 1) The apparent viscosity of the 0.6 wt% viscous slickwater is 80 mPa.s, which is close to conventional guar gum fracturing fluid; 2) When the linear flow rate reaches 5 m/s, the viscous slickwater drag reduction rate is greater than 75 %; 3) The viscous slickwater fluid static and dynamic sand carrying performance is better than conventional slickwater, which is close to guar gum fracturing fluid; 4) When the breaker concentration is equal to 50 ppm, the gel breaking time of viscous slickwater is about 35 mins and the residue content is less than 45 ppm. The conventional fracturing fluid will be more and more replaced by viscous slickwater during the fracturing of unconventional oil and gas reservoirs. This article provides a reference for researchers to understand its drag reduction and sand carrying performance.

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