Study On Preparation Of Low Density And High Strength Ceramic Proppants From Coal-Series Kaolin

Hydraulic fracturing technology is currently widely used in the oil and gas field to increase production,and the performance of oil fracturing proppant is directly related to oil and gas production.In view of the special mining conditions of unconventional oil and gas reservoirs,the future fracturing proppant will inevitably develop in the direction of low density and high strength.Ceramsite proppants are favored because of their good sphericity and high strength,but traditional ceramsite proppants have higher density and higher cost,which limits their application.The purpose of this study is to prepare low-density and high-strength ceramsite proppant using coal series kaolin as raw material.In this paper,three methods are mainly used to achieve the research purpose.First,Zn O and potassium feldspar are added to the coal series kaolin as additives.Secondly,WO₃ was added to the raw material as mullite whisker accelerator,and the raw material was mixed Zr O₂ ultra-short fibers used as the second reinforcement phase with higher strength.Finally,the ceramsite proppant was surface coated to optimize its performance.Research indicates:(1)The addition of Zn O and Si O₂ and Al₂O₃ in the raw material formed a ternary eutectic micro-region,which could effectively reduce the sintering temperature of the ceramsite.Adding appropriate amount of Zn O could increase the densification of the sample and increase the crushing resistance of the ceramsite proppant.Potash feldspar could effectively promote the sintering of ceramsite,fill the internal pores,and increase the strength of ceramsite by utilizing its own melting characteristics at relatively low temperature.(2)Adding WO₃ to the raw material provided suitable gas phase environment for the growth of mullite whiskers.A proper amount of WO₃could effectively promote the axial growth of mullite,significantly reduce the apparent density of the sample,and the mullite formed the network structure serves as the skeleton of the ceramsite,which greatly enhanced the anti-crushing ability of the ceramsite proppant.In addition,although the Zr O₂ ultra-short fibers doped in the raw materials adversely affect the density of the ceramsite proppant,it could still significantly improve the strength of the ceramsite.(3)Through the 3D model,the mechanism of the film treatment to reduce the density and increase the strength was explained.The coating treatment closed the pores on the surface of the ceramsite,greatly reduced its density,and changed the contact mode of the particles,and the presence of the"anchor"structure could effectively distribute the load and significantly improve the anti-breaking ability of the ceramsite.The highest crushing level could reach 15K.Compared with the uncoated ceramsite,the volume density of the coated ceramsite proppant decreased by 11.32%,the apparent density decreased by 14.73%,and the breaking rate at 69 MPa closing pressure was only 1.16%,a decrease of 96.51%.In this paper,low-aluminum coal-based kaolin was used as raw material,and low-density and high-strength ceramsite proppant was successfully prepared by adding suitable additives or coating the ceramsite,and the production cost of the proppant was effectively controlled.At the same time,it also provided reference solutions for proppant manufacturers.