Preparation And Properties Research Of Proppants Sintered At Low Temperature

With the development of society,gas and oil have been increasingly critical resources.The Hydraulic Fracturing technique becomes an important method which exploits oil and gases wells.However,the proppants used in oil and gases wells are extremely vital materials and their properties are dependent on the exploited content of oil and gas wells as well as the service life of wells,therefore preparing the excellent properties of proppants has a significant meaning.The paper analyzes the currently developed condition and existed problems of proppants at domestic and oversea,designs the rational test scheme and prepares ultimately the excellent proppants.The sintering temperature and the mount of additive feldspar having an effect on the bulk density,apparent density,breakage ratio,phase composition and microstructure are investigated.The results are listed as follows:The corundum-mullite proppants were prepared by the bauxite at 1300°C,1350°C,1400°C,1450°C and 1500°C.The bulk density and apparent density were upward while the breakage ratio was downward with the sintering temperature increasing.When the sintering temperature was 1500°C,the bulk density,apparent density and breakage ratio possessed the optical property.The corundum-mullite proppants were prepared by the bauxite and the additive feldspar with 2wt.%,4wt.%,6wt.%,8wt.% at 1300°C,1350°C,1400°C,1450°C and 1500°C.When the sintering temperature was 1400°C and the mount of feldspar was 4wt.% respectively,the breakage ratio obtained the lowest value of 2.2%.The result showed that the sintering temperature and the breakage ratio of proppants reduced by 100°C and 61% comparing with the proppants without the feldspar.With the sintering temperature increasing,proppants with 4wt% feldspar gradually were to densification and the liquid phase increased.At the same time,the pattern of mullite was transformed from the acicular to rodlike and grains size gradually increased.The high length-diameter ratio of mullite interspersed between corundum matrix,which led to densification of structure,thereby reducing the breakage ratio.When the sintering temperature was up to 1500°C,the excessive phase liquid was generated causing the grain boundary to blur.Ultimately,the mechanical strength decreased.With the amount of feldspar increasing,liquid phase gradually increased.For the proppants at 1400°C,the moderate phase liquid promoted mullite nucleation and inhibited the growth of mullite,which was beneficial for formation of network structure,thereby increasing of the strength of proppants.