Research On The Influence Of Modified Nano-SiO₂ On The Performance Of Water-based Fracturing Fluid

In the coming decades,the focus of mining is gradually shifting from conventional oil and gas to unconventional oil and gas.As a common fracturing fluid system for unconventional oil and gas,water-based fracturing fluid has the advantages of controllable viscosity,direct mixing in the field,good drag reduction efficiency,and low damage.However,with the deepening of unconventional oil and gas reservoirs,the formation salinity is too high,the formation pores are close to the nanometer level,and the formation is accompanied by harsh environments such as high temperature and high pressure,resulting in the fracturing fluid performance cannot meet the local construction requirements.To improve the performance of the water-based fracturing fluid system,reduce construction costs and improve construction efficiency,it has become the goal of many researchers to develop a high-performance water-based fracturing fluid system.In this paper,a modified nano-SiO₂ water-based fracturing fluid system was developed.Firstly,nano-SiO₂ was modified by a silane coupling agent.Then acrylamide,2-acrylamido-2-methylpropanesulfonic acid,and acrylic acid were used as polymerization monomers,and modified nano-SiO₂ was introduced into it.Through the optimization experiment of the polymerization reaction,the most suitable reaction monomer ratio,time,temperature,and p H were selected.Subsequently,the properties of modified nano-SiO₂ and modified nano-SiO₂ polymer were characterized to determine whether nano-SiO₂ was modified and whether the modified nano-SiO₂ polymer was successfully grafted.Finally,the evaluation experiment of the fracturing fluid system was carried out to analyze the effect of modified nano-SiO₂ on water-based fracturing performance.The results showed that the mass to fraction ratio of acrylamide,2-acrylamide-2-methylpropanesulfonic acid,acrylic acid,XY-SiO₂ and compound initiator was10:3:1:0.5:0.07,respectively,the p H of the reaction system is 7,the reaction temperature is 50°C,the reaction time is 6h,and the concentration of the reaction body is 25wt%.Through the horizontal comparison of three different fracturing fluid systems,it is found that the viscosity of the modified nano-SiO₂ water-based fracturing fluid system can be increased by 17%under the same conditions,and the drag reduction rate can reach 80%.Under 50000mg/L salinity brine,the viscosity can be maintained at 80%of the original viscosity,and the viscosity can be maintained at 90%of the original viscosity at 120°C and 170s-1 for 90 min.The sand-carrying rate of the fracturing fluid can be held at more than 90%in 80 min.The gel breaking time of fracturing fluid is shorter,the gel breaking is more thorough,and the core damage is lower.